Principle and classification of ball valves

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:D Ball Valve English name: ball valve Evolution and working principle of ball valves Ball valves evolved from plug valves. It has the same 90-degree rotation lift action; the difference is that the plug body is spherical, with a circular hole or passage running through its axis. The ratio between the sphere and the opening should be such that when the sphere rotates 90 degrees, the entire area at the inlet and outlet should be covered by the sphere, thereby blocking the flow. 　　A ball valve can be closed tightly with just a 90-degree rotation and a very small torque. The completely equal internal cavity of the valve provides a flow path with very low resistance and direct passage for the medium. It is generally believed that ball valves are most suitable for direct on-off operation, but recent developments have designed them to also serve the purpose of throttling and controlling flow rates. The main advantages of ball valves are their compact structure, ease of operation and maintenance. They are suitable for use with common working media such as water, solvents, acids, and natural gas, as well as for media under harsh working conditions, such as oxygen, hydrogen peroxide, methane, and ethylene. The ball valve body can be integral or modular. 　　The working principle and practical role of ball valves The working principle of ball valves is to allow the valve to stay open or closed by rotating the valve stem. Ball valves are easy to operate, compact in size, and can be manufactured in large diameters. They offer reliable sealing, a simple structure, and are easy to maintain. The sealing surface and the ball itself remain in a closed state, making them resistant to erosion by the medium flowing through them; as a result, they are widely used in various industries. 　　Ball valves and plug valves belong to the same type of valve; the only difference is that their closing element is a sphere, which rotates around the axis of the valve body to enable opening and closing. 　　Ball valves are primarily used in pipelines to cut off flow, distribute it, and change the direction of the fluid flow. Ball valves are a new type of valve that has been widely used in recent years. They possess the following advantages: 1. Low fluid resistance, with a resistance coefficient equal to that of a pipe section of the same length. 　　2. Simple structure, small size, and light weight. 　　3. Tight and reliable; currently, plastic is widely used as the material for the sealing surfaces of ball valves, providing good sealing performance, and it is also extensively utilized in vacuum systems. 　　4. It is easy to operate and opens/closes quickly; only 90° of rotation is required to go from fully open to fully 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 it convenient to remove and replace them. 　　6. When fully open or fully closed, the sealing surfaces of the ball and the valve seat are separated 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. 　　Ball valves are widely used in various industries such as petroleum, chemicals, power generation, papermaking, nuclear energy, aviation, and rockets, as well as in people’s daily lives. 　　Ball valves can be classified according to their structural design as follows: 1. Floating ball ball valve. In this type of ball valve, the ball is floating; under the pressure of the medium, the ball can move slightly and press against the sealing surface at the outlet end, thereby ensuring proper sealing at that outlet. 　　The floating ball valve has a simple structure and good sealing performance, but the load from the working medium acting on the ball is transmitted entirely to the outlet seal; therefore, it is necessary to consider whether the material of the seal can withstand the working load exerted by the medium. This structure is widely used in medium and low pressure ball valves. 　　II. Fixed ball valve: The ball of this valve is fixed and does not move under pressure. Fixed ball valves are equipped with floating valve seats; under the pressure of the medium, these seats move, causing the sealing ring to press tightly against the ball in order to ensure a secure seal. Bearings are usually installed on the upper and lower axes of the sphere, resulting in low operating torque; it is suitable for high-pressure and large-diameter valves. 　　To reduce the operating torque of ball valves and improve the reliability of sealing, oil-sealed ball valves have emerged in recent years. These valves inject a special lubricant between the sealing surfaces to create an oil film, which not only enhances the sealing performance but also reduces the operating torque; they are thus more suitable for high-pressure, large-diameter ball valves. 　　III. Elastic ball valve – The ball of this valve is elastic. Both the sphere and the valve seat seal ring are made of metallic materials, resulting in a very high sealing pressure. The pressure of the medium itself is not sufficient to achieve proper sealing, so an external force must be applied. This type of valve is suitable for high-temperature and high-pressure media. 　　An elastic sphere obtains its elasticity by having an elastic groove at the lower end of its inner wall. When the channel is closed, the wedge-shaped end of the valve stem is used to expand the ball and press it against the valve seat to achieve sealing. Before rotating the sphere, release the wedge head; the sphere then returns to its original shape, creating a small gap between the sphere and the valve seat, which reduces friction on the sealing surfaces as well as the operating torque. 　　Ball valves can be classified into straight-through, three-way, and right-angle types according to the position of their passages. The latter two types of ball valves are used to distribute the medium and change its flow direction. 　　　　Ball Valve Instructions 1. Scope: These instructions apply to electric (or pneumatic) ball valves with flange connections. 　　2. Composition: It consists of an electric (or pneumatic) actuator (20) and the ball valve body, which are connected through a bracket (18) and a connecting shaft (17). 　　3. Usage Restrictions – Temperature and Pressure Limits: The nameplate indicates the maximum operating pressure allowed for the ball valve at its maximum and minimum operating temperatures. 　　Use valve seats and seals made of PTFE or RTFE; the operating temperature should be between –290°C and 2000°C. The operating temperatures for other types of valve seats and seals shall be verified by the KI factory. 　　The nominal pressure class (PN) of the valve indicates the maximum operating pressure under normal temperature conditions. (For example: PN4.0 indicates that the maximum operating pressure at operating temperatures ranging from –290°C to 380°C is 40 Bar (4.0 MPa)). 　　For precautions regarding electric or pneumatic actuators, please refer to their respective manuals. 　　4. 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 wiring 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 pipelines. 　　7) After connecting to the pipeline, tighten the flange connection bolts crosswise using the specified torque. 　　4. 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 degrees) in the forward direction, the valve closes. The valve opens when rotated 1/4 turn (900) in the reverse direction. 　　3) When the direction indicator arrow of the actuator 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. 　　5. Maintenance A longer service life and maintenance-free period depend on the following factors: normal operating conditions, maintaining an appropriate 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 performing maintenance, relieve the pressure in the pipeline and ensure the valve is in the open position. ● Before maintenance, disconnect the power or gas supply. ● Before maintenance, separate the actuator from its support. 1) Re-tightening the packing l If there is slight leakage at the packing area, it is necessary to re-tighten the valve stem nut (13). l Be careful not to tighten it too much; usually, tightening it by 1/4 turn to 1 full turn will stop the leakage. 　　2) Replace the valve seat and seals. A) Disassembly l 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. l Close the ball valve, remove the connection bolts and nuts from both flanges, and then completely remove the valve from the pipeline. 　　l Remove the drive device-actuator (20), connection bracket (18), anti-loosening washer (14), valve stem nut (13), butterfly spring (12), gland (11), wear-resistant plate (10), and valve stem packing in sequence.
l Remove the body cover connection bolts (5) and nuts to separate the valve cover from the valve body, and take out the valve cover washer (16). 　　Ensure that the valve ball (3) is in the “closed” position, which makes it easier to remove it from the valve body, followed by removing the valve seat. 　　l Gently push the valve stem (6) downward through the hole in the valve body until it is completely removed, then take out the O-ring (8) and the packing below the valve stem (7). Note: Please proceed with care to avoid scratching the surface of the valve stem or the sealing areas in the valve body’s packing box. B) Reassembly l Clean and inspect the parts that have been removed; it is highly recommended to replace seals such as the valve seat and valve cover gaskets with those from a spare parts kit. l Assemble the components in the reverse order of disassembly. 　　Use the specified torque to cross-lock the flange connection bolts (5). 　　l Tighten the valve stem nut (13) using the specified torque. l After installing the actuator, send the appropriate signal to rotate the valve stem, thereby causing the valve disc to rotate and bringing the valve to the open or closed position. 　　l If possible, please conduct pressure sealing tests and performance tests on the valve in accordance with relevant standards before reinstalling it in the pipeline. 　　Model designation method: In valves like the previous Q11S-16C, the “S” denotes an older method, where it indicates a plastic seal; nowadays, “F” is used to indicate materials such as PTFE or polytetrafluoroethylene. Classification and characteristics of ball valves: Ball valves are divided into O-type ball valves and V-type ball valves. The O-type ball valve features a floating structure; its ball core is made of precision-cast material and coated with hard chromium on its surface. The valve seat is constructed from reinforced polytetrafluoroethylene. The flow passage has the same diameter as the pipeline, resulting in high flow capacity and very low flow resistance. There is no leakage when the valve is closed. It is generally used as a on/off valve and is particularly suitable for media with high viscosity, as well as those containing fibers or particles ； The V-type ball valve features a fixed structure, with a V-shaped cut on the ball core, enabling proportional control; its flow characteristic is approximately equal percentage. 　　Depending on the process equipment, pneumatic or electric actuators can be used to create pneumatic ball valves and electric ball valves respectively. For pneumatic ball valves, a valve positioner is required in order to achieve proportional control, while for electric ball valves, an electronic electric actuator or a servo amplifier is needed to achieve proportional control. 　　In terms of material, they can be classified into: carbon steel ball valves, stainless steel 304 ball valves, 316 ball valves, and copper ball valves. In terms of application, they can be divided into high-pressure ball valves and low-pressure ball valves. High-pressure ball valves are mainly used in industries such as petroleum, natural gas, hydraulic oil, and construction machinery. Low-pressure ball valves are primarily used in pipelines where the medium is water or other substances that are corrosive