1. Working Principle

A bimetallic strip is made by bonding two metals with different thermal expansion coefficients.
When temperature changes:

• The metals expand at different rates

• The strip bends or coils

• This mechanical movement drives the pointer on the dial to indicate temperature

No electricity is required.

2. Structure

A typical flanged bimetallic thermometer includes:

• Dial / Pointer — displays temperature

• Stem (Thermowell) — inserted into process

• Helical bimetal element — inside the stem

• Flange (ANSI / DIN standard) — for mounting

• Case — usually stainless steel

• Window — glass or polycarbonate

3. Flange Standards

Common flange connection options:

• ANSI / ASME B16.5

• 1", 1.5", 2" flanges

• Class 150 / 300

• DIN / EN 1092-1

• DN25 / DN40 / DN50

• PN16 / PN25 / PN40

The flange allows strong sealing, easy replacement, and safe use under pressure.

4. Advantages

• Mechanical, no power needed

• Economical & durable

• Fast response (depending on stem diameter)

• Clear dial reading

• Direct flange installation

• Suitable for liquid, gas, and vapor

5. Typical Applications

Used in:

• Petrochemical

• HVAC

• Boilers / steam systems

• Industrial pipelines

• Water treatment

• Food processing

• Machinery