Accumulators are typically used as the energy source to activate brake calipers on wind turbines in the case of an electrical or power failure. The brake force holding time required can be as long as several days which means the accumulators must have enough pre-charged gas pressure beforehand to ensure the turbine is held under control. If the accumulator does not have the correct charge the brake calipers can fail resulting in blades spinning out of control and causing a catastrophic failure. It is therefore a critical maintenance issue that all accumulators have the correct nitrogen gas pre-charge pressure at all times.
Usually wind turbines use piston type accumulators because of their smaller footprint and high pressure performance. Piston accumulators are most commonly fitted with Minimess gas charging valves due to their high pressure capability, leak free design and safe ease of use.
How to charge an accumulator:
1 Remove the sealing cap from the accumulator Minimess gas valve
2 Ensure the stem on the charging valve is retracted and fit the charging adaptor to the accumulator gas valve (using the relevant adaptor)
3 Fit the pressure regulator to the nitrogen bottle and fit the hose to the regulator
4 Fit the hose from the Nitrogen bottle to the accumulator charging valve
5 Ensure the regulator valve is unscrewed and turn on the Nitrogen bottle
6 Open the vent valve on the accumulator charging adaptor
7 Screw in the regulator valve slightly and allow the gas to purge through the hose for a few seconds before closing the accumulator charging kit vent valve
8 Slowly screw down the charging valve spindle until the accumulator gas pressure reads on the gauge
9 Increase the regulator valve setting, whilst reading the charging valve pressure gauge. When slightly above the recommended gas pressure stop
increasing the regulator valve setting. Wait for a few minutes before proceeding to the next step.
10 Isolate the gas bottle by closing the main valve
11 Using either the vent valve on the accumulator charging kit or the gas bottle regulating valve vent, slowly decrease the gas pressure to the required valve
12 Unscrew the charging kit spindle to release the accumulator gas valve
13 Open the vent valve on either the Accumulator charging kit or the gas bottle regulating valve vent to release trapped gas pressure.
14 Leaving the vent valve open, screw in the gas regulating valve until the gas pressure in the gauge is released
15 Remove the gas charging hose
16 Remove the gas charging valve, regulator valve and refit the accumulator gas valve sealing cover
Feel free to contact the Hydrotechnik team for further hints and tips when charging accumulators or alternatively leave a comment. Find our full suite of accumulator charging and testing kits.