Type III leak testing: EPA 608 Practice Questions

To leak-test a low-pressure chiller, the system must be raised above atmospheric pressure. What is the preferred way?

Heating the refrigerant raises its pressure without adding anything to the system. Controlled hot water in the tubes or heater blankets are common methods.

What is the maximum pressure normally used when leak-testing a low-pressure chiller?

Keep the test pressure at 10 psig or below so the rupture disc (usually 15 psig) does not open.

Why must the pressure in a low-pressure chiller be watched closely when it is raised for a leak test?

The shell and rupture disc are designed for low pressures. Overheating or overpressurizing can open the disc and release the charge.

When nitrogen is used to pressurize an empty low-pressure chiller for a leak test, what is required?

Nitrogen can be used once the refrigerant has been recovered. A regulator and relief valve keep the pressure at a safe level well below the rupture disc setting.

A chiller's purge unit has started running much more often than it used to. What does this usually indicate?

The purge unit removes air that leaks in. More frequent purging means more air is entering, so look for a leak.

How are leaks in the water tubes of a chiller's heat exchangers usually found?

Tube leaks are found by testing the tubes (eddy current or a hydrostatic test of the water side) with the water boxes open or drained.

After the chiller is pressurized for a leak test, which tool is used to locate the leak?

Once the system is above atmospheric pressure, refrigerant escapes at leaks and can be found with an electronic detector or bubbles.

After evacuating a low-pressure chiller, the technician valves it off and the pressure keeps rising steadily toward atmospheric. What does this indicate?

A rise that keeps climbing toward atmospheric pressure points to a leak. A rise that levels off points to moisture or refrigerant still evaporating.

Why is a pressure test with heat preferred over adding nitrogen when the chiller still holds its refrigerant charge?

Nitrogen added to a charged chiller becomes a non-condensable that the purge must remove later, releasing some refrigerant. Heat raises pressure without contaminating the charge.

Which finding most strongly suggests air is leaking into an operating low-pressure chiller?

Air that leaks in collects in the condenser and raises its pressure above the saturation pressure for the condensing temperature, and the purge unit has to run more often to remove it.

Why should the water side be drained or the water boxes opened before a tube leak test?

Tube testing needs access to the tube sheet. Each tube can then be checked, and leaking tubes plugged or replaced.

A 400-lb R-123 comfort cooling chiller exceeded the 10% threshold. Under 82.157, how often must it be inspected for leaks?

Comfort cooling appliances are inspected annually until they show one year under the threshold. Quarterly inspections apply to commercial or industrial process appliances of 500 lb or more.

Where are leaks common on a low-pressure chiller with an open-drive compressor?

Open-drive shaft seals, gaskets, flanges and fittings are common leak points on chillers.