Why We Set Valve in This Way?

This regulation applies to the setting of gate valves, globe valves, ball valves, butterfly valves and pressure-reducing valves in petrochemical plants. Check valves, safety valves, regulating valves and steam traps are set in relevant regulations. This regulation does not apply to the setting of valves on underground water supply and drainage pipelines.
 

 
Principle of valve layout

The valves shall be set according to the type and quantity showed on the PID. When PID has specific requirements for the installation position of some valves, it should be set according to the process requirements. The valve should be arranged in a place that is easily accessible, and convenient for operation and maintenance. The valves on the pipelines in rows should be arranged centrally, and an operation platform or ladder should be considered.
 
Installation position requirements of valves
 
1. Cut-off valves shall be set when the pipe gallery pipes in and out of the device are connected with the pipe gallery supervisors in the whole plant. The installation position of the valves shall be centrally arranged at one side of the device area, and the necessary operation platform or maintenance platform shall be set.
 
2. Valves that need a frequent operation, maintenance and replacement should be located on the ground, platform or ladder easily accessible. Pneumatic and electric valves should also be arranged in easily accessible places.
 
3. Valves that don't need to be operated frequently (only used when starting and parking), if they can't be operated on the ground, should also be arranged in places where temporary ladders can be erected.
 
4. The height between the center of the valve handwheel and the operating surface is 750-1500mm, and the most suitable height is 1200mm. The installation height of valves that do not need a frequent operation can reach 1500-1800mm. When the installation height cannot be lowered and frequent operation is required, the operation platform or step should be set in the design. Valves on pipelines and equipment of hazardous media shall not be set within the height of people's heads.
 
5. When the height of the center of the valve handwheel from the operating surface exceeds 1800mm, it is advisable to set up a chain wheel for operation, and the chain distance of the chain wheel from the ground should be about 800mm, and a chain wheel hook should be set to hang the lower end of the chain on a nearby wall or post, so as not to affect the passage.
 
6. For the valves set in the pipe trench, when the ditch cover plate is opened and can be operated, the handwheel of the valve should not be less than 300mm under the ditch cover plate. When it is less than 300mm, the valve extension rod should be set to make the handwheel within 100mm under the ditch cover plate.
 
7. When the valves installed in the pipe trench need to be operated on the ground, or the valves installed under the previous floor (platform), the valve extension rod can be set to extend to the ditch cover plate, the floor and the platform for operation. It is advisable that the hand wheel distance of the extension rod is 1200mm. The valves with nominal diameter less than or equal to DN40 and threaded connection should not be operated by sprocket or extension rod, so as not to damage the valves. Normally, the valve should be operated with a sprocket or extension rod as little as possible.
 
8. The distance between the valve wheelset around the platform and the edge of the platform should not be greater than 450mm. When the valve stem and handwheel extend above the platform and the height is less than 2000mm, they should not affect the operation and passage of operators, so as to avoid personal injury.
   
Setting requirements of large valves
 
1. Geared transmission mechanism should be used for the operation of large valves, and the required space position of the transmission mechanism should be considered when setting. Generally, valves with gear transmission mechanism should be considered when the size of valves is larger than the following grades.
 
2. For large valves, supports should be set on one side or both sides of the valve, which should not be set on the short pipe that needs to be removed during maintenance, and the support of the pipeline should not be affected when the valve is removed. Generally, the distance between the bracket and the valve flange should be greater than 300mm.
 
3. The installation position of large valves should have a site where cranes are used, or consider setting hanging columns and beams.
 
 Setting requirements of valves on horizontal pipelines
 
1. Unless otherwise required by the process, the handwheel of the valve installed on the general horizontal pipeline shall not face down, especially the handwheel of the valve on the dangerous medium pipeline shall not face. The orientation of the handwheel is determined in the following order: vertically upward; Level; Upward left and right tilt by 45; Vertical left and right tilt 45; Not vertically downward.
 
2. When the valve is opened, the valve stem shall not affect the traffic, especially when the valve stem is located at the head or knee of the operator.
 
Other requirements for valve setting
 
1. The center lines of the valves on the pipeline arranged in parallel should be as close as possible. When the valves are arranged adjacent to each other, the clear distance between handwheels should not be less than 100mm. The valves can also be staggered to reduce the pipeline spacing.
 
2. The valves that are technically required to be connected to the equipment nozzle shall be directly connected to the equipment nozzle when the nominal diameter, nominal pressure, sealing surface type, etc. are the same as or match with the flange of the equipment nozzle. When the valve is equipped with a concave flange, the equipment specialty should be asked to configure a convex flange at the corresponding nozzle.
 
3. Unless the process has special requirements, valves on the bottom pipelines of towers, reactors, vertical vessels and other equipment shall not be arranged in skirts.
 
4. When the branch pipe is led out from the main pipe, its cut-off valve should be located on the horizontal section of the branch pipe near the root of the main pipe, so that the fluid can be drained to both sides of the valve.
 
5. The branch cut-off valve on the pipe gallery is not often operated (only for parking and maintenance). If there is no permanent ladder, it should be considered to set aside a space for using a temporary ladder.
 
6. When the high-pressure valve is opened, the starting force is large, so a bracket must be set to support the valve and reduce the starting stress. Its installation height should be 500-1200mm.
 
7. Firewater valves, fire steam valves, etc. in the battery limit of the unit shall be arranged in a scattered way, and a safe area accessible to operators in case of an accident.
 
8. The valve group of the fire-extinguishing steam distribution pipe of the heating furnace should be easy to operate, and the distance between the distribution pipe and the furnace body should not be less than 7.5m
 
9. When installing a threaded valve on the pipeline, a union must be installed near the valve for easy disassembly.
 
10. Wafer valves or butterfly valves shall not be directly connected with flanges of other valves and pipe fittings, and a section shall be added in the middle.
Short pipe with flanges at both ends.
 
11. The valve should not bear the external load, so as to avoid excessive stress and damage to the valve.