The major contribution of this practice is that it enables a measurement of the real-time energy loss or gain through a chosen surface of an existing process insulation with minimal disturbance to the heat flux through the insulating body.

The primary use of this practice will be for the in-situ estimation of thermal transport properties of industrial insulation such as used on pipes, tanks, ovens, and boilers, operating under normal process conditions.

Errors attributable to heat flow measurements over a small area or short term testing can be misleading and this practice is intended to minimize such errors.

Insulation processes with large temperature differences across the insulation are best suited to HFT measurements because modest changes in ambient conditions have but minimal effects on HFT output.

While it would be ideal for the HFT and attachment system to have zero thermal resistance, this factor is insignificant to the measured result if kept to 5 % or less of the resistance of the insulating section being tested.

1.1 This practice covers the in-situ measurement of heat flux through industrial thermal insulation using a heat flux transducer (HFT).

1.2 This practice estimates the thermal transport properties of thermal insulation materials in-situ in field applications under pseudo steady-state conditions. It is not intended that this practice should be used as a substitute for more precise laboratory procedures such as Test Methods C 177, C 335, or C 518.

1.3 This practice is limited by the relatively small area that can be covered by an HFT and by the transient effects of environmental conditions.

1.4 Temperature limitations shall be as specified by the manufacturer of the HFT.

1.5 While accurate values of heat flux are highly depend-ent upon proper calibrations under the conditions of use, manufacturer's calibrations may be used with confidence for comparative work between similar materials, aging, or other conditions of use. Note 1 - Further information may be found in the literature (1-6).

This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.