Discussion on the causes of damage to heat exchange tubes
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Design parameters: Shell-side fluid: soft water; Tube-side fluid: nitric acid exhaust gas (nitrogen oxide gas). Operating temperature: inlet/outlet: 30/180 degrees, design temperature: 200 degrees. Operating temperature: inlet/outlet: 320/180 degrees, design temperature: 350 degrees. Operating pressure=
The inlet temperature of the soft water is increased to around 140 degrees; after heat exchange, the temperature becomes even higher and the soft water vaporizes, which may result in phenomena similar to cavitation on the heat exchange tubes
What is the controlled temperature at the soft water outlet? Is there any sound during normal operation? It might be that the soft water has vaporized, resulting in cavitation as mentioned on the 3rd floor.
The outlet temperature of the soft water is kept around 170, and there are no abnormal noises during operation
May I ask where the leakage in the heat exchange tube is? At the weld between the tube sheet and the heat exchange tubes, is it also the heat exchange tubes themselves? Is the leak at the outer edge of the tube sheet or is it discrete? What is a water softening process?
Original poster, please confirm the following question: 1. Is this heat exchanger a vertical or horizontal device? 2. How are the inlet and outlet ports for the tube side and shell side distributed? It would be best to have a simple diagram. 3. Where is the leakage in the heat exchange tube? 4. What are the forms of damage to the heat exchange tubes? Puncture or crack? 5. Does the flow rate change significantly when the inlet temperature of the soft water increases? The increase in flow rate also leads to erosion and thinning of the tubes on the shell side near the baffle, a phenomenon that cannot be ignored. The first impression is that the problem lies on the soft water side of the shell side, and it is related to a change in the process.
The equipment is currently in use. The heat exchanger is a horizontal type; the soft water enters the heat exchanger from the side and exits from its upper part. It is not yet possible to determine the manner in which the heat exchange tubes have been damaged. The flow rate of the soft water remains unchanged compared to before; only the temperature has increased, and the water at the outlet point has likely already vaporized
This post was last edited by Stay calm HAPPY on 2017-9-12 at 14:43. My speculation: 1. The leaking pipe should be located at the upper part of the horizontal heat exchanger. 2. If the pH value of soft water is too high, it may cause alkaline corrosion and perforation of the tubes at the vapor-liquid interface. 3. Chloride ions in water accumulate at the wet-dry interface of the butt joint in stainless steel (if there is a butt joint), resulting in stress corrosion cracking caused by chloride ions. Just to confirm again, are the high-temperature gas inlet on the tube side and the heated soft water outlet on the shell side adjacent to each other, located on opposite sides of the same tube sheet? Looking forward to your feedback! Thank you!
I will get back to you with specific details once the equipment is replaced. Additionally, the soft water used is the boiler soft water from the power plant; its pH level is normal. The inlet and outlet for this soft water are located at the tube sheet ends of the equipment
Your soft water circulation doesn’t have any head pressure