Design and selection of stop valve for power station
The globe valves used in various systems of thermal power plants are called power station globe valves. Due to the special working conditions and performance and technical characteristics, the power station shut-off valve is irreplaceable.
It is used for closing and discharging valves of thermal power plant high-feed drain, reheater drain and superheater drain and other systems. The sealing requirement is high. It must be opened and closed quickly, and it has the function of fault protection, automatic control and high reliability. . Therefore, the stop valve of the power station (commonly known as the steam trap in the power plant) has become the first choice for this type of system. Pneumatic control globe valve has long-lasting and stable sealing specific pressure, simple debugging, low maintenance requirements, low failure, high reliability, automatic protection for loss of gas and power loss, quick opening and closing, relatively low price, energy saving and environmental protection, so it is suitable for the evacuation and drainage of thermal power plants. condition.
Selection of pneumatic actuators and valves
Pneumatically controlled globe valves are generally fully open and fully closed. From the perspective of flow characteristics, globe valve and ball valve have the characteristics of short opening and closing stroke, fast speed, reliable sealing, and small opening and closing static torque, so both types of products are used. But from the perspective of reliability, the mainstream product is still the pneumatic globe valve.
The cylinder of the pneumatic control device is a stereotyped product, which can be divided into single-acting and double-acting according to the mode of action. The single-acting product has a return cylindrical spring, which has the function of automatic reset when the gas is lost, that is, when the gas is lost, the cylinder piston (or diaphragm) drives the cylinder push rod to return to the original position of the cylinder (original position of the stroke) under the action of the spring. The double-acting cylinder has no return spring, and the advance and retreat of the push rod must rely on changing the position of the inlet and outlet of the air source of the cylinder. When the air source enters from the upper cavity of the piston, the push rod moves downward. When the air source enters from the lower cavity of the piston, the push rod moves upward. Because there is no return spring, the double-acting cylinder has a larger thrust than the single-acting cylinder of the same diameter, but does not have the automatic reset function. Obviously the different intake positions cause the pushrod to move in different directions. When the intake position is in the back cavity of the push rod, the intake air moves the push rod forward, which is called a positive-acting cylinder. Conversely, when the intake position is on the same side of the push rod, the intake air makes the push rod retreat, which is called a reaction cylinder. Pneumatic globe valves generally use single-acting cylinders because they generally require loss of gas protection.
The above has introduced the design and selection of the stop valve of the power station. From the perspective of the application system, it has analyzed the design and selection of the stop valve of the power station. If you read it carefully, it will be of great help.