1.1 本试验方法包括测定预成型隔热材料暴露于均热时发生的线性收缩量和其他变化。本试验方法仅限于适用于热侧温度超过150°F（66°C）的预制高温隔热材料，但试验方法涵盖的隔热耐火砖除外 C210 . 1.2 以英寸-磅为单位的数值应视为标准值。括号中给出的值是到国际单位制的数学转换，仅供参考，不被视为标准值。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 本试验方法中使用的线性收缩是指试样在均热24小时，然后冷却至室温后，线性尺寸发生的变化。 4.2 大多数绝缘材料在一定温度下会开始收缩。通常，收缩量随着暴露温度的升高而增加。最终将达到收缩过度的温度。随着过度收缩，绝缘材料肯定超过了其有效温度极限。 当绝缘材料应用于热表面时，热表面的收缩最大。较热表面和较冷表面之间产生的差异收缩通常会产生应变，并可能导致绝缘层翘曲。高收缩率可能导致过度翘曲，从而可能导致开裂，这两种情况都是不可取的。高收缩也可能会在绝缘接头处过度打开间隙，从而导致应用效率降低且更危险。为了预测使用中的允许收缩极限，必须根据经验确定绝缘材料试样在承受均热时所能承受的线性收缩程度。 4.3 人们认识到，对于不同类型的绝缘材料，不能在均热下的线性收缩和使用中的实际收缩之间建立固定关系。通常，收缩量随暴露时间而增加。增加的数量和速度因材料而异。此外，各种类型的材料可能具有不同的最大允许收缩量。因此，每种产品都必须定义其在均热条件下的特定线性收缩极限。

1.1 This test method covers the determination of the amount of linear shrinkage and other changes that occur when a preformed thermal insulating material is exposed to soaking heat. This test method is limited to preformed high-temperature insulation that is applicable to hot-side temperatures in excess of 150°F (66°C), with the exception of insulating fire brick which is covered by Test Method C210 . 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. 1.3 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 Linear shrinkage, as used in this test method, refers to the change in linear dimensions that has occurred in test specimens after they have been subjected to soaking heat for a period of 24 h and then cooled to room temperature. 4.2 Most insulating materials will begin to shrink at some definite temperature. Usually the amount of shrinkage increases as the temperature of exposure becomes higher. Eventually a temperature will be reached at which the shrinkage becomes excessive. With excessive shrinkage, the insulating material has definitely exceeded its useful temperature limit. When an insulating material is applied to a hot surface, the shrinkage will be greatest on the hot face. The differential shrinkage which results between the hotter and the cooler surfaces often introduces strains and may cause the insulation to warp. High shrinkage may cause excessive warpage and thereby may induce cracking, both of which are undesirable. High shrinkage may also open gaps at the insulation joints to an excessive extent rendering the application less efficient and more hazardous. In order to predict the limit of permissible shrinkage in service, the degree of linear shrinkage to be tolerated by specimens of an insulating material when subjected to soaking heat must be determined from experience. 4.3 It is recognized that a fixed relation between linear shrinkage under soaking heat and actual shrinkage in service cannot be established for different types of insulating materials. Generally the amount of shrinkage increases with time of exposure. The amount and rate of increase varies from one material to another. In addition, the various types of materials may have different amounts of maximum permissible shrinkage. Therefore, each product must define its own specific limits of linear shrinkage under soaking heat.