What are the types of SMC pressure reducing valves

The working principle of SMC diaphragm pressure reducing valve is: pull the handwheel outward, and when the yellow circle is seen, rotate the handwheel clockwise. The pressure regulating spring is compressed, pushing the diaphragm component downwards. Through the valve stem, the valve core is opened, and the inlet pressure is throttled and reduced by the valve core, resulting in pressure output. The outlet pressure gas enters the lower chamber of the diaphragm through the feedback tube, generating an upward thrust on the diaphragm. When this thrust is balanced with the pressure regulating spring, the outlet pressure stabilizes at a certain value.

Rotate the handwheel counterclockwise, the force of the pressure regulating spring continuously decreases, the valve core gradually closes, and the compressed air in the lower chamber of the diaphragm is continuously discharged from the exhaust hole through the overflow valve until the outlet pressure drops to zero.

After the pressure adjustment is completed, press the handwheel back and lock it to maintain the set pressure. Therefore, it is called a locking handwheel.

Overflow pressure reducing valves are commonly used in situations where the secondary side load changes, such as frequent adjustments, and where there is a container (such as a cylinder) on the secondary side. During use, a small amount of gas often needs to be discharged from the overflow hole. When the medium is a harmful gas in the gas path, in order to prevent pollution of the workplace, a pressure reducing valve without an overflow hole should be selected, that is, a non overflow pressure reducing valve. Non overflow pressure reducing valves are also commonly used in blowing systems and air motors that frequently consume air.

Refer to the schematic diagram of SMC AR balanced direct acting pressure reducing valve structure above.

If there is a fluctuation in import pressure, such as an instantaneous increase in pressure, the outlet pressure will also increase accordingly. The thrust acting on the diaphragm increases, causing the diaphragm to move upward and compress the spring upwards, resulting in instantaneous overflow from the overflow hole in the middle of the diaphragm assembly. And relying on the reset spring and air pressure, the valve stem moves upward, the valve opening decreases, the throttling effect increases, and the outlet pressure drops back until a new equilibrium is reached. After rebalancing, the outlet pressure has basically returned to its original value.

When the inlet pressure remains constant and the output flow rate changes, causing fluctuations (increase or decrease) in the outlet pressure, relying on the overflow effect of the overflow hole and the balance effect of the force on the diaphragm to push the valve stem can still stabilize the pressure. When the output flow rate is zero, the outlet air pressure enters the lower chamber of the diaphragm through the feedback tube, pushing the diaphragm upward. The reset spring force pushes the valve stem upward, and the valve core closes, maintaining a constant outlet air pressure. When the output flow rate is large, high-speed flow causes a decrease in static pressure at the feedback pipe, that is, a decrease in pressure in the lower chamber of the diaphragm, an increase in valve opening, and still maintains force balance on the diaphragm.

Structure and principle of SMC ARP series direct acting precision pressure reducing valve

The following is the schematic diagram of the SMC ARP series direct acting precision pressure reducing valve structure. The main difference from ordinary pressure reducing valves is the presence of a constant discharge overflow hole. Its voltage stabilization accuracy is high, at 0.001MPa. But there are slight leaks. There are tubular connections and modular connections.

Schematic diagram of SMC ARP direct acting precision pressure reducing valve structure

Technical parameters of SMC AR series pressure reducing valve

categoryseriesConnection caliberMaximum import pressureinlet pressurevoltage regulation rangeEnvironment and medium temperature

普通型AR10M5×0.81set pressure

+0.05 or above0.05~0.3-5~60

AR20Rc1/8·1/40.05~0.7

AR30Rc1/4·3/8

AR40Rc1/4·3/8·1/2

AR40-06Rc3/4

AR50Rc3/4·1

AR60Rc1

Precision typeARP3000Rc1/40.8More than 10% higher than the export pressure0.05~0.85

Attention to the use of SMC AR series pressure reducing valve

1) For ordinary pressure reducing valves, the outlet pressure should not exceed 85% of the inlet pressure; Precision pressure reducing valve, the outlet pressure should not exceed 90% of the inlet pressure. The output pressure shall not exceed the maximum value of the set pressure.

2) The connecting piping should be thoroughly purged.

3) The direction of air flow should be installed in the direction of the arrow and should not be reversed.

4) When using plastic pressure reducing valves, direct sunlight should be avoided