Adams Valve (cutaway version)
Date of manufacture:
This valve reduces the declining cylinder gas pressure to an approximately constant reduced outlet pressure suitable for delivery to a flowmeter/needle valve assembly. When the cylinder valve is opened, gas enters the chamber below the diaphragm forcing the diaphragm to rise. Its attachment to the reversal linkage causes a downward movement of the valve seat, closing the valve and interrupting the flow of gas from the cylinder. If gas is permitted to exit the chamber via the outlet nozzle, the slight fall in pressure reduces the upward force on the diaphragm, permitting the valve seating to rise and thereby allowing more gas to enter the chamber from the cylinder. The outlet pressure is maintained more or less constant at a level that is set by adjusting the tension in the tensioning spring since its action is to tend to lower the diaphragm and open the valve seat. 5 psi is the maximum that can be contained by rubber tubing forced over a nozzle without it tending to blow off. The Adams Valve is unusual in that cylinder pressure tends to open the valve rather than close it.
Pressure Reducing Valve
Nitrous Oxide loses heat on expansion. This chills the Adams valve which would become jammed in the open condition by frozen water vapour that tended to contaminate medical gases. Consequently, some Adams regulators bore external fins to absorb heat from the surroundings and reducing the risk of this occurrence.