GA 12.137/2.02 - 05/2002
31
Maintenance
Topping up helium gas
Caution
Only helium of the highest purity (99.999%
or better) shall be used.
Use the pressure reducer and a suitable high-flexline to
connect the helium cylinder to the helium filling adapter
supplied with the unit; do not yet tighten the Swagelock
connector.
Open the valve at the cylinder.
Open the pressure reducer and the shut-off valve slightly
so that the high flexline and the filling adapter are purged
with helium.
Tighten down the Swagelock connector after purging the
configuration several times.
Set the pressure in the supply line to correspond to the
set-point value of the compressor unit. If there is insuf-
ficient pressure in the supply line, oil can pass from the
compressor unit into the supply line.
Observe the instructions given in Section 2.6.
Connect the coupling at the helium filling adapter to the
helium filling nipple.
Refill the compressor unit up to nominal value.
Detach the coupling from the helium filling nipple.
Close the valve at the supply cylinder.
Seal the helium filling nipple at the front of the compres-
sor unit tightly with a protective cap.
Warning
The filling hose at the helium cylinder will
still be under pressure of up to 16 bar (232
psig; 1.6 MPa). Relieve pressure from the
line before detaching the filling connector.
4.2 Replacing the adsorber
The adsorber is provided to keep the oil vapor out of the
flow of helium gas. It will have to be replaced after about
18,000 hours of operation. Otherwise oil can collect in
the cold head as a result of incomplete adsorption of the
oil vapors. This will cause a reduction in cooling
performance; extreme contamination of the helium gas
may cause the cold head to cease functioning entirely.
Caution
When making this replacement use only the
appropriate adsorber supplied by Leybold;
refer to Section 1.4.
Fig. 18 Topping up the helium filling
Helium supply
cylinder
Pressure reducer
Shut-off valve
Pressure gauge
Pressure gauge
Helium filling
connection with self-
sealing coupling
Helium filling with
Swagelock connector and
self-sealing coupling
Compressor unit
