Thermowells
Thermowells
(OP)
Do you guys have good information on sizing thermowells (U length)? I am looking for something to help with spec'ing out some themowells. This is a new area for me and would appreciate any help that you could give. Is there any chart that basically gives U lengths for just about all possible combinations of piping and accessories? Not sure if there is something out there like that, but worth asking. Thanks!





RE: Thermowells
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The U length depends on your process requirements. Typically, for tanks and vessels, we specify the length between 6-8 inches inside the vessel. Be careful on interference with equipment inside the tanks though, such as heating/cooling coils, etc. Thermowells for piping can be a bit trickier.
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RE: Thermowells
It is reasonably common for small piping to put the well in one side of a tee and let it protrude upstream a ways. That way you can put a 6" or 8" well in a 1" pipe.... Then the tee drains through the common port.
RE: Thermowells
RE: Thermowells
RE: Thermowells
For inside tanks, usually 6-8 inches off the wall is sufficient to get away from wall effects.
For pipes, usually to mid-line for pipes 4" and under. For 4" and larger, usually 1/4 D is enough. When you get really big, 10" and larger, a flow regime/character study may be needed to determine where exactly the well needs to be to get the reading that is representative of whatever you are trying to measure.
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RE: Thermowells
RE: Thermowells
As most wells these days are flanged, consider a flanged well. The pipe extension (top of pipe to flange face) may be six inches. Frequently the calculation will eliminate a 12-inch insertion length. I try to select thermowell insertion lengths for any temperature element that would match with dial thermometer stem lengths. A 10-inch "U" on a flanged well should match a 12-inch stem. This would be the longest well to consider in most piping cases. This issue is not a problem for vessels.
Consider wells that fit the following pattern except that threaded wells on insulated lines may require longer lag extensions.
Stem lengths in inches:
Stem, "U" NPT "U" Flanged
2.5, 1"
4, 2.5" 2"
6, 4.5 4"
9, 7.5" 7"
12, 10.5" 10"