Seeking help regarding leakage at the flange of the heat exchanger head
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A reboiler is installed, which is a U-tube heat exchanger. It is heated using 40 kg of superheated steam, with the steam inlet temperature being around 400 degrees (the outlet corresponds to the drain from the trap). Leaks often occur at the head flanges; some say this is due to large temperature differences between the tube sheet and the flanges, resulting in uneven deformation and thus leaks. I would appreciate it if you could provide a detailed analysis of the causes and suggest possible solutions. Thank you!
I suggest you post a picture for a look...
Describe the condition of your tube box gaskets.
Tighten it diagonally again when it’s cold; use a impact wrench or a hammer to do it~!
The gasket was not selected or installed properly.
There might be a problem with the flatness of the tube sheet (it is bulging in the middle). Welding deformation of the tube sheet caused the water chamber flange to fail to seal. Forcing the bolts to be tightened can prevent leakage, but leakage may still occur during operation at high temperatures. Solutions: 1. Use some new bolts, apply force, and tighten them diagonally again. (Some bolts may already be damaged.) 2. If leakage persists, disassemble it and measure the flatness of the tube sheet ； If acceptable, replace the gasket and tighten the bolts. 3. If the deformation is too large, grind the water chamber partition (adjust it to match the tube sheet deformation; a deformation of 1-2 mm is acceptable), replace the gaskets, and tighten them. The other ones are weird tricks. For example, thickening the gasket, wrapping the perimeter of the gasket with graphite paper to thicken it, creating custom-shaped gaskets based on the degree of deformation; I’ve even seen cases where the entire flange along with the bolts were enclosed in a steel ring and then welded together. 4. File a claim with the manufacturer
OP, does the flange at the head refer to the flange of the equipment that is connected to the tube sheet? The flange is leaking; check whether the gaskets are installed properly, whether the material of the gaskets matches the medium, pressure, and temperature, whether the fasteners are suitable, and whether there are any defects in the sealing surfaces of the flange and the tube sheet. Whether it meets the requirements of the drawings, etc.
It’s a tube box flange; there is a partition in the middle of the tube box, and the temperature difference between the upper and lower parts is over 100 degrees. Could this temperature difference cause the tube box to deform and leak?
The temperature difference between the upper and lower parts is a factor, but it is not the main factor. It is recommended to use a hydraulic wrench to apply the correct torque for tightening; special disc springs can be used if necessary.
It is likely due to an excessive pressure difference or a large temperature difference in the superheated steam; therefore, pay attention to this aspect during dough fermentation. If the pressure difference is too large, it is necessary to consider reducing the pressure difference across the tube and shell sides; if the temperature difference is large, then reducing that temperature difference range should be considered.
Try using a different gasket; we use asbestos gaskets wrapped with tape