Why are the valves designed this way?

This regulation applies 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, regulating valves, and steam traps are governed by relevant regulations. This regulation does not apply to the installation of valves on underground water supply and drainage pipelines.

1.Valve Layout Principles

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

1.2 Valves should be located in easily accessible, convenient locations for operation and maintenance. Valves on rows of pipelines should be centrally located, and consideration should be given to providing operating platforms or ladders.

2.Valve Installation Location Requirements

2.1 When pipelines entering or leaving the plant connect to the main pipes on the plant's pipeline corridor, shut-off valves must be installed. Valves should be centrally located on one side of the plant area, and necessary operating or maintenance platforms should be provided. 2.2 Valves requiring frequent operation, maintenance, and replacement should be located in easily accessible locations on the ground, platforms, or ladders. Pneumatic and electric valves should also be placed in easily accessible locations.

2.3 Valves that are not frequently operated (used only during start-up and shutdown) should be placed in locations where temporary ladders can be erected if they cannot be operated from the ground.

2.4 The center of the valve handwheel should be between 750 and 1500 mm from the operating surface, with an optimal height of 1200 mm. Valves that are not frequently operated can be installed at heights of 1500 to 1800 mm. When the installation height cannot be lowered but frequent operation is required, an operating platform or steps should be provided in the design. Valves on pipelines and equipment carrying hazardous media must not be installed within head height. 2.5 When the center of the valve handwheel is more than 1800mm above the operating surface, a sprocket should be used for operation. The sprocket chain should be approximately 800mm from the ground, and a sprocket hook should be provided to hang the lower end of the chain on a nearby wall or pillar to avoid obstructing passage.

2.6 For valves installed in pipe trenches, when the trench cover is open for operation, the valve handwheel should not be lower than 300mm below the trench cover. If it is lower than 300mm, a valve extension rod should be provided to keep the handwheel within 100mm of the trench cover.

2.7 For valves installed in pipe trenches that need to be operated from the ground, or valves installed below the floor level (platform), a valve extension rod can be provided to extend the operation to the trench cover, floor, or platform. The handwheel of the extension rod should ideally be 1200mm from the operating surface. Valves with a nominal diameter less than or equal to DN40 and threaded connections should not be operated using sprockets or extension rods to avoid damaging the valve. Under normal circumstances, the use of sprockets or extension rods to operate valves should be minimized.

2.8 The distance between the valve handwheel and the edge of the platform should not exceed 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 obstruct the operation and passage of personnel to avoid personal injury.

3.Requirements for the Installation of Large Valves

3.1 Large valves should be operated using geared transmission mechanisms. The space required for the transmission mechanism should be considered during installation. Generally, valves larger than the following sizes should be considered for the use of valves with geared transmission mechanisms.

3.2 Large valves should have supports installed on one or both sides of the valve. These supports should not be installed on short pipes that need to be disassembled for maintenance, and the removal of the valve should not affect the support of the pipeline. Generally, the distance between the support and the valve flange should be greater than 300mm.

3.3 The installation location of large valves should have space for crane use, or consider the installation of lifting columns or beams. 4. Valve Installation Requirements on Horizontal Pipelines

4.1 Unless otherwise specified by the process, valve handwheels installed on horizontal pipelines must not face downwards, especially those on pipelines carrying hazardous media. The handwheel orientation should be determined in the following order: vertically upwards; horizontal; vertically upwards with a 45° left or right tilt; vertically downwards with a 45° left or right tilt; never vertically downwards.

4.2 For horizontally installed rising stem valves, the valve stem must not obstruct passage when the valve is open, especially when the valve stem is located at the operator's head or knees.

5.Other Valve Installation Requirements

5.1 Valves on parallel pipelines should have their centerlines aligned as much as possible. When valves are arranged adjacently, the clear distance between handwheels should not be less than 100mm; valves can also be staggered to reduce pipeline spacing. 5.2 Valves that are required by the process to connect to equipment ports should be directly connected to the equipment ports if their nominal diameter, nominal pressure, and sealing surface type are the same as or compatible with the equipment port flanges. When the valve has a concave flange, the equipment specialist should be consulted to install a convex flange at the corresponding port.

5.3 Unless otherwise specified by the process, valves on the bottom pipes of equipment such as towers, reactors, and vertical vessels must not be located within the skirt support.

5.4 When a branch pipe is drawn from the main pipe, its shut-off valve should be located on the horizontal section of the branch pipe near the root of the main pipe to allow fluid to drain completely to both sides of the valve.

5.5 Branch pipe shut-off valves on pipe racks are not frequently operated (only used during shutdown maintenance). If no permanent ladder is provided, space should be reserved for the use of a temporary ladder.

5.6 High-pressure valves require significant starting force when opened and must be supported by brackets to reduce starting stress. The installation height should ideally be 500–1200 mm. 5.7 Fire water valves and fire steam valves within the plant boundary should be distributed in a safe area easily accessible to operators in the event of an accident.

5.8 The valve assemblies of the extinguishing steam distribution pipes for the heating furnace should be easy to operate, and the distribution pipes should be no less than 7.5m from the furnace body.

5.9 When threaded valves are installed on pipelines, union fittings must be installed near the valves for easy disassembly.

5.10 Wafer valves or butterfly valves must not be directly connected to the flanges of other valves and fittings; a short pipe with flanges at both ends should be added in between.

5.11 Valves should not be subjected to external loads to avoid excessive stress that could damage them.