Operation
17
4.1 Start-up
Check the pump motor’s direction of rotation and the oil
level in the bearing spaces (see Section 3.2 and 3.3).
RUVAC WAU
The RUVAC WAU can be started together with the
backing pump at atmospheric pressure.
It is protected against excessively high pressure
differentials by a bypass line.
RUVAC WA
Do not switch on the RUVAC WA until the backing pump
has evacuated the vacuum vessel to the cut-in pressure
(see Technical Data, Section 1.3).
For processes in which condensable vapours are
pumped, it is advisable to evacuate the vacuum vessel
via a roughing line to the cut-in pressure. Electrically
switch on the Roots pump together with the backing
pump and cut it in upon reaching the cut-in pressure. The
initial bypassing of the Roots pump serves to prevent
condensation of vapours in the cold pump.
The permissible cut-in pressure depends on the ratio
between the Roots pump and the backing pump. It can
be calculated according to the following formula:
p
max
p
E
= ———
k
th
- 1
p
E
=
Cut-in pressure
p
max
= Maximum permissible pressure differential
(see Technical Data)
k
th
=
Theoretical compression ratio
= nominal pumping speed of Roots pump /
pumping speed of backing pump
Example:
Pump combination:
RUVAC WA 501 / SOGEVAC SV 100
505 m
3
x h
-1
k
th
= —————
≈
5
100 m
3
x h
-1
80 mbar
p
E
= ———— = 20 mbar
5 - 1
With small vacuum vessels, the maximum permissible
pressure differential can be briefly exceeded (max. 3
min) upon start-up. If a pressure switch has been
installed, do not set it to this higher pressure because it
will fail to protect the pump against overload in the event
of a greater gas quantity.
It is advisable to switch the RUVAC WA on and off via a
pressure switch to ensure that it runs only in the
permissible pressure range.
4.2 Operation
Do not operate the pump without having
connected the flanges to a vacuum system.
The screws of the flanges on the suction
and the pressure side must not be loosened
in the presence of a vacuum even if the
pump is
not
running.
During operation of the RUVAC, check the oil level and
the condition of the oil in the oil level glass and the oiler
from time to time. Correct as required (see Section 5.2
and 5.3). Normally, the oil N 62 or HE-200 is light-brown.
If it turns dark, this is a sign of early ageing due to
excessively high temperatures.
Run the Roots pump exclusively under the
operating conditions for which it has been
designed. Any modification of the operating
parameters (e. g. intake pressure, intake
temperature, ratio between Roots pump
and backing pump) for a longer period may
place an inadmissible thermal load on the
pump. Increases in temperature which are
not compensated by taking suitable
measures may damage the Roots pump
and/or the backing pump.
During normal operation temperatures
exceeding 80
°
C may occur at the
discharge port, the oil chambers and the
line on the pressure side. When touching
these there is the danger of receiving burns.
Note the labels on the pump.
Never open the oil-fill or oil-drain screw (Fig.
11) in the presence of a vacuum or while
the pump is running. There is the danger
that oil may squirt out.
4 Operation
Warning
Caution
Warning