weight-loaded (or dead-weight) accumulators

 The construction and operation of a dead-weight type accumulator is illustrated in Fig.9.2.

WEIGHT-LOADED (OR DEAD-WEIGHT) ACCUMULATORS

1. Construction

The construction and operation of a dead-weight type accumulator is illustrated in Fig.9.2. It consists of a piston rod or plunger loaded with a dead weight and moving within a cylinder to exert pressure on the hydraulic oil. The dead-weight provides the potential energy to compress the fluid. The dead-weight may be concrete block, iron or steel block, or any other heavy material. The piston should have a precision fit with the accumulator tube so as to reduce the leakage past the piston. One side of the accumulator cylinder is connected to the fluid source (pump) and the other side to the work load (machine).

2. Operation

In the beginning, the ram is at the lower-most position. During idle periods of driven machine (say lift or crane) high pressure fluid (oil) supplied by the pump is admitted in the accumulator cylinder through the check valve. Fluid is allowed continuously till the ram. reaches its uppermost position. At this position, the accumulator cylinder is full of fluid and the maximum amount of pressure energy is accumulated.

During the working stroke of the driven machine (i.e., when it requires maximum amount of energy), the accumulated energy is discharged to the driven machine.

3. Advantages

The advantages of the weight-loaded type accumulators are:

1. The weight-loaded accumulators produce constant pressure for the full stroke i.e., until all the fluid is sent out.

2. They can supply large volume of fluid under high pressure.

3. The large volume of fluid makes them possible to supply pressure to several hydraulic circuits.

4. Disadvantages

The weight-loaded type accumulators are not often used in modern hydraulic systems because of the following disadvantages:

1. They are very heavy and expensive.

2. They are not portable and hence cannot be used for mobile applications.

3. They also do not respond quickly to changes in the system demand.