Project Case



Requirements and specifications for pipeline gate valve arrangement


General requirements for pipelines

1. The headroom height, channel width and foundation elevation of the pipeline layout shall comply with the regulations in Chapter 3 of the "Engineering Regulations on Layout and Design of Chemical Plant Equipment" (HG20546.2).  

2. The piping layout design shall be carried out in accordance with the provisions of the maximum allowable support spacing in the current national standards.  

3. The pipeline should be laid overhead as much as possible, and if necessary, it can also be laid underground or in trenches.

4. The pipeline layout should consider the convenience of operation, installation and maintenance, without affecting the operation of the crane. Pipes should not be routed in the area of building mounting holes.  

5. The layout design of the pipeline should consider the design of the support and hanger, so that the pipeline should be as close as possible to the existing buildings or structures, but it should avoid making the flexible components bear large loads.  

6. Where conditions permit, the pipelines should be concentrated and arranged in rows. The tube bottom of the bare tube is aligned with the bottom surface of the tube support to facilitate the design of the bracket.  

7. Pipes without heat insulation do not need support or support. Large-diameter thin-walled bare pipes and pipes with heat insulation layers should be supported by pipe holders or supports.  

8. Connection points that may cause leakage, such as flanges or threaded connections, should not be set on pipelines that span passages or convey corrosive media above rotating equipment.  

9. When the pipeline passes through the building separation wall for isolating highly toxic or explosive media, a sleeve should be added, and the gap in the sleeve should be filled with non-metallic flexible materials. The weld on the pipe should not be inside the casing, and the distance from the casing port should not be less than 100mm. Where the pipeline passes through the roof, rainproof measures shall be taken.  

10. Fire water and cooling water main pipes and sewer pipes are generally laid underground, and anti-corrosion measures should be taken on the outer surface of the pipes in accordance with relevant regulations.

11. The impact of vehicle loads should be considered for buried pipelines, and 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 "no bag shape", "with slope" and "with liquid seal", the piping shall be strictly in accordance with the requirements of PID.

13. When the branch pipe is connected from the horizontal gas main pipe, it should be connected from the top of the main pipe.

Pipeline gate valve

The spacing and installation space of parallel pipes

1. The net distance between parallel pipes shall meet the requirements for pipe welding, heat insulation layer and installation and maintenance of components. The clear distance between the protrusions on the pipe should 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.

2. The distance between pipes without flanges and without heat insulation should meet the requirements for pipe welding and inspection, generally not less than 50mm.  

3. For pipelines with lateral displacement, the net distance between pipelines should be appropriately increased.  

4. The clear distance between the pipe protrusion or the most protruding part of the outer wall of the pipe insulation layer and the pillar of the pipe frame or frame, and the building wall should not be less than 100mm, and the space required for tightening the flange bolts should be considered.

Pipeline exhaust and liquid discharge

① Due to the high point or low point formed by the pipeline layout, the exhaust and drain 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 liquid discharge port is DN20 (when the main pipe is DN15, the liquid discharge port is DN15). The minimum pipe diameter of the exhaust and liquid outlet of high-viscosity medium is DN25.  

(2) The high-point exhaust port of the gas pipe may not be provided with a valve, and shall be 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 may not have high-point exhaust ports.  

(3) Non-technical high-point exhaust and low-point liquid discharge ports may not be indicated on the PID.

② The exhaust and liquid outlets 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 port shall comply with the provisions of the current national standard "Code for Fire Protection Design of Petrochemical Enterprises" (GB50160).
④ The discharge points of toxic and flammable and explosive liquid pipelines shall not be connected to sewers, but shall be connected to closed systems. The venting point of the gas heavier than air should consider the impact on the operating environment and the protection of personal safety.

The position of the pipe weld

1. The distance between the center of the pipe butt weld and the bending point of the elbow should not be less than the outer diameter of the pipe, and not 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 pipes with a DN greater than or equal to 50mm , The net distance between the two welds should not be less than 100mm.

3. The girth 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 open holes and take over pipe welds and their edges.

5. The longitudinal weld of the pipe welded by steel plate roll welding should be placed in a position that is easy to repair and observe, and should not be at the bottom of the horizontal pipe.

6. For pipes with reinforcement rings or support rings, the butt joints of the reinforcement rings or support rings should be staggered from the longitudinal welds of the pipes, and not less than 100mm. The distance between the reinforcement ring or support ring and the pipe girth weld should not be less than 50mm.

Pipeline gate valve

Pipeline cold and heat compensation

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 it. Forces and moments acting on the equipment or pump connections must not be greater than the permissible values.

2. When the self-compensation ability of the pipeline cannot meet the requirements, the compensation element should be installed in the appropriate position of the pipeline system, such as "Π" shaped elbow; According to the calculation results, the model is selected reasonably, and the fixed frame and guide frame are considered to be set 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 connections.

General requirements for valves

1. The valve should be located in a place that is easy to operate, easy to install and maintain. The valves on the rows of pipelines (such as pipelines entering and exiting the device) should be arranged in a centralized manner, which is conducive to setting up operating platforms and ladders.  

2. Some valve positions have requirements for process operation and locking, which should be arranged and marked according to the instructions of PID.  

3. The 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 local instruments should be located close to the local instruments.

5. Regulating valves and safety valves should be arranged on the ground or on the platform where they are convenient for maintenance and debugging. The arrangement of steam traps shall comply with the provisions in Chapter 15 of the Design Regulations for Piping Layout of Chemical Plants (HG/T20549.5).  

6. The fire hydrants or valves used for fire fighting shall be set at a position where they can be safely approached in case of fire.

7. The valves of the buried pipelines should be set in the valve wells, and there should be room for maintenance.  

8. The valve should be located where the thermal displacement is small.

9. When there are bypass or offset transmission components on the valve (such as gear transmission valves), sufficient installation and operation space should be reserved for bypass or offset components.

Pipeline gate valve

Valve position requirements

1. The installation height of the valve stem centerline of the valve on the riser should be within the range of 0.7 to 1.6m above the ground or platform, and the valves of DN40 and below can be arranged at a height of 2m or less. When the position is too high or too low, a platform or control device, such as a sprocket or an extension rod, should be provided for easy operation.  

2. For very few infrequently operated valves whose operating height is not more than 2.5m from the ground and it is inconvenient to set up another platform, portable ladders or mobile platforms should be used to enable people to operate.  

3. The distance from the center of the valve handwheel arranged around the operation platform to the edge of the operation platform should not be greater than 400mm. When the valve stem and handwheel extend above the platform and the height is less than 2m, it should not affect the operation and traffic safety of the operator.  

4. When the valves are arranged adjacent to each other, the net distance between the handwheels should not be less than 100mm.  

5. The stem of the valve should not be installed vertically downward or inclined.  

6. For valves installed in pipe trenches or valve wells that are frequently operated, when the handwheel is lower than 300mm below the cover plate, an extension rod should be installed to make it within 100mm below the cover plate.

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