SELECTION OF THERMOWELLs
Material
Thermowell material chosen for an installation is governed by corrosive conditions. Occasionally, thematerial consideration is one of strength rather than acorrosive condition. Consult the pressure-temperature ratings given for each wel ltype for proper selection.
InsertionLength“U”
The distance from the end of thewell to the underside of the thread,or other connection means, designated as “U” is the insertion length. For best accuracy, this length should be long enought opermit the entire temperature sensitive part of the thermocouple to project in to the temperature medium being measured.
Bore Size
The bore size of wells shown as below the most commonly used temperature sensing elements as follows:
Bore Diameter —-> Element diameter
6.0 mm —-> 6.4 mm
6.6 or 7.0 mm —-> 6.35 mm
8.5 mm —-> 6.0 mm
10.0 mm —-> 9.5 mm
Tapered or Straight Shank
Tapered shank wells provide greater stiffness for the same sensitivity.The hight strength-to-weigh tratio gives these wells higher natural frequency than equivalent length straight shank wells, thus permitting operation at higher fluid velocity.
