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 reducing valves in petrochemical plants. The installation of check valves, safety valves, control valves, and steam traps shall comply with relevant regulations. This provision does 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 PID has specific requirements regarding the installation locations of certain valves, they shall be set according to 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 arranged centrally, with consideration given to providing an operating platform or ladder. 2. Requirements for the installation location of valves 2.1 Cutting valves must be installed at the points where the pipelines in the inlet and outlet ductwork connect to the main pipelines in the plant’s overall ductwork system. The valve installation locations should be concentrated on one side of the plant area, with necessary operation platforms or maintenance platforms provided.     2.2 Valves that require frequent operation, maintenance, and replacement should be located where they are easily accessible from the ground, platforms, or ladders. 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 from the center of the valve handwheel to the operating surface exceeds 1800 mm, sprocket operation is recommended. The distance from the sprocket to the ground should be approximately 800 mm. Additionally, a sprocket hook should be provided to attach the lower end of the chain to a nearby wall or column, so as not to impede passage through the area.
2.6 For valves installed in trenches, when the trench cover can be opened for operation, the handwheel of the valve must not be located more than 300 mm below the trench cover. If it is situated at a depth greater than 300 mm, an extension rod for the valve must be used so that the handwheel remains within 100 mm below the trench cover.     2.7 For valves installed in trenches that need to be operated from the ground level, or for valves installed beneath an upper floor (platform), extension rods can be fitted so that they extend above the trench cover, floor, or platform for operation. 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 from the edge of the platform to the valve handwheels located around it should not exceed 450 mm. When the valve stem and handwheel extend above the platform with a height of less than 2000 mm, they must not impede the operator’s movements or passage, so as to prevent any personal injury. 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 For large valves, supports should be provided on one or both sides of the valve. These supports must not be installed on short pipes that need to be removed during maintenance; it is also necessary to ensure that removing the valve does not affect the support of the pipeline. The distance between the general support and the 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 pipelines 4.1 Unless otherwise specified by the process requirements, the handwheels of valves installed on horizontal pipelines should not face downward; in particular, it is strictly prohibited for the handwheels of valves on pipelines carrying hazardous materials to face downward. The orientation of the valve handwheel is determined in the following order: vertically upward ； Horizontal ； 45° tilt left and right vertically upward ； 45° tilt left and right vertically downward ； It must not be directed vertically downward.     4.2 For horizontally mounted straight-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 parallel pipelines, their centerlines should be aligned as much as possible. When valves are arranged adjacent to each other, the minimum distance between their handwheels shall not be less than 100 mm ； Valves can also be arranged offset to reduce pipe spacing.     5.2 Valves that are required to be connected to the equipment ports in terms of process requirements shall be directly connected to those ports when their nominal diameter, nominal pressure, seal face type, etc., are the same as or compatible with those of the equipment port flanges. When the valve is equipped with a concave flange, 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 a branch pipe is led off from the main pipe, its isolation valve should be installed on the horizontal section of the branch pipe near the root of the main pipe, so that the fluid can flow out completely on both sides of the valve.     5.5 The branch cut-off 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 appropriate installation height is between 500 and 1200 mm.     5.7 Fire water valves, fire steam valves, etc., within the unit’s battery limit should be distributed in locations that are easily accessible to operators during emergencies.     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