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ACCUMULATORS.ppt
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ACCUMULATORS

Definition:

Accumulator is a storage device that has been added to the system. An Accumulator can store and release, a quantity of fluid at the required system pressure

FUNCTION OF ACCUMULATOR

  • Energy Source Storage: This is used to economise on Pump drive Power during installation which is operated intermittently. The storage also helps during periods of high demand.

  • Emergency Power Source: This is used in case of pump breakdowns.

  • Shock Absorption: Absorbs quantity of fluid above preset pressure, it can help to “cushion” a hydraulic system that is subject to instantaneous pressure surge.

  • Thermal Expansion Protection:

  • Compensation for Leakage Losses: It replaces oil that has leaked in the system.

  • Pulsation Dampening: To assist at snubbing pressure spikes.

TYPES OF ACCUMULATOR

There are three types of Accumulator commonly used.

Namely:

WEIGHT LOADED ACCUMULATOR

SPRING LOADED ACCUMULATOR

GAS CHARGED ACCUMULATOR

WEIGHT LOADED ACCUMULATOR

  • It is the first type of Accumulator developed.

  • Only used in an upright position.

  • Used to maintain constant pressure, whether the chamber is full or nearly empty.

  • Used in applications where unusually large volumes of fluid are required. [Bulky and Heavy.]

  • They are heavy and cumbersome, making their use limited

SPRING LOADED ACCUMULATOR

  • It can be mounted or placed in any position.

  • It is mostly suitable for shock absorption.

  • Where large quantities of fluid are required, the forces involved makes spring sizes impractical.

  • Not suitable for high cycle rates

  • Does not give constant pressure.

GAS CHARGED ACCUMULATOR (PISTON TYPE)

  • Mostly used for shock absorption.
  • It is light in weight
  • It can be used or installed in any positions.
  • Has a chamber that is pre charged with compressible gas (Dry Nitrogen)

GAS CHARGED ACCUMULATOR (PISTON TYPE)

  • Separate the Gas charge from Hydraulic fluid.

  • Piston under gas pressure on one side and constantly tries to force the fluid out of the opposite side of the chamber.

  • Pressure is the function of the Gas compression and will vary with the volume of oil in the chamber.

PISTON ACCUMULATOR OPERATING CYCLE

  • In the first step the accumulator is pre charged with Nitrogen gas, forcing the piston to the bottom of the accumulator.

  • Second step, fluid from the pump compresses the gas, partially filling the accumulator volume. Although the accumulator is fully charged with fluid, it may only 40 to 60% of the total accumulator volume, the remaining volume being the compressed gas.

  • Final step fluid flows out of the accumulator with the gas acting as a spring, pushing the fluid into the system

SAFETY – CHARGING AND MAINTAINING ACCUMULATORS

  • Never use Oxygen, Air, Acetylene or any explosive gas.

  • Never overfill an Accumulator.

  • Only fill with Dry Inert Gas e.g. Dry Nitrogen.

  • Always purge/remove hydraulic pressure in the system before removing an Accumulator.

  • Always remove Gas pressure before dismantling an Accumulator or doing maintenance.