Two-stage Gas Regulators

Two-stage pressure regulators reduce cylinder pressure to delivery or outlet pressure in two steps. Two stage regulators work in much the same way as single stage regulators with one main difference. Rather than having one diaphragm and poppet, they have two. The first stage reduces the pressure, but as the cylinder empties, the pressure exerted on the first stage decreases allowing the flow to increase. It happens in just the same way as the single stage regulator, but here is the clever bit: the outlet pressure still remains constant with no need to adjust the regulating knob. The reason for this is the second stage. This second stage is constructed in a similar manner to the first, but the pressure being exerted on the second diaphragm and valve stem is much less. Stage one is regulating very high pressures from the cylinder and reducing them down to extremely low pressures. Therefore it is low pressure gas that passes through the second poppet. The regulator outlet pressure doesn't creep because the low pressure passing through the second stage is too low to cause an imbalance on the diaphragm.