Air Heater Leakage Test

You can use helium gas for the leakage test too. It is detected /measurable/ by helium leak detector. (Try to looking for instruments or service companies by Google search engine.) I think it is normally used for detecting storage tank's leakage, but it is suitable for testing other equipment leakage too. Don't forget, the helium is much safer than methane.

PS: Sorry for the broken English

In order to perform your test does the equipment need to still be online? Do you have downtime to perform testing? If you do you can use smoke and pressurization to detect leakage.

Exactly, this is the normal procedure to test leakages in air heaters during plant shutdowns. But this needs plant shutdown.

The units are not scheduled for shut down for good few months. I'd like to conduct these tests while the unit is online. I'm not sure if helium would be the ideal selection during online conditions. Methane will burn in the furnace thus whatever is measured in the flue gas should be from the leak in the air heater.

Well Dick can you use delicately pressurized nitrogen and measure the flow through the leaks?

How would I measure the flow through the leaks on a regenerative air heater while online. Leakage is inherent in the design. Leakage is through the mechanical seals as well as entrained leakage. When the unit is off-line a leakage test will not be accurate as it does not take into account thermal expansion.

http://www.uesystems.com They have what you need.

Thanks Fredski but I'm not sure this is the solution. From the website it shows leak tests in pipelines. The air heater diameter at some of our stations are about 9m. Leakage occurs from the air side to the flue gas side due to the pressure difference. This leakage occurs internally. It wont be possible to use an ultrasound to detect. We know where the leak is. We want to quantify it.

Understood

Oxygen (excess) in flue gas before air heater and after air heater can be meassured. Difference can give you some idea to quantify leakages.

To check the leakage while the unit is online, you need to conduct an air heater leakage test. ASME 4.3. Measure the inlet and outlet Oxygen levels and run the calculations. If you also have accurate temperature measurement and moisture, you can also calculate air heater efficiency as well.