WARNING
Take care not to exceed the rated pressure of the unit refrigerant pressure relief valves.
Conducting the gas pressure hold test
1. Install a high-quality high-resolution analog pressure gauge on one of the shells to monitor
the system pressure over time. Ensure that the pressure gauge has a resolution of 2 psi
increments with a dial face at 3 in. (76 mm) in diameter or greater.
2. Before proceeding, ensure that the unit is at the initial evacuation level of 5 mmHg.
Important: To prevent freezing of any moisture that may be in the system, do not go
below 5 mmHg. See System evacuation for more details.
3. With the system in a vacuum, slowly charge nitrogen vapor only into the system.
4. Slowly build up the system pressure with dry nitrogen to design working pressure (DWP) as
found on the chiller vessel data plates:
a. Allow the pressure to remain in the chiller based on Figure 73. This table provides hold
times for pressure hold testing based on the vessel diameter and length.
b. For a unit with no loss of pressure, proceed to unit evacuation.
c. For units where a leak is suspected and there is any amount of drop in recorded pressure,
proceed to either of the leak detection methods Conducting the soap bubble visual gas
leak or Conducting the optional trace gas leak test.
Conducting the soap bubble visual gas leak
1. Install a high quality high resolution analog pressure gauge on one of the shells to monitor
the system pressure over time. Ensure that the pressure gauge has a resolution of 2 psi
increments with a dial face at 3 in. (76 mm) in diameter or greater.
2. Before proceeding, check that the unit is at the initial evacuation level of 5 mmHg.
Important: To prevent freezing of any moisture that might be in the system, do not go
below 5 mmHg. See System evacuation for more details.
3. With the system evacuated, charge the system with dry nitrogen to 100 psig (690 kPa).
4. Mix together soap and water. This solution forms bubbles when leaking vapor passes
through it.
5. Use the soap solution to test around each unit fitting joint and weld seams carefully and
thoroughly.
6. To enhance the test, use an ultrasonic leak detector. These devices are reliable at finding
leaks in low pressure testing where soap bubble testing might not provide results.
7. When all leaks have been identified, vent the nitrogen vapor, make the necessary repairs to
the chiller and repeat the gas pressure hold test until a satisfactory hold test is achieved.
147
YMC
2
Mod B with OptiView Control Center
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