Safety circuit for directly pressurised hose pinch valves in case the control air fails

Directly pressurised hose pinch valves are open-closed valves. The means of control - air, water or neutral gases - pinches together the middle of a cylindrical hose. lf the control pressure is removed, the hose opens again to its full cross-section due to its elasticity. The valve therefore fulfills the "safety position open" requirement.

It is nevertheless often necessary that the pinch valve closes automatically should the means of control fail, thus the valves moves to the safety position "closed". This position can also be achieved for directly pressurised hose pinch valves by a special circuit which is described below.

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The control pressure, 10 bar for example, is reduced to 4 bar via the reducer valve (1). This pressure drop, which occurs at the pneumatically-operated three-way solenoid valve (3), causes the valve to open the path from A to B. lf the three-way solenoid valve (2) is now operated electrically or manually, control pressure is then applied to the hose pinch valve.

Should the control pressure suddenly fail, the path from A to B at the pneumatically-operated three-way solenoid valve (3) is interrupted and the path from C to B opened. Compressed air is now fed to the hose pinch valve via the reservoir tank (4), which was previously pressurised via the check valve (5), and the reducer valve (6) - which reduces the control pressure of 10 bar from the reservoir tank (4) to 4 bar - and via the pneumatically-operated three-way solenoid valve (3) already switched from C to B, causing the hose pinch valve to close automatically.


With reservation of technical changes.