3 (3) GB
Replace the belt guard after adjustment.
Check the temperature control valve TAV 50 MV. The
unit should be running when this is done. The best way
of doing this is to heat the thermal switch (TS) with a
hot air pistol, figure 9, so that it reaches a temperature
of about 80 °C (176 °F), when it closes. A simpler check
is to bridge the contacts with a screwdriver, figure 10.
The valve should open in either case and release coo-
ling air to the fan. A distinct change in sound shows the
valve is working.
Check the start-up valve SUV 200. The spring should
hold it closed when the unit is not running as well as
when the motor is starting in the Y-mode. It should
open (the spring comes under tension) when the motor
switches to D-mode. The valve needs
compressed
air to work.
Check the bearing temperature, figure 11. Both bear-
ings are in the cage near the manual reset thermal
switches. Normal temperature range is 50-90 °C (122-
194 °F). If the temperature rises above 95 °C (203 °F)
or if one of the thermal switches has tripped (tempera-
ture > 110 °C (>230 °F)) the reason for this must be
established. Possible reasons are:
•
high ambient temperature or obstructed grids for
cooling air and ventilation.
•
belt loose and slipping.
•
belt too tight, increasing the load on the transmission
bearing.
•
bearings worn or damaged. They should be replaced,
see below.
After some 15,000 hours of operation, or sooner if
there is reason to suspect damaged bearings, these
should be changed. This can be done in three ways. The
mounting instruction MI12-002, gives fuller details of
these alternatives, the tools needed and how to per-
form the task.
Spare parts and additional documentation
Spare parts list MX12-001 for VAC 20 is
enc-
losed. VAC 2500 (30kW) corresponds to C-PAK 20-
1500 C. VAC 3000 (37kW) corresponds to C-PAK 20-
2500Ci.
Manual
144211
and spare parts list MX62-001 for
the temperature control valve TAV 50 MV are enclo-
sed if this valve is installed. (Should the option ASC be
installed its manual
144342
replaces the above
documents.)
Manual MA20-004 for the FlexFilter dust collector is
always enclosed. Should the FlexFilter be fitted with
type RF filter cleaning, then the AFC-RF manual
144366
is enclosed.
Manual
144364
for the High Vacuum Starter is
always enclosed.
Manual
144365
for flow restrictor FR 160 is enclo-
sed if FR 160 is installed..
Too high a temperature for a long period may dama-
ge the unit. While pumping may not be directly har-
mful the jerkiness and irregularity of the pumping
sound can be disturbing. Standard VAC 20 units
are fitted with a thermal switch (TS) linked to a
temperature control valve, TAV 50 MV, which opens
to permit an influx of cooling air if the temperature at
the fan reaches 79 °C (174 °F). The valve closes
when the temperature sinks to 60 °C (140 °F). At high
ambient temperatures the valve can remain open for
long periods.
The valve needs a supply of compressed air in
order to function. The parts list for TAV 50 is inclu-
ded with units so equipped.
An optional device against pumping is an Anti Surge
Control (ASC). This both adjusts temperature
(replacing TAV 50 MV) and prevents pumping.
The spare part list is supplied with all units fitted
with ASC.
On the bearing cage, close to the respective bear-
ings, are two manual reset thermal switches, RTS.
The circuit trips at about 110 °C (230 °F) and the
unit stops. An error indication is shown on the
starting equipment. The switches can be reset
when the temperature has fallen. The motor starter
must on no account allow a re-start before a safety
hold circuit has been reset.
As an option, a pressure-controlled switch (CAS) is
available, wired in series with the thermal switches
on the bearing cage. If the compressed air supply is
broken the circuit trips and the unit stops. An error
indication is shown on the starting equipment.
Maintenance
Read the section under Safety before carrying out
maintenance.
The following section is found in the manual for the
VAC 20. Maintenance of dust collectors with filters is
described in the manual for the dust collector.
An hour service meter is standard mounted in the
starter. The following service should be carried out
at intervals of 400-500 hours.
Check the tension of the belt transmission and
adjust if required. Replace worn or damaged belts.
New belts are liable to stretch slightly within the first
50-100 hours of use and should be more tightly ten-
sioned than used belts. The following figures can
serve as a guide for all VAC 20 models and give the
force F necessary to apply to one of the belts as
shown in figure 8 for 10 mm slack.
F = 24 N (5.4 lbf) for new belts.
F = 20 N (4.5 lbf) for used belts.
