Fossa piston accumulators are devices that can be adopted in a large number of applications to store and exchange energy with the hydraulic system to which they are connected.

The piston accumulator consists of two chambers separated by a floating piston equipped with proper seal and guides system. One of the chambers is filled with gas (usually nitrogen) under opportune pressure and the second one is connected to the hydraulic circuit.

The gas pressure must be chosen according to the working conditions of the accumulator and represents the pre-charge pressure. When the hydraulic system reaches a pressure value higher than the pre-charge one, the fluid flows into its chamber forcing the piston to move accordingly and pressing the gas contained in the opposite chamber. During this phase, the compressibility of gas allows the accumulator to store energy that will be release to the hydraulic system once its pressure value will be less than the gas one.


The piston accumulator consists of a steel cylinder, closed at both ends with screwed covers, in which slides a piston.

To maximize the time response of the system and to avoid the generation of pressure peaks, the piston is made of aluminum and its construction is lightened by a cavity, facing the gas chamber in order to increase the accumulation volume. As piston accumulator can be in a state of total fluid discharge with the piston lean on to the fluid side end, a concave cavity is also realized on the piston fluid side so that the pressure acts on almost its entire surface.

Together with the slender construction of the piston, the efficiency of the accumulator is assured by a special seals and guides system studied with the aim of component life, smoothness of movements and reduction of stick slip phenomena; the lower is the differential pressure necessary to move the piston, the better is the response speed of the accumulator.

The sealing materials are strictly correlated to the working temperature and to the nature of fluids and gas they separate. A wide range of solutions is available to meet the customer needs.



The Fossa piston accumulator is a product designed to ensure high performances and low maintenance even in extreme climatic conditions, multiple options in terms of reference codes and maximum working pressures, with a large variety of volumes to meet the market needs. More, a long list of accessories makes the piston accumulator able to be customized to fulfill the requirements of any applications.


The boost you need for your system


  • Various and fully customizable volumes available, by selecting the combination of diameter and length
  • Optional piston position monitoring system
  • Either vertical or horizontal installation position 
  • Total discharge is possible
  • Low friction sealing system for long life
  • Maintainable design
  • Very low gas permeability compared to bladder or diaphragm accumulators
  • Light piston construction for high dynamic performances
  • Different connections available on both fluid and gas side cover ends
  • In case of failure no sudden gas loss
  • Sealing systems available for different kinds of operating liquids, wide temperature range and applications



Fossa Hydraulics accumulators are manufactured respecting  European and American standard but can meet any international standard. 

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