Air Source Screw Water Chiller Unit – Installation Operation and Maintenance Manual
33
(3) Only dry nitrogen can be used as the medium for air tightness test. The pressure increasing in
difference phases is shown in the following table.
S/N Phase (Pressure Is Increased in Different Phases)
Acceptance
Criterion
1
Phase one: Large leak sources can be detected if the air pressure
is kept at 3.0 kgf/cm
2
for over three minutes.
No
pressure
drop
after
pressure
correction
2
Phase two: Relatively large leak sources can be detected if the air
pressure is kept at 12.0 kgf/cm
2
for over three minutes.
3
Phase three: Tiny leak sources can be detected if the air pressure
on R134a is kept at 20.0 kgf/cm
2
for over 24 hours.
2)
Pressure observation
(1) Increase the pressure of 20.0 kgf/cm
2
on R134a in the pipe and maintain the pressure for 24
hours. If the pressure does not drop after it is corrected based on the temperature change, the
test is passed. If the pressure drops, find and repair the leak source.
(2) Compensating method
The pressure increases/drops by 0.1 kgf/cm
2
when the ambient temperature increases/drops by
1
°
C.
Compensating formula: Actual value = Pressure during pressure increasing + (Temperature
during pressure increasing – Temperature during observation) x 0.1 kgf/cm
2
Compare the compensated value with the original pressure to see whether the pressure drops.
(3) Methods for checking leak sources
During the three phases, if pressure drops, use the following methods to find the leak sources:
①
①
①
①
Leak detection by ears: Air leakage of large leak sources can be heard.
②
②
②
②
Leak detection by hands: Touch pipe connections to feel whether any air leaks.
③
③
③
③
Leak detection by soapsuds: Apply soapsuds on pipes. Bubbles will appear at leak
sources.
④
④
④
④
Leak detection by halogen leak detector
A halogen leak detector is used when a tiny leak source is found, or when the leak source
cannot be found in the case of pressure drop during pressure increasing test.
a. Set the nitrogen pressure to 2.0 kgf/cm
2
.
b. Add the refrigerant and set the pressure to 3.0 kgf/cm
2
.
c. Use the halogen leak detector, alkane gas detector, and electric detector to check for leak
sources.
d. If no leak source is found, increase the pressure on R134a to 20.0 kgf/cm
2
and check again.
3)
Precautions
