Hydraulic accumulators are specialized pressure vessels designed to store and release energy within a hydraulic system. They hold incompressible hydraulic fluid under pressure, helping maintain system efficiency and stability. These devices provide ready power, allowing machinery to operate smoothly and effectively.
The Fundamental Mechanism
The core principle behind a hydraulic accumulator’s operation involves the compression and expansion of a gas. An inert gas, typically nitrogen, is pre-charged into the accumulator, establishing an initial pressure.
When the hydraulic pump generates pressure exceeding this pre-charge, hydraulic fluid flows into the accumulator. This incoming fluid compresses the gas, storing potential energy similar to a compressed spring. The gas volume decreases while its pressure increases, holding the hydraulic fluid under pressure.
If the system’s pressure drops or there is a sudden demand for hydraulic power, the compressed gas expands. This expansion forces the stored hydraulic fluid back into the system, releasing the accumulated energy. This interplay allows the accumulator to manage pressure fluctuations and provide immediate fluid flow.
Key Accumulator Types and Their Operation
Different hydraulic accumulator designs cater to specific operational needs, each employing a unique method to separate the gas from the hydraulic fluid. The most common types are bladder, piston, and diaphragm accumulators.
Bladder accumulators feature a flexible elastomeric bladder inside a steel shell. The bladder is pre-filled with nitrogen gas, while hydraulic fluid surrounds it within the shell. As hydraulic fluid enters, it compresses the gas within the bladder. When system pressure decreases, the compressed gas expands, expelling the fluid back into the system. These accumulators are known for their quick response times and shock absorption.
Piston accumulators separate gas and fluid chambers with a movable, free-floating piston. The gas chamber is on one side of the piston, and the hydraulic fluid is on the other. When hydraulic pressure rises, fluid enters, pushing the piston and compressing the gas. Conversely, when system pressure drops, the compressed gas expands, pushing the piston and forcing fluid out. This design is suitable for higher pressure ratings and larger fluid volumes.
Diaphragm accumulators utilize a flexible membrane to divide the gas and fluid compartments. The gas is pre-charged on one side of this membrane, while the hydraulic fluid occupies the other. As fluid enters under pressure, it pushes against the membrane, compressing the gas and storing energy. When the system requires fluid, the compressed gas expands, pushing the membrane and releasing the fluid. These accumulators are generally more compact and chosen for applications requiring smaller fluid capacities.
Common Applications
Hydraulic accumulators are applied across industries to enhance hydraulic system performance and longevity. A primary application is energy storage, capturing excess power during low-demand periods and releasing it during peak demand. This reduces pump workload and allows pumps to be sized for average rather than peak loads, improving system efficiency.
They are also used for pulsation dampening and shock absorption, smoothing out pressure fluctuations caused by pump cycling or sudden valve closures. This protects components from damaging pressure spikes and vibrations, extending equipment life. Accumulators also provide immediate pressurized fluid for emergency power, ensuring essential equipment can operate or safely shut down during outages.
Accumulators compensate for system leakage, maintaining consistent pressure by supplying fluid as needed. They also account for thermal expansion and contraction of hydraulic fluid, preventing pressure build-up or drops due to temperature changes. These roles make accumulators a common component in a wide range of hydraulic machinery, including construction equipment, manufacturing presses, aircraft landing gear, and wind turbines.