Hydraulic System Accumulator

Table of Contents

• What is a Hydraulic System Accumulator?
• Role and Functions of Accumulators in Hydraulic Systems
• Different Types of Accumulators and Their Applications
• Weight-Loaded Accumulator
• Spring-Loaded Accumulator
• Gas Accumulator
• Non-Separating Gas Accumulator
• Separating Gas Accumulator
• Bladder Accumulator
• Diaphragm Accumulator
• Piston AccumulatorApplications of Accumulator Systems in the Machine-Building Industry

 

What is a Hydraulic System Accumulator?

A hydraulic system accumulator is a reservoir equipped with a membrane or piston containing an inert pressurized gas (usually nitrogen) that is used to store energy. The hydraulic fluid is stored outside the reservoir, on the opposite side of the membrane or piston.

What Are the Roles and Functions of Accumulators in Hydraulic Systems?

Accumulators play a role similar to that of a car battery, with the key difference being that accumulators store hydraulic energy through pressurized fluid instead of electrical energy. They are used to:

• Maintain pressure
• Supplement pump flow
• Reduce pump capacity requirements

In addition to these functions, accumulators help control and minimize pressure fluctuations and shocks in closed hydraulic systems. They also provide auxiliary hydraulic power during emergency situations.

The use of accumulators significantly enhances the efficiency and performance of hydraulic systems.

Click here to learn more about hydraulic systems.

 

Different Types of Accumulators and Their Applications

Currently, there are three main types of hydraulic accumulators:

1. Weight-Loaded Accumulators
2. Spring-Loaded Accumulators
3. Gas Accumulators

These accumulators are categorized based on their operating mechanisms. Below is an introduction to each type:

Weight-Loaded Accumulator

As the name suggests, this type of accumulator uses a piston and weight (load) mechanism to store potential energy. When the piston moves within the cylinder, it applies pressure to the hydraulic fluid.

Due to their large size, weight-loaded accumulators are typically used in limited applications that require high volumes, such as heavy-duty presses.

Spring-Loaded Accumulator

The structure of a spring-loaded accumulator typically consists of a spring-loaded piston inside a cylinder. Hydraulic fluid enters the accumulator’s reservoir from the opposite side of the cylinder and is stored under the pressure exerted by the spring. As a result, the pressure in the accumulator reaches its peak when the spring is fully compressed. Conversely, when the spring extends to its maximum length, the pressure on the fluid drops to its minimum level.

Spring-loaded accumulators are commonly used in applications where space is limited and operations require smaller volumes and dimensions, such as in mobile or motorized systems.

Gas Accumulator

Gas accumulators, also known as hydro-pneumatic accumulators, use gas as the working fluid. These accumulators are categorized into two main types: non-separating and separating.

Non-Separating Gas Accumulator

In this type, gas is directly pressurized within the cylinder, creating pressure in the system. As the pressure increases, the oil port opens, allowing oil to enter the cylinder and compress the gas. The pressure continues to rise until it is sufficient to move the cylinder.

Separating Gas Accumulator

In separating gas accumulators, a piston acts as a barrier between the hydraulic fluid and the gas. When hydraulic oil applies pressure to the piston, it compresses the gas automatically.

The three main types of separating gas accumulators are:

1. Bladder Accumulator
   In this type, a flexible bladder serves as the separator between the gas and the hydraulic oil. The bladder is housed inside a steel casing with a valve located at its inlet.

Diaphragm Accumulator

As the name suggests, diaphragm accumulators use a diaphragm as an elastic separator. In this type of accumulator, the diaphragm is securely enclosed between the walls of the pressurized reservoir, effectively separating the hydraulic fluid from the gas.

Piston Accumulator

In this type of accumulator, the piston acts as the separator between the hydraulic oil and the compressed gas. The structure of a piston accumulator is quite similar to that of a spring-loaded accumulator, with the key difference being the use of pressurized gas instead of a spring.

Applications of Accumulator Systems in the Machinery Industry

Accumulator systems are widely used in industrial hydraulic equipment, such as hydraulic shears (guillotines). In the hydraulic section of these machines, a suitable fluid (oil) is used to move the pistons. Traditionally, piston movement is driven by fluid force, both during the forward and return strokes. However, in this method, continuous operation causes the oil to overheat, leading to damage to the hydraulic components. The overheating also reduces the oil’s density, thereby decreasing the machine’s cutting power.

In the modern method, a hydraulic system is combined with a nitrogen gas system to create an accumulator system. In this approach, nitrogen gas is compressed during the downward movement of the machine’s jaw, and the stored energy assists the hydraulic system in lifting the jaw. During the upward stroke, the hydraulic system is disengaged, and the pressure from the nitrogen gas lifts the upper jaw of the machine. This eliminates the overheating issue during continuous operation.

There are several reasons why Grand Dayyani Machine Manufacturing incorporates nitrogen gas in its machines. The most important factor is the stability of nitrogen gas and its non-reactivity with pressurized and potentially hot oil.

The primary reason other manufacturers do not use this method is either due to a lack of technical knowledge or the higher costs associated with this advanced method compared to the traditional approach.

Click here to view the specifications of the hydraulic shear (guillotine) by Diani Heavy Machinery.

Finally, a video is provided at the end, showcasing the introduction and functionality of various accumulators in hydraulic systems, along with practical examples.