Pneumatic Control Valve

Product introduction

Pneumatic control valve is to compressed gas as the power source, to the cylinder as the actuator, and with the help of valve positioner, converter, solenoid valve, holding valve, gas storage tank, gas filter and other accessories to drive the valve, to achieve switching or proportional adjustment. Receive the control signal of the industrial automation control system to complete the adjustment of the pipeline medium: flow, pressure, temperature, liquid level and other process parameters.

Product characteristics

S streamlined channel, so that its pressure drop loss is small, large flow, wide adjustable range, high accuracy of flow characteristics, compact structure, large output force.

Pneumatic control valve is a kind of automatic execution device using compressed air as power source, usually divided into straight stroke and Angle stroke two kinds. The typical structure of the pneumatic control valve is the valve body, internal parts, drive, actuator, etc., and the application of the valve in different working conditions needs to add accessories to assist the realization of the function. Pneumatic control valve includes positioner, EP converter, manual operation device, damper, etc. The basic performance of the pneumatic control valve determines the accuracy of its work, so when using this type of valve, it should be tested and performance analysis to ensure the application effect.

1 Analysis of functional characteristics of pneumatic regulating valve

The prominent functions of the pneumatic control valve in practical applications include throttling, regulating, cutting off, controlling pressure, blocking, corrosion resistance, etc. Its important function is the adjustment function. From this point of view, its performance characteristics are as follows :① Traffic characteristics. The opening and flow control of the reaction regulating valve can adapt to different working conditions, such as the adjustment of the flow rate and the adjustment of the speed. ② Adjustable range. The larger the control range of the response regulator on the flow rate, the higher its performance. ③ Small opening performance. The small opening performance is limited by the structure, and if the performance is poor, it is easy to shock and jump when the small opening. The high performance regulating valve allows small opening adjustment. ④ Flow coefficient. Represents the valve body passability, that is, the medium through performance, and the passability of the Angle stroke is relatively high. ⑤ Response efficiency. The time used to achieve the adjustment target parameter, i.e. the working speed of the working valve body.

2 Pneumatic control valve performance debugging and performance analysis

According to the above functional characteristics analysis, the regulating valve in the actual application will reflect the valve stroke, basic error, return difference, dead zone, leakage, flow characteristics and other performance characteristics. The performance cannot be tested one by one during debugging, so the stroke, error, leakage, flow characteristics, etc. are detected during testing. 2.1 Stroke debugging

The stroke test is the displacement of the valve stem from the safe closing of the valve to the full opening. The control signal can be accessed in the signal converter, and the adjustment performance of the valve can be tested from full opening to full closing through the input of the control signal.

2.2 Error and dead zone

After the initial debugging of the pneumatic control valve, it is necessary to test the basic error, return difference, dead zone of the valve, etc. The specific situation is as follows: measure the basic error and return difference, input the specified signal to the controller, increase or reduce the signal input to the actuator to measure the corresponding stroke of each point, calculate the theoretical relationship between the signal and the stroke and the difference between the actual curve. The maximum value is the basic error. The test point of the pneumatic control valve includes 0% to 100%, and each 25% is a test point. After the forward measurement is completed, the measurement can be carried out in reverse, that is, the maximum value is zero, and the input is divided into five times, and the record is made. The maximum error can be determined by calculating the basic error and the value of the positive and negative check. In the test, the rated signal is input to the pneumatic actuator, and after the pneumatic valve completes the stroke, there will be a difference between the actual stroke and the scheduled stroke, which is the deviation of the rated stroke and should also be recorded.

The dead zone includes zero dead zone, range dead zone, and 50% dead zone. The so-called "zero dead zone" is to input a signal (4mA) on the basis of 0%, confirm that the valve is completely closed, and then slowly increase the signal. When the valve starts to start, the recording begins, and the percentage of this input semaphore is the zero dead zone, for example, when the valve operates at 4.5 mA, the dead zone is 3%. The range dead zone is to calculate the input signal at 100%, confirm that the valve is fully opened, slowly reduce the input signal, until the valve begins to reset and stop, the calculation method is similar to the zero dead zone. 50% dead zone is the action to the middle position, that is, 50% control amount, after confirming the rest in the middle, increase or decrease the signal, that is, after the valve begins to operate, recorded as 50% dead zone, the dead zone calculation method is the same as the previous two. Under normal circumstances, the dead zone of the pneumatic control valve should be controlled within 3%, and this value should be compared in the actual test to test its performance, and if it exceeds the standard range, it should be checked and corrected in time.

2.3 Measurement of B.S value

The B.S value is defined as the force at which the valve can be closed or opened in its natural state to prepressure the spring. The measurement of B.S value is an important data basis for checking the function of the valve and adjusting the original state of the valve. It can make the valve obtain enough external force to open or close, that is, the force of the spring mechanism to meet the control requirements. To achieve the function of the pneumatic valve, the pneumatic rod and valve stem must be changed with the force loaded on the diaphragm, and the valve will change the range and force of the spring in the process of periodic replacement of the diaphragm and routine maintenance. At this time, the valve should be proofread, if it is found that it can not meet the formation needs, it needs to be B.S test, adjust the initial operating pressure of the spring to meet the needs of restoring the rated setting value of the pneumatic control valve and the diaphragm pressure. The operation steps are as follows: record the B.S value of the pneumatic nameplate; The compressed air source is connected to the system; The starting system triggers the pneumatic head actuator to check the working condition and air leakage of the barometer and the pneumatic head; Pressure relief to 0, adjust the pneumatic rod and slowly adjust the pressure reducing valve to the specified initial value, if the pneumatic rod moves, there is a phenomenon of advance or lag, it should adjust the spring nut to adjust its natural pressure until the pneumatic rod action under atmospheric pressure; After the initial value of the spring is set, the pushing distance of the pneumatic rod is measured, and the pressure is slowly reduced to the maximum B.S of the nameplate. Check whether the moving distance of the valve under pressure is consistent with the mechanical stroke. During the check, the error of B.S should be within 0.05 bar. Measure the distance between the bottom of the adjusted bullet nut and the support, and record it; Finally, according to the program, the coupling is connected with the pneumatic rod and the valve stem. 2.4 Leakage measurement

Use clean air or liquid to measure, and measure after the valve is completely closed, apply a certain pressure to the valve, according to the maximum working pressure difference environment. The signal pressure is zero, close the actuator, check whether the medium on both sides of the test valve is leaking, and measure the pressure difference and flow on both sides, that is, the leakage of the valve.

2.5 Traffic Characteristics Test

The flow characteristic is the proportional relationship between the flow rate of the medium flowing through the valve and the formation of the valve core when the pressure difference between the front and back is unchanged. That is, the change of flow and pressure under different opening and closing degrees. In the test, the value is tested according to every 10% for one measurement node. The pressure and flow curves form the flow characteristics. The common flow characteristics are fast opening, linear, and percentage, and the valve with different flow characteristics reflects different performance in actual work, and the actual flow characteristics can be obtained in the actual test, which is also one of the important data parameters for field debugging.

Quality inspection equipment

Complete testing equipment to ensure product quality.

Packaging & Shipping

FAQ

1. What is the Minimum Order Quantity?
5~1000 pcs.And we also accpet sample orders.
2. Can you manufacture according to customer's samples?
According to samples, we can make drawing, tooling and sample
3.How long will it take to make new samples according to customer's drawing or sample?
Totally 20 days. 10 days for tooling and another 10 days for sample.