Model HIR

Infrared Pyrometer, Claus SRU Service

The CLAUSTEMP® Model HIR Infrared Temperature Transmitter “looks” into the Claus Thermal Reactor and senses the amount and spectrum of the infrared energy being emitted relative to the heat. The sensed energy is converted into a signal which accurately displays the temperature. The HIR is designed to be nearly maintenance free. The steam jacketed lens body maintains the lens assembly at a high enough temperature to avoid sulfur buildup and interior coating of the lens window glass, reducing the need for repeated maintenance or procuring “back-up” units.

Operation and Technology

A Claus Thermal Reactor partially oxidizes hydrogen sulfide to sulfur dioxide as one of the steps in removing unwanted sulfur from process streams. The final reaction products are elemental sulfur and water. The internal temperature of the reactor must be high enough to carry the reactions forward efficiently, yet not high enough to damage the refractory lining. Enrichment with oxygen adds the potential to achieve very high temperatures, which can result in destruction of the refractory or even of the complete shell. The HIR can help keep this from occurring.

All materials radiate energy as a function of their absolute temperature. The HIR senses the amount and spectrum of the infrared energy being emitted by the refractory hot face. The sensed energy is converted into a signal, which is used to accurately display the refractory surface temperature. The infrared energy being sensed must pass through the reacting gases without being absorbed by them. The HIR must also “look” through those same gases without seeing them or sensing their high temperatures. This action is accomplished with notch optical filters and special sensors. The selected sensing light spectrum’s avoid significant errors due to luminosity and absorption.

The lens, sighting window, and nozzle are kept at a high temperature to avoid sulfur deposition and the need to perform frequent periodic maintenance. The use of stable electronics does not require cooling or frequent re-calibrations at the factory.

Monitoring System Schematic


  • Operates accurately and reliably with up to 100% oxygen enrichment
  • Measures refractory "hot face" temperature
  • Works in conjunction with the Delta Controls thermocouple
  • Verify calibration against the thermocouple temperature monitoring system; anytime, without the costs and hazards of opening the reactor
  • Limited maintenance required
  • Stable electronics; no periodic factory re-calibration required; no “spare” needed
  • Sulfur does not coat the sighting window
  • Nozzle clean-out “rodding” is eliminated
  • Insensitive to reaction gas infrared radiation absorption and flame luminosity
  • No instrument case cooling or high voltage supply power required
  • Accurate; 300°C to 1700°C range


  • Range: 300°C to 1700°C (572°F to 3092°F)
  • Accuracy: ±11°C (20°F)
  • Readout: High Contrast LCD Display
  • Output Signal: 4-20 mADC, 2 wire loop, HART® Protocol
  • Power Required: Powered by the 24 VDC loop
  • Fiber optic Cable: Flexible PTFE over SS armor; 3 Meter (10 foot) is the standard length
  • Hot Lens Mounting: On a flanged nozzle; steam jacketed 3” ANSI is standard, 2" ANSI and other types and sizes available
  • Approvals:
    Class I, Division 1, Groups B, C and D;
    Class II, Division 1, Groups E, F and G;
    Class III, Division 1
    Class I, Zone 1, Ex d IIB+H2
    Class I, Zone 1, AEx d IIB+H2
    II 2 G Ex d IIC T6 IP65 0575
  • Housing Mounting: On a vertical surface or a 2” pipe stand with vertical or horizontal orientation
  • Ambient Temperature Limits: Fiber Optics, Lens: -30°C to +200°C (-20°F to 400°F) Electronics: -15°C to +65°C (0°F to 160°F)
HART® is a registered trademark of FieldComm Group

Third Party Approvals

2496557Class I Div 1, Groups B,C,D
Class II Div 1, Groups E,F,G
Class I Zone 1, Ex AEx d IIB+H2 T6
Certificate of Compliance
Sira 17ATEX1232XII 2G
Ex db IIB+H2 T6 Gb
EU Declaration of Conformity
IECEx SIR 17.0057XEx db IIB+H2 T6 GbIECEx Certificate of Conformity


Instruction Manual (prior to 31 Jan 2019)00-HIR03revN3
Instruction Manual (effective 31 Jan 2019)00-HIR03
HART® Field Device Specification00-HIR35
HART® Device Driver (DD) files00610a

Additional Information


Infrared Pyrometer, Claus SRU Service

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