Requirements and specifications for pipeline valve layout
1 General requirements for pipelines
(1) The clear height, channel width, and foundation elevation of the pipeline layout should comply with the requirements in Chapter 3 of the "Design Engineering Regulations on the Layout of Chemical Plants and Equipment" (HG20546.2).
(2) The pipeline layout design shall be carried out in accordance with the regulations of the maximum allowable bracket spacing 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 pipeline layout should consider the convenience of operation, installation and maintenance, and does not affect the operation of the crane. Pipes should not be arranged in the area of the building installation holes.
(5) The pipeline layout design should consider the ease of design of supports and hangers, and make the pipelines as close as possible to existing buildings or structures, but should avoid making flexible components bear larger 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 to be pipe supports or supports. Large-diameter thin-walled bare pipes and pipes with thermal insulation layers should be supported by pipe supports or supports.
(8) On the pipeline that crosses the channel or above the rotating equipment that transports corrosive media, there should not be flanges or threaded connections that may cause leakage.
(9) When the pipeline passes through the isolation wall of the building to isolate highly toxic or explosive media, casing should be added, and the gap in the casing should be filled with non-metallic flexible materials. The weld on the pipe should not be inside the casing and not less than 100mm from the casing port. 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 laid buried in the ground, and anti-corrosion measures should be taken on the outer surface of the pipes in accordance with relevant regulations.
(11) Buried pipelines should consider the impact of vehicle load. The distance between the top of the pipeline and the road surface should not be less than 0.6m, and should be below the depth of frozen soil.
(12) For pipes with requirements such as "bagless", "slope", and "liquid seal", the pipes should be piping strictly in accordance with PID requirements.
(13) When connecting branch pipes from a horizontal gas main pipe, they should be connected from the top of the main pipe.
2 Spacing of parallel pipes and installation space
(1) The net distance between parallel pipes should meet the requirements for pipe welding, heat insulation and component installation and maintenance. The clear distance between the protrusions on the pipeline shall not be less than 30mm. For example, the net distance between the outer edge of the flange and the outer wall of the adjacent pipe insulation layer or the net distance between the flange and the flange, etc.
(2) The distance between pipes that cannot be flanged or insulated should meet the requirements of pipe welding and inspection, generally not less than 50mm.
(3) For pipelines with lateral displacement, the clear distance between the pipelines should be appropriately increased.
(4) The clear distance between the projecting part of the pipe or the outer wall of the pipe insulation layer should not be less than 100mm from the pillars of the pipe frame or frame, and the wall of the building, and the space required for tightening the flange bolts should be considered.
3 Pipe exhaust and drainage
1. Due to the high or low points formed by the pipeline arrangement, exhaust and liquid discharge ports should be set:
(1) The minimum pipe diameter of the high point exhaust port is DN15, and the minimum pipe diameter of the low point discharge port is DN20 (when the main pipe is DN15, the discharge port is DN15). The minimum pipe diameter of the exhaust and liquid discharge ports for high-viscosity media is DN25.
(2) The high-point exhaust port of the gas pipe does not need to be equipped with a valve, and it is closed with a threaded pipe cap or a flange cover. Except for the pipes on the pipe gallery, the pipes with DN less than or equal to 25 need not be equipped with high-point exhaust ports.
(3) The non-technical high-point exhaust and low-point discharge ports may not be indicated on the PID.
2. The exhaust and liquid discharge ports required by the process (including those connected to the equipment) should be set according to the requirements on the PID.
3. The height requirement of the exhaust outlet should meet the requirements of the current national standard "Code for Fire Protection Design of Petrochemical Enterprises" (GB50160).
4. Discharge points of toxic, flammable and explosive liquid pipes must not be connected to sewers, but should be connected to closed systems. The vent point of gas heavier than air should consider the impact on the operating environment and the protection of personal safety.
4 Position of pipe weld
(1) The distance between the center of the pipe butt weld and the bend point of the elbow should not be less than the outer diameter of the pipe, and it should not be less than 100mm.
(2) The net distance between two adjacent butt welds on the pipeline should not be less than 3 times the pipe wall thickness, and the net length of the short pipe should not be less than 5 times the pipe wall thickness and not less than 50mm; for pipelines with DN greater than or equal to 50mm , The net distance between the two welds should not be less than 100mm.
(3) The circumferential weld of the pipeline should not be within the scope of the pipe support. The clear distance between the edge of the weld and the edge of the bracket should be greater than 5 times the width of the weld and not less than 100mm.
(4) It is not advisable to make holes and take over the pipe welds and their edges.
(5) The longitudinal welds of steel coil-welded pipes should be placed in a position that is easy to inspect and observe, and should not be at the bottom of a horizontal pipe.
(6) For pipes with reinforcement rings or support rings, the butt joints of the reinforcement rings or support rings should be staggered with the longitudinal welds of the pipe, and not less than 100mm. The distance between the reinforcement ring or the support ring should not be less than 50mm from the pipe circumferential weld.
5 Pipeline cold and heat compensation
(1) The displacement, force and moment caused by thermal expansion or cold contraction of the pipeline must be carefully calculated, and the natural geometric shape of the pipeline arrangement should be used first to absorb it. The force and moment acting on the equipment or pump interface shall not be greater than the allowable value.
(2) When the pipeline self-compensation capacity cannot meet the requirements, compensating components, such as "Π"-shaped elbows, should be installed at appropriate positions in the piping system; The calculation result is reasonable selection, and the fixed frame and guide frame are considered according to the standard requirements.
(3) When it is required to reduce the force and moment, cold drawing is allowed, but it is not suitable to take over important sensitive machines and equipment.
6 General requirements for valves
(1) The valve should be located where it is easy to operate, install and maintain. The valves on the rows of pipelines (such as the pipelines entering and exiting the device) should be arranged in a centralized manner, which is conducive to the installation of operating platforms and ladders.
(2) Some valve positions have process operation requirements and locking requirements, and they should be arranged and marked according to PID instructions.
(3) Valves on the bottom pipes of towers, reactors, vertical vessels and other equipment should not be arranged in group seats.
(4) Manual valves that need to be operated according to the instructions of the local instrument should be located close to the local instrument.
(5) The regulating valve and safety valve should be arranged on the ground or platform where it is convenient for maintenance and debugging. The layout of the trap should be in accordance with the provisions of Chapter 15 in the "Specifications for the Design of Piping Layout of Chemical Plants" (HG/T20549.5).
(6) Fire hydrants or valves for fire fighting should be located where they can be safely approached in the event of a fire.
(7) The valve of the buried pipeline should be located in the valve well, and there should be room for maintenance.
(8) The valve should be located in a place with small thermal displacement.
(9) When there are bypass or offset transmission components on the valve (such as gear transmission valves), there should be enough installation and operation space for the bypass or offset components.
7 Valve position requirements
(1) The installation height of the valve stem centerline of the valve on the standpipe should be in the range of 0.7 to 1.6m above the ground or platform, and the valve of DN40 and below can be arranged below 2m. When the position is too high or too low, a platform or control device, such as a sprocket or extension rod, should be installed to facilitate operation.
(2) When a very small number of valves are operated infrequently, and their operating height is not more than 2.5m from the ground, and it is inconvenient to set up a permanent platform, use a portable ladder or a mobile platform to enable people to operate.
(3) The center of the valve handwheel arranged around the operating platform should not be greater than 400mm from the edge of the operating platform. When the valve stem and handwheel extend above the platform and the height is less than 2m, they should not affect the operator's operation and traffic safety.
(4) When the valves are arranged adjacently, the clear distance between the handwheels should not be less than 100mm.
(5) The valve stem should not be installed vertically or inclined downward.
(6) For frequently operated valves installed in pipe trenches or valve wells, when the handwheel is lower than 300mm below the cover plate, an extension rod should be installed to make it within 100mm under the cover plate.
Source: "Chemical Piping Design Manual-2 Piping Installation Design"