How to analyze the failure of pneumatic British NORGREN solenoid valve?
British NORGREN solenoid valve also causes the main problems of the control system to concentrate on the conditioning system's terminal installation, ie, the conditioning valve. The conditioning valve controls the operation signal in the process of controlling the fluid flow and completes the regulation of the flow according to the control law. Its action The flexibility of the UK NORGREN solenoid valve directly affects the quality of the entire control system. According to the application statistics of the control system in the soda industry, about 80% of the conditioning system's faults are caused by conditioning valves. Therefore, how to ensure the reliable and precise operation of the pneumatic diaphragm control valve in our factory consumption is a very important issue that we need to discuss.
1 Current Status Investigation UK NORGREN solenoid valve During the consumption of soda ash, due to the severe corrosiveness of ammonia brine, the nature of ammonium bicarbonate is easily crystallized below 25°C, making the conditioning valve in operation due to the internal wall blemishes and crystallization of the valve. Scaling leads to valve card, no action or dull action, so that the system can not stop the phenomenon of automatic conditioning compared to the general, accounting for 50% of the total number of conditioning valve problems, a greater impact on the formation of the consumer; conditioning valve packing aging, hardening valve Dull action or leakage from the valve stem and other problems up to 15%; due to diaphragm damage, leakage or hard core chipping caused the valve can not be conditioned phenomenon up to 12%; due to the positioner, relief valve, actuator and other corrosion caused valve problems The phenomenon accounted for 10%; the other causes 13% of the probability of incurring valve problems.
2 Analysis of the causes of faults Based on the analysis of the defects of pneumatic membrane conditioning valves used in the soda ash consumption field for many years, common causes and their causes can be summarized as follows:
2.1 Valve does not move
1) Due to faults in the conditioner, the conditioning valve has no electrical signal.
2) Due to leakage of gas source manifold, the positioner has no air source or air source pressure.
3) Locating the bellows of the positioner, so that the positioner has no air source output.
4) The diaphragm of the conditioning valve is damaged.
5) Due to the constant orifice throttling of the amplifier in the positioner, the compressed air containing water and the accumulation at the ball valve of the amplifier causes the positioner to have an air source but no output.
6) The valve still does not operate due to the following problems due to the following problems: 1 Spool stuck to the bushing or valve seat; 2 Spool drop (pin broken); 3 Stem bent or broken ; 4 Faults in the actuator: 5 Leakage in the seal of the reaction-type actuator; 6 Foreign matter in the valve.
2.2 The valve is not stable
1) The pressure of the air source changes frequently due to the malfunction of the pressure reducing valve.
2) The ball valve of the amplifier in the positioner is worn out by particles or scum, so that the ball valve does not close tightly, and output oscillation occurs when the gas consumption increases.
3) The nozzle baffle of the amplifier in the positioner is not parallel and the baffle does not cover the nozzle.
4) Leakage of the output line.
5) The rigidity of the actuator is too small and the fluid pressure changes to form a lack of thrust.
6) The stem has a large wear force.
7) The pipeline oscillates or has a vibrating source around it.
2.3 valve action dull
1) Steady movement of the valve rod during reciprocating stroke: 1 There is mud or viscous medium in the valve body, which makes the valve block or fouling;
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