This accumulator consists of a cylinder containing a freely floating piston with proper seals, as illustrated in Figure 7.17.
The piston serves as a barrier between the gas and oil. A threaded lock ring provides a safety feature that prevents the operator from disassembling the unit while it is precharged.
The main disadvantage of piston-type accumulators is that they are very expensive and have size limitations. In low-pressure systems, the piston and seal friction also poses problems. Piston accumulators should not be used as pressure pulsation dampeners or shock absorbers because of the inertia of the piston and the friction in the seals.
The principle advantage of the piston-type accumulator lies in its ability to handle very high- or low-temperature system fluids, through the utilization of compatible O-ring seals.