ASTM A717-12(R2018) pdf free download

ASTM A717-12(R2018) pdf free download.Standard Test Method for Surface Insulation Resistivity of Single-Strip Specimens
1. Scope
1.1 This test method covers a means of testing the surface insulation resistivity of single strips or punchings of flat-rolled electrical steel under predetermined conditions of voltage, pressure, and temperature. 1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the 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 appro- priate safety, health, and environmental practices and deter- mine the applicability of regulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4.Summary of Test Method
4.1 Ten metallic contacts of fixed area are applied to one of the surfaces of the specimen and electrical contact is made with the base metal by two drills. The effectiveness of the surface insulation is then indicated by a measurement of average electrical current flowing between the contacts and the base metal under specified applied voltage. This measurement can be used directly as an indicator of insulation quality or may be converted to an apparent surface insulation resistivity value.
5. Significance and Use
5.1 This test method is particularly suitable for quality control in the application of insulating coatings. 5.2 Surface insulation resistivity is evaluated from a dc current that can range from 0 (perfect insulator) to 1 A (perfect conductor). 5.3 Single readings should not be considered significant since the nature of the test device and specimen are such that successive measurements of a specimen often yield different values.
6. Apparatus
6.1 The apparatus, as shown in Fig. 1 and Fig. 2, shall consist of a contact unit or test head which is attached to the head of a hydraulic press. Its associated measuring equipment, which may be remotely located, includes an ammeter, voltmeter, and voltage regulated dc power supply. When measurements are to be made at elevated temperatures, the platen beneath the specimen is heated and controlled. Detailed descriptions of the various components are given in Annex A1.
9. Procedure
9.1 To ensure correct contact button conditions, make a short circuit test occasionally by testing a bare metal surface. When the short circuit current is less than 0.99 A, clean the contacts. The use of solvents for cleaning is preferred to abrasives because the latter can result in rounded tips with reduced contact areas. 9.2 The recommended standard pressure for purpose of comparative tests shall be 300 psi [2.1 MPa]. Other pressures, depending upon the application, may be agreed upon by the producer and the user. If more than one test pressure is to be used, apply the pressures in ascending order. During testing, apply the pressures only once, but an applied pressure may be increased to a higher value. 9.3 If both sides of the specimen are coated, do not use the same area to test both sides.