Why are the valves set up this way?

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These regulations apply to the installation of gate valves, globe valves, ball valves, butterfly valves, and pressure relief valves in petrochemical plants. The installation of check valves, safety valves, control valves, and steam traps shall comply with relevant regulations. These regulations do not apply to the installation of valves on underground water supply and drainage pipes. 1. Principles for valve layout 1.1 Valves should be installed according to the types and quantities specified in the Piping and Instrumentation Diagram (PID). When the PID has specific requirements for the installation location of certain valves, they should be set in accordance with the process requirements.     1.2 Valves shall be located in places that are easily accessible and convenient for operation and maintenance. Valves on rows of pipes should be grouped together, and provision for operating platforms or ladders should be considered. 2. Requirements for the installation location of valves 2.1 Cut-off valves must be installed at the points where the pipes in the inlet and outlet ductwork connect to the main pipes in the plant’s overall ductwork system. The valve installation locations should be concentrated on one side of the plant area, with necessary operation or maintenance platforms provided.     2.2 Valves that require frequent operation, maintenance, and replacement should be located at a height where they are easily accessible from the ground, platform, or ladder. Pneumatic and electric valves should also be placed in easily accessible locations.     2.3 Valves that do not need to be operated frequently (used only during startup and shutdown) should also be placed in locations where temporary ladders can be set up, if it is not possible to operate them from the ground.     2.4 The height of the center distance between the valve handwheel and the operating surface should be between 750 and 1500 mm, with 1200 mm being the most suitable value. For valves that do not need to be operated frequently, the installation height can range from 1500 to 1800 mm. When the installation height cannot be reduced and frequent operation is required, an operating platform or steps should be provided during design. Valves on pipelines and equipment carrying hazardous media shall not be installed within the height range of a person’s head.     2.5 When the height of the center distance between the valve handwheel and the operating surface exceeds 1800 mm, it is advisable to use sprocket operation; the chain length from the sprockets to the ground should be around 800 mm. Sprocket hooks should also be installed, with the lower end of the chain hung on a nearby wall or pillar, so as not to obstruct passage. 2.6 For valves located in pipe trenches, if the valves can be operated after the trench cover is lifted, the valve handwheel should not be more than 300 mm below the trench cover. If it is below 300 mm, an extension rod for the valve should be used to keep the handwheel within 100 mm below the trench cover.     2.7 For valves installed in trenches that need to be operated from the ground surface, or for valves installed beneath an upper floor (platform), extension rods can be fitted to enable operation from above the trench cover, floor slab, or platform. The distance from the handwheel of the extension rod to the operating surface should preferably be 1200 mm. Valves with a nominal diameter of 40 DN or less and those connected by threads should not be operated using sprockets or extension rods to avoid damaging the valves. Generally, effort should be made to use sprockets or extension rods as little as possible to operate the valve.     2.8 The distance between the valve handwheels located around the platform and the edge of the platform should not exceed 450 mm. When the valve stem and handwheel extend above the platform and their height is less than 2000 mm, they should not interfere with the operator’s operations or movement to avoid potential injuries. 3. Requirements for the installation of large valves 3.1 The operation of large valves should utilize gear-driven mechanisms, and when installing them, consideration must be given to the space required by such mechanisms. Generally, for valves whose size is larger than those of the following grades, it is advisable to consider using valves with gear drives.     3.2 Large valves should be provided with supports on one or both sides of the valve; such supports should not be located on short pipes that need to be removed during maintenance, and it should be ensured that removing the valve does not affect the support of the pipeline. The distance between a general support and a valve flange should be greater than 300 mm.     3.3 The installation location of large valves should have space for using a crane, or consideration should be given to installing lifting columns or beams. 4. Requirements for the installation of valves on horizontal pipes
4.1 Unless otherwise specifically required by the process, the handwheels of valves installed on general horizontal pipes must not face downward. In particular, for valves on pipelines carrying hazardous media, it is strictly prohibited for the handwheels to face downward. The orientation of the valve handwheel is determined in the following order: vertically upward ； Level ； Vertically upward; left and right tilted at 45° ； 45° left and right tilt vertically downward ； It must not be directed vertically downward.     4.2 For horizontally installed stem valves, when the valve is open, the stem must not obstruct passage; this is especially important when the stem is located at the operator’s head or knees. 5. Other requirements for valve installation 5.1 For valves installed on pipes arranged in parallel, their centerlines should be aligned as much as possible; when valves are placed next to each other, the clear distance between their handwheels should not be less than 100 mm ； The valves can also be arranged offset from each other to reduce the pipe spacing.     5.2 Valves that are required to be connected to the equipment ports in terms of manufacturing processes shall be directly connected to those ports when their nominal diameter, nominal pressure, and seal face type are the same as or compatible with those of the equipment port flanges. When a concave flange is used on the valve, it is necessary to request the equipment specialists to install a convex flange at the corresponding pipe end.     5.3 Unless the process has special requirements, valves on the bottom pipes of equipment such as towers, reactors, and vertical vessels shall not be installed within the skirt.     5.4 When branching off a branch pipe from a main pipe, its shut-off valve shall be installed on the horizontal section of the branch pipe near the base of the main pipe, so that the fluid can be completely drained on both sides of the valve.     5.5 The branch isolation valves on the pipe gallery are not operated frequently (only used during shutdown maintenance); if no permanent ladder is available, space should be reserved for using a temporary ladder.     5.6 High-pressure valves require significant force to open; therefore, supports must be installed to hold the valve in place and reduce the starting stress. The optimal installation height is between 500 and 1200 mm.     5.7 Fire water valves, fire steam valves, etc. within the device area should be distributed throughout the area and located in safe locations that are easily accessible to operators in the event of an accident.     5.8 The valve assembly for the fire-extinguishing steam distribution pipe in the heating furnace should be easy to operate, and the distance between the distribution pipe and the furnace body should not be less than 7.5 m.     5.9 When installing threaded valves on pipelines, a union must be installed near the valve to facilitate disassembly.     5.10 Wafer valves or butterfly valves shall not be directly connected to the flanges of other valves and pipe fittings; a short pipe with flanges at both ends must be used as an intermediate connection.     5.11 Valves should not be subjected to external loads to avoid damage due to excessive stress.