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2022

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08

Why are the valves set up like this?

Author:


This provision applies to the installation of gate valves, globe valves, ball valves, butterfly valves and pressure reducing valves in petrochemical plants. The settings of check valves, safety valves, regulating valves, and traps are subject to relevant regulations. This provision does not apply to the installation of valves on underground water supply and drainage pipelines.

 This provision applies to the installation of gate valves, globe valves, ball valves, butterfly valves and pressure reducing valves in petrochemical plants. The settings of check valves, safety valves, regulating valves, and traps are subject to relevant regulations. This provision does not apply to the installation of valves on underground water supply and drainage pipelines.

 

1. Valve layout principles

    1.1 Valves should be set according to the type and quantity shown on the Piping and Instrumentation Diagram (PID). When PID has specific requirements for the installation position of certain valves, they should be set according to process requirements.

    1.2 The valve should be arranged in a place that is easily accessible, easy to operate and maintain. Valves on rows of pipelines should be arranged centrally, and operating platforms or ladders should be considered.

    

2. Valve installation position requirements

    2.1 When the pipe gallery pipes entering and exiting the device are connected to the main pipes on the pipe gallery throughout the plant, they must be equipped with cutting valves. The installation position of the valves should be concentrated on one side of the device area, and a necessary operating platform or maintenance platform should be set up.

    2.2 Valves that require frequent operation, maintenance and replacement should be located on the ground, platform or easily accessible by ladder. Pneumatic and electric valves should also be placed in easily accessible locations.

    2.3 Valves that do not require frequent operation (only used when starting and stopping), if they cannot be operated on the ground, should also be arranged where temporary ladders can be erected.

    2.4 The height of the center of the valve handwheel from the operating surface is between 750 and 1500mm. The most suitable height is

1200mm. The installation height of valves that do not require frequent operation can reach 1500~1800mm. When the installation height cannot be lowered and frequent operations are required, an operating platform or steps should be set during design. Valves on pipelines and equipment for hazardous media must not be installed within the height of a person's head.

    2.5 When the height of the center of the valve handwheel from the operating surface exceeds 1800mm, a sprocket should be set up for operation. The distance between the sprocket and the ground should be about 800mm. A sprocket hook should be set up to hang the lower end of the chain on a nearby wall or pillar. to avoid affecting the passage of the passage

    2.6 For valves installed in pipe trenches, when the trench cover is opened and the valve can be operated, the handwheel of the valve should not be lower than 300mm below the trench cover. When it is lower than 300mm, an extension rod of the valve should be installed to make its handwheel Within 100mm under the trench cover.

    2.7 When the valve installed in the pipe trench needs to be operated on the ground, or the valve is installed below the upper floor (platform), the valve extension rod can be set to extend to the trench cover, floor, or platform for operation. , the distance between the handwheel of the extension rod and the operating surface is 1200mm. Valves with nominal diameters less than or equal to DN40 and with threaded connections should not be operated using sprockets or extension rods to avoid damage to the valves. Normally, sprockets or extension rods should be used as little as possible to operate the valve.

    2.8 The distance between the valve hand wheels arranged around the platform and the edge of the platform should not be greater than 450mm. When the valve stem and handwheel extend into the upper part of the platform and the height is less than 2000mm, they should not affect the operator's operation and passage to avoid personal injury.

    

3. Setting requirements for large valves

    3.1 The operation of large valves should use a gear transmission mechanism, and the space required for the transmission mechanism should be considered when setting up. Generally, geared valves should be considered for valve sizes larger than those listed below.

    3.2 Large valves should be equipped with brackets on one or both sides of the valve. The brackets should not be placed on short pipes that need to be dismantled during maintenance, and it should be considered that the support of the pipe should not be affected when the valve is removed. Generally, the distance between the bracket and the valve flange should be greater than 300mm.

    3.3 The installation location of large valves must have space for a crane, or consider installing hanging columns and hanging beams.

 

    4. Setting requirements for valves on horizontal pipelines

 

    4.1 Unless there are special requirements for the process, the handwheels of valves installed on general horizontal pipelines must not be facing downwards, especially the valves on dangerous medium pipelines are strictly prohibited from facing downwards. The orientation of the valve handwheel is determined in the following order: vertically upward; horizontally; vertically upward with an inclination of 45° to the left and right; vertically downward with an inclination of 45° to the left and right; not vertically downward.

    4.2 For horizontally installed rising-stem valves, when the valve is opened, the valve stem must not affect traffic, especially when the valve stem is located on the operator's head or knees.

    5 Other requirements for valve settings

    5.1 For valves arranged in parallel pipelines, their center lines should be as aligned as possible. When the valves are arranged adjacently, the clear distance between the handwheels should not be less than 100mm; the valves can also be arranged staggered to reduce the distance between the pipelines.

    5.2 For valves that are technically required to be connected to the equipment nozzle, when the nominal diameter, nominal pressure, sealing surface type, etc. are the same as or match the equipment nozzle flange, they should be directly connected to the equipment nozzle. When the valve has a concave flange, ask the equipment professional to configure a convex flange at the corresponding nozzle.

    5.3 Unless there are special requirements for the process, valves on the bottom pipes of towers, reactors, vertical vessels and other equipment shall not be arranged in the skirt.

    5.4 When a branch pipe is led out from the main pipe, the cut-off valve should be located on the horizontal section of the branch pipe close to the root of the main pipe so that the fluid can be drained to both sides of the valve.

    5.5 The branch pipe cut-off valve on the pipe gallery is not frequently operated (only used during shutdown for maintenance). If a permanent ladder is not installed, space for the use of a temporary ladder should be considered.

    5.6 When the high-pressure valve is opened, the starting force is large. A bracket must be installed to support the valve and reduce the starting stress. The appropriate installation height is 500 to 1200mm.

    5.7 Fire water valves, fire steam valves, etc. in the installation boundary should be dispersed and arranged in safe areas that are easily accessible to operators in the event of an accident.

    5.8 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.

    5.9 When installing a threaded valve on a pipeline, a union must be installed near the valve to facilitate disassembly.

    5.10 Wafer-type valves or butterfly valves must not be directly connected to the flanges of other valves and pipe fittings, and a section should be added in the middle.

Short pipe with flanges at both ends.

    5.11 The valve should not bear external loads to avoid excessive stress and damage to the valve.