A hydraulic accumulator can allow a system to increase its cost-effectiveness, offer continuous, dependable operation and can store emergency power should there be an electrical failure…
Hydraulic systems often include a hydraulic accumulator. They have two functions: one, to store energy and two, to smooth out pulsations. If your hydraulic system includes an accumulator it will also be able to operate with a smaller pump. This is because the accumulator is able to store energy from the pump when the demand is lower. The built-up energy is ready for use the moment it is needed and can be released at a rate much higher than that that would be released with the pump on its own.
A hydraulic accumulator can also double-up as surge or pulsation absorbers, just like an air dome used on pulsating piston or rotary pumps. Accumulators cushion the hydraulic hammer, which helps to reduce shocks caused by the quick movement or sudden starting and stopping of power cylinders in a hydraulic circuit.
There are four main types of hydraulic accumulator: the weight-loaded piston-type accumulator, the diaphragm accumulator (also known as a ‘bladder’), spring-type accumulator and the hydro-pneumatic piston type accumulator. The weight-loaded piston-type accumulator was the first to be used, however it is much larger and heavier than a modern piston or bladder accumulator. This version of the piston accumulator and the spring-type are seldom used nowadays, but the hydro-pneumatic accumulators are the kind that are most commonly found in modern hydraulic systems.
What is a hydraulic accumulator used for?
Storing energy – Hydropneumatic accumulators use a gas as well as hydraulic fluid, which can be compressed into smaller volumes at higher pressures. Potential energy is stored in the compressed gas and will be released once it is required. This kind of energy is similar to that of a raised pile driver transferring its huge energy upon the pile. With a piston accumulator, the energy in the compressed gas exerts pressure against the piston separating the gas and hydraulic fluid. This forces the fluid from the cylinder into the system and consequently to the location where it is required.
Pulsation absorption – In a hydraulic system, pumps create the power that needs to be used or stored. The majority of pumps distribute this power in a pulsating flow. As the piston pump is usually used thanks to its ability to operate under high pressure, the pulsations can be damaging to a system working under high pressure. An accumulator cushions the system against the pressure variations.
Shock cushioning – There are a number of hydraulic applications where the driven member of the system makes a sudden stop, which produces a pressure wave that moves back through the system. During operation, this means that the peak pressures that appear are much greater than the usual working pressures. This creates unpleasant noise or in severe circumstances, system failure. The accumulators gas cushion can help to reduce the shock.
Maintaining pressure – When the liquid in a hydraulic system is exposed to rising and falling temperatures, it causes pressure changes. There could also be drops in pressure due to a hydraulic fluid leak. By giving or taking a little bit of the hydraulic fluid, a hydraulic accumulator compensates for pressure changes.
Fluid dispensing – Accumulators are able to distribute small volumes of hydraulic fluid, including as soon as they are required.
A couple of examples of some of the projects we’ve undertaken included some Parker bladder accumulators that were for a UK-based electro-mechanical equipment exporter, and then on the right, these accumulators that were despatched to a company who specialise in the services and repair of plant and hydraulics. They were 10 litre nitrile bladder accumulators with elastomeric seals. They have a maximum pressure of 345 bar. We have also dispatched a .75 litre accumulator with a maximum pressure of 350 bar, pressure on port line: 10-70 bar, maximum back pressure on tank line: 3 bar, minimum pressure: 10 bar and oil capacity of 12 litres/minute.