The type of valve is expressed in Chinese Pinyin and numbers according to the type of valve, driving method, valve body structure, sealing or lining material, nominal pressure, and valve body material.

First, the gate valve

A gate valve is a valve in which the closing member (gate) moves in the vertical direction along the axis of the medium passage. It is mainly used as a cutting medium on pipes. The utility model has the advantages that the flow resistance coefficient is small, the torque required for opening and closing is small, and the flow direction of the medium is not limited. The disadvantage is that the structure size is large, the opening and closing time is long, the sealing surface is easy to be damaged, and the structure is complicated. The gate valve has various structural forms. The main difference is that the sealing elements used are different in structure. Therefore, the gate valves are often divided into different types. The most common forms are parallel and wedge gate valves. According to the structure of the valve stem, Divided into open and dark rod gate valves.

Second, the butterfly valve

Its name is derived from the wing of the wing structure. In the cylindrical passage of the valve body.

The disc-shaped disc rotates around its axis, and the valve can be opened and closed only by turning 90°, and it is mainly used for cutting and throttling on the pipeline. When the butterfly valve is used for cutting, the elastic sealing is used, the material is rubber, plastic, etc.; when used for throttling, the metal is hard sealed. The advantages are small size, light weight, simple structure, quick opening and closing, good adjustment and sealing performance, and low fluid resistance and operating torque.

The butterfly valve can be divided into a lever type (double rocker), a center symmetrical door type, a bias plate type and a swash plate type according to the structure. The central symmetrical door type (clip type) has a small flow resistance, but its upper and lower shaft ends are also part of the sealing surface, which is easy to wear and cause leakage. It is suitable for butterfly valves with a nominal diameter of DN< 800 mm.

The offset plate type overcomes this weakness, but the flow resistance is large. It is suitable for butterfly valve L-lever butterfly valve with DN ≥800mm. Due to structural reasons, it is not suitable for high-pressure water medium. Leaning plate butterfly valve is complicated due to its structure and process. It is used less in engineering. The structure and principle of butterfly valve make it suitable for large diameter pipe. There are two types of L butterfly valves: vertical and horizontal. If it is not restricted by installation space and position, large diameter butterfly valve should be horizontal.

Third, the stop valve

Refers to the valve that moves the body (valve) along the centerline of the seat. It is generally only used for cutting in the pipeline, not for throttling. The shut-off valve is widely used, but due to the large opening and closing torque and long structural length, the nominal diameter is usually limited to DN250 mm or less. Its advantages are simple structure, good sealing, convenient manufacturing and maintenance, and wear resistance. The opening height is much smaller than the gate valve. The disadvantage is that the pressure loss is large. There are many types of globe valves, which are generally divided into straight-through, angle-type and direct-flow types according to the structure. The straight-through pressure loss is small.

Angle type is widely used in refrigeration systems, which will produce pressure drop. The biggest advantage is that it is installed at the corner of the pipeline system, which saves 90° elbow and is easy to operate. The DC type valve body is made into a separate type, which is the smallest flow resistance in the shutoff valve. The valve stem is also divided into a clear rod and a dark rod. The low-pressure small-diameter shut-off valve usually adopts a dark rod structure. The sealing surface has two forms, a flat surface and a tapered surface. The flat sealing surface has the characteristics of small scratch and easy grinding; the tapered sealing surface is easy to be scratched, but the structure is compact.

Fourth, the ball valve

The ball valve is evolved from a plug valve, and the opening and closing member is a sphere. The ball is rotated around the axis of the valve stem to achieve the purpose of opening and closing. It is mainly used to cut, distribute and change the flow direction of the medium on the pipeline. It is characterized by minimal fluid resistance, its resistance coefficient is equal to that of the same length of pipe section, fast opening and closing, reliable sealing, compact structure, easy operation and maintenance, so it is widely used in many occasions.

The ball valve can be divided into three types according to the structure of the sphere: a floating ball valve, a fixed ball valve and an elastic ball valve. The floating ball valve has a simple structure and good sealing performance. Since the working medium load of the ball is transmitted to the outlet end seat sealing ring, the structure is only suitable for medium and low pressure applications. The disadvantages are that the assembly is difficult, the production precision is high, and the operating torque is also large. Fixed ball valves are suitable for high pressure and large diameter pipes. It is usually equipped with a movable seat seal, which generates displacement under the action of the medium pressure, so that the seal is tightly pressed to ensure the sealing performance of the valve. The elastic ball valve is suitable for high temperature and high pressure media. An elastic groove is formed in the ball body, which can reduce the grinding between the two sealing faces when opening and closing, and also reduces the operating torque.

Five, plug valve

It is a valve that opens and closes around the axis of the cavity in the valve body. It is mainly used to cut, distribute and change the direction of medium flow. An important feature of the plug valve is that it is easy to accommodate multi-channel construction so that one valve can achieve two, three or even four different flow paths. This simplifies the design of the piping system, reducing the amount of valves and some of the connecting accessories required for the equipment.

There are many types of plug valves, which can be generally divided into three types: compact type, packing type and self-sealing type. The compact plug valve does not have a packing, and the sealing of the plug and the plug sealing surface is achieved by tightening the nut below the plug, and is generally used for the case of PN ≤ 0.6M Pa. The stuffing plug valve plug has a packing body, and the sealing of the plug and the sealing surface of the plug body is achieved by pressing the packing L. The sealing performance is good, and a large amount is used for the case where the nominal pressure PN is >1.0 M Pa. The screw under the plug body can adjust the tightness of the plug and the plug body. The seal between the plug and the plug body in the self-sealing plug valve is mainly realized by the pressure of the medium itself, and is mostly used for the air medium. The spring under the self-sealing structure acts as a preload and compression.

Six, check valve

Also known as counterflow valve, check valve, back pressure valve and check valve L is a valve used to prevent backflow of the medium in the pipeline and equipment. It is automatically opened and closed by the force generated by the flow of the medium in the pipeline. The structure of the return valve is usually distinguished by the action of the valve flap, mainly in the lift type and the swing type. The lift check valve is also divided into vertical and horizontal type. The horizontal type can only be installed on the horizontal pipe. The pump bottom valve is a lift check valve dedicated to the bottom of the pump suction pipe. To prevent the medium from flowing backward when the pump is stopped, Keep the water column required for pumping. The valve flap of the swing check valve rotates around the pin shaft outside the valve seat, and is divided into a single flap and a plurality of flaps. The former is generally used for a nominal diameter of DN 50 to 500 mm, and the latter is generally used for a nominal diameter of DN ≥ 600 mm. In addition, there is an empty row check valve, which is used for the boiler feed water pump outlet to prevent the medium from flowing back and emptying. The new slow-closing check valve has the effect of eliminating water hammer. Diaphragm check valve to prevent water hammer performance L Ball check valve is the ideal product to prevent media counterflow.

Seven, pressure reducing valve

Through the throttling and adjustment of the opening and closing member, the pressure of the medium is lowered, and the pressure of the valve after the valve is directly acted upon, so that the pressure after the valve automatically meets the predetermined requirement. L. The pressure P2 after the pressure reducing valve should be less than the pressure before the valve. 0.5 times P. There are many types of pressure reducing valves, which are generally divided into two types: direct acting and indirect acting. The former controls the required pressure according to the energy of the medium; the latter uses external force such as air pressure, hydraulic pressure or electric power to control the required pressure. The pressure reducing valve is divided into a piston type, a film type, a bellows type, a spring film type, a lever spring type and the like according to the structure. The piston type pressure reducing valve has small volume, low sensitivity and high manufacturing process requirements, and is widely used when the medium temperature is high. The membrane type pressure reducing valve uses a universal L bellows type pressure reducing valve for water and air, etc., for non-corrosive medium pipes such as steam, water and air at temperatures below 200 °C. The inner spring diaphragm type pressure reducing valve is suitable for medium pipes such as air and water whose working temperature is lower than 50 °C. The lever type pressure reducing valve is suitable for medium and high pressure desuperheating and pressure reducing devices for regulating steam pressure.

Eight, safety valve

It is a safety device on equipment, equipment and piping to prevent the pressure of the medium from exceeding a specified value. When the working pressure in the equipment, equipment and pipeline exceeds the specified value, the safety valve will automatically open to discharge excess medium; when the pressure returns to normal, it will close itself to keep the seal leaking, thus ensuring safe operation of the equipment. The main structure of the safety valve is three types: lever type, spring type and pilot type (pulse type). The water system is usually spring-loaded, which uses a compression spring force to balance the flap pressure. The advantages are small size, light weight, high sensitivity, and unrestricted mounting position; the disadvantage is that the force acting on the valve stem changes with the deformation of the spring. The spring-loaded safety valve is divided into a micro-open type and a full-open type. It has a wrench and a wrench without a wrench, and has a closed type and an open type.

Nine, trap

The steam trap is suitable for steam heating equipment and pipelines to automatically remove condensate, air and other non-condensable gases, and to prevent the loss of steam, that is, to prevent steam and drainage. Proper selection of traps is essential to save steam energy and ensure proper operation of the steam condensate system. When selecting, first select according to the maximum displacement of condensate and the pressure difference between the inlet and outlet, and also modify it. The correction factor is 1.5~4; the second is reasonable to install. Steam traps can be divided into the following categories according to the opening and closing form:

1. Mechanical steam trap: Drives the opening and closing member L by the condensate level change. It also includes a free float type, a lever float type, a free half float type and an open up (down) float type steam trap.

2. Thermostatic steam trap: Drives the opening and closing member from the temperature change of the condensate. It also includes bellows, bellows and bimetal.

3. Thermodynamic steam trap: The opening and closing member L is driven by the change of the dynamic characteristics of the condensate. It also includes a disc type, a pulse type, a labyrinth or an orifice plate type.

Ten, balance valve

The balancing valve is a valve used in the hydraulic network to measure and adjust to the design flow and has the necessary measurement accuracy. Its role is to eliminate the residual differential pressure of the favorable loop to achieve design flow at all loops to achieve system balance. System balance is critical to high standard indoor thermal environments and low energy consumption.

The balancing valve must have at least the following characteristics:

1, can measure and adjust the amount of water, and has an accuracy of ± 10%;

2. Implicit memory device with opening value;

3. Cut-off function.

Most of the balancing valves combine several functions, such as the sewage function, and the measurement of pressure drop and flow rate. To ensure system balance, the return water of each boiler and chiller, all the main pipes, risers and branch pipes or A balancing valve is required at the water supply pipe, in all zone control loops with secondary pumps, and at the splitter three-way valve.