ASTM E797/E797M-21 PDF

SIGNIFICANCE AND USE 5.1 The techniques described provide indirect measurement of thickness of sections of materials not exceeding temperatures of 93 °C [200 °F]. Measurements are made from one side of the object, without requiring access to the rear surface. 5.2 Ultrasonic thickness measurements are used extensively on basic shapes and products of many materials, on precision machined parts, and to determine wall thinning in process equipment caused by corrosion and erosion. 5.3 Recommendations for determining the capabilities and limitations of ultrasonic thickness gages for specific applications can be found in the cited references.7,8 SCOPE 1.1 This practice2 provides guidelines for measuring the thickness of materials using the contact pulse-echo method at temperatures not to exceed 93 °C [200 °F]. 1.2 This practice is applicable to any material in which ultrasonic waves will propagate at a constant velocity throughout the part, and from which back wall reflections can be obtained and resolved. 1.3 This practice is primarily for flat components with parallel surfaces and has limited applicability for components with non-parallel or concentric surfaces per 1.2. 1.4 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 1.5 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. 1.6 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.