5.3　Installation of Medium and Low Pressure Pipes

5.3.1　The root pass of the weld must be welded by TIG for the pipes with a high standard of interior cleanness and hard to clean after welding.

5.3.2　The pipe casing shall meet the design requirements for pipes that pass through the wall and floor.When there is no design requirement,the length of pipe casing shall be greater than the width of the wall and the floor,and shall be elongated 25mm~33mm beyond the floor or wall.

5.3.3　The space between pipes and pipe casings shall be stuffed in line with design requirements.When the design has no specific requirements,incombustible soft materials shall be adopted.

5.3.4　The stainless steel pipes and pipe fittings shall not directly contact with ferrite materials during the storage,transportation and installation.Between stainless steel pipes and supports and hangers,stainless steel gaskets or nonmetal materials with chloride ions below 50mg/kg shall be inserted.

5.3.5　The installation of welded steel pipes shall meet the following requirements.

1　The type of welded grooves shall meet the design requirements.When there are no requirements,the installation shall meet requirements in Appendix E.

2　The longitudinal welds on the pipe segments shall be staggered with more than 100mm and located at the position facilitating examination during fitting up.

3　Pipes larger than or equal to DN1000mm shall adopt double-sided welding and back gouging.

4　The location of the steel pipe reinforcing ring and its welding method shall meet the design requirements.The butt weld of the reinforcing ring shall be staggered with the longitudinal welds of the pipe.The staggered value shall be greater than 100mm.

5.3.6　The pipes buried underground cannot be constructed until the supporting foundation is checked and qualified.When laying out pipes with underground water,the supporting foundation or the ground construction,pipe installation,the leak test of the pipe,and the backfilling of soil shall be carried out after removing the underground water.

5.3.7　Anti-corrosion of pipes and the construction of underwater pipes shall meet design requirements.

5.3.8　The anti-corrosion layers of buried steel pipes shall be completed before installation.The welding positions shall not be anticorrosion treated before passing the examination and acceptance of the welding.The anti-corrosion layers shall be prevented from being destroyed during transportation and installation.The destroyed anti-corrosion layers shall be repaired.

5.3.9　Buried pipes can be backfilled until qualified for leak test,anti-corrosion treatment and concealment project checking.Backfill construction shall meet DL/T 5190.1 Code for Electric Power Construction Part 1:Civil Engineering.

5.3.10　Oxygen and acetylene pipes shall be installed in line with the requirements of Appendix F.