1 Overview For the size specifications, please provide detailed parameters, the factory is produced according to the national designated standards. Infrared Vein Finder,High Quality Infrared Vein Finder,Infrared Vein Finder Details, CN Wuxi Biomedical Technology Co.,Ltd , https://www.wxbiomedical.com
It is used for high-hydrophobicity in thermal power plants, hydrophobicity of reheaters and hydrophobicity of superheater. The closing and discharging valves of the system have high sealing requirements, must be opened and closed quickly, and have fault protection function, automatic control function and high reliability. . Therefore, the power plant stop valve (commonly known as steam traps, water traps) is the first choice for such systems. Pneumatic control globe valve seal lasting stability, simple commissioning, low maintenance requirements, low failure, high reliability, automatic protection against gas loss, fast opening and closing, relatively low price, energy saving and environmental protection, so it is suitable for thermal power plant drainage condition.
2, document.write ('') valve document.write ('') and pneumatic actuator selection
The document.write('') ​​pneumatic control globe valve.write('') ​​is generally fully open and fully closed. Considering the flow characteristics, the shut-off valve and the ball valve have the characteristics of short opening and closing stroke, fast speed, reliable sealing, small opening and closing static torque, and so on. However, from the perspective of reliability, the mainstream products are still pneumatic shut-off valves.
The cylinder of the pneumatic control device is a fixed product, which can be divided into single action and double action depending on the mode of action. The single-acting product has a reset cylindrical spring with an automatic gas-resetting function. When the gas is lost, the cylinder piston (or diaphragm) is driven by the spring to drive the cylinder push rod back to the initial position of the cylinder (original position of the stroke). The double-acting cylinder has no return spring, and the push rod advance and retreat must rely on changing the inlet and outlet position of the cylinder air source. When the air source enters from the upper chamber of the piston, the push rod moves downward. When the air source enters from the lower chamber of the piston, the push rod moves upward. Since there is no return spring, the double-acting cylinder has greater thrust than the single-acting cylinder of the same diameter, but does not have an automatic reset function. Obviously different intake positions allow the push rods to move in different directions. When the intake position is in the back chamber of the push rod, the intake air advances the push rod, which is called a positive acting cylinder. On the contrary, when the intake position is on the same side of the push rod, the intake air retreats the push rod. This method is called a reaction cylinder. Pneumatic shut-off valves usually use a single-acting cylinder (Figure 1) because they generally require a loss of gas protection.
From the analysis, when the document.write('') ​​valve document.write('') ​​protection mode is turned off, a single-acting positive-acting cylinder must be selected. When the valve is protected by a lost gas shut-off, a single-acting reaction cylinder must be selected. The single-acting positive-acting cylinder must maintain a long-lasting stable source pressure when the valve is closed, and requires high stability and durability of the gas source. Normally closed valves avoid this design as much as possible. This structure is suitable for normally open valves. . Single-acting reaction cylinders are suitable for normally closed valves, but they are more demanding on springs and should have a stable and long-lasting spring force.
3, cylinder thrust calculation
In addition to the choice of mode of action, the calculation of the selected cylinder thrust is an important task of the meter, taking the common normally closed pneumatic shut-off valve (Figure 2) as an example. Due to the high pressure, in order to choose a smaller cylinder as much as possible, the upper inflow (backflow) valve design is adopted. To increase the seal specific pressure, a conical sealing surface is used.
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Selection and design of pneumatic shut-off valve