Tuthill KINNEY KC Series, Руководство оператора, Страница: 26 / 48

20
06
Troubleshooting
Manual 1807 Rev B p/n 001807 0000
3. Operate the pump for about 15 minutes until
the lowest pressure is reached. Note the
reading obtained.
The reading obtained should be between the
pump’s specification blank-off pressure (low end)
and the pressure needed for the process (high
end). Average blank-off readings are 0.5 to 2.0
microns with a McLeod gauge.
OTEE:
N
For practical consideration, pumps need
not obtain pressures lower than 90% of
the required operating pressure to be
usable. If the McLeod gauge reading is
low and the thermocouple gauge reading
is high, the pump oil is contaminated.
Change the oil and recheck the pump
blank‑off pressure. It may be necessary
to change the oil several times to flush
all traces of contamination from the
pump. If a thermocouple gauge is not
available and the pump oil has been in
service for a significantly long period, it
is best to change the pump oil several
times to eliminate pump oil contamination
as a possible cause of poor pump
performance. After changing the oil,
recheck the blank‑off pressure.
If both the McLeod and thermocouple gauge
readings are high, indicating that the oil is not
contaminated, the pump is leaking. Proceed as
described in Pump Leaks on page 20 .
PUMP LEAKS
If the pump is suspected of leaking after oil
contamination has been eliminated as the cause
of poor performance ( see Checking Pump
Performance on page 19 ), use a plastic
sealing compound, such as Apiezon Q, to seal
over suspected areas, and check pump blank-off
performance before making permanent repairs
with Loctite 515. If gasketed connections are
suspected, remake the connections with temporary
gaskets of plastic sealing compound. Do not make
these too thick since the material may be squeezed
into the equipment.
Check carefully around the head-to-cylinder joints,
securing bolts, plugs, shaft seal housing joints,
and generally any penetration into the vacuum
pumping portion of the pump. Check the shaft seal
for mechanical defects, such as a cracked carbon
washer or hardened rubber components.
CHECKING PROCESS EQUIPMENT
If the blank-off test shows that the vacuum pump is
functioning properly but that the process equipment
is faulty, apply the following procedure to further
isolate the trouble:
1. Pump down each segment of the process
equipment individually, starting at the segment
closest to the vacuum pump.
2. Check the lowest pressure attainable when
each segment is added. If the pressure is
close to that obtained previously, add the next
segment. If the pressure is not close, leak test
the last segment. When leak checking process
chambers, start at the air and gas inlet valves,
doors, sight ports, electrical and mechanical
feedthroughs, gauge tube fittings, and any
other penetrations, especially threaded,
gasketed, and O-ring connections.
After a suspected leak has been found, cover
it with plastic sealing compound, such as
Apiezon
®
Q, and check the equipment performance
before sealing the leak permanently. Continue
leak testing if necessary, and make all permanent
repairs at the same time.
PROCESS EQUIPMENT LEAKS
Attach a vacuum gauge to the connection on the
system side of the vacuum valve. For this test,
clear the system of any process work, which might
give off vapors and change the reading. Run
the pump to obtain the lowest possible pressure
and close the valve. Observe the pressure rise.
If the pressure rise is greater than desired, or
if the ultimate pressure is too high, check and
eliminate all leaks. Check the system carefully
for loose joints and obvious leaks. Use a leak
detector if available. If a leak detector is not
available, proceed as described in Leak Checking
Techniques on page 21 .