Problem Possible Cause Remedy
The vacuum pump does not reach the usual
pressure
The drive motor draws a too high current
(compare with initial value after commission
-
ing)
Evacuation of the system takes too long
The vacuum system or suction line is not
leak-tight
Check the hose or pipe connections for possi
-
ble leak
In case a vacuum relief valve/regulating system
is installed:
The vacuum relief valve/regulating system is
misadjusted or defective
Adjust, repair or replace, respectively
Contaminated oil (the most common cause) Change the oil
(Ú page 1: Maintenance)
No or not enough oil in the reservoir Top up oil
(Ú page 1: Maintenance)
The exhaust filter is partially clogged Replace the exhaust filter
(Ú page 1: Maintenance)
The screen (f, 261) in the suction connection
(e) is partially clogged
Clean the screen (f, 261)
If cleaning is required too frequently install a
filter upstream
In case a filter is installed on the suction
connection (e):
The filter on the suction connection (e) is par-
tially clogged
Clean or replace the inlet air filter, respectively
Partial clogging in the suction, discharge or
pressure line
Remove the clogging
Long suction, discharge or pressure line with
too small diameter
Use larger diameter
The valve disk of the inlet non-return valve is
stuck in closed or partially open position
Disassemble the inlet, clean the screen (f, 261)
and the valve as required and reassemble
The oil tubing is defective or leaking
The oil return line is broken
Tighten the connections
Replace the connections and/or the tubing
(replace with identically dimensioned parts
only)
A shaft seal is leaking Replace the shaft seal ring (Busch service)
An/The exhaust valve is not properly seated
or stuck in partially open position
Disassemble and reassemble the exhaust
valve(s) (Busch service)
A vane is blocked in the rotor or otherwise
damaged
Free the vanes or replace with new ones
(Busch service)
The radial clearance between the rotor and
the cylinder is no longer adequate
Readjust the vacuum pump (Busch service)
Internal parts are worn or damaged Repair the vacuum pump (Busch service)
The oil return line starts in an area vented to atmospheric pressure. Particularly on small model
pumps, a fairly large amount of air is sucked through the oil return line, which may prevent the
ultimate pressure from reaching 20 bar abs.
In order to exclude this possible cause:
either
temporarily disconnect the oil return line from its connection near the exhaust opening and
close it
or
squirt oil through the gas discharge (g)
KC 0016 D VEMAG
0870146800 / 100111 page 4
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