A UNS S 32654 , A STAINLESS STEEL FOR CONDENSER TUBES
The new superaustenitic stainless steel UNS S32654 (Avesta Sheffield 654 SMO) is proposed for condenser tubes in desalination and power plants. A number of tests illustrating its corrosion resistance in a variety of chloride containing environments are being reviewed in terms of pitting, crevice corrosion and stress corrosion cracking. Relevant mechanical and physical properties are described. Health hazards and the impact on the environment are discussed as well as the cost benefits of using a stainless steel for this application.
Behaviour of High Strength Molybdenum Containing Stainless Steels in Arabian Gulf Water. Part 1: Oxide Film Thickening
AbstractThe variation with time of the open circuit potentials of six molybdenum containing stainless steels was measured in Arabian Gulf water under conditions simulating operation in multistage flash evaporation distillers. The effects of temperature in the range 22–70°C and of sea water concentrated by cold evaporation to between 100 and 150% were examined in detail. With all steels, plots of potential as a function of logarithm of immersion time consisted of two straight line segments: the first, characterised by a lower slope, was attributed to the formation of a very thin, barrier type oxide layer, whereas the second related to longer times of immersion, indicating the formation of a thicker film. The mean rates of thickening of both forms of oxide (δ¯1 and δ¯2) were computed according to open circuit transient theory. Depending on the type of steel, δ¯2/δ¯1 varied between 4·6 and 11·0 below 40°0C and 1·1 and 1·6 at 70°C. Curves representing the variation of δ¯1 and δ¯2 with temperature exhibited ma...
Influence of pressure and fluidization velocity on the hydrodynamics of a fluidized bed containing horizontal tubes
Abstract An experimental investigation of the influence of horizontal tubes on the bubble behaviour and through-flow velocity of gas inside bubbles was carried out and the influence of pressure and fluidization velocity was studied. The visible bubble flow rate and the gas velocity through the bubbles were measured simultaneously in a pressurized fluidized bed, using capacitance and Pitot-static pressures probes respectively. Silica sand with a mean particle diameter of 0.7 mm was fluidized at pressures between 01. and 1.6 MPa, in a bed of 0.2 × 0.3 m cross-section. Six different horizontal tube configurations were used and comparisons were made with results obtained in the same bed operated without tubes. The results from the bed with tubes show that the influence of pressure and fluidization velocity is basically the same as in the bed without tubes; an increase in pressure and fluidization velocity increases the bubble activity. At low excess gas velocities, the influence of immersed tubes on the bubble behaviour is less pronounced than at high excess gas velocities. Measurements and visual observations show that a small tube pitch gives a more uniform distribution of the visible bubble flow over the bed cross-section. At a combination of high pressure, high excess gas velocity and a large tube pitch, a preferred bubble path was observed in the centre of the bed cross-section. The pressure probe measurements show that the through-flow velocity of gas inside the bubbles is in most cases higher when tubes are present in the bed. The through-flow velocity consistently decreases with increasing pressure in the bed without tubes. The tendency is largely the same at a low excess gas velocity when tubes are present, but at a high excess gas velocity the through-flow velocity first decreases and then increases as the pressure is increased.