1、Designation:C178516aStandard Test Method forConcentration of Pinhole Detections in Moisture Barriers onMetal Jacketing1This standard is issued under the fixed designation C1785;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year
2、 of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the con-centration of pinhole detections in a moisture barrier film orcoat
3、ing that is applied to the interior surface of metal jacketing.1.2 Since this method relies on the completion through themetal jacketing of an electrical circuit,this method is onlyapplicable to jacketing that is electrically conductive and has amoisture barrier applied which is not electrically con
4、ductive.1.3 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 This standard does not purport to address all of thesafety concerns,if any
5、,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2C168 Terminology Relating to Thermal InsulationC1729 S
6、pecification for Aluminum Jacketing for InsulationC1767 Specification for Stainless Steel Jacketing for Insula-tion3.Terminology3.1 DefinitionsDefinitions in Terminology C168 apply toterms used in this specification.3.2 Definitions of Terms Specific to This Standard:3.2.1 continuous pinhole detectio
7、nwhile the test is beingconducted,a continuous sounding of the audible test equip-ment alarm over an area larger than the contact area of thecellulose sponge.3.2.1.1 DiscussionIn some cases,large portions of one ormore of the test areas(see 8.2.1)or even all of one or more testareas will yield a con
8、tinuous pinhole detection.This concept ofa continuous pinhole detection and the area yielding thisperformance is necessary to quantify the number of pinholedetections in a sample exhibiting this phenomenon(see 9.2 and9.3)3.2.2 moisture barrier(moisture retarder)a layer of plas-tic film or other mate
9、rial applied to the inner side of metaljacketing to inhibit jacket corrosion by interfering with theformation of a galvanic cell between the dissimilar metals ofthe pipe and jacket or by preventing crevice or pittingcorrosion.3.2.3 pinholea hole completely through a moisture barriertypically too sma
10、ll to be seen by the eye.3.2.4 pinhole detectiona single sounding of the audibletest equipment alarm while the test is being conducted.3.2.4.1 DiscussionBecause pinholes are very small andthe dampened cellulose sponge contacts the moisture barrier inan area larger than a single pinhole(see 6.4),it i
11、s theoreticallypossible that multiple pinholes in close proximity to each otherwould register as a single detection.For this reason,this testmethod measures the concentration of pinhole detections ratherthan pinholes.3.2.5 holidaysynonymous with pinhole.4.Summary of Test Method4.1 A voltage is appli
12、ed across the nonconductive moisturebarrier on metal jacketing using an electrode consisting of acellulose sponge dampened with an electrically conductiveliquid such as tap water.Holes in the moisture barrier lead tocompletion of an electrical circuit which triggers an audiblealarm in the test equip
13、ment.The number of pinhole detectionscollectively in ten specified test areas is determined andreported.1This test method is under the jurisdiction ofASTM Committee C16 on ThermalInsulation and is the direct responsibility of Subcommittee C16.33 on InsulationFinishes and Moisture.Current edition app
14、roved Sept.1,2016.Published September 2016.Originallyapproved in 2013.Last previous edition approved in 2016 as C1785 16.DOI:10.1520/C1785-16A.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume
15、 information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.Significance and Use5.1 Corrosion on the interior surface of metal jacketing canbe caused by the formation of a
16、 galvanic cell between thedissimilar metals of the pipe and jacket or by crevice or pittingcorrosion.5.2 The application of a moisture barrier to the interiorsurface of the metal jacketing inhibits this corrosion byinterfering with the galvanic cell formation or by preventingwater from contacting the interior metal surface.5.3 Holes in the moisture barrier decrease its effectivenessin preventing corrosion.Large holes,scratches,or tears in themoisture barrier visible to the naked eye are easily d
