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.