Membrane Valve as Relief Valve (Spill Valve)

by Calvin McCarthy

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Membrane Valve as Relief Valve
I have been looking for a reservoir relief valve system which will provide positive sealing when closed, minimal pressure to keep closed, and easy opening. It would seem best to have the pressure of the air in the reservoir providing the force to seal the valve instead of depending on a spring strong enough to hold a cover shut against the pressure. The Open and Shut action is very quick, but I have found that the sound of the organ does not notice this.

In my internet reading of hobbyist Busker Organ construction I came across the website of Bernard and Philippe. It is filled with ideas and technical information about building crank organs.

They have a page describing valves called Tangential Membrane valves (TMC) and Concentric membrane valves (VMC). They are using the valves in an organ reading music “books”. I thought, “here is a solution to my relief valve problem!” A very small control pressure will hold the valve closed and a very simple lever will open a small hole which will open the actual large valve releasing a useful amount of air when required. Some diagrams show what is happening.

Construction may be challenging but the only part which is critical is the seal for the top chamber and the seal of the membrane on the input tube. Dimensions are not critical and can be adjusted for your particular installation.

Membrane valve closed

Membrane valve open

Bottom open

Bottom closed

Bottom with membrane

Top open

Valve package

Plan view

Membrane relief valve on Melvyn Wright bellows system

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