Accumulators come in a variety of forms and have important functions in many hydraulic circuits. They are used to store or absorb hydraulic energy. When storing energy, they receive pressurized hydraulic fluid for later use. Sometimes accumulator flow is added to pump flow to speed up a process. Other times the stored energy is kept in reserve until it is needed and may be independent of pump flow. This could be for emergency power when pump flow is not available. It could be used to hold pressure in a system when pump flow has stopped by providing fluid to compensate for leakage. There are several ways in which accumulators are used to absorb energy. The returning flow from a large-bore cylinder may be greater than should be conducted by the plumbing. A low-pressure accumulator can receive a portion of the flow and then discharge it at an appropriate rate for the plumbing. Hydraulic fluid has a relatively high rate of thermal expansion. If a volume of fluid is confined and unable to expand or contract due to temperature changes, there could be very high pressure that could damage equipment or low pressure that could cause air bubbles in the hydraulic fluid. Accumulators can be used to absorb the expanding fluid and/or supply the contracting fluid. They also absorb and dissipate energy when used to dampen pressure pulses, reducing noise and vibration.
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