Objective
Radiant heat flux meters (radiometers) are widely used in fire technics as calibration devices for the new generation of reaction to fire standard test methods. An intercomparative calibration of 4 different radiometers was performed at SP Fire Technology (SP) and Fire Research Station (FRS). The calibration was made for 2 radiation flux ranges (20 kW m{-2} and 50 kW m{-2}) and with Gardon type and Schmidt-Boelter type meters. 4 different radiometers used, 2 of each type. 3 sets of calibrations were performed, first one at SP, then one at FRS and then another set at SP.
At FRS the calibration was performed in a standard open configuration arrangement in which a gas fixed surface combustion radiant panel was used. First, an absolute radiometer was used to calibrate a secondary standard Moll type thermofile radiometer. This secondary standard was then used to calibrate the 4 radiometers.
At SP the calibration were performed in a semiclosed arrangement using an electrically heated spherical furnace chamber with the radiometer inserted in an opening at the bottom. First a standard precision thermocouple was used to calibrate a style S thermocouple. The 4 radiometers were then calibrated, with the incident radiation being calculated from the furnace temperature as measured by the type S thermocouple.
It was found that there was an overall difference in the results of less than 8%. The errors in the calibrations were calculated to the 2.9% at SP and 4.2% at FRS. As the difference in calibration results is of the same order as the combined error limits, it could have been explained, had it been of a random nature. It seems, however, as if the differences is systematic. The reason for this is not clear and further investigations are suggested.
The first part of the project investigated calibration methods for transducers measuring radiant heat flux. At SP calibrations were performed using a black-body cavity as a radiation source. At FRS calibrations were performed against a secondary standard radiant heat flux meter that was traceable to an absolute method of measuring radiant heat flux based on the temperature rise of a copper block as a function of time.
The second part of the project investigated the use of plate thermometers to measure the temperature to which construction products are subjected during fire resistance tests in furnaces of various designs. Plate thermometers have a much larger surface area than ordinary thermocouples and it had been suggested that they would ensure that furnaces of different designs would expose specimens to identical heating conditions. Two tests were carried out in four laboratories. In the first test the furnaces temperature was controlled using ordinary ISO standard thermocouples and in the second with plate thermometers.
RESULTS
Calibrations of radiant heat flux meters using the methods used by SP and FRS produced systematic differences of upto 8 %. The reasons for these differences are not clear and are still being discussed.
The differences in temperature between the different fire resistance furnaces were considerably less when the furnaces were controlled by plate thermometers instead of thermocouples. After 45 minutes, for example, the differences were less than 10 C instead of more than 100 C.
Topic(s)
Data not availableCall for proposal
Data not availableFunding Scheme
CSC - Cost-sharing contractsCoordinator
Sweden