1. Working Principle

Inside the stem, a helical bimetallic coil is made of two bonded metals with different thermal expansion.
When temperature increases, the coil twists and drives the pointer on the dial.
✔ No power supply needed
✔ High durability

2. Structure

A typical threaded bimetallic thermometer with thermowell includes:

• Dial / Pointer

• Stainless-steel case

• Helical bimetal element

• Stem (integrated with sensing coil)

• Threaded thermowell (separate, removable)

• Thread type:

• NPT (1/2", 3/4", 1")

• BSPP / BSPT

• Metric threads

The thermometer inserts into the thermowell and is held by a union or threaded connection.

3. Advantages

• Safe and durable — thermometer never contacts the process directly

• Easy replacement — remove thermometer without draining pipeline

• Good protection against pressure, flow velocity, corrosion

• Longer service life

• Wide measuring range

4. Typical Applications

Used in:

• Petrochemical pipelines

• Heat exchangers

• HVAC systems

• Water and steam pipelines

• Boilers

• Chemical and food processing

Especially when pressure or corrosion requires a protective sleeve.