Innovative approach replaces piston with bellows


Industry’s first maintenance-free accumulator greatly improves mission-readiness for U.S. Air Force.

The Challenge

The U.S. Air Force KC-135 Aerial Refueling Tanker was experiencing severe aircraft downtime due to a highly unreliable piston accumulator used on the fuel boom. The incumbent piston-style accumulator often failed under extreme operating temperatures. Premature wear and breakdown of the piston seal caused the accumulator gas charge to leak. As a direct result of this issue, aircraft mission availability greatly suffered.

The Solution

The Senior Metal Bellows team developed the industry’s first maintenance free accumulator.  Instead of using a sliding piston and seal to separate the gas charge from the hydraulic fluid, a welded metal bellows was employed.  This produced an all-metal, fully welded accumulator with a hermetically sealed gas charge.

Since every accumulator is permanently pre-charged at the factory, no maintenance is required on the component for the entire life of the aircraft. The accumulator’s frictionless design is effective in dampening surges, impulses, water hammer issues, and pump ripple in hydraulic systems.

The Results

Lower total life cycle costs, increased aircraft availability, zero gas leakage, never requires re-charging or seal replacement, compatible with virtually all fluids (hydraulic fluids, fuels, oils, cooling systems, etc.), allows for use of the accumulator in extreme temperatures.