ASTM C447 – Standard Practice for Estimating the Maximum Use Temperature of Thermal Insulations
Description:
Significance and Use
5.1 This practice is intended for use as a guide in evaluating the behavior of insulations at elevated temperatures, and in judging suitability for use under the conditions of an intended application. It is not intended for acceptance or certification testing on a lot basis.
5.2 No single test for estimating maximum use temperature can be used that will apply to all types of insulations, nor can any single maximum use temperature be applied to any insulation that will be applicable under all possible conditions of use. Maximum use temperature depends on thickness, temperature gradient, heating rate, and other factors. When the various test methods listed herein are employed, the test results serve as guides and, as such, shall be applied with good engineering judgment in arriving at an acceptable temperature limit for the products and applications being considered.
5.3 The criteria used to establish acceptable performance is provided in the material specification or as agreed upon by the purchaser and seller.
5.4 In most cases, the properties covered by the applicable material standards (for example, thermal transmission, strength, and so forth) are the properties important to the end use of the product. Major changes in those properties resulting from in-service conditions often causes failure or substandard performance of the installed system.
5.5 Unless removal and reuse of the insulation is an important consideration, properties that relate primarily to handling and installation shall be eliminated from the evaluation.
NOTE 1: Installation assemblies: some systems create conditions that affect the performance from the data obtained in the test procedures of this practice.
5.6 The listing of a test procedure in this practice does not imply that the performance of that particular procedure is required. Only those tests which are relevant to the requirements of the application involved, or which are agreed upon by the purchaser and the seller are preformed.
5.7 Most of the changes that occur in the functionally important characteristics of all types of thermal insulation during service result from changes in the matrix or binder system first, followed by changes in the bulk filler materials where such fillers have been used.
5.7.1 In general, these changes are temperature-dependent and the major portion of the change takes place quickly once the critical temperature has been reached.
5.7.2 Typically, organic thermoplastic materials or binders will change in the 140 °F to 240 °F (60 °C to 116 °C) temperature range. Thermosetting organic materials or binders will start to deteriorate above 350 °F (177 °C). Hydrated inorganic binders such as clays, Portland and lumnite cements, gypsum, sodium silicates, oxysulfates, and oxychlorides lose varying amounts of water of crystallization at temperatures from 250 °F to 900 °F (121 °C to 482 °C) depending on the compound. Glass fibers and glass foams start to sinter around 1000 °F (538 °C). Rock or slag wools, perlite and refractory fibers occasionally show change at temperatures in excess of 1300 °F (704 °C).
5.8 If, after testing specimens exposed to the maximum service temperature, additional tests are made of specimens exposed to intermediate temperatures (third or quarter points in the full service temperature range), the results of such tests, when plotted with proper curve-fit techniques, give indications of changes in product characteristics throughout the service range. These results are used to bracket the temperature range within which a change has occurred (for example, significant change in slope of curve).
5.9 Some properties of thermal insulations containing trapped gases other than air change with time at different rates depending on the age, thickness, facing and boundary conditions. Elevated temperature exposure often accelerates these changes. In many cases changes in properties continue over a very long period of time. It is beyond the scope of this recommended practice to establish a minimum time period for evaluation of long-term changes.
Scope
1.1 This practice covers estimation of the maximum use temperature of thermal insulation including loose fill, blanket, block, board, and preformed pipe insulation. It is based upon selected performance criteria, and characterization of product properties during and after use conditions.
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
ASTM C441