1、Designation:D478713Standard Practice forContinuity Verification of Liquid or Sheet Linings Applied toConcrete Substrates1This standard is issued under the fixed designation D4787;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the ye
2、ar 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 practice covers procedures that may be used toallow the detection of discontinuities in nonconductive liningsor
3、other non-conductive coatings applied to concrete sub-strates.1.2 Discontinuities may include pinholes,internal voids,holidays,cracks,and conductive inclusions.1.3 This practice describes detection of discontinuities uti-lizing a high voltage spark tester using either pulsed orcontinuous dc voltage.
4、NOTE1For further information on discontinuity testing refer toNACE Standard SP0188-2006 or Practice D5162.1.4 This practice describes procedures both with and with-out the use of a conductive underlayment.1.5 The values stated in SI units are to be regarded asstandard.The values given in parentheses
5、 are for informationonly.1.6 This standard does not purport to address all of thesafety concerns,if any,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
6、to use.For a specifichazard statement,see Section 7.2.Referenced Documents2.1 ASTM Standards:2D5162 Practice for Discontinuity(Holiday)Testing of Non-conductive Protective Coating on Metallic SubstratesG62 Test Methods for Holiday Detection in Pipeline Coat-ings2.2 NACE Standards:3SP0188-2006 Discon
7、tinuity(Holiday)Testing of ProtectiveCoatings3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 conductive underlayment,na continuous layer ap-plied to the prepared concrete surface prior to the application ofa nonconductive lining layer(s)that will allow high voltagespark testing
8、 for discontinuities in the lining,as it will conductthe current present when the spark is generated.3.1.2 current sensitivity,nsome high voltage testers haveadjustable current sensitivity that can be used to prevent lowlevels of current flow activating the audible alarm.The alarmsensitivity control
9、 sets the threshold current at which theaudible alarm sounds.If the high voltage can charge the lining,a small amount of current will flow while this charge isestablished.If the lining contains a pigment that allows alow-level leakage current to flow from the probe while testingthe threshold current
10、 can be set so that the alarm does notsound until this current is exceeded,that is,when a holiday orflaw is detected.Increasing the current threshold setting makesthe instrument less sensitive to this low level current flow,decreasing the current threshold setting makes the instrumentmore sensitive
11、to current flow.3.1.3 discontinuity,na localized lining site that has adielectric strength less than a determined test voltage.3.1.4 high voltage spark tester,nan electrical device(producing a voltage in excess of 500 V)used to locatediscontinuities in a nonconductive protective coating applied toa
12、conductive substrate.The high voltage is applied to thecoating or lining using an exploring electrode and any currentresulting from the high voltage passing through a discontinuityin the coating or lining is passed to the device via a signalreturn cable(also known as a ground or earth wire).3.1.5 ho
13、liday,nsmall faults or pinholes that permit currentto flow through the conductive substrate,also known as adiscontinuity.1This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.46 on In
14、dustrial Protective Coatings.Current edition approved Feb.1,2013.Published March 2013.Originallyapproved in 1988.Last previous edition approved in 2008 as D4787 08.DOI:10.1520/D4787-13.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.o
15、rg.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from NACE International(NACE),1440 South Creek Dr.,Houston,TX 77084-4906,http:/www.nace.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohock
16、en,PA 19428-2959.United States1 3.1.6 spark-over,nthe distance a spark,from a highvoltage tester,will jump across a space from a groundedsurface at a specific electrical voltage.3.1.7 telegraphing,ncurrent traveling through a moisturepath across the surface of the coating to a discontinuity,givingan erroneous indication of a fault.3.1.8 test voltage,nthat electrical voltage establishedwhich will allow a discontinuity at the thickest lining locationsite to be tested,but which will not damage the
