Print this page Thermowells – Basic Selection Criteria
David A. Snyder, P.E.
Course Outline
This course familiarizes the reader with the basic selection decisions that must be made in order to select the proper thermowell for each application. Standard lengths for temperature sensors and thermometers are discussed to help the reader choose a combination of thermowell process insertion length, lagging length, and extension length to fit an off-the-shelf temperature sensor or thermometer. There are many illustrations and several examples to clarify the meanings of terms like process insertion length and lagging length. This course gathers together the far-flung pieces of information about thermowells and arranges them in a cohesive, easily-understood presentation.
This course includes a multiple-choice quiz at the end, which is designed to
enhance the understanding of the course materials.
Learning Objective
At the conclusion of this course, the student will:
- Understand the advantages and disadvantages of thermowells;
- Differentiate between the various process connection types;
- Understand the difference between process insertion length, lagging length, and extension length;
- Understand the derivation of the formula for the sensor length of a thermowell;
- Choose the proper interior diameter (bore) of a thermowell to match a given temperature sensor or thermometer;
- Understand the different shapes or stem geometries of thermowells;
- Determine the proper thermowell material for common process media using a manufacturer’s corrosive service guide; and
- Become acquainted with other thermowell concerns, such as velocity rating and resonant frequency.
Intended Audience
Anyone who is involved in the specification, procurement, or installation of thermowells, or the temperature sensors and thermometers that are installed in thermowells, will benefit from this course.
Course Introduction
Thermowells are present in almost every industrial process but they are rarely discussed in any depth or with any completeness. The formula for calculating the sensor length for a given thermowell is very simple, but the derivation of that simple formula is not usually presented. The fragments of information that are available from widespread sources have been gathered together and arranged in this easy-to-understand course that includes many illustrations and several examples.
Course Content
The course content is in a PDF file:
Thermowells – Basic Selection Criteria
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Course Summary
Upon successful completion of the course, the reader will have a thorough understanding of standard thermowell lengths and how the sensor length is determined for each type of thermowell. The reader will be familiar with the decisions that must be made in order to select the proper thermowell for each application.
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
