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1. The regulating valves are mainly used to regulate the flow and pressure of the medium. Including regulating valve, throttle valve, pressure reducing valve, etc. 2. Check valves are used to prevent backflow of media. Including check valves of various structures. 3. Diversion valves are used to separate, distribute or mix media. Including distribution valves and traps of various structures. 4. Safety valves are used for safety protection when the medium is overpressured. Including various types of safety valves. 5. The cut-off valves are mainly used to cut or connect the medium flow. Including gate valve, globe valve, diaphragm valve, ball valve, plug valve, butterfly valve, plunger valve, instrument needle valve, etc.

1. Regulator

In the automatic control of modern factories, the regulating valve plays a very important role. The production of these factories depends on the correct distribution and control of the flowing medium. Whether these controls are energy exchange, pressure reduction or simple container charging, some final control elements are required to complete. The common control loop includes three main parts. The first part is the sensitive element, which is usually a transmitter. It is a device that can be used to measure the adjusted process parameters, such as pressure, liquid level or temperature. The output of the transmitter is sent to the adjustment instrument-the regulator, which determines and measures the deviation between the given value or the expected value and the actual value of the process parameter, and sends the correction signals one by one to the final control element-adjustment valve. The valve changes the flow of fluid, so that the process parameters have reached the desired value.

Performance characteristics:

The flow path of the regulating valve is simple and the resistance is small, and it is generally suitable for forward use (installation). However, in the case of high pressure drop, the regulating valve is used in reverse to improve the unbalanced force and reduce the damage to the valve core. At the same time, it is also conducive to the flow of the medium and avoids coking and clogging of the regulating valve. In general, regulating valves are not recommended for reverse use. Reverse use is only recommended for mediums with high pressure difference, high viscosity, easy coking and particles containing suspended particles. When using it in reverse, it should be avoided to run for a long period of small opening, especially when testing.

2. Throttle valve

The appearance structure of the throttle valve is no different from that of the globe valve, except that the shape of their opening and closing parts is different. The opening and closing parts of the throttle valve are mostly conical streamlines, which can adjust the flow rate and pressure by changing the cross-sectional area of the channel. The throttle valve is used to reduce the pressure of the medium when the pressure drop is extremely large.

Performance characteristics:

1. The structure is simple, easy to manufacture and maintain, and the cost is low.

2. The adjustment accuracy is not high and cannot be used for adjustment.

3. The sealing surface is easy to be eroded and cannot be used as a cutting medium.

4. Poor sealing.

3. Pressure reducing valve

The pressure reducing valve has a piston or diaphragm structure, and the output pressure acts on the piston or diaphragm to overcome the adjustable spring force to balance. Use the adjusting screw to adjust the secondary pressure, set the spring loading to open the main valve, and let the air flow from the initial pressure p1 input port to the secondary pressure p2 output port. When the circuit connection output reaches the set pressure, the air inside acts on the diaphragm and generates a lifting force relative to the spring force. If the flow rate decreases, p2 will increase slightly, and also increase the force acting on the diaphragm relative to the spring force. The diaphragm and valve will then rise until the spring force is balanced again, and the air flow through the valve will decrease until its consumption Until the quantity and output pressure remain balanced. If the flow rate increases, p2 decreases slightly. This decrease causes the force acting on the diaphragm to decrease relative to the spring force, and the diaphragm and valve fall until they are in equilibrium with the spring force again. This increased air flow through the valve until its consumption and output pressure remain balanced. There is no air consumption and the valve is closed.

Performance characteristics:

The difference between pressure relief valve and relief valve

(1) At rest, the valve port of the relief valve is normally open, and the valve port of the relief valve is normally closed;

(2) The pressure relief valve controls the outlet pressure to be stable, while the relief valve controls the inlet pressure to be stable;

(3) The valve port of the pressure reducing valve closes with the increase of the outlet pressure, and the valve port of the relief valve opens with the increase of the inlet pressure;

(4) The oil inlet and outlet of the pressure-reducing valve are all pressure oil circuits, and the oil returning through the pilot valve must be led back to the oil tank separately, while the overflow valve and the outlet are combined and flow back to the oil tank together.

4. Check valve

Check valve refers to a valve that automatically opens and closes the valve flap by relying on the flow of the medium itself to prevent backflow of the medium. It is also known as a check valve, check valve, reverse flow valve, and back pressure valve. The check valve belongs to an automatic valve. Its main functions are to prevent backflow of the medium, to prevent the pump and drive motor from reversing, and to release the medium in the container.

Performance characteristics:

Check valve is a valve used to prevent backflow of the medium in the pipeline. It opens when the medium flows downstream and automatically closes when the medium flows backward. Generally used in the pipeline that does not allow the medium to flow in the reverse direction to prevent the reverse flow of medium from damaging the equipment and mechanical parts. When the pump is stopped, the rotary pump is not reversed. On the pipeline, check valves and closed-circuit valves are often used in series. This is due to the poor sealing performance of the check valve. When the medium pressure is low, a small part of the medium will leak. A closed-circuit valve is required to ensure the closing of the pipeline. The bottom valve is also a kind of check valve, which must be submerged in water, and is specially installed at the front of the suction pipe of the pump that cannot be self-priming or has no vacuum suction and diversion.

5. Safety valve

The safety valve is a special valve whose opening and closing parts are normally closed under the action of external force. When the medium pressure in the equipment or pipeline rises above the specified value, the medium pressure in the pipe or equipment is prevented from exceeding the specified value by discharging the medium outside the system . Safety valves belong to the category of automatic valves, which are mainly used in boilers, pressure vessels and pipelines. The control pressure does not exceed the specified value, which plays an important role in protecting personal safety and equipment operation. Note Safety valves must be pressure tested before they can be used.

Performance characteristics:

1. Heavy hammer lever type safety valve

The heavy hammer lever type safety valve is simple in structure, easy to adjust and more accurate, and the applied load will not increase greatly due to the increase of the valve flap. It is suitable for high temperature occasions, and it has been commonly used in the past, especially It is used in boilers and pressure vessels with higher temperature. However, the structure of the heavy hammer lever safety valve is cumbersome, the loading mechanism is easy to vibrate, and often leaks due to vibration; its reseating pressure is low, and it is not easy to close and keep tight after opening.

2. Spring type safety valve

The spring-loaded safety valve has a light and compact structure, high sensitivity, and unlimited installation position. And because it has low sensitivity to vibration, it can be used on mobile pressure vessels. The disadvantage of this safety valve is that the applied load will change with the opening of the valve, that is, as the valve flap increases, the compression of the spring increases, and the force acting on the valve flap also increases. This is detrimental to the rapid opening of the safety valve. In addition, the spring on the valve will reduce the spring force due to the long-term influence of high temperature. When used on a container with a higher temperature, the thermal insulation or heat dissipation of the spring is often considered, which complicates the structure.

3. The pulse safety valve is composed of a main valve and an auxiliary valve. The pulse valve of the auxiliary valve drives the main valve to operate. Its structure is complicated, and it is usually only suitable for boilers and pressure vessels with a large amount of safe discharge.

6. Directional valve (switching valve, diverter valve)

The directional valve is combined on the basis of several DC-type shut-off valve types. It is used to change the flow direction of the process medium and control the way of combining or dividing the multi-path medium. For example, the fluid direction control of gear pumps and polymer filter systems and the multiple distribution of process media in polymerization systems. Directional valves are widely used in the chemical industry, petroleum industry, metallurgy, power sector, pharmaceutical industry, beer, food, dairy beverages, cosmetics and various types of engineering supporting piping systems.

Performance characteristics:

1. Made of stainless steel;

2. High polishing precision, which can meet the requirements of food grade and pharmaceutical grade;

3. The control system can be configured according to the user's actual situation to achieve fully automated operation and improve work efficiency;

4. The shell and main parts are casted by castings, with a solid structure, high strength and easy deformation, and beautiful appearance;

5. The conveying channel is smooth and clean, to ensure that the material flows smoothly and will not form a blockage;

6. In the occasions with pressure sealing requirements, special sealing structure can be configured to fully meet the use requirements.

Seven, trap

According to the temperature change in the hair cavity, the valve automatically deforms when it encounters the corresponding temperature. The valve core is driven to reset and move to close the seat hole to eliminate the steam. On the contrary, if there is condensate in the valve cavity, the temperature in the cavity will not deform the bimetallic sheet, so that the valve core and the valve seat remain open, so the condensate will always be drained out, and the temperature of the valve cavity after the condensate is drained It will change immediately, and the deformation of the bimetallic sheet will immediately close the valve seat hole so as to repeatedly open and close, so as to achieve the effect of drainage and gas barrier. It is suitable for the discharge and recovery of suspected water on any heat energy steam pipeline.

Performance characteristics:

1. Control the fluid velocity about 30m / S to prevent cavitation damage. The fluid channel is labyrinthine and continuously change the direction of the fluid; allow a pressure difference of 25MPa.

2. The throttle surface is separated from the sealing surface. Different throttle elements are provided for the hydrophobic flow. The surface of the valve components is hardened and the hardness can reach HRC70. The closure is tight and the life is long.

3. The valve body assembly adopts self-internal pressure sealing structure, the greater the pressure difference, the better the sealing.

4. The floating connection between the valve body assembly and the actuator can eliminate the stuck phenomenon caused by the eccentricity of the valve core and the push rod.