1. General requirements for pipes

(1) The headroom, aisle width, and foundation elevation of the pipeline's layout should comply with the requirements in Chapter 3 of the "Design Engineering Regulations for the Layout of Chemical Plants and Equipment" (HG20546.2).
(2) The pipeline's layout shall be carried out in accordance with the regulations of the maximum allowable bracket space in the current national standards.
(3) The pipeline should be laid overhead as much as possible. If necessary, it can also be laid in the ground or in a trench.
(4) The convenience of operation, installation and maintenance should be considered for the pipeline's layout, and the operation of the crane should not be affected. Pipes should not be arranged in the area of the building's installation holes.
(5) The design of the pipeline's layout should consider facilitating the design of supports and hangers, so that the pipeline should be as close as possible to existing buildings or structures, but avoid the flexible components bearing great loads.
(6) Where conditions permit, pipelines should be arranged in rows. Align the bottom of the bare tube with the bottom surface of the tube holder to facilitate the design of the bracket.
(7) Pipes without thermal insulation do not need pipe supports. Thin-walled bare pipes with large diameters and pipes with thermal insulation layers should be supported by pipe supports.
(8) There should not be flanges or threaded connections which may cause leakages for the pipeline that crosses the channel or above the rotating equipment which transports corrosive media.
(9) When the pipeline passes through the isolation wall of the building to isolate highly toxic or explosive media, the casing should be provided, and the gap in the casing should be filled with non-metallic flexible materials. The welding seam on the pipe should not be inside the casing and not less than 100 mm from the casing end. Rainproof measures should be taken where the pipe runs through the roof.
(10) Fire-fighting water and cooling water main pipes and sewer pipes are generally buried, and anti-corrosion measures should be taken on the outer surface of the pipes in accordance with relevant regulations.
(11) The impact of vehicle load should be considered for buried pipelines. The distance between the top of the pipe and the road surface should not be less than 0.6 m, and should be below the depth of frozen soil.
(12) Pipes with requirements such as slopes and liquid sealing should be arranged strictly in accordance with PID requirements.
(13) When branch pipes are connected from a horizontal gas main pipe, they should be connected from the top of the main pipe.
 
2. Space and installation space of equal pipes
(1) The clear distance between parallel pipes should meet the requirements for welding, heat insulation and component installation and maintenance of pipes. The clear distance between the protrusions on the pipeline shall not be less than 30 mm. For example, the clear distance between the outer edge of the flange and outer wall of the adjacent pipe insulation layer or the flanges.
(2) The distance between pipes should meet the requirements of welding and inspection of pipes, generally not less than 50 mm.
(3) For pipelines with lateral displacement, the clear distance between the pipelines should be appropriately increased.
(4) The clear distance of the protrusion of the pipe or outer wall of the pipe insulation layer pipe support and the wall of the building should not be less than 100 mm, and the space required for tightening flange bolts should be considered.
 
3. Exhaust and drainage of pipes
(1) Exhaust and liquid discharge ports should be set due to the high or low points formed by the piping arrangement. The following should be paid attention to:

(2) The exhaust and liquid discharge ports required by the process including those connected to the equipment should be set according to the requirements of the PID.
(3) The height requirement of the exhaust port should meet the requirements of the current national standard "Rules for Fire Protection Design of Petrochemical Enterprises" (GB50160).
(4) The discharge point of toxic, flammable and explosive liquid pipes shall not be connected to sewers, but shall be connected to a closed system. The impact on the operating environment and the protection of personal safety should be considered for vent points of gas that are heavier than air.
 
4. The location of the welding seam of the pipe
(1) The distance between the center of the pipe's butt welding port and the bending point of the elbow shall not be less than the outer diameter of the pipe and not less than 100 mm.
(2) The net distance between two adjacent butt welding seams on the pipeline should not be less than 3 times the pipe's wall thickness, and the net length of the short pipe should not be less than 5 times the pipe's wall thickness, not less than 50 mm. For pipelines with DN greater than or equal to 50 mm, the net distance between the two welding seams should not be less than 100 mm.
(3) The circumferential welding seam of the pipeline should not be within the scope of the pipe support. The net distance between the edge of the welding seam and bracket should be greater than 5 times the width of the welding seam and not less than 100 mm.
(4) It is not advisable to make holes and connect pipes on the pipe's welding seams and their edges.
(5) Longitudinal welding seams of steel coil welded pipes should be in a position which is easy to maintain and observe, and should not be at the bottom of a horizontal pipe.
(6) For pipes with reinforcement rings or support rings, the butt joint seam of the reinforcement rings or support rings should be staggered with the longitudinal welding seam of the pipe, and not less than 100 mm. The distance between the reinforcement ring or the support ring should not be less than 50 mm from the pipe's circumferential welding seam.
 

5. Cold and heat compensation of pipes

(1) The displacement, force and moment of the pipeline caused by thermal expansion or cold contraction must be carefully calculated, and the natural geometric shape of the pipeline layout should be used first to absorb. The force and moment acting on the equipment or pump interface shall not be greater than the allowable value.
(2) When self-compensation of the pipeline cannot meet the requirements, compensation components such as Π shaped elbows should be installed at appropriate positions in the piping system. When conditions are limited, bellows expansion joints or other forms of compensators must be selected based on the calculation result. Set the fixed frame and guide frame according to the standard requirements.
(3) When it is required to reduce the force and moment, cold drawing measures are allowed, but cold drawing is not suitable for important sensitive machines and equipment.