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2011 PETROLIAM NASIONAL BERHAD (PETRONAS) All rights reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the permission of the copyright owner.
PETRONAS Technical Standards (PTS) publications reflect the views, at the time of publication, of PETRONAS OPUs/Divisions. They are based on the experience acquired during the involvement with the design, construction, operation and maintenance of processing units and facilities. Where appropriate they are based on, or reference is made to, national and international standards and codes of practice. The objective is to set the recommended standard for good technical practice to be applied by PETRONAS' OPUs in oil and gas production facilities, refineries, gas processing plants, chemical plants, marketing facilities or any other such facility, and thereby to achieve maximum technical and economic benefit from standardisation. The information set forth in these publications is provided to users for their consideration and decision to implement. This is of particular importance where PTS may not cover every requirement or diversity of condition at each locality. The system of PTS is expected to be sufficiently flexible to allow individual operating units to adapt the information set forth in PTS to their own environment and requirements. When Contractors or Manufacturers/Suppliers use PTS they shall be solely responsible for the quality of work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, it is expected of them to follow those design and engineering practices which will achieve the same level of integrity as reflected in the PTS. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the owner. The right to use PTS rests with three categories of users: 1) 2) 3) PETRONAS and its affiliates. Other parties who are authorised to use PTS subject to appropriate contractual arrangements. Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) and 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards.
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PTS 22.214.171.124 January 2011 Page 4 TABLE OF CONTENTS 1. 1.1 1.2 1.3 1.4 1.5 2. 2.1 2.2 2.3 2.4 2.5 3. 3.1 3.2 3.3 3.4 3.5 3.6 4. 4.1 4.2 4.3 4.4 4.5 4.6 5. 5.1 5.2 5.3 5.4 5.5 5.6 6. 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 7. 7.1 7.2 8. INTRODUCTION ........................................................................................................ 6 SCOPE........................................................................................................................ 6 DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS ......... 6 DEFINITIONS ............................................................................................................. 6 ABBREVIATIONS ....................................................................................................... 8 CROSS-REFERENCES ............................................................................................. 9 MATERIALS ............................................................................................................. 10 GENERAL ................................................................................................................. 10 THERMOPLASTIC LINER MATERIALS .................................................................. 11 MATERIAL SELECTION GUIDE .............................................................................. 18 MATERIAL TESTING ............................................................................................... 19 END CONNECTORS ................................................................................................ 23 DESIGN .................................................................................................................... 24 INTRODUCTION ...................................................................................................... 24 MINIMUM LINER THICKNESS................................................................................. 25 LINER DESIGN PROCEDURE................................................................................. 26 VENT POINT DESIGN .............................................................................................. 32 PULL-IN LOADS AND INSERTION LENGTH .......................................................... 34 DESIGN OF END CONNECTORS ........................................................................... 35 MANUFACTURE OF THE THERMOPLASTIC LINER ............................................ 37 PROCESS OF MANUFACTURE .............................................................................. 37 FINISH AND WORKMANSHIP ................................................................................. 37 DIMENSIONS, WEIGHTS AND TOLERANCES ...................................................... 38 QUALITY PROGRAMME .......................................................................................... 38 EQUIPMENT MARKING ........................................................................................... 41 HANDLING AND STORAGE .................................................................................... 42 LINER INSTALLATION ............................................................................................ 43 GENERAL - INSTALLATION TECHNIQUES ........................................................... 43 PREPARATION PHASE ........................................................................................... 45 LINER FABRICATION PHASE ................................................................................. 47 LINER INSTALLATION ............................................................................................. 49 END FLANGES AND IN-LINE FLANGED JOINTS .................................................. 51 TESTING................................................................................................................... 52 OPERATION ............................................................................................................. 53 START-UP ................................................................................................................ 53 DE-PRESSURISING ................................................................................................. 53 PIGGING ................................................................................................................... 53 FLOW VELOCITY ..................................................................................................... 53 VENTING .................................................................................................................. 53 MAINTENANCE ........................................................................................................ 53 REPAIR ..................................................................................................................... 54 OPERATIONAL PROCEDURE FOR A LINED PIPELINE ....................................... 54 DOCUMENTATION .................................................................................................. 55 INFORMATION TO BE SUBMITTED BY THE PRINCIPAL ..................................... 55 INFORMATION TO BE SUBMITTED BY THE CONTRACTOR .............................. 55 REFERENCES ......................................................................................................... 56
PTS 126.96.36.199 January 2011 Page 5 APPENDIX 4 APPENDIX 5 MATERIAL PROPERTIES............................................................................... 65 PURCHASE ORDER INFORMATION ............................................................ 66
PTS 126.96.36.199 January 2011 Page 6 1. 1.1 INTRODUCTION SCOPE This PTS specifies requirements and gives recommendations for the selection, design, manufacture, installation and operation of thermoplastic liners in carbon steel pipelines and flowlines. It covers both the retro-fitting of thermoplastic liners inside existing carbon steel pipelines and flowlines as well as new pipelines and flowlines. In the context of this PTS, a liner consists of a number of thermoplastic pipe lengths which are fused together into sections of up to approximately 1 km. After pressure testing, the section of liner is inserted into a pre-welded carbon steel pipeline or flowline section. The carbon steel pipe provides the pressure containment and the liner the internal corrosion protection. At the ends of the section the liner is terminated in a thermoplastic flange or other (usually mechanical) connection system, to enable sections to be joined together. Onshore, offshore, buried and above-ground applications are considered. Within certain limitations, thermoplastic lined pipelines and flowlines may be used in oil, gas or water service. Although the scope is directed towards thermoplastic liners for carbon steel pipelines and flowlines, much of the content is also relevant for liners inserted in flexible flowlines and risers. The liners covered in this PTS are based both on currently applied thermoplastic materials and on those materials that have the potential to be applied in future, more demanding applications. This PTS only gives requirements for the thermoplastic liner. It is assumed that the carbon steel pipeline or flowline into which the liner is to be inserted has been designed and constructed in accordance with PTS 31.40.00.20.
Amended per Circular 05/02
Factory-applied liners inside steel pipe and fittings are covered by PTS 31.38.01.11-Gen. Hose lining techniques, using polyester materials with fibre tubes and epoxy to bond these to the pipe wall, are not covered by this PTS. Pipelines lined with thermoset materials such as GRE (Glass fibre Reinforced Epoxy) are not covered by this PTS either. 1.2 DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS Unless otherwise authorised by PETRONAS, the distribution of this PTS is confined to companies forming part of PETRONAS or managed by a Group company, and to Contractors and Manufacturers/Suppliers nominated by them. This PTS is intended for use in the design, procurement, manufacturing, transport and installation of thermoplastic liners for pipelines for oil and gas production, oil refineries, chemical plants, gas plants and supply/marketing installations. If national and/or local regulations exist in which some of the requirements may be more stringent than in this PTS, the Contractor shall determine by careful scrutiny which of the requirements are more stringent and which combination of requirements will be acceptable as regards safety, environmental, economic and legal aspects. In all cases the Contractor shall inform the Principal of any deviation from the requirements of this PTS which is considered to be necessary in order to comply with national and/or local regulations. The Principal may then negotiate with the Authorities concerned with the object of obtaining agreement to follow this PTS as closely as possible. 1.3 1.3.1 DEFINITIONS General definitions The Contractor is the party which carries out all or part of the design, engineering, procurement, construction, commissioning or management of a project, or operation or
PTS 22.214.171.124 January 2011 Page 7 maintenance of a facility. The Principal may undertake all or part of the duties of the Contractor. The Manufacturer/Supplier is the party which manufactures or supplies equipment and services to perform the duties specified by the Contractor. The Principal is the party which initiates the project and ultimately pays for its design and construction. The Principal will generally specify the technical requirements. The Principal may also include an agent or consultant to act for, and on behalf of, the Principal. The word shall indicates a requirement. The word should indicates a recommendation. 1.3.2 Specific definitions Acceptance criteria Annulus Bell hole Defined limits placed on characteristics of materials, products or services. Space between thermoplastic liner and the carbon steel outer pipe. Excavated area allowing access to a buried carbon steel pipeline e.g. for insertion of a section of thermoplastic liner. A process of fusing thermoplastic materials that entails squaring and aligning the pipe materials, heating the pipe ends, bringing the two aligned pipe ends together under pressure and a predetermined cooling time resulting in a fused joint having a hydrostatic strength equal to the parent pipe. Fluids in which the volume fraction of crude oil is at least 1% A device used to provide a leak-tight structural connection between two sections of lined pipe. The lining is terminated inside the end connector. Face flanges with a bolt circle according to ASME B 16.5 or ASME B16.47, including thermoplastic flanges with metallic backup rings. Voids in grout, which allow the transport of gas through the grout to venting ports. Technique whereby thermoplastic pipe is fused by smelting and re-solidification. System of terminating lined pipelines by compression of the liner between an internal ring and a CRA material. Individuals designated by the Principal to act on behalf of the Principal for monitoring Contractor's quality control testing and technical acceptance. Assignment of a unique code to each lot of pipes to maintain traceability. A lot is defined as being all pipes produced from the same base polymer batch with the same diameter and wall thickness, up to a maximum number of 50 pipes. Elastic modulus: proportionality constant between applied stress and strain. This is a measurement of the deflected set in a crosssection of pipe and is expressed as a percentage. It is
Lot number
Modulus Ovality
PTS 126.96.36.199 January 2011 Page 8 measured by taking the maximum measured diameter minus the minimum measured diameter (the out-ofroundness value) and dividing that sum by the average measured diameter and multiplying that result by 100. PA liner PE liner PK liner Point of fusion PP liner PPS liner PTFE liner PVC liner PVDF liner Permeation Records Standard Dimension Ratio (SDR) Thermoplastic materials Vent connection or point Liner based on Polyamide in combination with fillers and plasticisers. Liner based on Polyethylene in combination with fillers and plasticisers. Liner based on Polyketone in combination with fillers and plasticisers. The end of a liner which is available for trimming, heating and pressing together during the heat fusion process. Liner based on Polypropylene in combination with fillers and plasticisers. Liner based on Polyphenylene Sulphide in combination with fillers and plasticisers. Liner based on Polytetrafluoroethylene in combination with fillers and plasticisers. Liner based on Polyvinylchloride in combination with fillers and plasticisers. Liner based on Polyvinylidenefluoride in combination with fillers and plasticisers. Gradual diffusion of liquid and gas through thermoplastic layer under the influence of pressure. Retrievable information. A specific ratio of the average specified outside diameter to the minimum specified wall thickness (OD/t) for outside diameter-controlled plastic pipe. Plastic materials which retain their mechanical properties after heating and cooling. Hole in the carbon steel outer pipe to allow the release of gas accumulated in the annulus between the liner and the carbon steel pipe. The release of gas accumulated in the annulus between the thermoplastic liner and the carbon steel pipeline. Fluids in which the volume fraction of crude oil is less than 1% a
ABBREVIATIONS CRA ESC ID HDPE MDPE OD PA Corrosion Resistant Alloy Environmental Stress Cracking Nominal internal diameter High Density Polyethylene Medium Density Polyethylene Nominal outside diameter Polyamide
PTS 188.8.131.52 January 2011 Page 9 PE PK PP PPS PTFE PVC PVDF SDR UV XLPE or PEX Polyethylene Polyketone Polypropylene Polyphenylene Sulphide Polytetrafluoroethylene Polyvinylchloride Polyvinylidenefluoride Standard Dimension Ratio Ultra violet light Cross-linked Polyethylene consisting of long polymer chains in a 3-dimensional structure.
CROSS-REFERENCES Where cross-references to other parts of this PTS are made, the referenced section number is shown in brackets. Other documents referenced in this PTS are listed in (8).
PTS 188.8.131.52 January 2011 Page 10 2. 2.1 MATERIALS GENERAL The Contractor shall be responsible for the selection and supply of all materials required to meet the specified installation and service conditions (7). The Contractor shall have either measured test data (preferred) or documented methods for predicting the thermoplastic liner material properties for the specified service conditions. For the predictive methods, the Contractor shall have available, for review by the Principal, records of tests and evaluations, which demonstrate that the predictive method yields conservative results. If the conveyed fluid contains gas, it shall be demonstrated by testing or documented evidence of standard testing that the thermoplastic will not blister or degrade during service, i.e. startup, continuous operation or shut-down (rapid de-pressurisation). The Contractor shall also be responsible for documenting the mechanical, thermal, fluid compatibility and permeability properties of the thermoplastic liner material (2.4).
THERMOPLASTIC LINER MATERIALS A liner is made from a mix of a thermoplastic polymer material, colouring agent, anti-oxidant and plasticiser. Currently there are several thermoplastic polymer materials that are used for liners in pipelines or for similar applications in flexible flowlines and risers: Polyethylene (PE), Polyamide (PA), and Polyvinylidenefluoride (PVDF). Other polymers such as Polypropylene (PP), Polyvinylchloride (PVC), Polytetrafluoroethylene (PTFE), Polyphenylene Sulphide (PPS) and Polyketone (PK) have the potential to be used but are not in use at present. These thermoplastic polymer materials are produced in numerous grades and qualities. The differences in material properties between grades of the same polymer may be as great as the difference between different polymers. The following presents a limited introduction to the generic thermoplastic material types and commonly applied grades. In particular, for each polymer, it specifies the: Application envelope (in terms of maximum operating temperature as a function of fluid composition); Typical material properties at ambient conditions; Appropriate testing standards.
The typical material properties (un-aged) are listed for guidance only, based on an assumed lifetime of twenty years. They should be considered as minimum values at ambient un-aged conditions. Specific material data relating to actual service conditions (temperature, life-time) and fluid composition shall always be used in design and installation requirement analyses. The minimum design temperature for all thermoplastic materials covered in this PTS is minus 20 C. Lower temperatures may be tolerated but only provided that specific low temperature material data are available and the operating temperature does not fall below the brittleness temperature of the thermoplastic material. For a more complete specification of polymer properties, refer to PTS 30.10.02.13-Gen. 2.2.1 Polyethylene (PE) PE is the most commonly applied liner material. PE liners shall not be exposed to operating temperatures above 60 C in water service. In hydrocarbon service (combined liquid and gas phases), the recommended maximum operating temperature is lower and depends on the fluid composition but shall not exceed 50 C. If only a liquid phase or a dry gas phase is present, then a higher temperature (>50C) can be tolerated, but the maximum operating temperature shall be specified and agreed by the Principal. This reduction in operating temperature results from small organic compounds diffusing into the PE, causing swelling and softening. (Table 2.2.1a) lists the recommended maximum operating temperature as a function of fluid composition. Table 2.2.1a Maximum operating temperature for PE as a function of fluid composition Fluid Composition Oil/gas/water mixture Oil/water mixture Gas and condensate Dry gas Water Temperature (C) 50 50 50 60 60
Numerous PE grades are available. The differences between them primarily result from the polymerisation processes for the production of the base polymer, chemical modifications or enhancements with additives. Base polymer density is used to indicate PE type. Low, medium and high-density grades are distinguished as LDPE, MDPE and HDPE. This
PTS 18.104.22.168 January 2011 Page 12 characterisation applies to most vendor data. For lining applications, three types of PE are used; in increasing order of strength and chemical resistance, they are: MDPE, used in low-pressure water and gas distribution applications; HDPE, used in all types of service; Ultra High Molecular Weight (UHMW-HDPE) used in demanding applications.
MDPE (or PE 80) is a relatively soft grade and is used in (low) pressure applications at ambient conditions. It has good 50-year creep-rupture performance and is easy to manufacture (extrude) and install. HDPE (or PE 100) is the basic engineering grade of PE. Compared to MDPE, it has a higher yield and ultimate strength, a higher modulus and better chemical resistance. These improved properties come with the penalty of slightly more difficult extrusion and installation. However, HDPE is more sensitive to notches and has a lower environmental stress cracking (ESC) resistance than MDPE. UHMW-HDPE is developed for aggressive chemical environments and high toughness. Compared to HDPE it has a higher yield and ultimate strength, a higher modulus and better chemical resistance. This results in reduced swelling in crude oil and an increased capability of bridging pinhole leaks in the carbon steel outer pipe. However, these improved properties come with a penalty of considerably more difficult extrusion and installation. The above description is for general information only. There is a general trend away from merely specifying PE grades, and it is recommended to specify the material properties of PE listed in (Table 2.2.1b) instead. A summary of typical material properties of PE in ambient conditions is presented in (Table 2.2.1b). This Table is for comparison purposes only. Manufacturers shall submit the relevant (minimum) material property specifications at the specific service conditions. Table 2.2.1b "Typical" material properties of PE
Typical properties Density (g/cm3) Tensile properties at 23 C Yield strength (MPa) Stress at break (MPa) Elongation at break (%) Modulus (MPa) Thermal conductivity (W/m.K) Coefficient of thermal expansion (K )
Mechanical properties (function of temperature) 1
All PE pipe and fittings supplied to this PTS shall be stabilised against degradation by UVlight in accordance with standard practices by a minimum of 2% (by mass) of Carbon Black (ASTM D 3350). A UV stabiliser as specified by ASTM D 3350, code C or D shall be added.
PTS 188.8.131.52 January 2011 Page 13 2.2.2 Polyamide (PA) PA is a commodity engineering plastic that is more expensive than PE. Therefore, it should only be considered for application outside the range of PE. PA has excellent resistance to hydrocarbons but limited resistance to water at elevated temperatures. (Table 2.2.2a) lists the recommended maximum operating temperature as a function of fluid composition. Because of the molecular structure of PA, different grades e.g. PA-6 and PA-11, can essentially be considered as different materials. PA-11 is used as a liner in conventional flexible flowlines and risers transporting gas and crude with low water cuts. It has good material properties for liner applications, high modulus and strength, with relatively high strain to failure in its un-aged condition. It has been used to line carbon steel pipelines at temperatures up to 75 C. Table 2.2.2a Maximum operating temperature for PA-11 as a function of fluid composition Fluid Composition Oil/gas/water mixture Oil/water mixture Gas and condensate Dry gas Water Temperature (C) 65 75 80 80 75
A summary of typical material properties of PA is presented in (Table 2.2.2b). This Table is for comparison purposes only. Manufacturers shall submit the relevant (minimum) material property specifications at the specified service conditions. Table 2.2.2b "Typical" material properties of PA-11 Typical properties Density (g/cm3) Tensile properties at 23 C Yield strength (MPa) Stress at break (MPa) Elongation at break (%) Modulus (MPa) Thermal conductivity (W/m.K) Coefficient of thermal expansion 1 (K ) Mechanical properties (function of temperature) Modulus (MPa) Poisson ratio PA-11 1.04 40-60 80 >30 650-1400 0.25 100 x 10-6 23 C 650 0.35 40 C 500 0.36 60 C 400 0.37 80 C 300 0.38
PA liners shall comply with the requirements of ASTM D 4066 and ASTM F 1733. 2.2.3 Polyvinylidenefluoride (PVDF) PVDF is a fluoropolymer that is more expensive than both PE and PA. Therefore it should only be considered for applications outside the range of PE and PA, i.e. for hydrocarbon applications above 80 C and water applications above 60 C. PVDF has excellent chemical resistance. Superior thermal stability implies that the application envelope in terms of temperature for PVDF extends well beyond that of PA, up to 120 C for all applications. (Table 2.2.3a) lists the recommended maximum operating temperature as a function of fluid composition.
PTS 22.214.171.124 January 2011 Page 14 Table 2.2.3a Maximum operating temperature for PVDF as a function of fluid composition Fluid composition Oil/gas/water mixture Oil/water mixture Gas and condensate Dry gas Water Temperature (C) 120 120 120 120 120
PVDF has good mechanical properties. The modulus and yield strength are high but the yield strain is low. The pure polymer is difficult to extrude and to overcome this, plasticised grades (both homopolymer and co-polymer) are used, for example as pressure sheaths in flexible flowlines and risers. Only co-polymer grades of PVDF should be used to minimise problems associated with leaching out of the plasticiser. A summary of typical material properties of PVDF is presented in (Table 2.2.3b). This Table is for comparison purposes only. Manufacturers shall submit the relevant (minimum) material property specifications at the specified service conditions. Table 2.2.3b "Typical" material properties of PVDF
Typical properties Density (g/cm3)
Tensile properties at 23 C Yield strength (MPa) Stress at break (MPa) Elongation at break (%) Modulus (MPa)
55 40 >20 2200
25 35 >50 1000
0.19 130 x 10-6 23 C 2200 0.35 40 C 1750 0.35 75 C 1000 0.40 90 C 750 0.45 120C 400 0.5 23 C 1000 0.35
0.18 140 to 180 x 10-6 40 C 650 0.35 75 C 250 0.40 90 C 150 0.45 120C 110 0.5
PVDF liners shall comply with the requirements of ASTM D 3222 and ASTM F 491. 2.2.4 Polypropylene (PP) PP is a commodity engineering plastic. It is not currently used as a thermoplastic liner material but has the potential for such use in the future. Although chemically similar to PE, PP has important mechanical property differences. It can tolerate a higher operating temperature than PE, and it is not susceptible to ESC. PP has excellent resistance to water and liquid hydrocarbons, but limited resistance to aromatics. (Table 2.2.4a) lists the maximum recommended operating temperature as a function of fluid composition. Table 2.2.4a Maximum operating temperature for PP as a function of fluid composition Fluid Composition Oil/gas/water mixture Oil/water mixture Gas and condensate Dry gas Water Temperature (C) 70 70 70 85 85
In general, the mechanical properties of PP, i.e. high modulus and high yield strength with sufficient strain to failure, are sufficient for liner installations. A summary of typical material
PTS 126.96.36.199 January 2011 Page 15 properties of PP is presented in (Table 2.2.4b). This Table is for comparison purposes only. Manufacturers shall submit the relevant (minimum) material property specifications at the specified service conditions. Table 2.2.4b "Typical" material properties of PP Typical properties Density (g/cm3) Tensile properties at 23 C Yield strength (MPa) Stress at break (Mpa) Elongation at break (%) Modulus (MPa) Thermal conductivity (W/m.K) Coefficient of thermal expansion 1 (K ) PP 0.9 35 40 >100 1200 0.22 180 x 10-6
PP liners shall comply with the requirements of the ASTM D 2657, ASTM D 4101 and ASTM F 492. 2.2.5 Polyphenylene Sulphide (PPS) PPS is an engineering plastic with a price similar to that of PVDF. It is not currently used as a thermoplastic liner but has the potential for such use in the future. It has excellent high temperature properties and should only be considered for applications in the temperature range of PDVF and beyond. It has good chemical resistance to water, dry gas and most hydrocarbons, except aromatics. (Table 2.2.5a) lists the recommended maximum operating temperature as a function of fluid composition. Table 2.2.5a Maximum operating temperature for PPS as a function of fluid composition Fluid Composition Oil/gas/water mixture Oil/water mixture Gas and condensate Dry gas Water Temperature (C) 150 150 150 180 180
There are many different grades of PPS available but because of its molecular structure PPS shall be plasticised to enable extrusion and to provide the flexibility required to enable insertion as a liner. PPS has good mechanical properties, high modulus and strength but a limited strain to failure. A summary of typical material properties of PPS is presented in (Table 2.2.5b). This Table is for comparison purposes only. Manufacturers shall submit the relevant (minimum) material property specifications for the liner material at the specified service conditions.
PTS 18.104.22.168 January 2011 Page 16 Table 2.2.5b "Typical" material properties of PPS
Typical properties Density (g/cm3) Tensile properties at 23 C Yield strength Stress at break Elongation at break Modulus (MPa) Thermal conductivity (W/m.K)
Specifications for PPS liners shall be agreed between the Contractor and the Principal. 2.2.6 Cross-linked Polyethylene (PEX) PEX is an engineering plastic manufactured by cross-linking PE. It is more expensive than PE. PEX has excellent resistance to hydrocarbons and water at elevated temperatures up to 85 C. (Table 2.2.6a) lists the recommended maximum operating temperature as a function of fluid composition. Table 2.2.6a Maximum operating temperature for PEX as a function of fluid composition Fluid Composition Oil/gas/water mixture Oil/water mixture Gas and condensate Dry gas Water Temperature (C) 85 85 85 85 85
The cross-linking of PE implies that PEX is stiffer than PE with a corresponding reduction in flexibility. For liner applications the material properties, modulus and yield strength are good, with a strain-to-failure strength sufficient for insertion. A summary of typical material properties of PEX is presented in (Table 2.2.6b). This Table is for comparison purposes only. Manufacturers shall submit the relevant (minimum) material property specifications for the liner material at the specified service conditions. Table 2.2.6b "Typical" material properties of PEX Typical properties Density (g/cm3) Tensile properties at 23 C Yield strength (MPa) Stress at break (MPa) Elongation at break (%) Modulus (MPa) Thermal conductivity (W/m.K) Coefficient of thermal expansion
Specifications for PEX liners shall be agreed between the Contractor and the Principal. 2.2.7 Polyketone (PK) Polyketone (PK) is a relatively new thermoplastic polymer. It has good chemical resistance to both water and hydrocarbons. However, it is susceptible to oxidation and stabilisers shall
PTS 126.96.36.199 January 2011 Page 17 be used to limit degradation. (Table 2.2.7a) presents the recommended maximum operating temperature as a function of fluid composition. Table 2.2.7a Maximum operating temperature for PK as a function of fluid composition Fluid Composition Oil/gas/water mixture Oil/water mixture Gas and condensate Dry gas Water Temperature (C) 105 105 105 105 105
A summary of typical material properties of PK is presented in (Table 2.2.7b). This Table is for comparison purposes only. Manufacturers shall submit the relevant (minimum) material property specifications at the specified service conditions. Table 2.2.7b "Typical" material properties of PK Typical properties Density Tensile properties at 23 C Yield strength Stress at break Elongation at break Modulus (MPa) Thermal conductivity (W/m.K) (g/cm3) PK 1.24 (MPa) (MPa) (%) 55 63 350 1600 0.25 110 x 10-6
Specifications for PK liners shall be agreed between the Contractor and the Principal. 2.2.8 Other materials Other thermoplastic materials, e.g. PVC, PTFE or co-extruded liners, i.e. multiple layered liners made from more than one thermoplastic material, can be considered for liner applications. If such materials are proposed, the material data supplied by the Contractor shall at least comprise the data listed in (Tables 2.2.1a and 2.2.1b) and also satisfy the requirements of (2.4).
MATERIAL SELECTION GUIDE Material selection is a procedure of matching system requirements to the property data of available materials. The loading conditions should be systemically identified and could comprise combinations of temperature, pressure, axial load and environment as a function of time. They are matched to materials property acceptance criteria in the design analysis. The following strategy facilitates thermoplastic polymer material selection by identifying acceptance criteria in a structured manner: 1. 2. 3. 4. 5. 6. 7. Define pipeline function and requirements. Identify fixed boundary conditions. Design system and/or analyse design. Define function of the individual components. Identify service conditions of individual components. Identify material requirements to maintain function throughout service life. Identify acceptance criteria.
(Table 2.3) gives an example of the applied loads acting on a thermoplastic liner from transport from the manufacturing plant through to operation. Table 2.3 Applied loads acting on the liner system Mechanical loading Transport Storage Construction Operation Mis-operation Removal
Handling Stack weight Pull-in, reduction Hydrostatic pressure Vacuum Pull-out
Thermal loading
Ambient, - 40 C /+ 50 C Ambient Ambient + friction Fluid, operating temp. Rapid cool-down Ambient
Ambient Ambient Lubricant Fluid, slugs Air Residue
Weeks Weeks, months Minutes, hours Years Days Hours, days
The material selection process involves matching the material properties of the candidate thermoplastic liner materials to the loads and boundary conditions listed in (Table 2.3) to provide the most appropriate material option.
MATERIAL TESTING A full material qualification programme is required to the satisfaction of the Principal, before the Contractor can start production of the liner. Thermoplastic pipe material shall be qualified according to API Spec 15 LE. Thermoplastic pipe material qualified to ISO 4427 may also be supplied provided that the following requirements are met: equivalent strength grade to API Spec 15 LE and elevated temperature characteristics to ISO 4427, Section 4.4, Type A. Changes in the method of manufacture will require additional qualification tests.
NOTE: API Spec 15 LE and ISO 4427 are specific to PE. However, the general principles of material testing outlined in both API Spec 15 LE and ISO 4427 are also applicable to other thermoplastics. Specific temperatures for elevated temperature tests shall be proposed by the Contractor and agreed with the Principal.
The following list of tests (mechanical, thermal, permeation, compatibility and ageing tests) represents a complete material qualification programme (Table 2.4). For most applications only a restricted qualification programme will be required. Additional tests, specific to the unique operating conditions, shall be agreed between the Contractor and the Principal. Other standard test procedures may replace those listed in (Table 2.4) on agreement between the Contractor and the Principal. (Table 2.4) also indicates for which applications the tests are required along with the purpose of the tests. A chemical analysis of the compounds comprising the thermoplastic pipe material shall be available for review by the Principal.
or ISO 527 R or ISO 868 or ISO 180 or ASTM D 1044 or ASTM D 1505
Thermal properties
All applications
Permeation/ Characteristics
ISO 1133 Method A Or glass transition temperature (ASTM E 1356) For gas phase components at design conditions At design conditions
Compatibility ageing
PTS 188.8.131.52 January 2011 Page 21 2.4.1 Fluid permeability test The following conditions shall apply as a minimum for the fluid permeability test: a) Test sample shall be taken from the extruded polymer. b) Minimum sample thickness is 1 mm. c) Minimum sample diameter is 50 mm. d) A sufficient number of tests shall be performed to allow for linear interpolation of the results as a function of temperature. The procedure for the fluid permeability test may be to pressurise one side of the specimen and measure fluid flow at the other side when steady state flow conditions are reached. Alternatively, the test can be performed with the same absolute pressure on both sides using the partial pressure of the component gas as the driving force. The purpose of the permeability test is to provide an estimate of the gas permeation rate into the annulus and is for information only. Therefore this test is only necessary if a gas phase is present. 2.4.2 Blistering resistance test Blistering resistance tests shall reflect the design requirements along with fluid conditions, pressure, temperature, and number of decompressions and decompression rate. As a minimum, the following conditions shall apply: a) Only gas components of the specified environment shall be used. b) Conditioning time shall be sufficient to ensure full saturation. c) Number of decompressions should be a minimum of 20 cycles or the number expected in practice. d) The decompression rate should be the expected rate, otherwise a minimum 70 bar per minute should be used (from design pressure to zero). e) Sample thickness shall be the same as the wall thickness of the liner. f) The expected decompression temperature shall be used. g) The design pressure shall be used as a minimum. The test procedure is that after each depressurisation the sample shall be examined at a magnification of 20 times for signs of blistering, swelling and slitting. The acceptance criterion is that no blister formation or slitting is observed. 2.4.3 Ageing test The Contractor shall have either documented test data of the samples aged in the service environment according to ASTM C 581, or ageing prediction models for the thermoplastic polymer. The fluid used in ageing tests shall be representative of the service conditions fluid. Materials that will be subjected to tensile or compressive loads in service shall be tested under equivalent stress conditions. The ageing model shall be based on testing and experience and shall predict the ageing or deterioration of the polymer under the influence of environmental and load conditions that represent the service conditions. As a minimum, polymer-ageing models shall consider temperature, chemical environment and mechanical load. Special attention should be given to de-plasticisation, fluid adsorption and changes in dimensions. Creep and stress relaxation shall be investigated on aged and un-aged samples. Ageing may be determined from changes in either specified mechanical properties or in specified physico-chemical characteristics which includes reduction in the plasticiser (if relevant) content of the material. The purpose of the ageing test to provide the elastic modulus and yield strength and strain for the material aged in the flow conditions. 2.4.4 Swelling test The following conditions shall apply for the swell test procedure:
PTS 220.127.116.11 January 2011 Page 22 5 cubic specimens, each approximately 125 mm3, shall be machined from a sample of the actual thermoplastic liner. Specimen dimensions shall be recorded to the nearest 0.01 mm. Specimen weight shall be recorded to the nearest 0.001 g.
The samples shall be exposed to 500 cm of the liquid hydrocarbon mixture of the pipeline fluid for 500 h and at the design temperature in a sealed container. After exposure, the dimensions and weights shall be recorded to the same accuracy as the pre-expose samples. Linear swell of the liner, swell (%), is related to the volumetric swell and shall be calculated as follows;
END CONNECTORS Steel flange material shall comply with the requirements of PTS 184.108.40.206-Gen. Thermoplastic flange material shall be the same as the liner. Retainer rings shall be made from ASTM A 106 grade B or equivalent material. Bolts shall be ASTM A 193 grade B7. Nuts shall be ASTM A 194 grade 2H.
PTS 22.214.171.124 January 2011 Page 24 3. 3.1 DESIGN INTRODUCTION The Contractor shall be responsible for the design of the liner system and shall take into account the selected installation method and service requirements. Thermoplastic liners in carbon steel pipelines can fail due to (in no order of preference): Environmental stress cracking. Collapse of the liner due to pressure build-up in the annulus between the liner and the carbon steel pipe. Gases can permeate through certain thermoplastics and can accumulate in the annulus. During depressurisation of the pipeline, expansion of this accumulated gas may cause collapse of the liner. Excessive material shrinkage. Buckling due to excessive swelling. Lack of strength (short term but also long term after ageing). Cracks due to lack of liner impact resistance or prior exposure to UV light. Material defects. Construction defects (gouges, scores). End termination failures due to creep.
Factors that influence such failures include: Choice of liner material (amounts and type of thermoplastic, fillers and plasticisers, anti-oxidants, UV stabilisers). Thickness of liner. Quality assurance and control during manufacturing, fabrication and installation. Exposure to UV light prior to installation. Installation method used and tightness of fit inside the carbon steel pipe line. Fluid composition (incl. inhibitors, chemicals, etc.). Minimum and maximum operating temperatures. Rate of depressurisation. Spacing of vent points. Frequency of venting.
For liners in hydrocarbon service, factors such as stress relaxation, loss of plasticiser, permeation and absorption of gases and liquids into the polymer should be taken into account. The design procedure for a thermoplastic liner consists of determining the thickness to limit both stress and strain to acceptable levels and to prevent collapse. Factors such as creep rate, permeation rate and ESC should also be considered, particularly in terms of how they are affected by liner wall thickness. The outside diameter of the liner shall be determined taking into account the inside diameter of the carbon steel pipe, the requirements of the installation technique and handling and storage requirements. Thermoplastic liners often have to be tailor-made to the application implying that often non-standard dimensions are used.
MINIMUM LINER THICKNESS For water service the minimum thickness shall be 5 mm to avoid difficulties in installation and fusion bonding. For hydrocarbon service a thicker liner shall be used as determined by the procedure given in (3.3).
LINER DESIGN PROCEDURE The calculation for the required wall thickness of the liner is determined from three conditions: handling and storage (A), installation (B) and collapse (C). The greatest thickness calculated from requirements (A), (B) and (C) is taken as the design wall thickness. For requirement (C) it is conservatively assumed that the pressure in the annulus is the same as the bore pressure. A flow diagram visualising the design process is presented in (Figure 3.3). The Contractor shall supply to the Principal the liner design sheet in Appendix 3 as part of the tender documentation. The liner design procedure for determining wall thickness is described in the following steps: 1. 2. 3. 4. 5. 6. Determine the liner outer diameter taking into account both the inside diameter of the carbon steel pipe and the requirements of the installation technique. Determine the wall thickness from handling and storage requirements (3.3.1). Determine the wall thickness from installation requirements (3.3.2). Select the larger wall thickness from steps 2 and 3. Select the modulus of the thermoplastic material and swelling strain for the service conditions. Calculate the liner fit depending on the chosen installation technique (18.104.22.168).
If no gases are present, then go to step 9. 7. 8. Calculate the collapse pressure from (126.96.36.199), (188.8.131.52) or (188.8.131.52) as appropriate, depending on liner fit. Include liner swell if appropriate. Determine the design pressure (including safety factor) and maximum operating pressure for either the "intrinsically safe" or "allowance for gas expansion" design procedure (3.3.4).
If no liquids are present, then go to step 10. 9. If the liquid service conditions result in liner swell, then calculate the collapse resistance of the liner (3.3.5).
10. Correct the wall thickness to compensate for any reduction of liner wall thickness during installation. 11. If the collapse resistance of the liner is not sufficient then repeat steps 5 to 10 with an increased liner wall thickness. The output of successful completion of steps 1 to 11 is the required liner wall thickness, sufficient to withstand the requirements of handling and storage, installation and collapse. Once the required liner wall thickness has been determined, a final check shall be made to ensure that the resulting liner internal diameter does not have an unacceptable impact on the pipeline hydraulics i.e. pressure drop and fluid velocities (6.4). In this design procedure it is assumed that the annular volume is not vented. (Table 3.3) summarises the design procedure for determining the thickness of a liner as a function of fluid type and tightness of liner fit.
PTS 22.214.171.124 January 2011 Page 27 FIGURE 3.3 LINER DESIGN PROCESS
PTS 22.214.171.124 January 2011 Page 28 Table 3.3 Fluid type Water Design procedure as a function of fluid type and tightness of fit Tightness of fit Loose, partially loose, tight Loose, partially loose, tight Loose Design procedure Liner thickness determined from maximum of handling or storage (3.3.1) and installation (3.3.2) requirements Liner thickness determined from maximum of handling and storage (3.3.1) or installation (3.3.2) requirements or swelling (3.3.5) Liner thickness determined from maximum of handling and storage (3.3.1) or installation (3.3.2) requirements or collapse (18.104.22.168) Liner thickness determined from maximum of handling and storage (3.3.1) or installation (3.3.2) requirements or collapse (220.127.116.11) Liner thickness determined from maximum of handling and storage (3.3.1) or installation (3.3.2) requirements or collapse (126.96.36.199)
Liquid hydrocarbons Gas, liquid hydrocarbons and water mixtures Gas, liquid hydrocarbons and water mixtures Gas, liquid hydrocarbons and water mixtures 3.3.1
Partially loose
Liner thickness - handling and storage To maintain roundness of the liner and dimensional stability during storage, possibly for several months and to minimise distortion during handling, Manufacturers recommend a minimum Standard Dimension Ratio (SDR) ranging from 26 to 17. A minimum SDR of 26 is recommended for less onerous applications, although in consultation with the Manufacturer a thinner liner may be used. For all other applications an SDR of 17 is recommended.
Liner thickness installation Liners are installed by pulling a pre-fabricated length of thermoplastic pipe into the carbon steel outer pipe. The axial stress carried by the liner shall be limited to 50% of the tensile yield strength of the thermoplastic polymer. The pulling load consists of the friction load of dragging the liner into the carbon steel pipe, the deformation load, which is a function of the installation technique, plus friction loads due to pipe bends etc. (3.5).
3.3.3 188.8.131.52
Liner thickness - collapse Liner fit Collapse of a liner can occur if, during normal operation, gases within the bore of the pipeline permeate into the annulus volume between the liner and the host carbon steel pipe. Depressurising the pipeline, e.g. for maintenance, can cause the liner to collapse if the wall thickness is not sufficient. If only liquids are present in the pipeline, e.g. in water injection lines, then collapse due to gas expansion cannot occur. However, liquids can be absorbed in the liner causing swelling. Excessive swelling can also cause the liner to collapse. The pressure required to cause collapse of the liner is dependent on the installation technique or more precisely the liner fit within the outer steel pipe. (Table 188.8.131.52) distinguishes liner fit for the different installation techniques into three categories: loose, partially loose and tight.
PTS 126.96.36.199 January 2011 Page 29 Table 188.8.131.52 Categories of liner fit as a function of installation technique Installation technique Slip lining (no grout) Folded pipe, Slip lining (with grout) Swagelining, Roll-down, Tite liner Category of liner fit Loose Partially loose Tight
where (mm) is the difference between the inner radius of the carbon steel pipe and the outer radius of the thermoplastic liner. The following inequalities define the liner fit:
where, t= R= liner wall average radius of the liner (mm) defined as thickness (mm)
where the subscripts o and i refer to the outer and inner radius of the thermoplastic liner pipe. 18.104.22.168 Loose fitting liners When the outer steel pipe provides no restraint during collapse, the fit of the liner is defined as loose and the collapse pressure, Pc (bar), is given by:
Partially loose fitting liners When the outer steel pipe provides partial restraint during collapse, the fit of the liner is defined as partially loose and the collapse pressure, Pc (bar), is given by:
Tight fitting liners When the outer steel pipe provides restraint during collapse, the fit of the liner is defined as tight and the collapse pressure, Pc (bar), in the absence of swell is given by:
If liquids present in the service conditions cause swelling of the liner, then the collapse pressure, Pc (bar), is given by:
where, swell =
Design pressure of pipeline The design pressure, Pdes, of the pipeline is defined as the maximum operating pressure, Pmop, multiplied by a safety factor, J:
A safety factor, J, of 1.33 is recommended. 220.127.116.11 Intrinsically safe If the collapse pressure, Pc, of the liner calculated from (126.96.36.199) to (188.8.131.52), is less than the design pressure, Pdes, of the pipeline, then the liner wall thickness is not sufficient to prevent collapse. If it is greater, then the liner will not collapse. The following inequality defines the intrinsically safe design pressure procedure:
Allowance for gas expansion In (126.96.36.199) it is implicitly assumed that there is an infinite supply of gas to the annulus to drive the collapse process. In reality there is a finite volume of gas in the annulus. It is possible to account for the expansion of the gas during collapse. However, the initial volume of the annulus is required. It may not be possible to accurately determine this initial volume. The following provides a simplified guide to determining initial annular volume as a function of the liner fit. For a loose fitting liner the initial volume, Vinit (mm3/mm), is:
where, Rs = Inside radius of the steel pipe (mm) For a partially loose fitting liner, the initial volume is;
For a tight fitting liner it is conservatively assumed that the annulus volume is proportional to the surface roughness of the outer steel pipe. The initial volume is given by:
During the collapse process the product of annulus pressure times annulus volume remains constant. If the collapse pressure, Pc, calculated from (126.96.36.199) to (22.214.171.124), times the annulus volume at collapse, Vc, is less than the design pressure, Pdes, of the pipeline times the initial annulus volume at collapse, Vinit, then the liner wall thickness is not sufficient to prevent collapse. If the product is greater then the liner will not collapse. The following inequality defines the allowance for gas expansion procedure:
Swelling If the pipeline fluids are liquid then a possible collapse mechanism can be driven through swelling of the liner. For example, PE can swell by up to 10% in certain hydrocarbon environments (aromatics). To prevent the liner from collapsing due to swelling only, then the following design inequality formula shall be used to determine if the liner wall thickness is sufficient to prevent liner collapse (refer 2.4.4):
If there is a possibility of the liner swelling while gas is present in the pipeline fluids, then (3.3.3) shall be used to determine the collapse pressure.
VENT POINT DESIGN All thermoplastic lined pipelines shall incorporate vent points unless otherwise agreed by the Principal. The vent point assembly shall ensure venting of gases from the annulus throughout the service life of the pipeline. The assembly shall include a valve to allow closure of the vent. The design of the vent point assembly shall be proposed by the Contractor and agreed with the Principal. The minimum number of vent points shall be one at each flanged end of a section of lined pipe. The vent points have three functions: To vent (ambient) gas and/or fluids from the annulus during installation. To vent the permeated gas accumulated in the annulus to prevent collapse. To allow monitoring of the liners integrity.
Vents can be designed to be: Continuously closed (plugged) Valved (closed or open during normal operation)
For water injection lines venting during operation is not necessary and therefore vents are normally plugged. Lines transporting multi-phase hydrocarbons with H2S concentrations lower than 50 ml/m can have continuously open vents (vents shall be valved in order to be able to close the annulus in case of liner leakage or collapse). For gas transport and for H2S concentrations of 50 ml/m3 and higher, vents will have to be opened and closed on a periodic basis after consultation with the local HSE regulator. There are two strategies to determine the spacing between vent points: 1. Minimum vent point spacing - determined from the lined pipe section length, i.e. one vent at each flanged end. This vent point spacing is suitable for: intrinsically safe designed liners (126.96.36.199); water service; stabilised dead crude oil or oil/water mixture service.
2. Calculated vent point spacing - determined from (3.4.1). This spacing is required for critical applications defined as: NOTE:
Vent point spacing The requirement for additional vent points shall be determined as follows. During the collapse sequence, the instantaneous product of annulus volume, V, and pressure, P, remains constant (assuming the annulus temperature remains constant), i.e.:
where Pinit is the initial pressure in the annulus. The other terms are defined in (3.3). The units for pressure and volume are (bar) and (mm 3) respectively. The initial volume may be difficult to accurately determine. (184.108.40.206) provides a guide for estimating this initial volume as a function of liner fit. Summarising (18.104.22.168), the initial volume per unit length of the lined pipe (mm3/mm) is given by;
where = gap between the liner and the steel pipe (mm). The initial annulus volume, Vinit (mm3), is determined from the product of the vent point spacing, Lvent (mm), and the initial volume per unit length, Vinit/L, (18.104.22.168) and is given by:
The annulus volume at collapse per unit length Vc/L (mm3/mm), is given by:
To calculate the collapse volume, Vc (mm3) at collapse, the following assumptions are made to determine the axial collapse length, Lc: axial profile of the collapsed liner is triangular; radial liner profile remains similar; collapse length, Lc (mm), extends over 5 times the diameter of the liner, i.e.
Under these assumptions the total critical volume at collapse, Vc (mm3), is:
Using values of Pinit, Vinit, Pc and Vc, defined above, the vent point spacing, Lvent (mm), is given by:
It is assumed (conservatively) that the initial pressure in the annulus, Pinit is equal to the bore pressure. A sensitivity analysis with respect to the influence of initial annulus gap size, (mm), on the vent point spacing, Lvent, shall be performed.
PULL-IN LOADS AND INSERTION LENGTH The pull-in load, Fpull (N), for a thermoplastic liner is calculated from the sum of three force components: Ffriction, the friction load from dragging the liner into the steel pipe, Fbend, the additional friction loads caused by bends etc. and Freduce, the load applied to the liner from the installation technique:
The calculation procedure for determining the maximum loads and stresses acting on the liner during installation shall be as outlined in this Section. If the Contractor wishes to use an alternative procedure this shall be submitted to the Principal for agreement. 3.5.1 Friction load, Ffriction The friction load contribution to the overall liner pull-in load is derived from two components. One component is due to the weight of the liner and the associated friction factor, the other is due to superficial damage to the outside of the thermoplastic liner, i.e.:
where Lliner is the length of liner (m) to be installed and W is the weight of the liner per unit length (N/m). f is the friction factor and for new pipelines is taken as 0.4. For retro-fitting, higher friction factors may be required to simulate the surface roughness of the pipe. If the installation procedure includes liner lubrication then f should be reduced to 0.1. Fscore is generally zero, unless otherwise quoted by the installer. 3.5.2 Bending load, Fbend The bending load is defined as a function of the pull-in load, the friction factor and the angle of the bend:
where f is the friction factor, Fpull (N) is the pull-in load and is the bend angle (radians). 3.5.3 Reduction load, Freduce The reduction load, Freduce (N) is a function of the installation technique. For each installation technique a reduction pressure, Preduce (MPa), is quoted and the reduction load is derived by multiplying this pressure by the cross-sectional area of the liner:
where t (mm) is the liner wall thickness and D (mm) is the internal diameter of the steel pipe. For the different installation techniques (Table 3.5.3) lists the reduction pressure. Table 3.5.3 Reduction pressure as a function of installation technique Installation technique Slip-lining Roll-down Tite-lining Swage-lining 3.5.4 Reduction pressure (MPa) 0 0 5 5
Total pull-in load and maximum installation length The total pull-in load, Fpull (N), is calculated from the individual load components described in (3.5.1) to (3.5.3).
The maximum allowable tensile load on the liner is limited to 50% of the tensile yield strength, yield (MPa).
3.6 3.6.1
DESIGN OF END CONNECTORS General The Contractor shall select the end connection and shall submit this for approval to the Principal. The Contractor shall demonstrate by means of a qualification test that the end connections meet the same operational requirements as the thermoplastic liner. The design shall account for shrinkage, creep, ageing of the thermoplastic material and operational pressure fluctuations. In general, only flanged connections shall be considered for termination at the ends of pipeline sections, see (Figure 3.6.2) for typical arrangement. Screwed connectors shall not be allowed. Compression-type fittings may be allowed for in-situ retro-fitting. An example of a compression type fitting is presented in (Figure 3.6.1). FIGURE 3.6.1 TYPICAL THERMOPLASTIC LINER COMPRESSION JOINT
Flange type connections The carbon steel parts of flanged type connections shall comply with the general requirements of PTS 220.127.116.11.Gen.
PTS 184.108.40.206 January 2011 Page 36 FIGURE 3.6.2 TYPICAL THERMOPLASTIC LINER FLANGE CONNECTION
The inside diameter of the steel flange shall be identical to that of the carbon steel pipeline. The outside diameter of the thermoplastic flange face shall have the same diameter as the raised face of the carbon steel flange. The liner weld shall be made by butt fusion welding. If the liner has been pulled in from the other end, then the flange shall be welded to the liner before the axial tension is released. The thermoplastic flange shall be made from the same material as the liner and have the same internal diameter as the liner. The minimum length of the flange shall be 150 mm. The steel retainer rings shall be such that they fit between the thermoplastic flange and inside the bolt circle of the steel flanges.
PTS 126.96.36.199 January 2011 Page 37 4. 4.1 MANUFACTURE OF THE THERMOPLASTIC LINER PROCESS OF MANUFACTURE The thermoplastic liner shall be manufactured by extrusion. Extrusion involves melting, converging and forming the thermoplastic into a tubular product. Other manufacturing processes shall not be used by the Manufacturer to produce the thermoplastic liner unless agreed by the Principal. Only virgin polymers shall be used for the production of the liner, with a maximum of 0.2% wt of additives. Use of reworked (or re-cycled) materials shall not be permitted. The use of colouring agents should be avoided. A larger quantity of additives may be added if electrically conductive properties are required. Manufacturing of the liner shall not proceed until the material qualification programme has been completed to the full satisfaction of the Principal. The Contractor shall be responsible for the manufacturing of the liner The Contractor shall complete the data sheets in Appendix 4 and supply these as part of the tender documentation. The data provided by the Contractor shall be used as baseline data for the QC requirements (Section 126.96.36.199) 4.1.1 Flange material Flanges shall be moulded or machined from extruded material and shall be from the same material as the pipe. The wall thickness of the flanges shall be equal to the wall thickness of the pipe. Flared flanges may be used only for limited lengths which cannot be fitted with fused flanges, and only with the approval of the Principal. 4.1.2 Rotational moulded spools Rotational moulded spools may be used only with the approval of the Principal. The material used shall have minimum material properties provided by the Contractor as listed in Appendix 4 unless otherwise agreed with the Principal. The wall thickness of the liner in the spools should be equal to the minimum wall thickness determined in (Section 3.3)
NOTE: There is a maximum wall thickness which can be rotationally moulded.
There shall be no reliance on adhesion of the polymer to the steel surface. For live crude or gas service, vents shall be provided on the spool pieces. 4.2 4.2.1 FINISH AND WORKMANSHIP Pipe ends Pipe ends shall be plain and square. Cut pipe ends shall be clean without ledges, shaving tails, burrs or cracks. The interior of the pipe shall be blown or washed clean of cuttings and shavings. 4.2.2 Finish The internal and external surfaces of the plastic liner shall be free from defects such as blisters, cracks, scratches, dents, nicks or sharp tool marks which can affect the performance of the liner. Absence of these defects shall be determined visually or with a liquid penetrant. 4.2.3 Microscopic examination Microscopic examination at 10 times magnification or visual examination by means of transmitted light shall show no voids, foreign inclusions or other internal defects which affect the performance of the liner. For alternative non-destructive testing techniques the Principal shall be consulted.
PTS 126.96.36.199 January 2011 Page 38 4.3 4.3.1 DIMENSIONS, WEIGHTS AND TOLERANCES Size, tolerances Pipe furnished to this PTS shall comply with the dimensions and tolerances given in Table 3 of API Spec 15 LE or Tables 3 to 6 of ISO 4427. The Contractor shall specify nominal values of liner outside diameter and wall thickness. Tolerances on the outside diameter are listed in (Table 4.3.1): Table 4.3.1 Tolerances on liner outside diameter Minimum diameter - 0 mm - 0 mm - 0 mm Maximum diameter + 0.5 mm + 1 mm + 0.01*ND
The tolerance on the liner wall thickness shall be -0%/+5% of the specified value. 4.3.2 Length of liner pipe joints The length of individual joints of liner pipe shall be as long as possible, to minimise the number of field welds, consistent with transportation, handling and any other project constraints. No jointers (two pieces fused together to make a length) shall be permitted. The average, maximum and minimum liner joint lengths shall be agreed between the Contractor and the Principal. 4.3.3 Ovality and out-of-roundness The ovality of the pipe shall not exceed 5% when measured in accordance with ASTM D 2513. During production both ovality and out-of-roundness shall be monitored and recorded at the frequencies specified in (Table 220.127.116.11). 4.4 4.4.1 QUALITY PROGRAMME Quality Manual The Manufacturer shall maintain a Quality Manual which describes the quality programme. All prior revisions shall be retained for a period of not less than five years. 4.4.2 Process and quality control requirements The Quality Manual shall include a documentation programme to assure communication of approved manufacturing and inspection procedures to qualified receiving, manufacturing and quality control personnel. The Quality Manual shall be submitted to the Principal for review and approval, and shall cover at least the following aspects: 4.4.3 raw material acceptance; extrusion procedures; pipe manufacturing practices; welding procedures and qualifications; inspection and test procedures; acceptance criteria; repair procedures.
Quality control equipment Equipment used to inspect, test or examine material shall be calibrated at specified intervals in accordance with the Manufacturers Quality Manual and consistent with referenced industry standards.
PTS 220.127.116.11 January 2011 Page 39 4.4.4 126.96.36.199 Quality control tests Conditioning Unless otherwise specified, all Quality Control (QC) specimens shall be conditioned for a minimum of 4 hours prior to test in air or 1 hour in water at 23 C 2 C. When conditioning is required for witness tests the specimens shall be conditioned in accordance with Procedure A of ASTM D 618 at 23 C 2 C and at an agreed level of relative humidity and conditioning time. 184.108.40.206 Test conditions Tests shall be conducted at the Standard Laboratory temperature of 23 C 2 C unless otherwise specified in the test methods. 220.127.116.11 Material property requirements and frequency This PTS adopts periodic sampling to determine batch quality control. The Manufacturer shall be responsible for ensuring that all pipes meet the specified requirements. Acceptable QC shall be demonstrated by successfully completing the tests listed in (Table 184.108.40.206) of API Spec 15 LE at the specified frequency. Where the Manufacturer has agreed to the supply of pipe produced to ISO 4427, the equivalent quality control tests prescribed by ISO 4427 shall be applied.
NOTE: API Spec 15 LE and ISO 4427 are specific to PE. However, the general principles of quality control through material testing outlined in both API Spec 15 LE and ISO 4427 are also applicable to other thermoplastics. Minimum strength and specific temperatures for elevated temperature tests shall be proposed by the Contractor and agreed with the Principal.
The melt flow rate shall not deviate by more than 30% from the value specified by the Manufacturer. The change in melt flow rate caused by processing, i.e. the difference between the measured value for material from the pipe and the measured value for the compound, shall not be more than 25%.
PTS 18.104.22.168 January 2011 Page 40 (Table 220.127.116.11) lists the quality control tests that are required along with the appropriate standard test procedure, testing frequency and acceptance criterion. The total number of QC tests shall be agreed between the Contractor and the Principal. Table 184.108.40.206 QC requirements on material properties during production Property Outside diameter Wall thickness Burst pressure (up to 100 mm diameter) Strength (Over 100 mm diameter) Hydro-test Out of roundness Ovality Density Melt flow rate Modulus ESC resistance Carbon black ASTM D 2122 D 2122 D 1599 D 2122 Acceptance criteria API Spec 15 LE, Table 3 API Spec 15 LE, Table 3 To be agreed between Contractor and Principal To be agreed between Contractor and Principal See 22.214.171.124 < 5% of quoted value < 5% of quoted value < 2% of quoted value < 30% of quoted value < 5% of quoted value < 5% of quoted value 2% min. unless otherwise agreed. Frequency Once every hour or once every coil, whichever is less frequent
For quoted values refer to (Section 4.1) 188.8.131.52 Hydro-testing Liner pipe sections shall not show any sign of leakage (burst or weep) or ballooning when subjected to a hydrostatic pressure test. The hydrostatic test pressure shall be agreed between the Principal, Contractor and Manufacturer and is maintained for at least 3 minutes. As a guide the test pressure should be 1.5 times the rated pressure for the stand-alone thermoplastic pipe. Failure is defined as: Ballooning Burst Weep Any abnormal localised expansion of a pipe specimen while under internal hydraulic pressure. Failure by a break in the pipe with immediate loss of test liquid and continual leakage of test liquid independent of applied pressure. Failure that occurs through microscopic breaks in the pipe wall, frequently only at or near the test pressure. At lower pressures, the pipe may maintain its integrity.
Retest and rejection If a sample fails to meet any of the QC requirements, additional tests shall be made on the previously produced samples back to the previous acceptable sample. Pipes produced in the interim that do not pass the requirements shall be rejected. Testing frequency shall be every 10th pipe back to the previously acceptable sample.
4.4.5 126.96.36.199
Inspection and rejection Inspection by the Principal All Quality Control tests shall be witnessed by an Inspector approved by the Principal at the start of production and monitored thereafter at the Principals discretion.
Significant defects Significant defects are those which adversely affect the service life of the liner pipe, e.g. inclusions, bends, dents, scratches, visible cracks, foreign material contaminants or any other imperfection reducing the wall thickness below minimum acceptable limits (4.3.1). Material which contains significant defects on inspection shall be rejected. Significant defects include:
PTS 184.108.40.206 January 2011 Page 41 Scratches in pipe: Surface scratches and nicks in thermoplastic liner may not exceed a depth of 5% of the nominal wall thickness. Scratches in flanges: thermoplastic flange surfaces shall be free of scratches and nicks. Bends: bend angles in thermoplastic liner pipes shall not exceed 5. Bend radii shall not be less than 5 times the nominal liner diameter. Dents: The maximum depth shall be the lower of 6.5 mm or 2% of the pipe OD. 184.108.40.206 Repair of defects Repair of defects is not permitted. 4.4.6 126.96.36.199 Quality control records requirements Purpose Quality control records are necessary to substantiate that all pipe manufactured to this PTS conforms to the specified requirements. 126.96.36.199 Records control Quality control records required by this PTS shall be legible, identifiable, retrievable and protected from damage, deterioration or loss. Quality control records required by this PTS shall be retained by the pipe supplier and Contractor for a minimum of five years following the date of manufacture. All quality control records required by this PTS shall be signed and dated by the pipe supplier's designated authorised person.
The following records shall be maintained and supplied by pipe supplier: 1. Quality manual in accordance with (Section 4.4.1). 2. Quality control test results in accordance with (Section 4.4.4). 3. Design and material qualification data in accordance with (Section 3.1) and (Section 4.1). 4. All procedures utilised by the pipe supplier in the process of fulfilling the order 5. Quality assurance records for all materials supplied by the pipe supplier.
EQUIPMENT MARKING Pipe shall be marked by the Manufacturer as follows: The markings on each length of pipe or fitting shall include in any sequence: Manufacturer's name or trademarks; base specification shown on purchase order, e.g. API Spec 15 LE or ISO 4427; nominal pipe size; date of manufacture; SDR; appropriate material code; Manufacturer's lot number; additional markings, as agreed between the Manufacturer, Contractor and Principal.
Pressure rating shall not be marked on the pipe. The markings on pipe shall be paint stencilled or printed on the outside surface at intervals of not more than 1.5 m or on each fitting. Indentation marking may be used provided: The marking does not reduce the wall thickness to less than the minimum value. The marking has no effect on the long-term strength.
PTS 188.8.131.52 January 2011 Page 42 4.6 4.6.1 HANDLING AND STORAGE Storage Coils shall be stored stacked flat one on top of another. Straight lengths shall be stored on horizontal racks and given support to prevent damage. In either storage form, pipe shall not come into contact with hot water or steam and shall be kept away from hot surfaces. Coils containing pipes of diameters greater than 1.5 inches (38 mm) and larger shall not be stored on edge. Pipe shall be covered with adequate protection from direct sunlight. If the pipe has to be stored in the open air before, during or after shipment, it shall be protected from environmental contamination. Pipe end covers shall be used to prevent ingress of moisture or dirt to the inside of the pipe. 4.6.2 Handling All pipes shall be cleaned, dried and packed before handling and transportation. Thermoplastic pipe can be susceptible to damage by abrasion and by sharp objects. Dragging pipe sections or coils over rough ground shall not be permitted. If, due to unsatisfactory storage or handling, a pipe is damaged it shall be rejected. 4.6.3 Transportation The minimum requirements for transportation shall be as specified in the following: API RP 5L1 for railroad transportation; API RP 5LW for marine transportation.
Pipe transported by sea shall not be shipped as deck cargo. 4.6.4 Coiling Coil diameter should be sufficiently large to prevent excessive strain being applied to the pipe. The minimum recommended inside coil diameter shall be determined by:
Coiling diameters are based on maximum allowable axial strain. For thin-walled pipes, buckling could induce extra axial strain and therefore, before coiling thin-walled pipe, the Manufacturer should be consulted for recommendations.
PTS 18.104.22.168 January 2011 Page 43 5. 5.1 LINER INSTALLATION GENERAL - INSTALLATION TECHNIQUES There are several commercially available liner installation techniques. An overview of the generic types is given below and is illustrated by specific examples. The scope of this PTS covers lining technologies that involve pulling a discrete length of thermoplastic pipe into a host steel pipe. All technologies require an insertion clearance between the liner and the host pipeline. The scope covers both onshore and offshore installation cases. There are three generic liner installation techniques: undersizing; consecutive reduction and pull-in; simultaneous reduction and pull-in.
The following summarises these three main types of installation techniques currently available and is for information only. The Contractor shall propose a specific installation technique and submit it to the Principal for approval. 5.1.1 Undersizing Undersized liner installation involves inserting a liner of outside diameter less than the inside diameter of the host pipe. The difference in diameter is the insertion clearance. It is the simplest technique for lining pipes and has been applied for many years in oilfield applications. 22.214.171.124 Slip-lining Slip-lining is a technique where the undersized liner is simply pulled into the host steel pipe. The liner is expanded in place by internal pressure, with or without heating, to yield the liner while the annulus is vented. There is always a remaining annular gap. Internal pressure, creep and swell are relied upon to obtain a tight liner fit, often after weeks of operation. This time period depends strongly on the insertion clearance, liner material properties and service conditions. If the pipeline is not pressurised for long periods then there is a risk of the liner reverting to its original undersized dimensions. 184.108.40.206 Grouting Grouting is a technique where an undersized liner is pulled into the steel host pipe, as in slip-lining. The insertion clearance is filled with a liquid grout that solidifies, e.g. Bentonite based systems (concrete-type materials). To ensure complete filling of the annulus, the initial insertion clearance has to be comparatively large. The consequence of this is that liner installation is simple but a significant reduction in pipe inside diameter results. 5.1.2 Consecutive reduction and pull-in Consecutive reduction and pull-in techniques reduce or deform the liner to generate the insertion clearance. The reduction step shall be stable, to allow subsequent liner installation. During the pressure expansion stage the annulus shall be continuously vented. 184.108.40.206 Folded pipe Two manufacturing options of folded pipe are available: hot-forming or cold-forming. In hot-forming, the liner is hot folded into a flat ribbon shape after leaving the extrusion die. It is then reeled and can be installed using slip-lining. As the liner is hot-formed, it shall be heated (usually using steam) to above its softening point during the pressure expansion stage or else it will revert to its original flat shape. In cold-forming, the liner is mechanically folded into shape using a die. The deformed shape is tied up with a wrap to maintain the insertion clearance. Installation is by slip-lining and internal pressure is used to break the wrap and yield the liner to fit the host pipe. 184.108.40.206 Diameter reduction by deformation The diameter reduction by deformation technique involves an oversized liner being reduced in diameter by cold-forming through a die. The liner is plastically deformed and is
PTS 22.214.171.124 January 2011 Page 44 therefore stable in its reduced state. The diameter reduction results in a wall thickness increase. Installation is by slip-lining, with the pressure expansion step applied to achieve the initial fit with the annulus continuously vented. As the liner has been plastically deformed its yield strength is lowered. This implies that the initial liner fit is tighter than with standard slip-lining. Also the time to establish a stable fit is much shorter with little risk of reversion to initial liner diameter. 5.1.3 Simultaneous reduction and pull-in Simultaneous reduction and pull-in techniques reduce the liner diameter elastically through a die during the installation process. The immediate elastic recovery forces the liner into a tight fit inside the host pipe. However, to maintain the insertion clearance during pull-in the liner shall remain under tension at all times, implying that the liner shall be fed through the die and straight into the host steel pipe in one continuous pull. 188.8.131.52 Reduction forming (with die) Reduction forming or swageing (with die) is a British Gas proprietary lining system, designed to maximise remaining bore diameter. Using a simple die, diameter reduction is converted into an axial length increase. When the tension is released, the elastic recovery is immediate with the liner length reducing as the liner diameter increases. The annulus is continuously vented with the end result being a very tight interference fit between the liner and the host pipe. This technique provides the tightest possible liner fit but is the most demanding in terms of engineering tolerances. 18.104.22.168 Reduction forming (with rollers) Reduction forming (with rollers) is similar to reduction forming (with die), where instead of a static die, a set of profiled rollers is used to forge the reduced diameter in several stages, with the reduction deformation imposed more gradually on the liner than by reduction forming (with die). The last set of rollers is powered. By controlling both the pull-in and roller loads an optimum conversion of length and wall thickness is achieved. Alternatively the rollers may not be powered, in which case the liner is pushed through the rollers. 5.1.4 Summary (Table 5.1.4) summarises the pros and cons in terms of liner fit, installation length and internal pipe dimensional tolerances of the various installation techniques, where + is defined as a strength, 0 as neutral and a weakness. Table 5.1.4 Pros and cons of liner installation techniques As-installed liner fit Undersized Consecutive reduction Simultaneous reduction 0 + Installed section length + + 0 Dimensional tolerances + 0
5.2 5.2.1
PREPARATION PHASE General Whether the liner is to be installed in a new pipeline or retro-fitted into an existing pipeline will influence the preparation of the inside surface of the carbon steel pipeline. An accurate assessment of the condition of the host pipeline is critical to ensure a successful lining operation. For rehabilitation of existing pipelines, the preparation considerations shall include: corrosion damage; presence of leaks; internal deposits; diameter variations and mismatches; weld protrusions and misalignment; general lay-out with bends, road, river crossings, pig traps, manifolds etc.
In particular, the following checks should be performed. The condition of the steel pipe should be assessed to determine that sufficient mechanical strength is retained to meet the design pressure rating for the proposed service, based on hydrotest and/or inspection survey data. This test should be carried out at a minimum test pressure of 1.25 times the design pressure with the aim to reach a stress level as defined by PTS 31.40.00.10-Gen. The internal condition and dimensions of all lines should be evaluated to ensure that the liner can be pulled through each segment without significant damage e.g. due to excessive local weld penetration (icicles). These should be checked by gauging pigs/plates and/or by pulling a test sample of liner through every flanged pipe section. Locations for cutting and flanging of the line and any requirement for separate spooled sections should to be determined. The longest continuous length of liner which can be installed in straight pipe depends on diameter and wall thickness, but is generally reduced in practice by local curvature of the line. Breaks are also required at road crossings, changes in ID and any bends of radius less than 20D, (recommended minimum where possible is 40D). Flanges welded to the steel line should be of matching bore and with a minimum radius at the inside edge of about 6 mm. Vents shall be welded to the line in accordance with (Section 3.4) of this PTS.
For lining existing buried pipelines, bellholes should be placed at the ends of the line and at any other locations where breaks in the liner need to be made. In addition to the normal safety considerations in excavating, sizing and ensuring stability of the bellholes, the following factors should also be considered: The working area within the bellhole should be of sufficient size to accommodate the pipe fusion machine and operator. The entry slope should be sufficiently shallow to enable the liner pipe to bend smoothly from ground level to the pipeline depth without severe abrasion against the steel flange during pull-through. (Provision may also be required for pulling from two directions within a single bellhole). Provision of sufficient length and width to enable the pipe ends to be offset for flange welding and pulling in of the liner.
For new installations, preparation consideration shall include: site conditions; steel material selection (surface roughness); weld specification.
For both a new or existing pipeline, the pipe inner surface shall be thoroughly cleaned before liner installation. Particularly for offshore liner installation, special attention shall be paid to ensuring that there are sufficient space, weight and anchoring provisions (e.g. for pull-in winch) for all the equipment required for the installation and testing of the liner.
PTS 18.104.22.168 January 2011 Page 46 5.2.2 Liner unloading and stockpiling Unloading and stockpiling of the liner pipes and reels shall be done in accordance with Manufacturer's recommendations. When the liner pipe is cut from a coil, it should be supported to minimise stresses during installation. The pipe should not be subjected to reverse curvature. Plastic pipe hangers may be used to support the pipe. Care shall be taken not to over-tighten and cause the hanger clamps to cut into the pipe. Pipe hangers should be correctly aligned and should provide a flat smooth surface for contact with the pipe. Supports having sharp edges shall not be used. 5.2.3 220.127.116.11 Inspection of liner materials General Material which shows injurious defects on site inspection shall be marked and rejected and the Contractor so notified. 18.104.22.168 Defects a) In pipe, surface scratches and nicks shall not exceed a depth of 5% of the nominal liner wall thickness. b) Flange surfaces shall be free of scratches and nicks c) The maximum depth of dents shall be the smaller of 6.5 mm or 2% of the pipe OD. 126.96.36.199 Repair of defects Defects in any form shall not be repaired. Pipe lengths with defects exceeding the acceptance criteria of this PTS in (Section 18.104.22.168) shall be discarded and marked as rejects. 5.2.4 Vent point assemblies Vent point assemblies shall be installed in accordance with the design and shall be installed prior to installation of the liner. The design of the vent point assembly shall be agreed with the Principal. Every lined pipeline and flowline should incorporate vent points. The minimum number of vent points should be one on each flanged end of a section of lined pipe. Vent holes should be designed such that no extrusion of the liner will occur. For larger diameter lines, vent discs with multiple holes or wire screens may be used. Vent holes should not be larger than 3 mm in diameter. All vents should be valved (except for water service where vents can be plugged) and should have a "snorkel" to prevent ingress of dirt, moisture and/or air.
5.3 5.3.1
LINER FABRICATION PHASE General The thermoplastic liner pipe shall be joined using the butt fusion welding process, as defined in ASTM D 2657, Technique II. Any proposal by the Contractor to use a different technique, e.g. hand welding, shall be subject to agreement by the Principal. Contractor personnel performing the butt fusion welding shall be certified by the liner Manufacturer in the liner joining procedure. Joining of liners with a wall thickness difference of more than 2 mm shall not be permitted. Procedures requiring the introduction of additional filler may also be used where appropriate. Measures to avoid oxidation and thermal degradation of the liner shall be taken. After completion of the fusion weld, the internal and external bead of the weld shall be trimmed. After trimming, the surface of the joint shall be visually examined for evidence of good fusion. Nicks, gouges or undercuts caused by bead trimming are not acceptable and shall be removed or cut-out.
Butt fusion welding procedure The Contractor shall prepare a detailed procedure for each type and size of joint and fitting to be welded. Separate procedures shall be prepared for shop and site welding. Each butt fusion welding procedure shall detail the following information: welding equipment type and model; material grade and Manufacturer; pipe/fitting dimensions at the joint; welding sequence.
Essential parameters to be controlled as detailed in the welding equipment operating manual for both the pre-heat and fusion stages include: temperatures, times, pressures, hot plate condition in terms of roughness and cleanliness; weld dimensions and tolerances.
For each pipe butt fusion welding procedure to be used a test spool shall be prepared and welded. This shall consist of three pipe sections butt fusion welded together with a flange welded at each end, i.e. 4 circumferential welds in total. The assembly shall be tested as follows: weld dimensions - within tolerances of approved welding procedure; visual inspection - no visible defects; ultrasonic and/or radiographic examination when specified by the Principal acceptance criteria to be agreed; pressure test using water at the maximum design temperature and at a pressure agreed with the Principal or 1.5 times the equivalent rated pressure for the standalone thermoplastic pipe - no leakage after 2 hours.
For each material grade and weld type, four additional test samples shall be prepared from the largest diameter represented. The test samples shall be tested to short-term burst pressure according to ASTM D 1599. The acceptance criterion is that the pipe shall not fail at the weld. All butt fusion welding operators who successfully complete the above welding procedure qualification shall be considered qualified for butt fusion welds of the same type, material grade and diameter range as represented by the procedure. All qualified welders shall wear an ID card including a pass photo and stating name, validity (end date of project) diameter range, wall thickness and material grade for which they are qualified. The ID card shall be signed by the Principal. 5.3.3 Testing The Contractor shall conduct an air test on the fused liner section prior to installation of the liner. A maximum pressure of 0.3 bar shall be applied for a duration of not more than 3
PTS 188.8.131.52 January 2011 Page 48 hours unless otherwise specified by the Principal. The pipe should be anchored at 5 to 7 metre intervals with back-fill material before pressuring. A vacuum should not be pulled. All fusion joints shall be soap-tested in the presence of an Inspector, approved by the Principal. Alternatively a water test may be performed. The pressure of the water test shall be 1.5 times the equivalent pressure rated (stand-alone) thermoplastic pipe. This test pressure shall be agreed between the Principal and the Contractor.
5.4 5.4.1
LINER INSTALLATION General All equipment and material required for the installation and testing of the liner shall be provided by the Contractor unless otherwise agreed. Procedures to cover the installation of the thermoplastic liner inside the carbon steel pipeline shall be prepared by the Contractor and submitted to the Principal for approval.
5.4.2 184.108.40.206
Preparation Pre-installation communications The Contractor shall establish communication procedures between the ends of the pull section prior to the start of the liner pull-in.
Pull wire The pull wire shall be certified to a load of at least four times the anticipated maximum pull load.
Pipe cleaning Before installation, the Contractor shall clean the pipeline and demonstrate that the bore of the carbon steel pipeline is free from obstructions (e.g. excessive weld penetration, dents, etc.) that could interfere with or damage the liner during pull-in. A gauging plate shall be used to assess the internal diameter variations within the carbon steel pipeline.
Pull head and winch The design of the pull head shall be such that sufficient clearance between the pull head and the pipe shall be maintained. The winch shall contain as a minimum a distance indicator and recorder and a calibrated load indicator and recorder.
Wireline and pig train The wireline unit should be suitably instrumented with footage and weight indicators, an overload control set to a maximum of 100% of the calculated maximum allowable pulling force and fitted with a speed controllable reel with cable spooling and braking facility. The Contractor should provide suitable pigs and launching equipment to propel the wireline and pig train through the pipeline A typical pig train should include: Sizing pig Cleaning pig Cup pig Wegment of liner pipe (for loose liner)
Once the wireline has been passed through the pipeline section, the pig train is pulled through, the pulling force being continuously monitored to determine the location of any constrictions. For loose fitting liners, the disc plate diameter should generally be about midway between the OD of the liner and the ID of the steel pipe. For tight liners, the disc plate should be of sufficient diameter to verify that internal weld beads do not protrude excessively, taking into account the dimensional tolerances of the steel pipe. The outer diameter of the liner pipe segment should be such that any excess weld penetration which could result in liner puncture during normal operation is detected. For loose liners this could imply that a larger diameter liner pipe may be necessary for test purposes than during operation.
PTS 184.108.40.206 January 2011 Page 50 The liner test segment attached to the pig train should emerge without serious damage. Scuffing of the liner surface is permissible but sharp longitudinal scars or other penetration damage exceeding 0.5 mm or 5% of the wall thickness, which ever is larger, is unacceptable and would require rectification by further pigging using a breaker pig or by other means before continuing with liner installation. After rectification another liner test segment should be pulled through. 5.4.3 184.108.40.206 Insertion General Liner insertion techniques depend on the method of installation chosen as outlined in (5.1). Installation methods and procedures proposed shall include as a minimum: description of equipment used; length of sections; maximum allowable and planned axial pull load. The maximum allowable axial stress in the liner should be limited to 50% of the tensile yield stress; type of lubrication - Lubricants can be water or bentonite. The use of grease is not allowed unless by testing it is proven to be compatible with the thermoplastic liner and will not lead to stress cracking; pull-in rate; methods for continuous load monitoring with calibrated equipment; precautions shall be taken to ensure that no debris is introduced into the line on the external or internal surface of the liner.
Pull-in load The actual pull-in load shall be continuously monitored during pull-in. It shall not be allowed to exceed the maximum allowable pull-in load (3.5.4).
5.4.4 18.104.22.168
Expansion General For all methods, with exception of grouting, the liner shall be expanded. The Contractor shall propose procedures for this to the Principal. Thermoplastic polymers have a thermal coefficient of expansion greater than that of carbon steel. Consequently, allowance for thermal expansion and contraction after pull-in and during service should be made during the liner expansion phase of installation. A practical allowance is 20 mm per 10 m of pipe for each 10 C change in temperature. For fully constrained pipe, a detailed stress analysis shall be performed by the Contractor.
Grouted liners For liners that are grouted into place, an external extruded or machined anchor pattern should be considered. Before grouting the annulus gap should be at least 5 mm. The pipeline should be pressurised during grouting to prevent collapse. The grout pressure should be 1 bar below pipeline pressure. The liner should be centred before inserting the grout, using spacers. Grouting should start from the first vent point until it emerges from the second point. Upon completion this second vent point becomes insertion point. A quality check of grout (density) at emergence at vent points should be performed. The shear strength of the grout should be at least 5 MPa. For cementitious grouts, entrapment of air in grout should be between 1% and 2% to allow porosity and permeability of gas through the grout to the vent holes.
END FLANGES AND IN-LINE FLANGED JOINTS Connections between thermoplastic lined pipes and metallic piping shall be flanged. No other joining methods (e.g. flared or screwed connections) shall be permitted, except for in-situ retro-fitting where compression-type fittings may be used. The design of the thermoplastic lined flanges shall be proposed by the Contractor and agreed with the Principal. The design of the lined flanges should be raised face with spacer/backing rings. When the liner has been pulled in, flange adapters should be fusion welded to each end. The method should be detailed by the Contractor but will generally involve the following steps: Welding a flange adapter to the liner segment trailing end and pulling in to the steel flange. Clamping and stretching the liner from the leading end, sufficient to trim to required length and butt the second flange adapter. (Normally a minimum 100 m segment length is required for this technique to accommodate the necessary elastic strain). Releasing the clamp to allow the liner to contract on to the steel flange face. Fitting metal retaining rings around the liner flanges. These are designed to a controlled thickness to limit compression of the flanges to a pre-determined value when bolting adjacent segments and to prevent spreading of the flange material under load.
Flange bolts shall be tightened with a torque wrench, using greased bolts and nuts, in sequence and to the torque values as specified by the Manufacturer. Too great a bolt loading may damage the plastic facing on the flanges. Appropriate spring washers should be used between the nut and the flange. Bolts should be re-torqued after an initial service period of 24 hours.
TESTING The complete lined pipeline system shall be hydro-tested with water at ambient temperature at the lower of 1.5 times the maximum operating pressure or the pressure of the pipeline strength test for a period of 24 hours. For the duration of the test all vent points shall remain open (refer to Section 5.2.3). The pressure may fluctuate due to variations in ambient temperature, and care shall be taken that the test pressure does not exceed the lowest rated element in the system. During hydrotesting, temperature and pressure shall be recorded continuously unless otherwise agreed with The Principal. During the hydrotest the pressure shall be increased first to 3 times the liner pipe freestanding pressure rating with all vents open to allow annular fluids to escape. If all fluids have escaped or after one hour, which ever takes longer, the pressure shall be increased to the required hydrotest pressure. All end terminations and vents shall be visually inspected. Acceptance criterion shall be that no weeping at flanges or through vent holes, if present, is witnessed during the test. At the end of the hydrotest the vents shall all be closed whilst the line is still under pressure. Two to four weeks after commissioning all vents should be opened and closed again to allow fluids which may have permeated through the annulus to the vents to escape as well as to check whether any liner defects have developed.
PTS 22.214.171.124 January 2011 Page 53 6. 6.1 OPERATION START-UP Immediately prior to starting up lined pipeline systems in gas service, any accumulated pressure shall be bled off at all the vents. As soon as the pipeline is up to operating pressure, the pressure at each vent point shall be checked and recorded. This should be repeated after 48 hours' operation. 6.2 DE-PRESSURISING Before de-pressurising the pipeline the vent points should opened for at least one hour. The rate at which the vent point can relieve the gas trapped in the annulus should be estimated to ensure that the venting rate, during de-pressurisation, is sufficient to prevent a positive pressure difference between the annulus and the pipeline, i.e. at no time during de-pressurisation should the annulus pressure be greater than the line pressure. 6.3 PIGGING Pipelines with liners do not usually require pigging. However, if the line requires pigging to remove fluids, then only foam pigs shall be used. 6.4 FLOW VELOCITY (Table 6.4) presents the maximum recommended flow velocities for lined carbon steel pipelines. Table 6.4 Maximum recommended flow velocity Normal flow (m/s) Maximum continuous flow (m/s) 10 20 Maximum intermittent flow (m/s) 15 40
1-8 5-15
The above velocities are based on the assumption that no hard particles are present in the flow. Hard particles can be tolerated but the potential erosion rate shall then be assessed.
VENTING Venting procedures are required to prevent liner collapse during process upset conditions (large pressure fluctuations) or shutdowns. Venting is required when gases are present in the pipeline fluids. Venting is not required for liquid lines. Vents shall be opened for the following conditions: before changes in the operating conditions; before shutdown; at least monthly to evacuate the permeated gas accumulated in the annulus.
Venting operations shall be recorded in a log and include: date, length of time vent remained open, vent pressure, volume of gas vented and other general observations. The requirement for monthly venting may be revised according to experience using the log entries to justify revising the venting frequency. Alternatively it may be decided to operate the pipelines with the vents open (assuming approval from the appropriate Health, Safety and Environment authority), i.e. continuously venting the annulus. Open vents shall be inspected at least monthly to check integrity of the thermoplastic liner and blockage of the vent points. 6.6 MAINTENANCE Vent points shall be kept free from paint or other deposits. Blocked vent points, pipes and fittings should be cleaned with low-pressure water only. The use of rods, steam jets or sharp tools for cleaning shall not be permitted.
PTS 188.8.131.52 January 2011 Page 54 The vent holes and flange bolt torques shall be checked regularly.
Amended per Circular 39/08
If very toxic gases (see PTS 01.00.01.30-Gen.) are present the local HSE authority shall be consulted before venting operations. 6.7 REPAIR Lined pipes and fittings shall not be repaired by welding, since heat could cause damage to the liner. If damage occurs to a component of an installed lined piping system, the damaged component shall be replaced. Consideration may be given to returning damaged pipes to the Contractor for relining. Leakage at flanged connections shall be remedied by the measures in the following sequence: 6.8 Re-torquing of flange bolts to the specified values. Care shall be taken that these values are not exceeded. Replacement of the pipe spool having the suspect flange face.
OPERATIONAL PROCEDURE FOR A LINED PIPELINE An operational procedure shall be developed for all lined pipelines and flowlines. This procedure shall as a minimum address the following aspects: system description; operating envelope; venting; pigging; start-up procedure; routine operations; de-pressuring.
PTS 220.127.116.11 January 2011 Page 55 7. 7.1 DOCUMENTATION INFORMATION TO BE SUBMITTED BY THE PRINCIPAL The following information should be supplied by the Principal: Internal/external diameter of carbon steel pipeline. Length of pipeline. Right-of-Way access. Location (onshore/offshore, buried/above ground). Elevation profile of pipeline. Location, radius and angle of all bends. Location of any valves and fittings (e.g. tees) installed in the pipeline. Condition of internal surface of the carbon steel pipeline (new/used, roughness, penetration of welds, etc.) Fluid composition (incl. inhibitors, chemicals etc.). Expected minimum/maximum ambient temperatures during installation. Minimum/maximum operating temperature of the system. Minimum/maximum operating pressure of the system. Maximum rate of de-pressurisation of the system. Indication of likelihood of large pressure fluctuations. Preferred type of liner material and thickness (if known). Possibility and frequency of local venting. If nothing is specified it can be assumed that the venting frequency is once per one to three months. Requirements for valves at gas venting points, requirements for gas monitoring, limitations on gas venting rates and any restrictions on venting locations. Design life.
Appendix 5 lists the data that the Principal should provide in the Purchase order. 7.2 INFORMATION TO BE SUBMITTED BY THE CONTRACTOR The Contractor shall submit information on the liner system to be used. This information shall contain as a minimum: Liner system identification. Manufacturer's material data. Material pre-qualification information. Type and thickness of liner material. Expected short-term and long-term volumetric swelling or shrinkage for the range of operating conditions. Expected thermal deformations due to operating temperatures. Liner manufacturing procedure. Liner installation procedure. Anticipated insertion forces for each liner section in relation to liner strength. Bend limitations for the steel pipe. Maximum allowable weld penetration of carbon steel pipeline girth welds. Vent connection details and spacing.
PTS 126.96.36.199 January 2011 Page 56 8. REFERENCES In this PTS, reference is made to the following publications:
NOTE: Amended per Circular 05/02 Unless specifically designated by date, the latest edition of each publication shall be used, together with any amendments/supplements/revisions thereto.
Definition of temperature, pressure and toxicity levels Piping - general requirements Pipeline and riser engineering Carbon and low alloy steel pipeline flanges for use in oil and gas operations (amendments/supplements to MSS SP-44) Non-metallic materials selection and application AMERICAN STANDARDS Pipe flanges and flanged fittings NPS 1/2 through NPS 24 Large diameter steel flanges NPS 26 through NPS 60
Issued by: American Society of Mechanical Engineers 345 East 47th Street New York NY 10017 USA
Specification for polyethylene line pipe (PE) Recommended practice for railroad transportation of line pipe Recommended practice for transportation of line pipe on barges and marine vessels
Issued by: American Petroleum Institute Publications and Distribution Section 1220 L Street Northwest Washington DC. 20005 USA
Standard specification for seamless carbon steel pipe for high-temperature service Standard specification for alloy-steel and stainless steel bolting materials for high-temperature service Standard specification for carbon and alloy steel nuts for bolts for high-pressure or high-temperature service, or both Standard practice for determining chemical resistance of thermosetting resins used in glassfiber-reinforced structures intended for liquid service Standard test methods for determining the Izod pendulum impact resistance of plastics Standard practice for conditioning plastics for testing
PTS 18.104.22.168 January 2011 Page 57 Standard test method for tensile properties of plastics Standard test method for deflection temperature of plastics under flexural load Standard test method for brittleness temperature of plastics and elastomers by impact Standard test methods for flexural properties of unreinforced and reinforced plastics and electrical insulating materials Standard test methods for density and specific gravity (relative density) of plastics by displacement Standard test method for resistance of transparent plastics to surface abrasion Standard test method for flow thermoplastics by extrusion plastometer rates of ASTM D 638 ASTM D 648 ASTM D 746 ASTM D 790
Standard test method for density of plastics by the density- gradient technique Standard test method for short-time, hydraulic failure pressure of plastic pipe, tubing and fittings Standard test method for carbon black in olefin plastics Standard test method for environmental stresscracking of ethylene plastics Standard test method for determining dimensions of thermoplastic pipe and fittings Standard test method Durometer hardness for rubber property
Standard practice for heat fusion joining of polyolefin pipe and fittings Standard test methods for tensile, compressive, and flexural creep and creep-rupture of plastics Standard specification for unmodified polyvinylidenefluoride (PVDF) molding extrusion and coating materials Standard Specification for polyethylene plastic pipe and fitting materials Standard test method for oxidative-induction time of polyolefins by differential scanning calorimetry Standard test method for abrasion resistance of organic coatings by the taber abraser Standard classification system for nylon injection and extrusion materials (PA) Standard specification for propylene plastic injection and extrusion materials Standard test methods for stress relaxation tests for materials and structures Standard test method for linear thermal expansion of solid materials by thermomechanical analysis Standard test method for assignment of the glass transition temperatures by differential scanning
PTS 220.127.116.11 January 2011 Page 58 calorimetry or differential thermal analysis Standard specification for polyvinylidenefluoride (PVDF) plastic-lined ferrous metal pipe and fittings Standard specification for propylene and polypropylene (PP) plastic-lined ferrous metal pipe and fittings Standard specification for butt heat fusion polyamide (PA) plastic fitting for polyamide (PA) plastic pipe and tubing
Issued by: American Society for Testing and Materials 1916 Race Street, Philadelphia Pa 19103 USA
INTERNATIONAL STANDARDS Plastics Determination of Izod impact strength Plastics Determination of tensile properties Plastics and ebonite Determination of indentation hardness by means of a durometer (Shore hardness) Plastics Determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics Polyethylene (PE) Specifications pipes for water supply ISO 180 ISO 527 R ISO 868
Determination of ring
Issued by: International Organisation for Standardisation 1, Rue de Varemb CH-1211 Geneva 20 Switzerland Copies can also be obtained from national standards organizations.
PTS 126.96.36.199 January 2011 Page 59 APPENDIX 1 CURRENT RANGE OF SERVICE EXPERIENCE
The Shell Group has more than 10 years of favourable operating experience with thermoplastic liners in water injection, gas and crude oil applications in moderate operating conditions. FIGURE A.1 GROUP EXPERIENCE OF THERMOPLASTIC LINED PIPELINES IN TERMS OF PRESSURE - DIAMETER RANGE
(Figure A.1) presents the broad range of application currently in Group service in terms of pressure-diameter range. (Figure A.2) presents the current usage as a function of fluid transported. FIGURE A.2 GROUP EXPERIENCE OF THERMOPLASTIC LINED PIPELINES AND FLOWLINES IN TERMS OF FLUID TRANSPORTED
PTS 220.127.116.11 January 2011 Page 60 The bulk of liner applications are for water transport, although several long low-pressure gas transport lines are also in service. Polyethylene (PE) is the most commonly used thermoplastic polymer material to date. The bulk of current applications are limited to operating temperatures below 60 C. It is anticipated that this service temperature will rise as the application envelope of lined carbon steel pipelines and flowlines is broadened, implying that other thermoplastic polymer materials will have to be considered.
The following example is taken from the Shell Canada, Waterton 24 inch gas pipeline. A.2.1 Scope Due to excessive internal corrosion on the existing Waterton 24-inch steel pipeline, a 31.5 mm polyethylene liner has been installed. PE liners do not corrode therefore no corrosion inhibitor injection is required. The maximum operating pressure of the pipeline has been de-rated to 99.30 bar. The high-pressure setting on check valves at the upstream and downstream end of the line has been set to 90 bar to provide additional protection. A.2.2 Vents The liner has been pulled into the pipeline in six segments. These segments are joined by flanges which are buried underground. On each side of the flange a half-inch vent pipe rises to surface, isolated with a valve. A 1/8" hole has previously been drilled through the steel pipeline only to vent any annular gas which may permeate through the plastic liner and migrate up into the vent pipes. Vents are also required to check the integrity of the liner. When checking the vents for pressure or bleeding-off the pressure, they shall be dealt with in the same manner as breaking the integrity of any system: 2 men are required; 1 safety person; self-contained breathing apparatus shall be worn by worker performing task; safety person shall be upwind and a safe distance away; record the vent pressure on the venting log sheet; annular pressure should be kept below 50 bar at all times; vents are to be left in the closed position at all times; during normal operation the pipeline vents will be filled with 100% glycol. This will reduce the volume of H2S that can accumulate in the vent lines.
CAUTION: Do not use pressure to fill vent lines. A.2.3 Temperature If the gas in the line reaches high temperatures the liner could soften. This can cause weakening of the liner and collapse. A.2.4 At no time should the temperature of the fluid entering the liner be greater than 45 C. The upstream heater shall be set to maintain a temperature at 40 C with the hightemperature alarm set at 45 C.
Pigging Pipelines with liners do not usually require pigging. However, if the line requires pigging to remove fluids then it can be pigged with the following restrictions: 3 lb (psi) density foam pigs to be used; do not pig with ball or hard style pigs. There are signs located at each end to alert operators to this.
Start-up procedure Immediately prior to start-up bleed the pressure off all the vents. Introduce gas into the pipeline. As soon as the pipeline is up to operating pressure, check and record all vent pressures. Maintain/record each vent pressure after first 2 days on venting log sheet.
PTS 18.104.22.168 January 2011 Page 62 A.2.6 Operation/routine Check liner pressure and record on venting log sheet once per month. If time to bleed off annulus pressure is very short (<10 s) leave closed and continue to check on monthly basis. A.2.7 De-pressuring pipeline Immediately (within 1 hour) before de-pressuring the pipeline, the pressure on all the vents shall be bled off and then closed. Following de-pressuring of the pipeline the vents shall be left open for 1 hour, then closed. CAUTION: Failure to remove pressure from vents before pipeline de-pressurisation could lead to collapse of the liner. A.2.8 Drop in normal operating pressures A drop in normal operating pressure of greater than 7.5 bar for extended periods of time could cause a collapse of the liner. Therefore, the maximum differential pressure should not exceed 7.5 bar.
PTS 126.96.36.199 January 2011 Page 63 APPENDIX 3 LINER DESIGN DATA SHEET
The following information shall be provided by the Contractor during the tender: Installation technique to be used:
Step 1 OD (liner outside diameter) h (liner wall thickness) R = 0.5 * (IDsteel - h) Step 2 handling and storage requirements SDR ratio h Step 3 installation requirements Maximum allowable stress during pulling Maximum load during pulling h Step 4 Maximum h from Steps 2 and 3 Step 5 Service (water, crude oil or multiphase) Maximum design temperature Maximum linear swell, swell Modulus, E at service conditions Step 6 Liner fit, C calculate from (Section 126.96.36.199) Step 7 only for multi-phase or gas applications Collapse pressure, Pc calculate from (Sections 18.104.22.168, 18.104.22.168, 220.127.116.11) depending on liner fit using maximum h (Step 4) Step 8 only for multi-phase or gas applications Design pressure, Pdes (Section 3.3.4) Choose operational procedure, intrinsically safe or allowance for gas expansion For intrinsically safe procedure, is Pdes > Pc (Section 18.104.22.168) If yes, increase liner wall thickness and return to Step 6 If no, go to Step 10 For allowance for gas expansion procedure calculate initial annulus volume, Vinit (Section 22.214.171.124) For allowance for gas expansion procedure calculate critical volume, Vc (Section 22.214.171.124) For allowance for gas expansion procedure, is Pdes > Pc* Vc/ Vinit (Section 126.96.36.199)
Units mm mm mm
MPa N mm
mm /mm mm /mm
If yes, increase liner wall thickness and return to Step 6 If no, go to Step 10 Step 9 only for liquid applications Critical swell, crit, calculate from (Section 3.3.5) swell > crit (Section 3.3.5) If yes, increase liner wall thickness and return to Step 5 If no, go to Step 10 Step 10 Minimum liner wall thickness mm
The following information shall to be provided by the Contractor during the tender for: - Pipe material Flange material Lined spools
Property Pipe, flange or spool? Raw Material manufacturer Material type and grade (unique identification as used by manufacturer) Pipe supplier Poisson ratio Coefficient of thermal expansion (K ) Carbon black content (only for PE) Density (g/cm ) Melt index (g/10min at 190 C, 2160 g load) Modulus (MPa) at 20 C Modulus (MPa) at design temperature Tensile strength (MPa at 50 mm/min) Environmental stress crack (Condition C for 192 hours) Oxygen (at 200 oC) Induction resistance Temperature
3 -1
Test Method ASTM D 3350 ASTM D 1505 ASTM D 1238 ISO 9969 ISO 9969 ASTM D 638 ASTM D 1693 ASTM D 3895 ASTM D 1599
Manufacturer data
The following information shall be provided by the Principal in the purchase documents: Process design data Tmax, Maximum design temperature Tmin, Minimum design temperature Minimum ambient temperature Maximum ambient temperature Minimum pressure Maximum design pressure Pressure fluctuation during normal operation Pressure fluctuation frequency Gross throughput Watercut For crude oil lines: Bubble point GOR (gas/oil recovery) at normal conditions Partial pressure of H2S in gas phase Well stimulation chemicals Well lift mechanism (ESP, beam pump, etc.) CITHP (closed in tubing head pressure) FTHP (flowing tubing head temperature) Carbon steel line details ID carbon steel line Internal condition (corroded/new) Internal condition (max weld penetration) Design life Buried or above ground Coating (presence/colour/type) Liner supply data Pipeline length Specified length or coil size Delivery/shipping instructions m m mm years mm bar C bar m /m bar
3 3