When inserted in the gas side of a hydraulic accumulator, elastomeric foams can reduce the thermal loss and significantly improve the efficiency of this device. In this study, an open-cell polyester-urethane foam was placed in a 2.5-liter piston-type accumulator and cycled 36,000 times at 0.025 Hz. No significant chemical breakdown was measured in the foam, but a 25 percent compression set occurred due to foam cycling. This resulted in a reduction in accumulator efficiency from 84 percent with the new foam to 81 percent with the 36,000-cycle foam. To counteract the compression set, a quantity of new foam was added to the old foam. This increased the efficiency to 83 percent. The accumulator had an efficiency of 66 percent without the foam. The foam reduced the steady-state accumulator wall temperature significantly. It did not cause any problems in the hydraulic system.

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