Non-separator type accumulators

 Fig.9.4 shows a diagram of a non-separated pneumatic-loaded actuator in a circuit.

NON-SEPARATOR TYPE ACCUMULATORS

1. Construction

Fig.9.4 shows a diagram of a non-separated pneumatic-loaded actuator in a circuit. It consists of a fully enclosed shell containing a gas-charging valve on the top and an oil port on the bottom. The gas confines at the top and the oil remains at the bottom and there is no physical separator between them. Since the gas has direct contact with the oil, this type is termed as non-separator type accumulator.

2. Operation

In this accumulator type, pressurisation is achieved by introducing a pressurizing gas into a container above the oil level. When the system pressure increases, the oil enters through oil port and pushes the gas. The reduction of volume of gas increases its pressure. This gas pressure is used as the potential energy to force the oil out when it is required in the circuit. Limit switches, which are actuated by oil level, are usually used to limit pressure.

3. Advantages

The non-separator type accumulators can handle large volumes of oil.

4. Disadvantages

1. Due to the absence of separator, the gas is absorbed and also entrapped in the oil.

2. This accumulator type is not preferred for use with high speed pumps because the entrapped gas in the oil may cause cavitation and damage to the pump.

3. The absorption of gas in the oil makes the oil compressible, and thus results in spongy operation of hydraulic actuators.

4. Always this type of accumulator must be installed vertically so as to keep the gas confined at the top of the shell.

5. The problem of aeration of the oil often limits their use in hydraulic systems.