Bladder type accumulators

 The construction of a typical bladder type accumulator is depicted in Fig.9.7.

BLADDER TYPE ACCUMULATORS

1. Construction

The construction of a typical bladder type accumulator is depicted in Fig.9.7. It consists of a bag or bladder of synthetic material which is precharged with gas to a determined pressure. This bladder is placed within the accumulator shell and the balance of the space filled with oil. Thus the bladder serves as an elastic barrier between the gas and oil.

2. Operation

When the fluid (oil) under pressure enters the accumulator, the gas in the bladder is compressive, thus forming a reservoir of pressure. When oil is called for from the accumulator, the bladder expands and forces the oil out into the circuit.

The large poppet valve, placed at the fluid entry port, closes when the accumulator is exhausted. This prevents the bladder from extruding out into the inlet pipe.

3. Advantages

1. The bladder type accumulators respond quickly to changes in the system demand.

2. They posses positive sealing between the gas and oil chambers.

3. Because of the low inertia of the bladder, they are especially suitable for damping pulsations.

4. This bladder type can be used for ratios of maximum to minimum pressure upto about 5 to 1.

4. Disadvantage.

There is a possibility of bladder failure.

5. Other Important Concepts

1. Why is nitrogen gas preferred in a most of the gas-operated accumulators?

The air or oxygen cannot be used in the system due to the danger of explosion. But the nitrogen gas is an inert and a non-poisonous gas. Since the nitrogen does not support combustion and does not combine easily with other elements, the nitrogen gas is preferred in most of the gas-operated accumulators.

2. Comparison of various gas-loaded type accumulators

Table 9.1 presents the comparison of important parameters of various gas-loaded type accumulators.

Table 9.1. Comparison of various gas-loaded type accumulators

3. Accumulator Symbols

Fig.9.8 shows the various graphic symbols used to represent different types of accumulators.