A detailed introduction to ball valves in industry

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A ball valve, as defined in GB/T21465-2008 \"Terms for Valves\", is a valve in which the closing element (the ball) is driven by a valve stem and rotates around the axis of the valve stem. It is mainly used to shut off or open the medium in pipelines, and can also be employed for the regulation and control of fluid flow. In the case of hard-sealed V-ball valves, the strong shear force exists between the V-shaped ball core and the metal seat coated with cemented carbide, making them particularly suitable for media containing fibers, tiny solid particles, and similar substances. The multi-port ball valve allows for flexible control of the merging, splitting, and direction change of the fluid flow in the pipeline; it can also close any one channel, thereby connecting the other two channels together. Valves of this type should generally be installed horizontally in pipelines. Definition The ball valve was introduced in the 1950s. With the rapid advancement of science and technology, as well as continuous improvements in manufacturing processes and product design, it has rapidly developed into a major type of valve within just 40 years. In the industrially developed countries of the West, the use of ball valves is increasing year by year. In China, ball valves are widely used in industries such as oil refining, long-distance pipelines, chemicals, papermaking, pharmaceuticals, water management, power generation, municipal services, and steel manufacturing; they play a crucial role in the national economy. Edit this section: Working principle. A ball valve operates by rotating 90 degrees; its plug is in the form of a sphere, with a circular opening or passage running through its axis. Ball valves are primarily used in pipelines to shut off flow, distribute it, and change the direction of the fluid flow; they can be closed tightly with just a 90-degree rotation and a very small amount of torque. Ball valves are most suitable for use as on/off and shut-off valves, but recent developments have designed ball valves to also serve the purpose of throttling and controlling flow, such as V-ball valves. Main features of this version The main advantages of ball valves are their compact structure, reliable sealing, simple design, and ease of maintenance. The sealing surface and the ball itself remain in a closed state, making them resistant to erosion by the medium flowing through them. They are easy to operate and maintain. Ball valves are suitable for use with various common working media such as water, solvents, acids, and natural gas; they are also appropriate for use with media under harsh conditions, such as oxygen, hydrogen peroxide, methane, and ethylene. They are widely used in various industries. The ball valve body can be integral or modular. Advantages of this version 　　1. Low fluid resistance – ball valves with a full bore have virtually no flow resistance. 　　2. Simple structure, small size, and light weight. 　　3. Tight and reliable. It has two sealing surfaces, and currently, various plastics are widely used as materials for the sealing surfaces of ball valves; these materials provide good sealing performance and enable complete sealing. It is also widely used in vacuum systems. 　　4. It is easy to operate and opens/closes quickly; only 90° of rotation is required to go from full open to full closed, facilitating remote control. 　　5. It is easy to maintain; the ball valve has a simple structure, and the sealing rings are usually movable, making disassembly and replacement straightforward. 　　6. When fully open or fully closed, the sealing surfaces of the ball and the valve seat are isolated from the medium; thus, as the medium passes through, it does not cause erosion of the valve’s sealing surfaces. 　　7. It has a wide range of applications, with diameters ranging from a few millimeters to several meters, and it can be used in conditions ranging from high vacuum to high pressure. 　　8. Due to the wiping action of ball valves during opening and closing, they can be used in media containing suspended solid particles. When installing and maintaining ball valves, the following points should be taken into consideration: floating ball valves, fixed ball valves, elastic ball valves, and oil-sealed ball valves ； Based on the channel configuration, ball valves can be classified into straight-through ball valves, angle ball valves, and three-way ball valves; the latter can further be divided into T-type ball valves and L-type ball valves. Based on the method of connection, ball valves can be divided into three types: threaded ball valves, flanged ball valves, and welded ball valves. The following points should be noted for the installation and maintenance of ball valves: 1. Space must be left for the valve handle to rotate. 2. It cannot be used for throttling. 3. Ball valves equipped with a belt drive mechanism should be installed vertically. Nominal pressure or pressure class: PN1.0–32.0 MPa, ANSI CLASS 150–900, JIS10–20K. Nominal diameter: DN6–900, NPS 1/4–36. Connection methods: flange, butt welding, threading, socket welding, etc. Operating temperature range: -196°C–540°C. Actuation methods: manual, worm gear drive, pneumatic, electric, hydraulic, pneumatic-hydraulic, electro-hydraulic. Valve body materials: WCB, ZG1Cr18Ni9Ti, ZG1Cr18Ni12Mo2Ti, CF8 (304), CF3 (304L), CF8M (316), CF3M (316L), Ti. Classification and Characteristics Ball valves are categorized into: floating ball valves, fixed ball valves, track ball valves, V-ball valves, three-way ball valves, stainless steel ball valves, forged steel ball valves, ash discharge ball valves, sulfur-resistant ball valves, pneumatic ball valves, electric ball valves, socket ball valves, and welded ball valves. 　　Classified by the material of the housing/main body, ball valves can be divided into: 1. Metal material valves: such as carbon steel valves, alloy steel valves, stainless steel valves, cast iron valves, titanium alloy valves, Monel valves, copper alloy valves, aluminum alloy valves, lead alloy valves, etc. 　　2. Valves with metal bodies lined with other materials: such as rubber-lined valves, fluorine-lined valves, lead-lined valves, plastic-lined valves, and enamel-lined valves. 　　3. Non-metallic material valves: such as ceramic valves, glass valves, plastic valves. 　　There are many manufacturers of ball valves in China, and their connection dimensions are mostly not standardized. It is mainly divided into the following categories: (1) General categories based on JB/T2203–1999 \"Structural Length of Ball Valves\". At present, most ball valve manufacturers in China design and produce products in accordance with this standard. Hai’an Valve Factory, etc. However, this standard is not perfect either; its specifications are incomplete. The maximum nominal diameter for floating ball valves is DN1200, while that for fixed ball valves is DN2000. Based on the specifications of the valves produced by the factory and the available information, the minimum nominal diameter for floating ball valves is currently DN6, while the minimum nominal diameter for fixed ball valves is DN50. Upon verification, the connection dimensions provided by different manufacturers are not consistent. To establish a unified standard that allows components of the same specification to be interchanged during selection and installation, it is recommended that the **General Machinery Research Institute revise JB/T2203‑1999 \"Structural Length of Ball Valves\". It is recommended that design institutes and users select products in accordance with the standards, while ball valve manufacturers should design them for suitable applications. Since rubber, nylon, and polytetrafluoroethylene are commonly used as materials for the seat seals in ball valves, their operating temperature is limited by the properties of these seal materials. The shut-off function of a ball valve is achieved by the metal ball pressing against the plastic seat under the influence of the medium (in the case of a floating ball valve). Under a certain contact pressure, the valve seat seal ring undergoes elastoplastic deformation in localized areas. This deformation can compensate for the manufacturing accuracy and surface roughness of the sphere, ensuring the sealing performance of the ball valve. 　　Furthermore, since the seat seals of ball valves are usually made of plastic, when selecting the structure and performance of ball valves, their fire resistance and flame retardancy must be taken into account. This is especially important in industries such as petroleum, chemicals, and metallurgy, where ball valves are used in equipment and piping systems handling flammable and explosive substances. 　　Generally, ball valves are recommended for pipeline systems that require two-position control, high sealing performance, resistance to mud and wear, operation in converging channels, rapid opening and closing (1/4 turn), high-pressure shut-off (large pressure difference), low noise, presence of cavitation and vaporization phenomena, slight leakage to the atmosphere, low operating torque, and low fluid resistance. 　　Ball valves are also suitable for pipeline systems with light structures, low-pressure shut-off (small pressure difference), and corrosive media. Ball valves can also be used in low-temperature (cryogenic) equipment and piping systems. In the oxygen pipeline systems of the metallurgical industry, ball valves that have undergone strict degreasing are required. When the main pipelines in oil and gas transmission lines need to be buried underground, full-bore welded ball valves must be used. When regulatory performance is required, ball valves with a special structure featuring V-shaped openings should be selected. In the petroleum, petrochemical, chemical, power, and urban construction industries, ball valves with metal-to-metal sealing can be used for pipeline systems where the operating temperature is above 200 degrees Celsius. Installation 1) Remove the protective covers on both sides of the flange end, and clean it by flushing while the valve is fully open. 　　2) Before installation, the entire unit should be tested using the specified signals (electrical or pneumatic) (to prevent vibrations caused by transportation from affecting its performance); it can only be installed after passing the test (wiring shall be carried out in accordance with the circuit diagram of the electric actuator). 　　3) Before preparing for connection to the pipeline, it is necessary to flush and remove any remaining impurities from the pipeline (such substances may damage the valve seat and ball). 　　4) During installation, do not use the actuator part of the valve as a lifting point to avoid damaging the actuator and its accessories. 　　5) Valves of this type should be installed horizontally or vertically in the pipeline. 　　6) The pipes near the installation point must not sag or be subjected to external forces; pipe supports or braces can be used to eliminate any deviation in the piping. 　　7) After connecting to the pipeline, cross-lock the flange connection bolts using the specified torque. Operation and Use 1) Before operation, ensure that the pipelines and valves have been flushed. 　　2) The operation of the valve is accomplished by the actuator using the input signal to rotate the valve stem; when it rotates 1/4 turn (90°) in the forward direction, the valve closes. The valve opens when rotated 1/4 turn (90°) in the reverse direction. 　　3) When the actuator’s direction indicator arrow is parallel to the pipeline, the valve is in the open position ； When the indicator arrow is perpendicular to the pipeline, the valve is in the closed position. Maintenance: A long service life and maintenance-free period depend on several factors, including normal operating conditions, a proper temperature/pressure ratio, and accurate data regarding corrosion.
Note:
● Even when the ball valve is closed, there is still pressurized fluid inside the valve body.
● Before carrying out maintenance, relieve the pressure in the pipeline and ensure the valve is in the open position.
● Disconnect the power or gas supply before maintenance.
● Separate the actuator from its support before maintenance.
● It is necessary to confirm that the pressure has been released from both the upstream and downstream pipes of the ball valve before proceeding with disassembly.
● Be careful to avoid damaging the sealing surfaces of the parts, especially those made of non-metallic materials, during disassembly and reassembly; use special tools when removing O-rings.
● When assembling, tighten the bolts on the flanges symmetrically, gradually, and evenly.
● The cleaning agent must be compatible with the rubber, plastic, metal components in the ball valve, as well as the working medium (such as gas). When the working medium is gas, gasoline (GB484-89) can be used to clean metal parts. Non-metallic parts should be cleaned with pure water or alcohol. ● The individual parts that have been separated can be cleaned by immersion. Metal parts that still contain unbroken non-metallic components can be scrubbed using a clean, fine silk cloth soaked in cleaning solution (to prevent fibers from falling off and sticking to the parts). During cleaning, all grease, dirt, residue, dust, and other substances adhering to the wall surfaces must be removed. ● Non-metallic parts should be taken out of the cleaning solution immediately after cleaning; they should not be left in it for an extended period. ● After cleaning, assembly can take place once the cleaning solution on the surface has evaporated (this can be done by wiping with a silk cloth that hasn’t been dipped in the cleaning solution), but the parts should not be left untreated for long, as this could lead to rusting or contamination by dust. ● New parts also need to be cleaned thoroughly before assembly. ● Lubricate with grease. The grease should be compatible with the ball valve’s metal materials, rubber components, plastic components, as well as the working medium. When the working medium is gas, a lubricating grease such as Te221 can be used. Apply a thin layer of grease to the surface of the seal mounting groove, as well as to the rubber seal. Apply a thin layer of grease to the sealing surfaces and friction surfaces of the valve stem. ● During assembly, it is not allowed for metal shavings, fibers, grease (other than those specified for use), dust, and other impurities or foreign objects to contaminate, adhere to, or remain on the surfaces of the parts or to enter their internal cavities. 1) The packing area must be tightened again. If there is slight leakage at the packing area, the valve stem nut must be tightened again. 　　Note: Do not tighten it too much; usually turning it another 1/4 turn to 1 full turn will stop the leakage. 2) Replace the valve seat and seals A) Disassembly Place the valve in a semi-open position, and flush to remove any hazardous substances that may be present inside or outside the valve body. 　　Close the ball valve, remove the connection bolts and nuts from both flanges, and then completely remove the valve from the pipeline. 　　Remove the drive device-actuator, connection bracket, lock washer, valve stem nut, butterfly spring, gland, wear plate, and valve stem packing in sequence. 　　Remove the body cover connection bolts and nuts, separate the valve cover from the valve body, and take off the valve cover gasket. 　　Ensure that the valve ball is in the “closed” position, which makes it easier to remove it from the valve body, after which the valve seat can be taken out. 　　Gently push the valve stem downward through the hole in the valve body until it is completely removed, then take out the O-ring and the packing at the bottom of the valve stem. 　　Note: Please proceed with caution to avoid scratching the surface of the valve stem and the sealing areas of the valve body packing box. 　　B) Reassembly Clean and inspect the removed parts; it is highly recommended to replace seals such as the valve seat and valve cover gaskets with those from a spare parts kit. 　　Assemble in the reverse order of disassembly. 　　Lock the flange connection bolts crosswise using the specified torque. 　　Lock the valve stem nut using the specified torque. 　　After installing the actuator, by sending the appropriate signal, the valve stem rotates, which in turn causes the valve core to rotate and moves the valve to the open or closed position. 　　If possible, please conduct pressure sealing tests and performance tests on the valve in accordance with relevant standards before reinstalling it in the pipeline