Supplemental Information, 1268
Supplement 1268 provides additional information to Spec. Sheet No. 1201268, to help apply the inherent advantages of using pilot operated valves as a means of achieving two stage decompression. The key is utilizing the pilot to system ratios available.
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 vesel 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.
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.
SD2-3S Housing, Spec. Sheet No. 1201268
82H6041681 Stage 1 Valve, 168:1, 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 valve 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 will soon be offering an orifice option for the stage one vale, which will provide an additional means of controlling the decompression cycle.
Thank you for your interest in using Doering products. Please feel free to contact our engineering department for clarification or additional assistance or to provide feedback regarding the clarity or usefulness of this supplement or other pages and documents contained in our web site.