Hydac SK Series, Operating Instructions Manual

Page: 46 / 97

GB
46
INT 3.301.BA4/05.16
Charging
– The pressure setting of the pressure reducer
must not exceed the operating pressure of
the accumulator.
– Slowly open the nitrogen bottle so that the
nitrogen can flow into the accumulator.
– Interrupt the charging process from time to
time and check the pre-charge pressure
reached on the pressure gauge (M).
– Once the temperature has equalised,
re-check the pre-charge pressure and adjust
if necessary. The nominal values are
generally based on a charging temperature
of 20 °C.
– If the pressure is too high, it can be reduced
via the unloading valve (B).
– Once the required pre-charge pressure has
been reached, the allen screw (210) on the
piston accumulator must be closed by
turning in a clockwise direction.
– Close the shut-off valve on the nitrogen
bottle, depressurise the FPU-1 via the
unloading valve and remove the charging
unit by loosening the lock nut. Tighten the
allen screw (210) (20 Nm).
– Check the sealing of the gas valve with a
suitable leak detector spray.
– Screw on the protection cap (230).
Testing (non) re-chargeable piston
accumulators without the FPU-1
charging and testing unit
If the accumulator is set up as per the fold-out
page or by using the safety and shut-off block
(SAF or SAB), the pre-charge pressure can
also be checked via the fluid side.
– Disconnect hydraulically charged piston
accumulators from the system with shut-off
valve

.
– Slowly drain the piston accumulator on the
fluid side with release valve

.
– Watch the pressure gauge

.
– The pressure will initially fall slowly. It will
drop suddenly only after the accumulator has
drained completely. This pressure is the
same as the pre-charge pressure of the
piston accumulator.
– If the indicated pre-charge pressure is
different from the required pressure, the
piston accumulator (if re-chargeable) should
be charged as described above.
5.4 Checking for oil leakage into
the gas side
When the accumulator is operated fast and
continuously, oil can leak through the piston
seals into the gas side. This can be detected as
follows:
– A loss of power of the machine or system,
– A higher gas pre-charge pressure than
before,
– Escape of oil or oil mist on loosening the
allen screw (210).
NOTE
The oil must only be removed by
appropriately qualified persons. Detailed
instructions are available on request.