【国外标准】 Standard Test Methods for Holiday Detection of Coatings used to Protect Pipelines

5.1 Method A—Low voltage holiday detection is used to locate holidays and pinholes in thin-film coatings (up to 0.508 mm (20 mils) using a sponge wetted with tap water (and a wetting agent for coatings thicker than 10 mils). The water carries the current from the electrode through the holiday to the conductive substrate. The detector is grounded to the coated substrate. When the detector senses this flow of current it alarms.5.2 Method B—High voltage holiday detection is used to locate holidays and pinholes in thick-film coatings (greater than 20 mils), but can be used on coatings as low as 10 mils thick. A test voltage is selected and set. A charged Electrode is placed in contact with the coating, and the Detector is grounded to the coated substrate. When Electrical Breakdown occurs, electric current flows between the Detector’s electrode and the conductive substrate and emits an audible alarm.5.3 This standard does not apply to holiday detection of tape wraps used to protect pipe or coatings containing conductive raw materials such as conductive pigments and extenders.5.4 The thickness of a coating applied to ductile iron pipe, fittings, or other iron castings may vary substantially due to the inherent roughness of the substrate. For these applications, consult the coating manufacturer for their recommended test voltage setting when using Method B. The coating manufacturer’s recommended test voltage setting may be subject to approval by the owner.NOTE 1: Use of voltage settings lower than those listed in this standard may increase the likelihood of non-detection.1.1 These test methods cover the apparatus and procedures for detecting pinholes and holidays in coatings used to protect pipelines.1.2 Method A is designed to detect pinholes and holidays in thin-film coatings from 0.025 mm to 0.254 mm (1 mils to 10 mils) in thickness using ordinary tap water and an applied voltage of less than 100 V d-c. It is effective on films up to 0.508 mm (20 mils) thickness if a wetting agent is used with the water.1.3 Method B is designed to detect pinholes and holidays in thick-film coatings >0.508 mm (20 mils) This method can be used on any thickness of pipeline coating and utilizes applied voltages between 3.4 and 35 kV d-c.1.4 The values stated in SI units to three significant decimals are to be regarded as the standard. The values given in parentheses are for information only.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.