Papers by Keyword: Pressure Pipe

Abstract: Quality control of construction materials is one of the entire pressure pipeline installation project an important part of quality control. The quality control includes the procurement, acceptance testing, storage, distribution and use during the installation.

Abstract: In order to ensure the safety of production, a new method for strengthening pipe with carbon fiber reinforced polymer sheet is introduced. The experimental research on the effect of this method has also been done. In the experiment, the pipe that wrapped with one and two layers of CFRP sheets respectively are tested. And the relation between the hoop strain in the tested pipe and the internal water pressure is given according to the experiments. The results show that it can be a substantial increase in the bearing capacity of the pipes. The construction of this method is simple and a short period is required; so it not affect the normal operation of generating unit. It has a good practical value in the production practice.

Abstract: This paper investigated the effect of outer polypropylene (PP) skin thickness on the density and calculated hardness of a polyethylene (PE) core pressure pipe. Density of PE pipes with different PP skin thicknesses (including a PE pipe without a skin) was compared and found that the density distribution can be described well by an exponential function and it increased and flattened with increased PP thickness, which was equivalent to a PE layer 2~3 times as thick. Thermal analysis showed that the density increment is derived from the thermal insulation provided by the PP skin and allowed annealing occur during pipe cooling, particularly close to the outer wall. According to the crystallinity and hardness relationship, the relative strengthening effect on hardness and its relationship with PP layer thickness was quantified.

Abstract: ASTM A106/B is commonly used for pressure piping in alumina refineries. Due to the problem of caustic cracking in alumina refineries, piping must be stress relieved after welding, usually through a post-weld heat treatment (PWHT) process at a temperature of 635°C. However, multiple PWHT procedures tend to degrade the mechanical properties of steel and design standards have set limits on the length of time PWHT can be carried out before steel should be replaced. In this study, the effect of PWHT time on the properties of A106/B parent metal was examined, with particular emphasis on the effect on toughness. PWHT was carried out for 1, 8 and 40 hours and the results were compared with those for as-received material. Impact transition temperature and room-temperature tensile results were determined using standard tests. The reference temperature, To, was determined using ASTM E1921 with arc-shaped tension specimens. The results showed that the ductile-to-brittle transition temperature increased significantly as PWHT time increased and the implications of this to a fracture mechanics analysis of plant operations are discussed.