ASTM C1785-17 Standard Test Method for Concentration of Pinhole Detections in Moisture Barriers on Metal Jacketing.pdf
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1、Designation: C1785 17Standard 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
2、year 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 fi
3、lm orcoating 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 electr
4、ically conductive.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 conc
5、erns, if any, associated with its use. It is theresponsibility 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.1.5 This international standard was developed in accor-dance with
6、internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2
7、C168 Terminology Relating to Thermal InsulationC1729 Specification for Aluminum Jacketing for InsulationC1767 Specification for Stainless Steel Jacketing for Insula-tionE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDe
8、termine the Precision of a Test Method3. 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 detectionwhile the test is beingconducted, a continuous sounding of the audible test
9、 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 continuous pinhole detection. This concept ofa continuous pinhole detection
10、 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 material applied to the inner side of metaljacketing to inhibit jacket co
11、rrosion 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 small to be seen by the eye.3.2.4 pinhole detectiona single sounding of
12、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 is theoreticallypossible that multiple pinholes in close proximity t
13、o 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 applied across the nonconductive moisturebarrier on metal jacketing u
14、sing an electrode consisting of acellulose sponge dampened with an electrically conductive1This 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 approved Sept. 1,
15、 2017. Published October 2017. Originallyapproved in 2013. Last previous edition approved in 2016 as C1785 16a. DOI:10.1520/C1785-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume infor
16、mation, 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 StatesThis international standard was developed in accordance with internationally recognized principles on standardizati
17、on established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.137 liquid such as tap water. Holes in the moisture barrier lead tocompletion of an electrical cir
18、cuit which triggers an audiblealarm in the test equipment. The number of pinhole detectionscollectively in ten specified test areas is determined andreported.5. Significance and Use5.1 Corrosion on the interior surface of metal jacketing canbe caused by the formation of a galvanic cell between thedi
19、ssimilar 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
20、 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 discernedand are cause for rejection of the metal jacketing.5.4 Small holes called pinholes or holidays that are notvisible to
21、 the naked eye but are large enough to allow corrosionare a significant concern and should be avoided to the extentpossible.5.5 This test method is used to quantify the concentration ofpinhole detections present in a moisture barrier for the purposeof quality control on metal jacketing with an appli
22、ed moisturebarrier.5.6 Examples of standards which have specific requirementsfor the maximum allowable concentration of pinhole detectionsin the moisture barrier are Specifications C1729 and C1767.6. Apparatus6.1 Test equipment shall be a pinhole or holiday detectorwith an output voltage of 65 to 75
23、 volts DC that emits anaudible signal when a connection between the two leads isdetected.NOTE 1These instruments can be found by performing a web searchfor “wet sponge pinhole detector” or “wet sponge holiday detector”.6.2 One lead of the pinhole detector shall have a springtensioned metal clamp cap
24、able of being attached to the metaljacketing.6.3 The other lead of the pinhole detector shall have a metalclamp capable of securing a cellulose sponge.6.4 The cellulose sponge clamped to the pinhole detectorlead shall have a size capable of touching the moisture barrierof 2 6116 by 2 6116 in. (50.8
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