1. Ball valve
Ball valve, a valve in which the opening and closing part (ball) is driven by the valve stem and rotates around the axis of the ball valve.
Features:
1. Wear resistance: Since the valve core of the hard-sealed ball valve is spray welded with alloy steel, and the sealing ring is welded with alloy steel, the hard-sealed ball valve will not produce too much wear when it is switched on and off. (Its hardness coefficient is 65-70):
2. Good sealing performance: Because the sealing of the hard-sealed ball valve is manually ground, it cannot be used until the valve core and the sealing ring are completely matched. Therefore, its sealing performance is reliable.
3. Light switch: Since the bottom of the sealing ring of the hard-sealed ball valve adopts a spring to make the sealing ring and the valve core tightly hug together, the switch is very light when the external force exceeds the pre-tightening force of the spring.
4. Long service life: It has been widely used in petroleum, chemical, power generation, papermaking, atomic energy, aviation, rockets and other departments, as well as people's daily life.
advantage:
1. The fluid resistance is small, and its resistance coefficient is equal to that of a pipe section of the same length.
2. Simple structure, small size and light weight.
3. It is tight and reliable, and the sealing surface material of the ball valve is widely used in plastics, with good sealing performance, and it has also been widely used in vacuum systems.
4. Convenient operation, rapid opening and closing, only need to rotate 90° from fully open to fully closed, which is convenient for remote control.
5. Convenient maintenance, simple structure of the ball valve, the sealing ring is generally movable, it is convenient to disassemble and replace.
6. It has a wide range of applications, with a diameter ranging from a few millimeters to a few meters, and can be applied in high vacuum or high pressure.
Two, gate valve
(1) Rising stem gate valve: Turn the hand wheel to advance or retreat through the thread of the hand wheel and the valve stem to raise or lower the valve plate connected to the valve stem to open and close.
The rising stem gate valve has the following advantages:
1. The fluid resistance is small, and the sealing surface is less eroded and corroded by the medium.
2. It saves effort to open and close.
3. The flow direction of the medium is not restricted, does not disturb the flow, and does not reduce the pressure.
4. The shape is simple, the length of the structure is short, the manufacturing process is good, and the scope of application is wide.
The disadvantages of rising stem gate valves are as follows:
1. It is easy to cause erosion and scratches between the sealing surfaces, and it is difficult to maintain.
2. The external size is large, a certain amount of space is required for opening, and the opening and closing time is long.
3. The structure is more complicated.
(2) Dark rod gate valve: also called rotating rod gate valve (also called dark rod wedge gate valve). The valve stem nut is set on the gate. The rotation of the handwheel drives the rotation of the valve stem to lift the gate. There is usually a trapezoidal thread at the bottom end of the valve stem. The thread on the bottom end of the valve and the guide groove on the disc will rotate the gate. It becomes linear motion, that is, the operating torque is changed to operating thrust.
3. Butterfly valve: Butterfly valve, also called flap valve, is a kind of regulating valve with simple structure. The butterfly valve that can be used for switching control of low-pressure pipeline medium means that the closing part (valve or butterfly plate) is a disc, which rotates around the valve shaft. A valve that achieves opening and closing.
4. Stop valve: Check valve refers to the valve that automatically opens and closes the disc depending on the flow of the medium itself, and is used to prevent the medium from flowing back. It is also called check valve, one-way valve, reverse flow valve, and back pressure valve. The check valve is a kind of automatic valve, its main function is to prevent the back flow of the medium, prevent the pump and the drive motor from reversing, and the discharge of the container medium.
V. Safety valve: The safety valve is a normally closed state of the opening and closing parts 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 pipeline or equipment is prevented from exceeding the specified value by discharging the medium to the outside of the system Special valves with specified values. 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.
6. Low-leakage and high-seal valve: The function of the low-leakage and high-seal valve: It is a valve set in the pipeline to prevent the system from malfunctioning due to the accumulation of driving gas leakage. It is installed on the system start-up pipeline, it is open under normal conditions, and it closes only when the inlet pressure reaches the set pressure. Its main function is to eliminate the leakage of the gas source.
Seven, pressure reducing valve
(1) Proportional pressure reducing valve: the opening of the pilot valve is to use the adjusting bolt on the top to turn clockwise, so that the elastic force generated by the spring shrinks, the pilot valve diaphragm is recessed, and the force acting on the pilot valve connecting rod , Make it move downward to open the pilot valve. When the pilot valve is opened, the steam in the A cavity of the upstream steam inlet pipe section passes through the α channel (steam supply regulating channel), enters the pilot valve annular steam cavity through the pilot valve, and is directly sent to the lower piston cylinder upper cavity from the β channel. With the continuous supply of steam in the A cavity, the pressure continues to rise, pushing the piston down to open the main valve. At this time, the steam continuously flows from the A cavity to the B cavity. When the load of the B cavity in the downstream outlet pipe section is satisfied, the excess steam causes the pressure in the B cavity to continue to rise. The rising pressure is fed back to the lower cavity of the pilot valve diaphragm through the γ channel (pressure sensing channel), which causes the pilot valve diaphragm to protrude upward, overcoming the pressure of the upper regulating spring, and the pilot valve is closed or closed. Thus, the steam source from the upstream α channel is turned off or down. When the pressure in the upper chamber of the piston cylinder drops, under the action of the return spring below, the main valve is closed or closed. At this time, the pressure in the B chamber begins to drop, so that the purpose of pressure regulation is achieved over and over again.
(2) Direct pressure reducing valve: Direct acting spring diaphragm pressure reducing valve Direct acting spring diaphragm pressure reducing valve is mainly composed of adjusting spring, diaphragm, piston, valve seat, valve clack and other parts. The diaphragm is used to directly sense the downstream pressure to drive the valve flap, and control the opening of the valve flap to complete the function of pressure reduction and stabilization.
(3) Pilot-operated pressure-reducing valve: The pilot-operated pressure reducing valve adjusts the flow of the medium by controlling the opening of the opening and closing parts in the valve body, reduces the pressure of the medium, and adjusts the opening and closing with the help of the pressure behind the valve. The opening degree of the parts keeps the pressure behind the valve within a certain range. When the inlet pressure is constantly changing, the outlet pressure is kept within the set range to protect the subsequent living and production appliances.
8. Float valve: The float always floats on the water. When the water surface rises, the float also rises. When the drift rises, the connecting rod also rises. The connecting rod is connected with the valve at the other end. When it rises to a certain position, the connecting rod supports the rubber piston pad to close the water source. When the water level drops, the float also drops, and the connecting rod drives the piston pad to open.