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Specs at a glance
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Accuracy
Class special or standard acc. to ASTM E230
Class 1 or 2 acc. to IEC 60584-2 -
Response time
depending on configuration
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Operating temperature range
Type K:
max. 1.100 °C
(max. 2.012 °F)
Type J:
max. 700 °C
(max. 1.292 °F)
Type N:
max. 1.150 °C
(max. 2.102 °F) -
Max. immersion length on request
up to 20.000,0 mm (787,4'')
Field of application
iTHERM SurfaceLine TM691 is a dedicated tube skin thermometer that measures tube wall temperature directly on the outside of process tubes, helping operators monitor thermal performance, detect overheating and protect tube integrity. Combining a standardized product structure, high configuration flexibility and specialist expertise, it enables reliable application-specific solutions for demanding thermal processes and harsh environments.
Usage in the Oil & Gas, Chemical as well as Power & Energy industries
Typically for fired heaters, reformers, heat exchangers, boilers
Specifically designed for harsh environments with high temperatures, corrosion and vibration
Benefits
Increased plant and process safety: early detection of overheating and critical operating conditions of process pipes
Improved energy efficiency: Assessing and optimizing burner operation and heat distribution
Improved product quality: stabilized process conditions due to accurate temperature measurement
iTEMP temperature transmitter with all standard communication protocols and optional Bluetooth® connectivity
Xpert selection
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Specialized products
- Designed for demanding applications
Technical excellence
Simplicity
Variable
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Standard products
- Reliable, robust and low-maintenance
Technical excellence
Simplicity
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Specialized products
- Designed for demanding applications
Technical excellence
Simplicity
Variable
| FLEX selections | Technical excellence | Simplicity |
|---|---|---|
Fundamental selection Meet your basic measurement needs |
Technical excellence
|
Simplicity
|
Lean selection Handle your core processes easily |
Technical excellence
|
Simplicity
|
Extended selection Optimize your processes with innovative technologies |
Technical excellence
|
Simplicity
|
Xpert selection Master your most challenging applications |
Technical excellence
|
Simplicity
Variable |
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Success stories
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Technical Information (TI)
TI iTHERM SurfaceLine TM691
Surface thermometer
Metric/imperial TC tube skin thermometer for harsh environments such as fired heaters, reformers, heat exchangers, boilersEN 01/09/2026Language:
English
Version:
01/09/2026
File size:
2.7 MB
File name:
TI01898TEN_0126-00.pdf
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Innovation (IN)
Durable tube skin thermometer.
iTHERM SurfaceLine TM691: Built for the toughest conditions.
Language:
English
Version:
30/09/2026
File size:
1.9 MB
File name:
IN01422T09EN01.26.pdf
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Innovation (IN)
Robustes Oberflächenthermometer.
iTHERM SurfaceLine TM691: Für härteste Einsatzbedingungen entwickelt.
Language:
German
Version:
07/10/2026
File size:
1.9 MB
File name:
IN01422T09DE01.26.pdf
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AI (Application note)
Rohrwandtemperaturmessung
in einem Steamcracker-Ofen für die Ethylenproduktion
Language:
German
Version:
30/09/2026
File size:
715.8 KB
File name:
AI01391T09DE02.26.pdf
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AI (Application note)
Tube skin temperature measurement
in a steam-cracking furnace for ethylene production
Language:
English
Version:
30/09/2026
File size:
712.1 KB
File name:
AI01391T09EN02.26.pdf
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