What is U-length of Thermowell?

U-length is also known as insertion length i.e. the length of which thermowell is inserted into the pipe plus its nozzle if any.

Insertion length is measured from edge of connection to the tip of the well.

For Flange connection thermowell the U-length is measured starts from the flange to the tip, while for threaded connection the U-length is measured from the thread to the tip.