Pressure Maintaining And Leak Hunting - Gree DC Inverter Multi VRF Service Manual

DC INVERTER MULTI VRF

6.9 Pressure Maintaining and Leak Hunting

1 Pressure maintaining of refrigerant piping
After refrigerant piping of a system is welded
A refrigerant filling nozzle shall be welded respectively on the big pipe and on the small pipe on the
outdoor unit side.
Pipes connected to the end of indoor unit and outdoor unit shall be clamped to be flat and welded
to be sealed.
Steps of pressure maintaining and leak hunting of refrigerant piping are as follows:
Operating Steps:
Complete the
installation of
piping
Pressurization
Use nitrogen to add pressure from Freon nozzle of the gas and liquid pipe on outdoor unit side:
Step 1: Increase the pressure to 0.5MPa and wait for 5 minutes or longer
Step 2: Increase the pressure to 1.5MPa and wait for 5 minutes or longer
The step 1 and 2 are focused on checking the significant leakage point. If any, reweld immediately
or repair the leakage point.
Step 3: Increase the pressure to 4.15MPa and keep it for approx. 24 hours to check the small
leakage.
Though the pressure is increased to 4.15MPa, it cannot be guaranteed to find out the small
leakage if the waiting time is too short. Therefore, the pressure in Step 3 must be kept for 24
hours.
Note: During pressure maintaining after nitrogen is filled, the pressure gauge shall not be
dismantled, because activities of dismantling or mounting pressure gauge would affect pressure
change.
Check pressure drop
Criteria for Inspection eligibility:
Except for temperature influences (pressure changes about 0.01MPa for temperature change
of 1 ), if pressure drop is not more than 0.02MPa within 24h, the system will be eligible. For
example, nitrogen is filled to reach 2.5MPa at 30 ; after 24 hours, when temperature becomes
25 , the system will be eligible if pressure is over 2.43 MPa and ineligible below 2.43 MPa.
If ineligible, leak sources must be located. After leak sources are found, re-welding or repair
welding is necessary. Then, the above procedures shall be repeated. Nitrogen is filled,
pressurized and maintained until pressure drop remains within required range.
Leak check
[Check 1] When pressure drop is found, leak hunting shall be performed in the ways as follows:
a. By ears.......to listen voices related to leakage
b. By hands......to sense whether leakage is existent at connecting parts
[Check 2] If no leakage is found using the above methods, nitrogen shall be discharged and
refrigerant shall be filled in to reach 0.5MPa.
a. By soap and water......soap bubbles will show leakage positions if any.
b. Detector (such as halide detector) can be used for leak hunting
Using the above methods, check all possible leak sources.
If leakage still fails to be located, sectional check shall be taken for refrigerant piping that would be
divided into multiple check portions for locating leak source in a certain section.
2 Pressure maintaining and leak hunting of the system
connection with indoor unit and outdoor unit
When refrigerant piping is to be installed, pressure maintaining and leak hunting is required for the
piping. After refrigerant piping is in connection with indoor unit and outdoor unit, pressure
maintaining and leak hunting is also required. The purpose of the test is to check whether any leak
is existent at threaded connection of indoor unit and outdoor unit and at new welded points.
Pressurization
Check
pressure drop
Locate and repair
leakage
with refrigerant piping in
INSTALLATION
Finish
155