Hydraulic Accumulators: Ensuring System Stability and Safety

In the world of hydraulic engineering, system reliability and safety are paramount. Hydraulic accumulators play a critical role in maintaining both, acting as energy storage devices that help stabilise pressure, absorb shocks, and improve system responsiveness. At Neilson Hydraulics, our expertise in hydraulic system design and integration ensures that accumulators are implemented effectively to enhance both performance and protection.

What is a Hydraulic Accumulator? A hydraulic accumulator is a device that stores pressurized fluid under the action of an external force. It consists of a pressure vessel, an oil to gas separator (bladder / diaphragm / piston), fluid port and a gas valve. When hydraulic fluid is pumped into the accumulator, it compresses the gas inside, storing potential energy that can be released when required.

Types of Hydraulic Accumulators:

Bladder Accumulators:

Bladder accumulators feature a flexible bladder that separates the hydraulic fluid from the gas.
As fluid enters the accumulator, the bladder compresses the gas, storing energy.
These accumulators are known for their high energy storage capacity and minimal maintenance requirements.

Diaphragm Accumulators:

Diaphragm accumulators use a flexible diaphragm to separate the gas and fluid.
As fluid enters, it compresses the gas, storing energy.
These accumulators are valued for their compact design and suitability for low-pressure applications.

Engineering Considerations for Accumulator Selection

To ensure system stability and safety, engineers must carefully evaluate the following:

1. Pre-charge Pressure (P₀)

The gas pre-charge should be optimally set (typically 90% of the system’s minimum pressure) to ensure the accumulator functions within its effective range. Incorrect pre-charge levels can lead to loss of functionality or damage.

2. Volume Sizing

Accumulator size must be calculated based on required fluid volume, allowable pressure range, and intended function (energy storage vs damping vs emergency use). Oversizing can lead to sluggish response; undersizing may result in insufficient performance or rapid cycling.

3. Mounting Position

Orientation (vertical vs horizontal) can affect accumulator efficiency and longevity. Bladder and diaphragm types are generally mounted vertically for optimal gas/fluid separation.

4. System Pressure Rating

Ensure compatibility between accumulator pressure rating and system maximum operating pressure, factoring in pressure surges and safety margins.

5. Hydraulic Fluid Compatibility

Material selection for bladders, diaphragms, and seals must be compatible with the hydraulic medium used (e.g., mineral oils, synthetic fluids, fire-resistant fluids).

Safety and Maintenance Protocols

Accumulators are pressure vessels, and as such, they require careful handling and compliance with safety standards:

Follow PED (Pressure Equipment Directive) or UKCA markings for systems operating in Europe/UK.
Regularly check pre-charge pressure.
Inspect for external damage, leaks, and pressure retention issues.
Install safety devices such as burst discs or pressure relief valves where appropriate.
Label accumulators clearly and ensure trained personnel perform maintenance tasks.

Application Examples from Neilson Hydraulics

At Neilson Hydraulics, we integrate hydraulic accumulators across a broad spectrum of industries, including:

Mobile machinery – to absorb shock loads and enable safe emergency stops
Industrial presses – to deliver consistent high-force energy bursts
Wind turbine systems – for brake and pitch control redundancy
Marine and offshore – for stabilising steering and winch systems

Conclusion: Hydraulic accumulators play a vital role in hydraulic systems, offering energy storage, shock absorption, and emergency power capabilities. Understanding the different types of accumulators and their applications is essential for optimizing system performance and ensuring reliable operation. With leading manufacturers like Bosch Rexroth offering high-quality accumulators, industries can benefit from enhanced efficiency and productivity in their hydraulic applications.

At Neilson Hydraulic we can help you with all your hydraulic requirements and needs. To enquire about Boch Rexroth accumulators and all your hydraulic requirments, please call 01709 821002, email: sales@neilson-hydraulics.co.uk or visit: www.neilson-hydraulics.co.uk