Interlocking three on/off valves

[olame]

Helpfull members,
I want to interlock three on/off valves with a pneumatic 3/2 solenoid valve on each valve such that only one of the valve can open at a time. Can anybody propose a scheme for this?

 

[gerhardl]

How safe or redundant do you want the system? Failsafe positions by no air or no elctricity? Details on applications?

3/2 way pneumatic valves suggest spring return operated actuators.

Suggestion 1. Straightforward/simplest - electrical operation.

All solenoid valves normally closed, open with electrical current. All pneumatic operated valves, normally closed (by spring) opens by air. Failsafe all: closed (by no air and/or no current).

Each valve operated by one common electrical control switch with four positions: all off, current to either of solenoid valve 1, 2 or 3.

Suggestion 2. Manual and/or electrical by 5/3 valve.

Open or closed for each main valve electrically by 3/2 valve, generally as above, or separately for each

In addition is installed a manual or electrical operated 5/3 valve for the operating air. In end positions the 5/3 is connected as to give air to for instance main valve 1 and 3 separately (one each end position)

In the mid position the 5/3 is selected with function 'airaition' air return for valve 1 and 3.

You put in addition a pneumatically operated spring return valve (2/2 pneumatical) for the airline for mainvalve number 2 between mainvalve 2 and the mid position of 5/3 valve operater of the 2/2 connected to airaition (air return posrts) in this position.

If the 2/2 pneumatical operater is given air (connected to) both airlines for for mainvalve 1 and 3, and the 2/2 is closed by air it will always remain closed when 1 and 3 is open (has operating air pressure).

Only way to open the 2/2 wich is controlling the airline in to mainvalve 2's solenoid valve is mid function of the 5/3, where mid position is air airaition (return).

In this way you can use all the three positions of the 5/3 as selector for operation of one dedicated single of your main valves.

3. Other solutions.
Other combinations of normally closed/open mainvalves, solenoid valves or one or more 2/2 valves.

4. Redundant solutions
Some producers (for instance Norgren) will be able to suggest redundant combinations of solenoid valves for added safety, but you have to give specific information of wished function.

 

[olame]

Many thanks Gerhard,

To explain a little better:

I already have two valves interlocked together with the attached schematic, but I want to add a third valve with a simple modification to the existing scheme. The condition remains that only one valve will be open at the same time. Note also that the interlock has to be purely by pneumatic solenoids.