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HF02 heat flux sensor

Flare radiation monitor / heat flux sensor

HF02 is a sensor that measures radiant heat flux or thermal radiation in the outdoor environment. A common application is monitoring the radiation emitted by flares. HF02 is certified for use in potentially explosive atmospheres, and is rated for radiation levels up to 15 x 10³ W/m². We recommend use of HF02 in a decision-supporting role only, and not to use measurements of HF02 as the main or sole source of information for judging safety.

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HF02 is certified for use in potentially explosive atmospheres

HF02 is used in alarm systems, using the heat flux measurement to issue a warning in case of high thermal radiation exposure of equipment or personnel. It is typically installed close to a flare. A common assumption is that the heat flux level in a safe environment for personnel must not exceed 5 x 10³ W/m² (or 1.5 x 10³ BTU/(hr∙ft²)). Above that heat flux level, or when the temperature of the sensor body exceeds 70 °C, an alarm is activated. A typical alarm system will include multiple HF02 sensors, all aimed at the main source of radiation, as well as other decision-supporting devices such as camera systems and temperature sensors. The sensor in HF02 measures the heat flux to its black (absorbing) surface, in the plane of the sensor, from a source in the field of view angle. It offers a measurement of the effective exposure for personnel and equipment from a source in the direction it is aimed at the location of the sensor. As the detector is essentially open (it has no protective windows) the measurement is influenced by wind in the same way as any exposed surface such as clothing worn by personnel or the surface of equipment; increased wind speed leads to a reduction of the measured heat flux. Rain on the detector can also lead to cooling and a reduction of the measured heat flux.


Measurand heat flux, temperature
Measurement range -30 to + 100 °C-30 to + 100 °C0 to 15 x 10³ W/m²
Sensitivity (nominal) 0.3 x 10⁻⁶ V/(W/m²)
Model name according to EU type examination LEX30
Heat flux sensor thermopile
Temperature sensor thermocouple type KX
EC type examination certificate included in delivery
ATEX rated operating conditions II 2G Ex db IIC T6
Electrical data U[max] 5 V, I[max] 5 x 10⁻³ A
Rated process temperature range sensor and high temperature cable -50 to +300 °C
Rated operating temperature range transition piece, low temperature extension cable and cable end -20 to +70 °C
-High temperature cable 3 m (see options)
-Low temperature extension cable 3 m (see options)
IP protection class :
-Sensor and high temperature cable IP68
-Low temperature extension cable IP67
Safety notes see manual
Maintenance requirements see manual
Shielding options LEX30 Option A, LEX30 Option B or LEX30 Option C
  • longer cable: standard length of the high temperature metal sheathed cable as well as the low temperature extension cable is 3 m. Both can be extended up to 100 m
  • sensitivity: we offer dedicated converters for HF02 to provide a standardised output
  • shielding options: the standard version has the sensor body and the high temperature cable connected to the shield/drain wire of the low temperature plastic cable. A shield disconnected from the high temperature metal cable and sensor body is offered as an option


Suggested use

  • outdoor flare monitoring
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