The HIPRES^® Accumulator has been designed with a proprietary metal bellows configuration. The metal bellows forms a chamber, which contains the hydraulic fluid and separates it from the gas charge. The benefit of the metal bellows design is the elimination of the elastomeric seals normally used in traditional piston or bladder type accumulators. The seals of the piston or bladder type accumulator eventually leak, allowing the gas charge to migrate into the hydraulic fluid and thus degrade accumulator and hydraulic system performance. With the HIPRES^® Accumulator, the metal bellows acts as the barrier (dynamic seal) between the gas charge and the hydraulic fluid. The gas charge is hermetically sealed and thus, never leaks nor degrades.

The all-welded stainless steel construction is impervious to the corrosive effects of all common hydraulic fluids. These units may operate in systems up to 8000 PSI and temperature ranges from -65° to 275° F (-54° to 135° C).

HIPRES^® Accumulators are pre-charged and hermetically sealed at the factory. During manufacture the accumulators are tested using a Helium Mass Spectrometer leak test. This ensures that there will be no appreciable leakage of charge gas in over 10 years of service.

As an alternative, for very high pressure applications (8000 PSI), HIPRES^® may be charged with helium rather than nitrogen. The hermetic sealing performance of the proprietary metal bellows design allows helium to be used as an option for the charge gas. In very high pressure systems the use of helium allows a reduction in accumulator size by as much as 50%. Conventional accumulators cannot use helium, because the elastomeric seals are subject to permeation of the charge past the seals causing loss of charge pressure.

All HIPRES^® Accumulators are designed to meet or exceed the requirements specified in ARP 4378. This Aerospace Recommended Practice specifically defines the specification and qualification requirements for maintenance free accumulators.

Lightweight Composite Housing Technology

HIPRES® accumulators are available with a lightweight composite housing. The composite housing designs are 30%-40% lighter than our steel housing accumulators. The accumulator housing consists of a metallic liner covered with a graphite-epoxy composite.

Burst Testing

The composite housing has been tested to sustained pressures of 20,400 psig. Actual rupture occurred above 25,000 psig.

Ballistic Fragmentation Testing

The composite housing technology has been tested to the SAE ARP4378 requirements for ballistic fragmentation. In this test the accumulator is struck with a .50 caliber tumbling M-2 armor piercing bullet with a muzzle velocity of 2800 ±100 fps at a range of less than 25 yards. The requirements state that “when struck by gunfire, the accumulator shall remain in one piece and the greatest dimension of the opening (cut and tear) created by the projectile shall not exceed the dimensions of the hole (cut) created by the projectile by more than 3 inches in any one direction.”

This new technology offers significant weight savings and the ability to pass ballistic fragmentation.