the answer to this month's trouble shooter is provided by Parker Hydraulics.
Q How do I choose between bladder, diaphragm and piston accumulators?
A These three types of accumulator are all able to carry out a number of important functions in hydraulic applications, including reducing shock, maintaining system pressure, compensating for leakage, and providing a back up power supply when system demands are higher than the pump can deliver.
Bladder accumulators offer quick response times, hysteresis-free operation and good tolerance against contamination from the system fluid; however, they only offer a limited compression ratio (up to 4:1) and limited flow rates when compared with piston accumulators. The failure mode of bladder accumulators is immediate.
Alternatively, piston accumulators offer extremely high flow rates, a wide operating temperature range, high compression ratios (up to 10:1) and resistance to external forces. They also offer virtually unlimited size availability, large gas ports for use with supplementary gas bottles in applications where additional or remote gas capacity is required, position monitoring of the piston, and more versatile mounting possibilities.
Diaphragm variants will withstand compression ratios of up to 8:1 and offer the same advantages as bladder types. Compact in design, they are available in small sizes and are particularly suitable for applications such as pilot valve operation. Ideal for 'tamper-proof' applications, diaphragm accumulators are non-repairable and, like bladder accumulators, their failure mode is immediate.