Repeatable Cylinder Decompression: The "Balanced" Way
Since this stored energy in the cap end of a cylinder is a "fact of life" (and don't forget that the machine frame and product being compressed can also add to the total stored energy), the goal is to release this energy in a controlled and consistent manner, in the shortest time that will achieve an "acceptable" decompression rate (which is usually determined subjectively). The use of dedicated decompression circuit components (i.e. staged pilot ratio check valves, orifices, solenoid valves controlled using electrical time delay logic, etc.) can be expensive, have questionable reliability, not always be consistent, and consume excess cycle time.
Here's a simplified solution:
By using Sun DK*R Balanced Logic Elements with a 2-way DAAL-*CN pilot valve and a Sun PRDB pressure reducer/reliever, the result is a zero leak, reliable, consistent, uncomplicated, and cost effective cap-end-to-tank, normally closed logic element. (A DO*R cartridge can be used in place of the DK*R if a normally open function is desired. Either cartridge can also include Sun's T-8A cavity, i.e. DK*R-8 and DO*R-8, to accommodate the pilot control function as an integral unit.) Since this product is "balanced", operating pressures on the work ports have no effect on the opening speed of the valve. (A typical "poppet style" logic element exposes more and more area as the poppet moves to the open position, with the attendant increase in opening force.) So, by adjusting the pilot pressure via the reducer, an acceptable, and repeatable opening time can be very easily set. This approach has proved to be an acceptable solution in minimizing decompression shock in the shortest time with consistent results. (By the way, using the newer DAAL-SCN "soft shift" 2-way as the pilot valve, can further enhance tuning for shock reduction.)