Can a floating-head heat exchanger isolate only the cooling medium without isolating the hot medium?
Thread Content
I would like to ask the experts here: we have two hot water heat exchangers of the floating-head type. Due to process requirements, these two heat exchangers are no longer in use. However, only the cold medium (circulating water, which flows through the shell side) has been isolated using blind flanges, while the hot medium (high-temperature hot water) continues to be used as usual. As a result, the temperature of the fluid inside the tube bundle is very high; today I checked and found that the outlet temperature was 82°C. I’m not sure if this will have any adverse effects on the heat exchangers over time Should the high-temperature hot water be isolated and the medium inside the tube bundle drained? Thank you all for your help and answers!
This post was last edited by ylb913 on 2015-6-19 08:53. Floating-head heat exchanger, with only the fluid in the tube side, at 82 degrees. I don’t think it matters. What medium is it? As long as it doesn’t increase the degree of corrosion, there’s no problem.
If the heat exchanger is not intended to be used anymore in the future, it can be used in this way......
Logically, there should be no problems. The design temperature on the hot medium side is certainly set based on the worst-case conditions; even if the cold medium is not used, the operating temperature of the hot medium will not exceed the design temperature of the entire heat exchanger tube bundle, nor will it exceed the allowable temperature for the materials used. This can also be determined using the strength calculation formulas for the various components of a floating-head heat exchanger. Pressure is also not an issue, so there are definitely no problems with using it.
As long as the operating temperature does not exceed the design temperature, it is fine.
If the tube sheet material is low-alloy steel, since the allowable stress is the same at 100°C and at room temperature, as long as the design pressure on the tube side remains unchanged, there should be no problem； However, if it is a material with reduced allowable stress at 100°C, or if the design pressure on the tube side increases, it may be necessary to recalculate the strength of the tube sheet as well as the axial stress and pulling force on the heat exchange tubes.
Hot water, but due to a leak in the coking heat exchanger, it contains some dirty oil.
The poster’s concern is valid. The folks upstairs have no issues with the design, materials, and condition analysis. But using it in this way is incorrect: from an operational perspective, a heat exchanger cannot allow the medium to flow in only one direction; then why do the operating procedures specify detailed steps for starting up and shutting down a heat exchanger? ! If not needed, treat it as a complete resection (add a cross-line if one is required).
Use it with confidence; the strength verification during equipment design takes three scenarios into account: only the fluid in the tube side flowing, only the fluid in the shell side flowing, and both flowing simultaneously. . . . . . . If the answer is negative, don’t press it,,,
You still approach things from a design perspective. Regarding the specific example given by the original poster, there is no problem with it, but can this represent that all heat exchangers can be used in this way? Isn’t it still necessary to handle each situation on its own?