Air Pre Heater Leak Test

Best testing method is to hydro-test at, say, 150 PSIG using a bright (fluorescent) dye and black light during the test.

Any leakage will be readily apparent from both the pressure drop and the visible leakage (likely a spray), including the likely location of the leak. Finding and fixing will be much easier.

When fixing, just preheat that area with a fan-flame torch to burn off any dye without harming more fins that necessary before you start brazing process.

Dear Mr Energy God

Thank you very much for your immediate reply.But APH is in line with the Reformer.Removal of APH is difficult.Blinding of this system is very difficult for doing hydrotest.We have to enter through air side to see any leak by pressurizing the flue gas side.What else can be done for finding leak?

Regards

Manish

Apply air or nitrogen pressure to to the tubes, not exceeding the design working pressure, and swab the joints with a soap solution and watch for bubbles. The soap solution is available in refrigeration supply houses. Lou Bindner

We have used a soap solution called "Snoop Leak Detection Solution" in our industry. When the snoop is applied, leaks can be detected at even low air pressures (~10 in-H2O).

Since it appears that you are looking for gross leakage, application of the soap solution (snoop or a mild soap solution) at low pressures for testing purposes can result in small bubbles that can be more difficult to observe. Obviously at higher pressures the leaks will be much more easily observed.

Man it is not every day I get to start out as an expert and go down hill from there.

So that we don't break anything let us test at a regulated pressure under the maximum rating for your heater. If your device can be connected to an air supply of 50 to 100 psig on the inlet with the outlet plugged this will work.

Determine the volume of the heater being tested with water the following procedure with compressed air.

If the volume of the heater being tested is know skip on down to ***NOW TEST***

If the heaters are all the same this only need be done once and water is accurate and inexpensive or compressed air may be used as follows.

Connect a regulated source of compressed air through an inlet ball valve to the tank with an outlet ball valve between the tank and heater to be tested. A gage should be placed between the tank outlet valve and the test.

Through an inlet shut off (ball valve), pressurize a tank (Assume a 5 gallon [.67 cu. ft] @100 psig)

Connect the tank to your heater (with the outlet of the heater blocked). Close the inlet ball valve to the tank and open the outlet ball valve.

Note the pressure of the tank and heater. Assume the it were 75 psig. P1 V1 = P2 V2

100 x .67 = 75 x V2 V2 = .89 cu ft. - .67 cu ft = .22 cu ft is heater volume. (Vt)

***NOW TEST***

Fill the the heater to 100 psig.

Simultaneously start a stop watch and block the pressure to the heater at the outlet of the tank and observe the test gauge. If the pressure falls stop the clock when the gauge reads 37 psig or 37% of starting gauge pressure. Test volume Vt x (P1/14.7) x 60 / t sec = Leak rate L SCFM

For our example if the decay period was 15 seconds then .22 x 6.8 x 60 /15 = 5.98 SCFM

If price is no object a good flowmeter would work and only require good pressure regulation through it to the test.

Tom