This NAMUR mount control valve is a 5/2 monostable spool valve ideal for double acting & spring return Mercon quarter turn valve actuators. The 5 in the designation refers to the number of ports, 1…
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This NAMUR mount control valve is a 5/2 monostable spool valve ideal for double acting & spring return Mercon quarter turn valve actuators. The 5 in the designation refers to the number of ports, 1 air supply, 2 exhaust ports & 2 working ports (outlets to each end of the actuator). The 2 in the designation refers to the positions of the spool. Either activated, by the electrical solenoid, or reset, by the return spring.
Using a 5/2 monostable control solenoid & a spring return actuator makes the design of a fail safe system very simple. Because of the spring return of the solenoid spool, its de-energised or power fail position is known. Similarly the spring return function of the actuator returns it to a known position in the event of air fail. At the time of assembly it can be determined that the valve will fail to the open position, or fail to the close position, on loss of air and/or power.
It is possible to operate a spring return actuator with a 3/2 solenoid valve & this does reduce air consumption by allowing the spring alone to return the actuator to the initial position.
However we strongly recommend the 5/2 solenoid on our actuated valves for the following reason. The actuator is moved by compressed air in both directions, this air supply will have been dried & filtered and hence non corrosive. The purpose of the spring is to provide a fail safe function in the event of a loss of compressed air &/or electrical supply to the control solenoid.
If a 3/2 solenoid is used with a spring return actuator, the actuator will “breathe” through the exhaust port. When the actuator is operated by compressed air the back side of the pistons will expel air out through the exhaust port. When the actuator is returned by the spring the back side of the pistons will draw air back into the cylinder through the exhaust port. If this air is damp or the atmosphere is corrosive, rapid wear of the internal surfaces will occur.
For a double acting actuator, a 5/2 valve must be used. A single 3/2 valve will not work, it does not have a working port that can be pressurised to return the actuator to it’s initial position. For some applications 2 x 3/2 valves are used so different pressures can be applied to each side of the actuator piston. Occasionally a free moving piston may be required, with 2 x 3/2 valves both sides of the actuator piston can be vented. Generally these applications are not encountered with quarter turn ball or butterfly valves.
