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2. Guideline for each installation process
2) Vacuum pump maintenance
Because of their nature, most vacuum pumps contain large amounts of oil which lubricates bearings, etc., and functions to
enhance airtightness of pistons. When using a vacuum pump to discharge air from refrigerant piping, moisture in the air
tends to get mixed in with the oil. You must therefore change oil periodically and make sure the proper oil level is main-
tained. (Perform periodic inspections in accordance with the operating instructions.)
3) Degree of vacuum measurement
An extremely accurate vacuum gauge is required to test degree of vacuum. You cannot accurately measure degree of vacu-
um with the compound gauge on the gauge manifold. A Pirani vacuum gauge is required to measure degree of vacuum
accurately. Because Pirani gauges are very sensitive and require extreme care when using, they are not very suitable for
use in the field. You should therefore use the Pirani gauge to calibrate the attached vacuum gauge on the gauge manifold
and the degree of vacuum of the vacuum pump.
4) Calibration method
① Connect a Pirani vacuum gauge and the gauge manifold vacuum gauge (760 mmHg) to the vacuum pump at the same
time, and run the pump for about 3 minutes.
② Make sure the reading of the Pirani vacuum gauge is 5 Torr (667 Pa ) or less. The reading of conventional vacuum
pumps lowers to about 0.2 Torr.
If the reading is not 5 Torr or less, check the vacuum pump oil. (Oil is low in many cases.)
③ Check the attached gauge on the gauge manifold. Adjust the gauge if the reading is not exactly correct.
④ Adjust the gauge manifold valve so that the Pirani vacuum gauge reads 5 Torr.
⑤ Mark the position indicated by the gauge manifold gauge with an oil based ink pen.
⑥ Use the mark of the gauge manifold as a target when vacuuming in the field.
Pressure detection section
(Reference) Types of vacuum pump with respect to maximum degree of vacuum
Type
Oil rotary
(Oil using)
Oilless rotary
(No need of oil)
Indicator
Maximum degree of vacuum
Expulsion capacity
0.02 mmHg
100 l/min
10 mmHg
50 l/min
0.02 mmHg
40 l/min
Gauge manifold
Vacuum pump
Use
Vacuum drying
Air expulsion
Suitable
Suitable
Unsuitable
Suitable
Suitable
Suitable
Heat pump 50Hz/R410A
Many handy
pumps fall into this
category
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