ZHAN pneumatic diaphragm double-seat control valve

I. Introduction:

     The ZHAN pneumatic diaphragm double-seat control valve consists of two parts: the ZHA type pneumatic diaphragm multi-spring actuator and the VN type straight-through double-seat valve. Principle: The working principle of the pneumatic double-seat valve is as follows: The signal pressure from the regulator is input into the air chamber of the pneumatic diaphragm multi-spring actuator, acting on the diaphragm to generate thrust. This force compresses the spring set, causing the push rod to displace, and drives the valve core through the connecting rod to produce a corresponding stroke, changing the throttling area between the valve core and the valve seat to achieve the purpose of regulating the medium flow. Features: It has advantages such as large flow capacity, small unbalanced force, and convenient replacement of action modes; it also has advantages like compact structure, large output force, low height, light weight, and convenient installation and calibration. There are two action modes of the pneumatic double-seat valve: air-to-close type and air-to-open type. The valve core adopts a double-guided structure. Simply install the valve stem into the other guide end of the valve core, invert the valve body, and swap the positions of the upper valve cover, then the air-to-close type can be converted to the air-to-open type.

II. Principle:
     When the pneumatic diaphragm double-seat control valve is used in series, the pressure difference before and after the valve changes with the opening degree, which causes the working characteristic curve of the valve to deviate from the ideal characteristic. If the pipeline resistance is large, the linear characteristic will become a quick-opening characteristic and lose its regulating ability. The equal percentage characteristic will become a linear characteristic. In the case of small flow, since there is little pipeline resistance, the above characteristic distortion is not significant, so the equal percentage characteristic is actually unnecessary. From the manufacturing perspective, when Cv is below 0.05, it is impossible to produce the side shape of equal percentage. Therefore, the main problem for small flow valves is how to control the flow within the required range.

III. Performance Indicators:
1. Spring range: 20-100, 40-200 KPa
2. Supply air pressure: 140-300 KPa
3. Air source interface: Rc1/4
4. Ambient temperature: -30 to +70℃
5. Accessories: Positioner, air filter regulator, holding valve, limit switch, handwheel mechanism, etc.

IV. Main Parameters:
1. Model: ZHAN
2. Type: Double-seat
3. Valve body material: WCB, 304, 304L, 316, 316
4. Valve core material: WCB+PTFE, 304+PTFE
5. Process medium: Crude brine (2% solids), sodium chloride solution (containing solids), sodium chloride solution
6. Medium state: Liquid (containing solids)
7. Operating pressure: (0.6MPa ≤ 32MPa), (PN10 ~ PN320), (150LB ~ 2500LB)
8. Pressure before valve: ≤0.5MPa
9. Pressure after valve: ≤0.2MPa
10. Leakage class: Class V, Class IV

V. Working Principle:
     When applied in pipe networks, the flow control valve can directly set the flow according to the design. Under the action of water, the valve can automatically eliminate the residual head of the pipeline and the flow deviation caused by pressure fluctuations, maintaining the set flow constant regardless of changes in system pressure. These functions of the valve enable one-time completion of pipe network flow regulation, simplifying the pipe network adjustment work to simple flow distribution, and effectively solving the hydraulic imbalance of the pipe network. The flow control valve is mainly applied in water systems such as central heating (cooling), to distribute the pipe network flow as required, eliminate hydraulic imbalance in water systems, solve the problem of uneven heating and cooling, and can save energy and electricity by 15%-20%.