A quick and simple method for detecting air leaks in the heat exchange tubes of heat exchangers
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In a heat exchanger with thousands of heat exchange tubes, if corrosion leads to the mixing of SO2 and SO3 gases, how can one determine which tube is faulty? 1: Close the flue gas valves at the inlet and outlet of the heat exchanger. 2: Open the manhole in the middle of the heat exchanger (for SO2) as well as the upper and lower manholes (for SO3). Use an axial flow fan to blow air through the manhole in the middle. 3: Bring a flashlight and a candle with you. 4: Enter through the lower manhole, light the candle, and point it at each outlet of the heat exchange tubes; if a particular tube is leaking, the flame of the candle will be deflected or extinguished when pointed at that outlet. 5: Make marks with chalk, and after inspection, seal and weld them shut with end caps. (Both the upper and lower heat pipe openings must be sealed and welded shut.)
Start the fan directly at low speed; use a small spray bottle along with soapy water or dishwashing liquid for testing. It enables rapid leak detection over large areas; the process takes no more than about ten minutes.
What you’re referring to is checking the upper and lower ceilings; but how should each pipe outlet be sprayed? The outlet of each heat pipe is φ50
Open the manholes at the top and bottom of the heat exchanger pipes. Under normal circumstances, if the pipes are unobstructed, it will be possible to hear or feel the fan operating once it is turned on. If the weld on the pipe is intact, you can simply spray soapy water on the welded area of the pipe; bubbles will form as a result, and even in tiny cracks bubbles will appear. Don’t ask me about how to prepare soapy water; you know how to do laundry at home. Or you know how much to use each time you wash the dishes, right?
Block the upper tube sheet with something, and check at the lower tube sheet using the aforementioned method.
1. A dedicated plug can be made to block one side of the tube sheet while allowing air to pass through the other side. 2. Alternatively, observe the tube ends from below the heat exchanger; those that are relatively damp or clean are more likely to have leaks, so it’s sufficient to check those tube ends carefully. 3. Another option is to seal the inlet and outlet pipes on the shell side and use compressed air to detect leaks; generally, the pressure of the compressed air should not exceed 0.05 Mpa, and in cases of severe leaks, sounds can be heard at the upper and lower tube sheet areas