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Various types of valves: Butterfly valves. The butterfly plate of a butterfly valve is installed in the diameter direction of the pipeline. Within the cylindrical passage of the butterfly valve body, the disc-shaped butterfly plate rotates around its axis by an angle ranging from 0° to 90°; when it reaches 90°, the valve is in its fully open position. Butterfly valves have a simple structure, are small in size and light in weight, consisting of only a few components. Moreover, it can be quickly opened and closed by just a 90° rotation, making it easy to operate; at the same time, this valve boasts excellent fluid control properties. When the butterfly valve is in the fully open position, the thickness of the butterfly disc is the only resistance to the flow of the medium through the valve body; as a result, the pressure drop across this valve is very small, giving it excellent flow control properties. Butterfly valves come in two types of sealing: elastic sealing and metallic sealing. Elastic-sealing valves, where the sealing ring can be embedded in the valve body or attached around the butterfly disc. Valves with metal seals generally have a longer lifespan than those with elastic seals, but it is difficult to achieve complete sealing. Metal seals can withstand higher operating temperatures, while elastic seals have the drawback of being limited by temperature. If a butterfly valve is to be used for flow control, the key is to correctly select its size and type. The structural principle of butterfly valves makes them particularly suitable for manufacturing large-diameter valves. Butterfly valves are widely used not only in general industries such as petroleum, gas, chemicals, and water treatment, but also in the cooling water systems of thermal power plants. The commonly used butterfly valves are wafer-type butterfly valves and flanged butterfly valves. A wafer-type butterfly valve is connected between two pipe flanges using bolts, while a flanged butterfly valve has flanges on it, with the flanges at both ends of the valve being connected to the pipe flanges via bolts. The strength performance of a valve refers to its ability to withstand the pressure of the medium. Valves are mechanical devices that are subjected to internal pressure; therefore, they must possess sufficient strength and stiffness to ensure they do not crack or deform over long periods of use. Ball valve The ball valve evolved from the plug valve. It has the same 90-degree rotation action, but 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 inner cavity of the valve provides a flow path with very low resistance and a direct route 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. 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 operating conditions, such as oxygen, hydrogen peroxide, methane, and ethylene. The ball valve body can be integral or modular. Globe valve The axis of the globe valve’s stem is perpendicular to the sealing surface of the valve seat. The valve stem has a relatively short opening or closing stroke, and it provides a very reliable shut-off action, which makes this type of valve highly suitable for shutting off, regulating, or throttling fluids. Once the valve disc of a globe valve is in the open position, there is no longer any contact between its seat and the sealing surface of the valve disc, resulting in a very reliable shut-off action; this makes such valves highly suitable for shutting off, regulating, or throttling fluids. Once a globe valve is in the open position, there is no longer any contact between its seat and the sealing surface of the disc; as a result, mechanical wear on these sealing surfaces is minimal. Moreover, since the seat and disc of most globe valves are easy to repair or have their sealing elements replaced without the need to remove the entire valve from the pipeline, this makes them particularly suitable for situations where the valve is welded to the pipeline. The flow direction of the medium changes as it passes through such valves; therefore, the flow resistance of globe valves is higher than that of other valves. The commonly used globe valves include the following: 1) Angle-type globe valve ； In angular stop valves, the fluid only needs to change direction once, resulting in a lower pressure drop across the valve compared to stop valves with conventional designs. 2) DC globe valve ； In direct-acting or Y-type globe valves, the flow channel of the valve body forms an angle with the main flow path; as a result, the degree of disruption to the flow pattern is less than that in conventional globe valves, and consequently the pressure loss across the valve is also lower. 3) Plunger-type globe valve: This type of globe valve is a variant of the conventional globe valve. In this valve, the valve disc and seat are typically designed based on the plunger principle. The valve disc is polished to form a plunger that connects with the valve stem, and sealing is achieved through two elastic sealing rings fitted over the plunger. The two elastic sealing rings are separated by a collar, and the sealing rings surrounding the plunger are pressed firmly in place by the load applied to the valve cover by the valve cover nut. The elastic sealing ring can be replaced and is made from a variety of materials. This valve is primarily used for opening or closing, but it also features a special type of plunger or special rings that allow it to be used for regulating flow. Gate valve: A gate valve is used to shut off the flow of a medium; when it is fully open, the flow path is completely unobstructed, resulting in the lowest pressure loss for the medium flowing through it. Gate valves are typically suitable for applications where frequent opening and closing are not required, and where the gate plate needs to remain fully open or fully closed. Not suitable for use as a regulator or throttle. For media flowing at high speeds, partial opening of the gate plate can cause vibration in the gate, and this vibration may damage the sealing surfaces of the gate plate and the valve seat; moreover, throttling exposes the gate plate to erosion by the medium. In terms of structural form, the main difference lies in the type of sealing element used. Based on the design of the sealing element, gate valves are often classified into several different types, such as wedge gate valves, parallel gate valves, parallel double-plate gate valves, and wedge double-plate gate valves. The most commonly used types are wedge gate valves and parallel gate valves. Valves of the BHsb0 type function by allowing the medium to flow in only one direction and preventing flow in the opposite direction. Typically, such valves operate automatically; the valve disc opens under the pressure of fluid flowing in one direction ； When the fluid flows in the opposite direction, the fluid pressure together with the weight of the valve disc causes the valve disc to act on the valve seat, thereby stopping the flow. Check valves belong to this type of valve; they include swing check valves and lift check valves. A swing check valve has a hinge mechanism, as well as a valve disc that resembles a door and rests freely on an inclined valve seat surface. To ensure that the valve disc always reaches the appropriate position on the valve seat surface, it is designed with a hinge mechanism, allowing sufficient rotation space for the valve disc and enabling it to make true, full contact with the valve seat. The valve disc can be made entirely of metal, or leather, rubber, or synthetic covers can be embedded in metal, depending on the requirements of its performance. When a swing check valve is fully open, the fluid pressure encounters little resistance; therefore, the pressure drop across the valve is relatively small. The disc of the lift-type check valve is seated on the seat sealing surface of the valve body. Apart from the valve disc, which can move up and down freely, this valve operates in a similar manner to a globe valve: fluid pressure lifts the valve disc off the sealing surface of the valve seat, while backflow causes the valve disc to return to the valve seat, thereby stopping the flow. Depending on the operating conditions, the valve disc can be of a fully metal structure, or it can consist of a frame with rubber gaskets or rings embedded in it. Like globe valves, the flow passage through lift check valves is also narrow; as a result, the pressure drop across lift check valves is greater than that across swing check valves. Moreover, the flow rate of swing check valves is subject to fewer restrictions.@q!G\] During the production process, in order to ensure that parameters such as pressure and flow rate of the medium meet the requirements of the manufacturing process, regulating mechanisms need to be installed to adjust these parameters. The main working principle of the regulating mechanism is to adjust the aforementioned parameters by changing the flow area between the valve disc and the valve seat. Valves of this type are collectively referred to as control valves. Those that are driven by the energy of the medium itself are known as self-acting control valves, such as pressure reducing valves and pressure stabilizing valves. Those that are driven by external energy sources such as electricity, compressed air, or hydraulic power are called externally driven control valves, such as electric control valves, pneumatic control valves, and hydraulic control valves. B5D Electrically driven valves Electrically driven valves are a commonly used type of valve actuator; this type of actuation device is often referred to as an electric valve actuator. The characteristics of electric valve actuators are as follows: 1) They enable rapid opening and closing, which helps to **reduce the time required to open or close the valve** ； 2) It can **reduce the workload on operators, and is particularly suitable for high-pressure, large-diameter valves** ； 3) Suitable for installation in locations where manual operation is not possible or where access is difficult; it enables easy remote control, and there are no restrictions on the installation height ； 4) Conducive to the automation of the entire system ； 5) Power sources are easier to obtain than gas and liquid sources, and the installation and maintenance of their wires are also much simpler than those of compressed air and hydraulic pipelines. The disadvantage of valve actuators is their complex structure; they are more difficult to use in humid environments, and explosion-proof measures are required when used with explosive media. Valve actuators can be divided into two main categories, Z-type and Q-type, depending on the type of valve they drive. The output shaft of the Z-type valve actuator can rotate many times, making it suitable for driving gate valves, globe valves, diaphragm valves, etc ； The output shaft of the electric actuator for Q-type valves can only rotate 90 degrees. It is suitable for driving plug valves, ball valves, butterfly valves, etc. Based on their protection type, they include standard type, flameproof type (denoted by B), heat-resistant type (denoted by R), and three-in-one type (i.e., outdoor, corrosion-resistant, and flameproof, denoted by S). A valve actuator generally consists of a transmission mechanism (reducer), a motor, a travel control mechanism, a torque limitation mechanism, a manual-electric switching mechanism, an opening indicator, etc. Pneumatic and hydraulic valves: Pneumatic valves and hydraulic valves use air, water, or oil under certain pressure as a power source; they rely on the movement of cylinders (or hydraulic cylinders) and pistons to operate the valves. Generally, the air pressure used in pneumatic systems is less than 0.8 MPa, while the water or oil pressure in hydraulic systems ranges from 2.5 MPa to 25 MPa. or diaphragm valve ； Rotary gas and liquid actuation devices are used to drive ball valves, butterfly valves, or plug valves. Hydraulic actuators have a high driving force and are suitable for operating large-diameter valves. When used to drive plug valves, ball valves, and butterfly valves, the reciprocating motion of the piston must be converted into rotational motion. In addition to being driven by the pistons of cylinders or hydraulic cylinders, there are also those driven by pneumatic diaphragms; due to their limited stroke and driving force, they are mainly used in control valves. Manual valve A manual valve is the most basic type of valve in terms of driving mechanism. It includes two types: direct drive using a handwheel, handle, or wrench, and drive through a transmission mechanism. When the starting torque of the valve is high, it can be driven via gear or worm gear transmission in order to eliminate this requirement. Gear drives are divided into straight cylindrical gear drives and bevel gear drives. Gear drives offer a low reduction ratio and are suitable for gate valves and globe valves, while worm gear drives provide a higher reduction ratio and are appropriate for plug valves, ball valves, and butterfly valves. 1. Gate valves: Also known as gate cocks, gate valves are characterized by their high level of sealing performance. They are commonly used in water supply pipes and hot water heating systems. Since it is not feasible to prevent foreign objects from getting in when the gate is opened, they are used as drain valves in heating systems as well as in small boilers (such as vertical tube boilers). This type of valve is generally not used in steam pipelines, as at high pressures, gate valves find it difficult to open due to the pressure acting on one side only. Gate valves are suitable for operating in the fully open or fully closed position, and are appropriate for regulating flow. If the gate plate operates for an extended period in a semi-open state, its sealing surface will become less tight due to erosion by the medium. 2. Globe valves and throttle valves: These two types of valves were formerly collectively referred to as ball valves. Although stop valves are used to shut off steam and water flow paths, while throttle valves are primarily used to regulate flow rate, it is difficult to distinguish them based on their appearance; the only difference lies in the valve core. The end of the valve plug in a globe valve is flat, whereas that of the valve plug in a throttle valve is conical. Globe valves with copper cores can be used in both steam and water pipelines. Thermal stop valves equipped with a rubber gasket, rubber piece, or plastic element (commonly known as rubber gasket valves) are used only in water or low-temperature hot water pipelines; otherwise, the rubber, rubber piece, or plastic will deteriorate and lose their sealing properties. 3. Plug valves and ball valves: Plug valves are also known as stop valves; they are commonly referred to as rotary valves. Small plug valves were formerly called cock valves. They are types of quick-opening valves, and depending on their flow distribution patterns, they can be straight-through, three-way, four-way, etc. The stem of the plug is integrated with the valve core, which is in the shape of a frustum; a rectangular through-hole is provided on it, while smaller plugs have circular through-holes. When the groove on the top of the valve stem or the handle is parallel to the inlet and outlet directions of the plug, the valve is fully open; when it is perpendicular, the valve is fully closed. A ball valve is actually a variant of a plug; like a plug, it operates by changing the angle of the valve core to open the valve. The valve element of a ball valve is a sphere, on which there is a cylindrical hole; fluted rings made of fluoroplastic are located on both sides of the sphere and serve as the valve seats – seals. Both plug valves and ball valves are quick-opening valves with low resistance and high flow rates. However, its sealing surface wears easily, it requires significant force to operate, and it tends to get stuck; therefore, it is not suitable for high-temperature and high-pressure conditions. The specifications for plugs and ball valves are generally 15mm (1/2in) to 50mm (2in). A plug used to open and close the medium in a pipeline can also serve as a throttle valve ； Ball valves are used only for opening and closing pipeline media, and should not be used as throttling valves, to prevent the valve from losing its tightness due to prolonged exposure to the medium. 4. Check valve: Also known as a non-return valve, it is commonly referred to as a one-way valve. It opens automatically based on the pressure difference before and after the valve, and its function is to automatically control the direction of fluid flow, allowing it to move in one direction while preventing reverse flow. Check valves are commonly used in water supply pipelines, and they have a strict orientation requirement during installation – they must not be installed in the wrong direction. Elevator check valve. The upper part of the valve core of this type of valve is equipped with a guide rod; the guide rod and the valve core can move up and down freely along the guide sleeve on the valve cover. When fluid flows from left to right, it pushes the valve core open, while when the fluid flows in the opposite direction, the valve core descends onto the valve seat, thereby shutting off the flow path. The swing check valve, also known as the rotary check valve, operates on a principle similar to that of the lift check valve. The above two types of check valves are only installed on horizontal pipelines. Spring-type check valve, this type of valve is a development of the lift-type valve. Ordinary lift-type check valves can only be installed in horizontal pipes, while spring-lift type check valves are not restricted by direction. It is used in horizontal pipes, vertical pipes, and pipes at an angle. Spring-lift check valve. The sizes of these valves range from 15 mm (1/2 in) to 50 mm (2 in). Bottom valve. A one-way valve specifically installed at the inlet of the water pump’s suction pipe, commonly known as a \"well bottom valve\" or \"shower head\", etc. 5. Straight valves and right-angled valves: Straight valves are a type of valve specifically designed for radiators; they can be used at the inlet of steam heating radiators, as well as at the outlet and inlet of water heating appliances. The inlet and outlet of a right-angle valve are at 90 degrees to each other. Right angle. The right-angle valves used in heating systems are commonly known as figure-8 valves. It is specifically used on radiators; during steam heating, it is placed at the steam inlet for heat dissipation, and during water heating it can be used at the inlet and outlet of the radiator to regulate the amount of steam or water. 6. Pressure relief valve: The pressure relief valve is used to reduce the pressure of the medium in the pipeline, so that the pressure meets the requirements of production. Commonly used pressure relief valves include piston-type, diaphragm-type, membrane-type, and spring-type valves. The pressure relief valve should be installed vertically on a horizontal pipe, with its valve cover perpendicular to the horizontal pipe; pay attention to the direction of the arrow on the valve body during installation. Valves should be installed on both sides of the pressure relief valve. Pressure gauges are installed on both the high-pressure and low-pressure pipes, while a safety valve is also required for the low-pressure system. The purpose of these devices is to regulate and control pressure in a convenient and reliable manner, which is particularly important to ensure the safe operation of low-pressure systems