A New Method of Creep Ruptures Data Extrapolation Based on the Work
For structural and machine components in service at high temperature and pressure, such as those used in power generating and petrochemical plants, as well as aero-engines and metallurgical machineries, creep life assessment is a major concern because of safety and economic reasons. In this paper, a new model for creep life prediction is proposed based on energy processes. The work of making the material failure of applied loads is used to describe the creep processes respectively. By mathematical technique, the expression of the model is, where is Larson-Miller constant, and is also material constant at certain condition. This function Moreover, owing to its simple expression, it is very easy to use this model to predict the creep life. To check the validity of the new model proposed in this paper, the 250000h creep rupture strength estimates for 2.25Cr1.0Mo steel under stress control at 743~793K have been performed. The results are in a good agreement with the experimental data.
Life management of refinery furnace tubing
Abstract The 2PTR and 3PTR furnaces at the MOBIL (Altona) Refinery have tubing that have been in operation for over 20 years. API RP 530 creep rupture life calculations showed that the tubes have limited remaining life. Therefore accelerated creep rupture testing was undertaken of a material from the likely worst case tube sample. However, going from creep rupture test results to assess the remaining life of furnace tubing is complicated by the fact that• the tested tubes may not have been exposed to the maximum temperature for the life of the furnace;• the test stress is different from the service stress because various pressure and wall thickness combinations exist. To overcome such issues detailed heat transfer calculations were carried out to understand tube temperatures based on thermography data and assessment of consumed life fraction was undertaken. Deterministic modelling of total life based on wall thickness data and operating pressure was carried out using most appropriate creep rupture database. It was found that there was sufficient remaining life for tubes in 2PTR furnace such that replacements were not required prior to the next normal outage. However, it is found that if high temperatures are experienced in 3PTR furnace a failure could occur in the near future. The information from the life assessment study was integrated into a risk based inspection program and set temperature limits to allow planned replacement of the tubing.
Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 ? 1 Rib Cotton Knitted Fabrics
This study investigates the impact of yarn count and stitch length of 100% cotton knitted fabrics. 1 × 1 ribs structured fabrics were used in this research work. The stitch length 2.50 mm, 2.52 mm, 2.60 mm, 2.70 mm, 2.80 mm and 2.96 mm were used of the yarn count of 26Ne, 28Ne and 36Ne. The areal densities of the grey fabrics were in various amounts. The impacts of yarn count and stitch length were measured concerning pilling resistance, abrasion resistance, and shrinkage and tightness factor. The result showed that the fabric pilling grade decreased while number of cycle increased. Abrasion resistance decreased but length wise shrinkage increased despite the fact that the stitch length increased. The results also exposed that the tightness factor of the fabric increased with the increase of the stitch length in both dyeing and washing state and finished state compared to grey state for the yarn count 26Ne and homogeneous result not found for yarn count 28Ne and 36 Ne. Evaluation of Impact of Yarn Count and Stitch Length on Pilling, Abrasion, Shrinkage and Tightness Factor of 1 × 1 Rib Cotton Knitted Fabrics