What is Bladder Accumulator? Construction, Diagram, Working & Advantages

In Bladder Accumulator a gas charged bag/bladder is fixed in a shell of accumulator. When pressurised oil enters into accumulator, the gas bag compresses. When system requires oil under pressure, the oil goes out and bladder expands.

Construction and Working of Bladder Accumulator

Figure 1: Bladder Accumulator.

Fig. 1 shows static position of accumulator. Oil comes in and also goes out through port (A). We can fill the gas through port (B) so that flexible bag will expand.

Figure 2: Bladder Accumulator fully precharged.

To operate this accumulator first we have to fully precharge the gas into the gas bag. The position of the gas bag after fully precharging the gas (This gas is generally Nitrogen gas or any inert gas) is shown Figure 2. When we fill the gas in the bag through port (B), the gas bag fully expands. During this step oil is under normal pressure. Now the oil under pressure will start accumulating into the accumulator through port A.

Figure 3: Bladder Accumulator with compressed gas and bag.

The pressure of oil is higher than the pressure of gas filled in the gas bag. Due to this pressure difference the oil will compress the gas bag. This is shown Figure 3. The compressed gas and bag are clearly seen. Now oil under pressure is stored in the shell. This is ‘fully charged’ position of this accumulator.

Now when system in which this accumulator is connected, if demands hydraulic oil under pressure, then oil will start flowing out through port A. As oil goes out, the pressure on gas bag will reduce slowly and the bag will expand. As bladder goes on expanding, the pressure of outgoing oil will go on reducing.

Advantages of Bladder Accumulator

1. The accumulator is compact and light in weight.
2. A gas bag is of flexible material like rubber. Hence, bag gives quick response to minute changes in expansion and compression.
3. It is having very few functional parts and hence cheap.

Disadvantages of Bladder Accumulator

1. The pressure of outgoing oil will not be constant. As gas bag (bladder) goes on expanding, the pressure of oil reduces.
2. The volume of oil stored in the accumulator is small.
3. We have to change the gas bag after specific period of service.
4. We cannot handle high temperature fluids in this accumulator.