The 101 on Hydraulic Accumulators

Reading Time: 3 minutes

Hydraulic accumulators are energy storage devices. They function much like rechargeable batteries in electric systems. They are used to improve the efficiency of hydraulic systems, and they also store and release energy through pressurized fluid. Accumulators are high-pressure chambers that store a variety of hydraulic fluids and compressible gases such as nitrogen. Their shell or housing unit is comprised of assorted materials such as aluminum, titanium, stainless steel, or steel. The exterior is reinforced by fiber composites for strength and durability.

How Hydraulic Accumulators Work

Hydraulic accumulators compress hydraulic fluids in a device called a hydropneumatic unit. The hydraulic fluids within the hydropneumatic unit are only put under minimal pressure, which means they are only slightly compressed. Accumulators can be put under regulated pressure based on different engineering designs. In any case, the compressed gas stores potential energy, which is deployed on-demand and ultimately forces oil to move from the hydraulic accumulator to a larger circuit.

Before it is added to the hydraulic accumulator, the gas must be compressed for storage. In order to use the device, an engineer must precharge the gas to reach 80% and 90% of the minimal working pressure. After the gas is precharged, it is mostly filled with pressurized gas and only small amounts of oil. Valves within the accumulator regulate oil flow into and out of the unit for proper operation. The hydraulic pump is the accumulator function that increases system pressure and forces fluids into the accumulator. Depending on the design, the accumulator is equipped with either a bladder or a piston. One of these mechanisms is used to compress the volume of stored gas. Otherwise, fluid pressure will exceed pressure of the precharged gas. The compressed gas is then the source of energy stored in the hydraulic accumulator. The hydraulic pump and piston continue to move fluids and gases until a pressure balance is reached. When a component in the system signals a need for compressed gas, it is released and pressure consequently drops. When the appropriate amount of gas is released, the process starts again with recharging of the gas.

Types of Accumulators

There are three main categories of accumulators: diaphragm, piston, and bladder. Bladder accumulators have larger ports that enable a faster discharge of fluids and more efficient accumulator function. Bladder accumulators are also designed to keep dirt, debris, and other sources of contamination out of the unit. Bladder accumulators are usually mounted vertically. However, they can sometimes be mounted horizontally. They have a pressure ratio of 4:1. Bladder accumulators are ideal for general purposes. They come in many sizes and are suitable for a variety of applications. Piston accumulators contain fluids and gases. They are ideal for large volumes of stored gas that reach 100 gallons or more. These systems have high flow rates. They are commonly used in heavy-duty applications. Piston accumulators must be cleaned frequently, as they are more prone to contamination than other types of accumulators. Diaphragm accumulators function in a similar way to bladder accumulators. However, they have an elastic diaphragm rather than a rubber one. This makes it easy for them to separate gas and oil volumes. These accumulators are smaller and more compact than the others. They are ideal for small volumes that are one gallon or less. A diaphragm hydraulic accumulator is suitable for higher compression ratios up to 8:1 or 10:1 due to their smaller degrees of distortion. Because of their smaller size, these hydraulic accumulators have flexible mounting solutions and can be affixed to a variety of surfaces. They are also highly resistant to contamination.

Hydraulic accumulators are ideal for compressing gases. They come in several styles that are ideal for a wide range of applications. Hydraulic accumulators are valuable tools for many industries.