Decompression

2 Stage Decompression

Our decompression systems use pilot operated valves as a means of achieving two stage decompression.

The objective is to gradually reduce the system pressure until the threat of decompression shock no longer a factor and at that point of the pressure reduction cycle, open a second valve with greater flow capacity which will allow the cylinder or vessel to complete the drain to reservoir (tank) cycle.

The relationship of decompression to pressure is complicated by cylinder or vessel diameter, length and diameter of hoses in the system. Each system may be unique and safe stage two decompression pressure should be determined based on testing by the OEM and then determining a safe PSI for each system design.

Product	Spec Sheet No.
Housings
SD2 Housing for Two Stage Decompression	1201268
SD842 Housing for Two Stage Decompression	1203114
Valves Used in conjunction with above housings for 2 stage decompression
Air Pilot, 1-1/2 GPM, Hex Base, N/C 1 to 2, Pilot to Open, Ratios to 255:1, Uni-directional	1201235
Air Pilot, 1-1/2 GPM, Tamper-Resistant, N/C 1 to 2, Pilot to Open, Ratios to 255:1, Uni-directional	1201457
Manually-Operated, 1-1/2 GPM, Hex Base, N/C 1 to 2, Push to Open Force (PSIx.013+15PSI)	1201499
2 Way, N/C, Pilot with Manual Override, Orifice Option	1202392

Decompression Example

An example of the Doering Company approach to decompressing from 5,000 PSI to 650 PSI in stage one and 650 PSI to Zero or tank return line pressure in stage two. Valves to be air pilot operated using 45 to 55 PSI pilot air. Effective pilot pressure is reduced 5 to 10 PSI due to springs in valve. This is not a recommendation of 650 PSI being an appropriate stage one PSI. It is only intended to be an example of how to select a housing and valves that will provide the example function.

Example Components:

SD2-3S Housing	Spec. Sheet No. 1201268
82H0151681 Stage 1 Valve, 168:1, with .015 Orifice	Spec. Sheet No. 1201235
84H2090191 Stage 2 Valve, 19:1	Spec. Sheet No. 1201653

Apply air pilot signal of 45 to 55 PSI to both Stage 1 and Stage 2 valves simultaneously. The Stage 1 valve will open first due to the pilot to system ratio (effective pilot pressure 35 PSI X 168 pilot ratio = 5,880 which is well above the starting pressure of 5,000 PSI.

Stage 2 Valve will open for increased flow when system pressure reaches approximately 650 PSI (effective pilot pressure 35 PSI X 19:1 Pilot ratio = 665 PSI). Both valves will remain open as long as pilot pressure is applied.

To increase or decrease the pressure at which Stage 2 Valve opens, increase or decrease the pilot pressure. Actual tests should be conducted to determine the ideal settings.

Doering Company offers a range of pilot to system ratios. We also offer a range of orifice diameters to best suit your application.