26
•
Shut off the main vacuum pump valve. Check for vacuum rise using the manifold
compound gauge. A rise would indicate a large leak.
•
If vacuum holds for 10 minutes, break vacuum with nitrogen and pressurize to 20 bar.
Check for leaks and repair leakage.
- Leak Check
The success of all the subsequent commissioning depends on a leak free
system, free of contaminants, free of oxides, free of non-condensable’ s, that
has been evacuated to a low vacuum and charged with the prescribed
refrigerant.
Leak test is particularly important for field-connected systems. Typically, field
systems lose as much as 20%–30% of their refrigeration charge annually. This
is not only an unnecessary expense but also damages the environment.
Compressor oil can be lost at the same time as refrigerant and eventually lead
to compressor failure. (Time spent on leak test will eventually reduce the
time spent on the evacuation process).
Ensure that all service valves are open during the leak test process. It is
important to recheck all joints within the unit as well as the external joints.
a. The unit is shipped with a holding charge of dry nitrogen and should be leak
free.
b.
Ensure that the test pressure do not exceed the system design pressures.
c. Do not expose system pressure control LP to test pressures below the design
pressure. This can damage the pressure controls.
d. Using an approved, calibrated electronic gas leak detector, leak test the entire
system paying attention to all joints.
e. Periodically check functionality of the electronic leak detector during this
process.
f. To further check system integrity, spray a soapy water solution over joins
then visually inspect for bubbles.
g. Leave the system under pressure for a designated period (24 Hours).
h. Check and record the ambient temperatures and the system pressure with
calibrated approved instruments. This process is to be carried out every 8-12
hours during the pressure testing process.
i.
If the test pressures cannot be maintained, repeat the leak testing process
employing the isolation of sections of the system to determine the source of
leaks. Repair the leak and repeat the leak testing process until system can be
signed off as leak free and approved by authorized personnel.
j. Record findings and confirm pressure testing process completion.
