Abstract: The long-term hydrostatic pressure test curves of overlap-welding aluminum-plastic pipes with diameters of 16mm to 32mm were extrapolated to 50 years by considering the same overall design factor as 1.25 with butt-welding aluminum-plastic pipes. It showed that at 95 ℃ long-term operating temperature, 16-32 type overlap-welding aluminum-plastic pipes had a comparative allowable working pressure P0 compared with butt-welding aluminum-plastic pipes, and could meet the requirements of the 50-year service life under 95 ℃ and 1.25 MPa. According to the requirements of minimum thickness and minimum tensile strength of aluminum layer in national standards, P0 of the overlap-welding aluminum-plastic pipes and butt-welding aluminum-plastic pipes with diameters of 16mm to 50mm was calculated. The results showed that both had the same P0 for the small size, but butt-welding aluminum-plastic pipes had the obvious advantage for the large size.

Key words: aluminum-plastic pipe, overlap-welding, butt-welding, long-term hydrostatic pressure strength