Leak Detection and Repair Procedures Flashcards

Low-pressure chillers usually leak in which direction during normal operation?

Answer: Air and moisture leak into the system

Low-pressure chillers run below atmospheric pressure, so leaks pull air and moisture in.

What is a common sign that a low-pressure centrifugal chiller has a leak?

Answer: Excessive purge unit run time

The purge unit removes non-condensables, so frequent purging indicates air is leaking in.

To leak test a low-pressure chiller, a technician raises its internal pressure. What is the maximum pressure that should be used?

Answer: 10 psig

Low-pressure chillers should not be pressurized above 10 psig because the rupture disc is set at 15 psig.

Which method is acceptable for raising the pressure inside a low-pressure chiller for leak testing?

Answer: Circulating controlled hot water or using heating blankets

Controlled hot water or heating blankets raise refrigerant pressure safely without adding contaminants.

During a standing vacuum test, pressure rises and then levels off. What does this usually indicate?

Answer: Moisture still boiling off inside the system

Pressure that rises and stabilizes points to moisture vaporizing, while a steady continuous rise indicates a leak.

Before leak testing a system that has been fully recovered, a technician may add a small amount of HCFC-22 to nitrogen. Why?

Answer: To serve as a trace gas that electronic detectors can sense

Nitrogen alone cannot be sensed by halogen detectors, so a trace of HCFC-22 lets the detector find the leak.

When using fluorescent dye for leak detection, which requirement is most important?

Answer: The dye must be compatible with the system oil and approved by the equipment manufacturer

Incompatible dye can damage the system or void warranties, so it must match the oil and be manufacturer-approved.