Accumulators are necessary for good closed loop control. In a closed loop system the purpose of the accumulator is to keep the system pressure as constant as possible by supplying oil when the pump can’t respond fast enough to current flow demands. In the field I see 3 main problems with how accumulators are misused.
- The accumulators are misplaced. Often the accumulator is placed near the pump. The accumulator should be placed neared the valves. This is where the energy must be stored. This also minimizes pressure loses between the accumulator and the valves.
- The accumulators are sized too small. Obviously the accumulator should hold enough oil so that the accumulator will not empty but the oil does not store energy, the pressurized nitrogen does and it is critical that the size of the nitrogen volume changes as little as possible so the pressure changes as little as possible.
- The accumulators are pre-charged at too low a pressure. When this happens there will be more oil in the accumulator than necessary but the gas volume will be too small so that changes in the gas volume cause big pressure drops.