Piston Accumulators are a cost effective option for numerous functions involving energy storage, and sometimes shock absorption in a hydraulic or fluid system. They are well suited for applications needing:
HYDAC piston accumulators consist of:
Precise information about the proposed operating conditions is required in order to select the most appropriate sealing system. Important criteria for this selection are:
TYPE 2 Without Check Valves
Application (without Check Valve)
Low-friction design for higher piston speeds, slow movements without stick-slip effect and high number of actuations (millions). Actual cycles achieved will vary with operating parameters. Notes: Filtration ≤ 10 µm absolute. (ISO 17/15/12) Max. continuous velocity = 12 ft/sec
TYPE 2 With Check Valves
Application (with Check Valve)
The addition of a check valve drastically reduces the oil pumping to the gas side of the piston.
TYPE 3
Application
Actual cycles achieved will vary with operating parameters.
Notes: Filtration ≤ 10 µm absolute. (ISO 17/15/12)
Max. continuous velocity = 3 ft/sec
The following sealing elastomers are available, depending on the operating conditions:
Suitable materials are also available for low temperature applications.
The following sealing materials are suitable for the fluids listed below:
NBR, resistant to:
NBR, not resistant to
FPM, resistant to:
FPM not resistant to:
PUR resistant to:
PUR not resistant to:
For use with certain aggressive or corrosive fluids, or in a corrosive environment, HYDAC offers protective coatings and corrosive resistant materials (i.e. stainless steel) for the accumulator parts that come in contact with the fluid, or are exposed to the hostile environment.
HYDAC piston accumulators may operate in any position. Vertical installation is preferable with the gas side up. We recommend the use of our mounting components, which are detailed on page H21, to minimize risk of failure due to system vibrations.
The permissible piston velocity depends on the sealing friction. Higher piston velocities are possible where there is less sealing friction.
HYDAC piston accumulators with low friction piston seals allow continuous operating velocities of up to 12 ft/sec with short bursts, up to 15 ft/sec (see type 2 piston).
Small pressure differentials between gas and oil side improve the effectiveness of HYDAC piston accumulators. To emphasize the friction effect on the pressure curve during an accumulation cycle, measurements with various sealing systems are illustrated.
The measurement graphs below are a true representation of the gas and oil pressure of piston accumulators with different sealing systems. The comparison of these two measurements clearly shows the difference in the pressure differential between gas and oil side:
Graph 1: ∆p max. ≈ 125 psi
Graph 2: ∆p max. ≈ 14.5 psi
The effect of the sealing friction on the working pressure is particularly striking in traditional piston designs. Abrupt piston movements (the stick-slip effect) are caused by the seal friction as shown in Graph 1. The low sealing friction of HYDAC type 2 pistons drastically reduces the stick-slip effect therefore maximizing piston responsiveness.
(Non-ASME) 3000 psi
Advantages
The piston accumulator series SK210 is an intermediate bore diameter with repairable design. They are HYDAC certified, designed in accordance with ASME pressure code. Features of this series are:
Application
(Non-ASME) 4000 psi
Advantages
The piston accumulator series SK280 is a weight optimized, nonrepairable design. The non-repairable design and special production process of these HYDAC accumulators save cost, making this series an economic option.
Application
(Non-ASME) 5000 psi
Advantages
The piston accumulator series SK350 are an intermediate bore diameter with repairable design. They are HYDAC certified, designed in accordance with ASME pressure code. Features of this series are:
Application
(ASME) 3000 psi & 5000 psi
Advantages
The piston accumulator series SK350 & 600 are HYDAC’s most versatile series with a repairable design and large selection of options. The largest range of possible sizes, material construction, and other options are offered. Standard and Low Friction piston designs are available for superior performance and flow rates. Features of this series are:
Application