Press Release

Date: November 15, 2004
Contact: Michael Grandinetti
(781) 781 302-1214
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Lighter, Tougher, Safer
Lightweight composite housing for HIPRES® accumulators passes ballistic and burst tests

Sharon, MA... Anytime you can reduce the weight of a component on an aircraft, the commercial and military markets will be interested. When you achieve that weight loss and can still meet standards for strength and toughness, it’s even more impressive. Senior Aerospace Metal Bellows today announced the release of new HIPRES® accumulators using a composite housing technology to reduce weight and still pass the ballistic fragmentation test necessary for military aircraft and the burst test for both commercial and military use.

"The new HIPRES® accumulators are suitable for use in commercial and military aircraft hydraulic systems," said Peter Fontecchio, CEO of Senior Aerospace Metal Bellows. “With a new composite housing, they achieve a weight reduction of 30-40% as compared with standard steel accumulators.”

“In addition, the composite housing is capable of passing the ballistic fragmentation requirement for military craft,” Fontecchio added. “This toughness is important to commercial aircraft as well, where the added safety is a benefit.”

Passing the Ballistic Fragmentation Test

The ballistic fragmentation testing was conducted per SAE ARP4378 on an accumulator that incorporated a composite housing. Per section 3.4.9 of ARP4378, “the accumulator, when struck by gunfire as specified in 4.7.10, 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.”

The test was conducted on an accumulator that had been charged to 2,000 psig. The accumulator was mounted using two ratchet straps, one on each side of the accumulator, and was pressurized with water to an operating pressure of 5,000 ±50 psig. The accumulator was struck with a tumbling .50 caliber M-2 armor piercing bullet with a muzzle velocity of 2800 ±100 fps at a range of less than 25 yards.

The test result clearly demonstrates that an accumulator with the composite housing design successfully passed fragmentation testing per ARP4378. The housing remained in one piece with an entrance hole through the center of the accumulator and no exit hole. The dimensions of the entrance hole were well within the test standards and no fragments were expelled from the accumulator.

Composite Accumulator	After Ballistic Fragmentation Test

Test Proof & Burst Test

Proof pressure and burst pressure testing was conducted on a prototype accumulator housing that consisted of a metallic liner covered with a graphite-epoxy composite. The test unit was hydraulically pressurized with distilled water. Initially, it was pressurized to an operating pressure of 5,225 psig, which was held for 5 minutes. The pressure was then increased to a proof pressure of 15,300 psig. After dwelling at the proof pressure for five minutes, the housing was drained and mass spectrometer helium leak tested. The leak rate was found to be less than the allowable 1 x 10-7 standard cc/sec helium maximum. Following leak testing the test unit was re-pressurized to the required burst pressure of 20,400 psig, which was then held for two minutes. After dwelling at the burst pressure, the pressure was increased to failure, which occurred above 25,000 psig.

The ballistic fragmentation, proof and burst test results clearly demonstrate the effectiveness of the composite housing. This technology provides up to 40% weight reduction with the added benefit of being able to pass ballistic fragmentation requirements. This significantly lighter weight and added safety is of great benefit to both commercial and military aircraft applications.

Senior Aerospace Metal Bellows

Since 1955, Senior Aerospace has provided custom-engineered solutions to meet and exceed customers' mechanical and electromechanical component and assembly requirements. At Metal Bellows, we apply our welded bellows technology to applications requiring superior performance and high reliability.

Senior Aerospace Metal Bellows is a Senior plc company.

Senior is an international engineering group with operations in 12 countries. Senior designs, manufactures and markets high technology components and systems for the principal original equipment producers in the worldwide aerospace, automotive and specialized industrial markets.