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Principles and requirements for valve installation I. Introduction 1.1 The role and importance of valves in petrochemical plants Valves are a crucial component in petrochemical plants. It acts like a \"commander\" in a piping system, responsible for controlling fluid flow, regulating pressure, and protecting the equipment. By being opened and closed, valves can precisely control the start and stop of fluid flow, as well as its volume and direction, thereby enabling complex chemical production processes to proceed in an orderly manner. In terms of ensuring safety, valves can prevent dangerous situations such as fluid backflow and overpressure; in the event of any abnormalities, they can promptly shut off or release the flow, thereby protecting both equipment and personnel. For example, in high-pressure systems, safety valves can automatically release fluid that exceeds the set pressure, thereby preventing pipe rupture and equipment damage. Such examples highlight the crucial role of valves in preventing accidents. It can be said that valves are the cornerstone of the safe and efficient operation of petrochemical plants, and their performance directly affects the stability and reliability of the entire production system. 1.2 Characteristics of petrochemical plants and special requirements for valve installation Petrochemical plants are characterized by high temperatures, high pressures, flammability, explosiveness, as well as the presence of toxic and harmful substances; their production processes involve various complex chemical reactions and material transfers. This determines that it has special requirements for valve installation. Firstly, the valve must have good corrosion resistance as well as the ability to withstand high temperatures and pressures in order to function well under harsh operating conditions. Secondly, to ensure production safety, the sealing performance of valves must be reliable to prevent accidents caused by leaks. Furthermore, due to the complex network of pipes within the device, the valve installation locations must be convenient for operation and maintenance, while also meeting the requirements of the process flow to ensure smooth flow of fluids. The quality of valve installation is directly related to the stable operation and safe production of petrochemical plants; any negligence can lead to serious consequences. II. Principles for Valve Placement 2.1 Setting valves based on PID diagrams In petrochemical plants, the Piping and Instrumentation Diagram (PID diagram) serves as an important basis for determining where valves should be placed. The PID diagram shows in detail the layout of pipes within the plant, the flow of materials, the connections between equipment, as well as the installation of various instruments and control points. The type and quantity of valves must strictly comply with the requirements specified in the PID diagram; when the PID diagram sets specific requirements for the valve installation locations, these should be followed precisely in accordance with the process requirements. This ensures that the valve is installed in line with the entire process flow, allowing fluids to flow smoothly along the predetermined path, meeting the requirements of production operations and safety measures, and ensuring the stable and reliable operation of the equipment. 2.2 Layout principles for easy operation and maintenance: The layout of valves should take full account of the convenience of operation and maintenance. The valve should generally be placed in a location that is easily accessible, free from obstruction by equipment, pipes, or other obstacles, so that operators can reach it easily. Valves on rows of pipes should be arranged together, as this not only facilitates centralized operation but also allows for efficient use of space. An operating platform or ladder can be installed according to actual conditions, providing operators with a stable standing and working area. Ensure there is sufficient maintenance space around the valve, so that it can be easily disassembled, inspected, and repaired in case of failure, thereby reducing the difficulty and cost of maintenance. Furthermore, the design of the operating platform and ladder should comply with relevant safety standards, such as the installation of guardrails to prevent falls and ensuring the structure is sturdy enough to bear the weight of the operators, which further enhances operational safety. III. Requirements for Valve Installation Locations 3.1 Valves on the pipes in the inlet and outlet device ductwork: When the pipes in the ductwork of inlet and outlet devices are connected to the main pipes in the plant’s ductwork, cut-off valves must be installed. This is to ensure the safe operation of the equipment and facilitate maintenance; therefore, the valve installation locations should be concentrated on one side of the equipment area. Such a layout not only facilitates centralized management and operation by the operators, but also ensures that the pipelines can be quickly shut off or connected in emergency situations. Furthermore, it is necessary to establish appropriate operation platforms or maintenance platforms to provide a stable working surface for daily operations and maintenance, ensuring the safety of the operators. 3.2 Installation height of valves with different operating frequencies: For valves that need to be operated frequently, the height from the center of the handwheel to the operating surface should be between 750 and 1500 mm, with 1200 mm being the most suitable value; this ensures the operation is both effortless and convenient. Valves used only for starting and stopping, with an installation height of up to 1500–1800 mm. Valves that are not operated frequently, and which cannot be operated from the ground, should be installed in locations where temporary ladders can be set up. When the height of the valve handwheel exceeds 1800 mm, it is advisable to use sprockets for operation; the sprockets should be placed at a height of 800 mm above the ground, and hooks should be used to secure the chain so as not to impede passage. 3.3 Height and orientation requirements for handwheels: The height of the center of the valve handwheel above the operating surface should be between 750 and 1500 mm, with 1200 mm being the most suitable value to facilitate operation. The orientation of the handwheel is determined in sequences such as vertically upward and horizontally; vertical downward orientation is strictly prohibited. For valves on pipelines carrying hazardous media, the handwheel must not face downward to prevent the medium from spraying directly onto the operator in case of a leak. In all other cases, it is also necessary to ensure that the handwheel is positioned appropriately, making it easy to operate without interfering with surrounding equipment and passages. 3.4 Installation requirements for valves in trenches: For valves installed in trenches, if they can be operated by lifting the trench cover, the handwheel should be at a height of no less than 300 mm below the trench cover. When it is below 300 mm, a valve extension rod should be installed to keep the handwheel within 100 mm below the trench cover plate. Valves that need to be operated from the ground level or the floor above can also be equipped with an extension rod, so that the handwheel is 1200 mm away from the operating surface. Valves with threaded connections of DN40 and below should not be operated using sprockets or extension rods to prevent damage to the valves, and their use should be minimized as much as possible. 3.5 Distance requirements from the platform and channels: The distance between the valve handwheels located around the platform and the edge of the platform should not exceed 450 mm. This ensures that operators can easily operate the valves while standing on the platform, while also preventing operational difficulties or collisions caused by being too close. When the valve stem and handwheel extend above the platform and their height is less than 2000 mm, it is necessary to ensure that they do not interfere with the operator’s operations or movement, in order to prevent personal injury. IV. Requirements for the Installation of Large-Size Valves 4.1 Installation with Gear Drives Due to their large size and high operating torque, large-size valves require the use of gear drives. This reduces the difficulty of operation and makes the valve open and close more smoothly. When making the settings, consideration should be given to the spatial location of the transmission mechanism, to ensure that there is sufficient space for installation and operation, without interference from other equipment or pipes. It should also facilitate daily maintenance and repair, so as to ensure the stable operation of the transmission mechanism and its ability to assist in operating the valve. 4.2 Installation of supports: Large valves have a significant weight, and opening and closing them generates considerable stress. To ensure the stable operation of the valves and the safety of the piping system, it is necessary to install supports. The support location should be appropriate; it must not be placed on short pipes that need to be removed during maintenance, to ensure that removing the valve does not affect the pipe support. Generally, the distance between the support and the valve flange should be greater than 300 mm to provide sufficient space for valve maintenance and pipeline inspection. 4.3 Requirements for lifting equipment: The installation site of large valves should have space for cranes to facilitate lifting operations. If space is limited, consideration should be given to installing suspension columns and beams. The suspension columns and beams must be firmly and reliably installed, capable of bearing the weight of the valves, to ensure that the valves remain stable during lifting, safeguard the safety of the installers, improve installation efficiency, and enable large valves to be accurately installed in their designated positions. V. Requirements for the installation of valves on horizontal pipes 5.1 Orientation of the handwheel When installing valves on horizontal pipes, the handwheel should not face downward, to prevent the medium from accumulating at the bottom of the valve stem due to gravity when the valve is opened or closed, which could lead to difficulties in operating the valve or damage to the sealing surfaces. The sequence for determining the orientation of the handwheel is as follows: first, vertically upward; second, horizontally; then, 45° tilts to the left or right in a vertical direction; and finally, 45° tilts to the left or right in a downward vertical direction. This ensures that the valve can be operated easily and safely. 5.2 Avoid installing visible stem valves in a way that affects traffic and operation; when these valves are opened, the stem extends outward, and improper placement can easily hinder traffic and operations. To avoid this situation, the valve should be installed in such a way that its stem does not extend into walkways or equipment operation areas once it is opened. By properly planning the pipeline layout, valves can be installed at the edges of passages or in locations that do not interfere with pedestrian movement. Rotating valves can also be used in place of straight-stem valves to reduce space consumption and ensure safe passage and operation. VI. Other requirements for valve installation 6.1 Valve arrangement in parallel pipes: For valves installed on pipes that are arranged in parallel, their centerlines should be aligned as much as possible, which not only improves the aesthetic appearance but also facilitates operation. The clear distance between valve handwheels should not be less than 100 mm to ensure that they do not interfere with each other during operation. To reduce the spacing between pipes, valves can be arranged offset from each other; this approach is particularly useful in situations with limited space, as it helps to improve space utilization and results in a more compact and efficient pipe layout. For example, in the piping design of a chemical plant, by arranging valves at staggered positions, the issue of limited space was resolved while still ensuring ease of operation. Specifically, a row of valves is arranged alternately so that each valve’s handwheel has sufficient operating space in the horizontal direction, without affecting the operation of adjacent valves. This layout not only optimizes the distance between the pipes but also improves the efficiency of maintenance and repairs in practical operations. 6.2 Connection valves to equipment ports When connecting valves to equipment ports, the flange type must match, such as concave flanges to convex flanges, to ensure reliable sealing. Ensure good sealing performance to prevent leaks. Pay attention to the details during installation: verify the specifications and models of the valves, check that all components are in good condition and operate smoothly, ensure that the sealing surfaces are undamaged, and conduct pressure tests as specified to guarantee firm connections that meet the process and safety requirements. 6.3 Placement of valves at the bottom of special equipment: Valves on the pipelines at the bottom of equipment such as towers, reactors, and vertical vessels should generally not be installed within the skirt. If installation is required, it must be ensured that the structural strength of the equipment foundation and skirt is not compromised, and that operation and maintenance are facilitated. The properties of the medium should be taken into account to prevent impurity deposition from damaging the valve sealing surfaces; where necessary, a filter should be installed at the front end of the valve to ensure its proper operation and the safe production of the equipment. 6.4 Installation of branch cut-off valves: When a branch is led off from the main pipe, the cut-off valve should be installed on the horizontal section of the branch near the root of the main pipe. Such a setup facilitates the complete drainage of fluid from both sides of the valve, ensuring that fluid can be effectively cut off during maintenance or replacement of branch piping equipment, preventing leaks of the medium and allowing other parts of the main pipeline to function properly. This enhances the safety and maintainability of the piping system. 6.5 Operation of the branch pipe isolation valve in the ductwork: If the branch pipe isolation valve located in the ductwork is not used frequently (only during shutdowns for maintenance) and no permanent ladder is available, space should be reserved for using a temporary ladder. Ensure that temporary ladders can be easily set up when necessary, allowing personnel to reach the valve location safely for operations, without disrupting the normal operation of the surrounding pipes and equipment. 6.6 Installation requirements for high-pressure valves: High-pressure valves require significant force to open; therefore, an installation height of 500–1200 mm is appropriate, as it facilitates operation and reduces safety risks. Supports must be installed to hold the valve in place and reduce startup stress. These supports need to be sturdy and reliable, capable of withstanding the weight of the valve as well as the forces generated during operation, thereby ensuring the stable functioning of the valve and preventing damage to the valve or issues with the piping system due to vibration or excessive stress. When selecting the material for brackets, factors such as the material’s strength, corrosion resistance, and suitability for the working environment should be taken into account. Common materials like carbon steel and stainless steel are used to ensure the long-term durability and safety of the brackets. 6.7 The fire water valves and fire steam valves located in the areas designated for fire-related valve installations should be arranged dispersedly, so as to ensure that they are in safe locations easily accessible to operators in the event of an accident. The valve assembly for the steam distribution system used to extinguish fires in heating furnaces should be easy to operate. The distance between the distribution pipes and the furnace body should not be less than 7.5 meters; this ensures both an effective fire-extinguishing effect and protection of the valves from damage caused by the fire, thereby enabling the fire suppression system to function quickly and effectively in emergency situations. 6.8 Threaded Connection Valves: When installing threaded connection valves on pipelines, a union fitting must be installed in the vicinity. This is to facilitate the disassembly and maintenance of the valve; when the valve malfunctions or needs to be replaced, it can be easily removed using a swivel joint, without the need to take down the entire pipeline. This significantly reduces the difficulty and cost of maintenance, thereby improving the maintainability of the piping system. VII. Conclusion and Summary of Valve Installation Principles and Requirements This article details the principles for arranging valves in petrochemical plants, the requirements regarding their installation locations, the requirements for large-scale valves, the requirements for installing valves on horizontal pipelines, as well as other relevant requirements. Valve installation must be carried out in accordance with the PID diagram to ensure ease of operation and maintenance. Special considerations should be given to special equipment and pipe racks, attention should be paid to the position and height of handwheels, and proper support structures and lifting equipment should be installed. These principles and requirements are key to ensuring the safe and efficient operation of petrochemical plants, and must be strictly adhered to.