How to Charge HYDAC Hydro-pneumatic Bladder Accumulator

This video has been prepared in order to explain the process of charging the Nitrogen pre-charge pressure of a bladder type accumulator.

HYDAC Australia host regular training courses on many topics, including hydraulic accumulator technology in Melbourne, Australia. For more information, please visit our website, www.hydac.com.au.

What is an accumulator?

Hydraulic accumulators are specifically designed to store and then discharge pressurized fluid as needed. They are classified as pressure vessels. Hydropneumatic accumulators are charged with nitrogen, which is separated from the fluid by a piston, bladder or diaphragm. There are risks involved when working with high-pressure gasses and fluids. On no account must any welding, soldering or any mechanical work be carried out on the accumulator shell. Work on systems employing hydraulic accumulators must only be carried out once the pressure in the fluid and/or the gas have been released. This tutorial video has been prepared in order to explain the process of charging the nitrogen pre-charge pressure of a bladder type accumulator.

Charging:

Hydropneumatic accumulators need to be pre-charged with an inert gas in order to work at all. Selection of the correct gas pressure is vital, as it defines the stored hydraulic fluid volume and pressure, which are important for the safe and correct operation of any machine. It is important that the correct gas pressure is maintained, and periodic inspection is therefore necessary.

This gas used in hydro-pneumatic accumulators is almost always industrial grade nitrogen. The use of other gasses in these applications is dangerous, and should not be considered.

The nitrogen pre-charge pressure of an accumulator can only be assessed when it has been fully depressurised of hydraulic fluid. This means that the accumulator must be positively isolated from a live system and released of all hydraulic energy, or that the entire system has been completely shut-down and fully depressurised, or that the accumulator is not currently connected to a system, for example, it is on a work bench.

The HYDAC FPU-1 Universal charging and testing unit can be fitted directly to HYDAC diaphragm and piston accumulators, but it uses an adaptor to connect to a bladder type accumulator. This is known as the A3 adaptor. It is clearly stamped A3.

The accumulator gas valve will be opened and closed by pushing the valve plunger down. This will be operated by the centre screw of the A3 adaptor. Due to the high pressures involved, this should never be done by hand. Due to the high pressures involved, this valve should never be opened by hand. Use only the correct equipment, that is the universal charging and testing unit.

Important:

The purpose of this video is to give you some guidance of how to charge an hydro-pneumatic accumulator. Note that only people with special technical training should undertake this task.