1、Designation: D7240 18Standard Practice forElectrical Leak Location Using Geomembranes with anInsulating Layer in Intimate Contact with a ConductiveLayer via Electrical Capacitance Technique (Conductive-Backed Geomembrane Spark Test)1This standard is issued under the fixed designation D7240; the numb
2、er immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the 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
3、.1 This practice is a performance-based standard for anelectrical method for locating leaks in exposed conductive-backed geomembranes. For clarity, this practice uses the term“leak” to mean holes, punctures, tears, knife cuts, seam defects,cracks, and similar breaches in an installed geomembrane (as
4、defined in 3.2.7).1.2 This practice can be used for conductive-backedgeomembranes installed in basins, ponds, tanks, ore and wastepads, landfill cells, landfill caps, canals, and other containmentfacilities. It is applicable for conductive-backed geomembranesmade of materials such as polyethylene, p
5、olypropylene, poly-vinyl chloride, chlorosulfonated polyethylene, bituminousgeomembrane, and any other electrically insulating materials.This practice is best applicable for locating conductive-backedgeomembrane leaks where the proper preparations have beenmade during the construction of the facilit
6、y.1.3 For electrical leak location of conductive-backedgeomembranes using methods in lieu of or in addition to thespark testing method, the installation must be electricallyisolated (as defined in 3.2.5).1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement a
7、re included in thisstandard.1.5 The spark test may produce an electrical spark andtherefore should only be used where an electrical spark wouldnot create a hazard. This standard does not purport to addressall of the safety concerns, if any, associated with its use. It isthe responsibility of the use
8、r of this standard to establishappropriate safety, health, and environmental practices anddetermine the applicability of regulatory limitations prior touse.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the D
9、ecision 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:2D4439 Terminology for GeosyntheticsD5641/D5641M Practice for Geomembrane Seam
10、Evalua-tion by Vacuum ChamberD5820 Practice for Pressurized Air Channel Evaluation ofDual Seamed GeomembranesD6747 Guide for Selection of Techniques for Electrical LeakLocation of Leaks in Geomembranes3. Terminology3.1 Definitions:3.1.1 For general definitions used in this practice, refer toTerminol
11、ogy D4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 conductive-backed geomembrane, na specialtygeomembrane manufactured using coextrusion technology,featuring an insulating layer in intimate contact with a conduc-tive layer.3.2.2 coupling pad, nan electrically conductive padplaced on
12、top of the geomembrane and connected to the sparktesting apparatus used to induce electrical potential across theconductive-backed geomembrane.3.2.3 current, nthe flow of electricity or the flow ofelectric charge.3.2.4 electrical leak location, na method which useselectrical current or electrical po
13、tential to locate leaks in ageomembrane.1This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-thetics and is the direct responsibility of Subcommittee D35.10 on Geomembranes.Current edition approved Feb. 1, 2018. Published February 2018. Originallypublished in 2006. Last previous
14、edition approved 2011 as D7240 06 (2011). DOI:10.1520/D7240-18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM websit
15、e.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 standardization established in the Decision on Principles for theDevelopment of Int
16、ernational Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.5 electrically isolated conductive-backed geomembraneinstallation, nan installation of conductive-backed geomem-brane that achieves a continuously conductive surfa
17、ce on thebottom layer, while electrically isolating the bottom conductivelayer from the top insulating layer of the entire geomembraneinstallation.3.2.6 false positive, nan alarm or spark, or both, generatedby the spark testing equipment on a feature that is not an actualbreach in the geomembrane.3.
18、2.7 leak, nfor the purposes of this document, a leak isany unintended opening, perforation, breach, slit, tear,puncture, crack, or seam breach. Significant amounts of liquidsor solids may or may not flow through a leak. Scratches,gouges, dents, or other aberrations that do not completelypenetrate th
19、e geomembrane are not considered to be leaks.Types of leaks detected during surveys include but are notlimited to: burns, circular holes, linear cuts, seam defects, tears,punctures, and material defects.3.2.8 wand, nfor the purposes of this document, any rodthat has a conductive element that is atta
20、ched to a power sourceto initiate the spark test.4. Significance and Use4.1 Geomembranes are used as barriers to prevent liquidsfrom leaking from landfills, ponds, and other containments. Forthis purpose, it is desirable that the geomembrane have as littleleakage as practical.4.2 The liquids may con
21、tain contaminants which, ifreleased, can cause damage to the environment. Leakingliquids can erode the subgrade, causing further damage.Leakage can result in product loss or otherwise prevent theinstallation from performing its intended containment purpose.4.3 Geomembranes are often assembled in the
22、 field, eitherby unrolling and welding panels of the geomembrane materialtogether in the field, unfolding flexible geomembranes in thefield, or a combination of both.4.4 Geomembrane leaks can be caused by poor quality ofthe subgrade, poor quality of the material placed on thegeomembrane, accidents,
23、poor workmanship, manufacturingdefects, and carelessness.4.5 Electrical leak location methods are an effective andproven quality assurance measure to detect and locate leaks.5. Principles and Context of Exposed GeomembraneElectrical Leak Location Methods5.1 Principles of the Electrical Leak Location
24、 Methods forExposed Geomembranes:5.1.1 The principle of the electrical leak location methods isto place a voltage across a geomembrane and then locate areaswhere electrical current flows through leaks in the geomem-brane.5.1.2 The spark testing method is only applicable toconductive-backed geomembra
25、nes.5.1.3 Typical installations of conductive-backed geomem-branes can be spark tested to within about 100 mm of the seamedge. The seams are then tested with the appropriate seamtesting method such as Practice D5641/D5641M or D5820.5.1.4 In electrically isolated conductive-backed geomem-brane instal
26、lations, it may also be possible to spark test theseams.5.1.5 Electrical leak location methods in addition to thespark testing method may be used on electrically isolatedconductive-backed geomembrane installations. Availablemethods for exposed and covered geomembranes are detailedin Guide D6747.6. S
27、park Testing Method6.1 A summary of the method is presented in Table 1.6.2 Principles of the Spark Testing Method:6.2.1 The principle of this electrical leak location method isthat the nonconductive (insulating) layer(s) of the geomem-brane acts as a dielectric in a capacitor, which provides a lowim
28、pedance through the geomembrane. The capacitor formedby the conductive pad, the geomembrane, and the conductivelayer provides capacitive coupling between one output of ahigh-voltage power supply to the underlying conductive layer.The area is then swept with a test wand to locate points wherethe capa
29、citor discharges through a leak. Once the system sensesthe discharge current, it is converted into an audible alarm.6.2.2 Fig. 1 shows a diagram of the coupling pad, powersupply, and test wand for the electrical leak location method ofTABLE 1 Summary of Spark Testing MethodGeomembranes Bituminous, C
30、SPE, CPE, EIA, fPP, HDPE, LLDPE,LDPE, PVC, VLDPEX not applicableConductive-backed geomembrane U requiredEPDM X not applicableSeams All types: welded, tape, adhesive, glued, and other See footnoteAJunctions At synthetic pipes and accessories U applicable: project specificAt grounded conducting struct
31、ures X not applicableSurvey During construction phase (installation of GM) U applicablePre-service testing (exposed) U applicableSlopes U applicable: project specificInsufficiently conductive subgrade U applicableDuring the service life (if exposed) U must be generally clean and dryClimate Sunny, te
32、mperate, warm U applicableRainy weather X not applicableFrozen conditions U applicableLeaks detected Discrimination between multiple leaks U applicableACan test to within 4 in. (100 mm) of seams in typical installations. It may be possible to test seams directly on electrically isolated conductive-b
33、acked geomembraneinstallations.D7240 182a geomembrane with a lower conductive layer. Once allnecessary connections are made, the pad is placed on the uppersurface of the geomembrane.6.3 Leak Location Surveys of Exposed Geomembrane Usingthe Spark Testing Method:6.3.1 Agrid, test lanes, or other accep
34、table system should beused to ensure that the entire area is tested with the test wand.6.3.2 Either a handheld wand or a larger wand mounted toan all-terrain vehicle may be used. Generally, a handheld wandis a more efficient method unless the area is quite large and flat.6.4 Preparations and Measure
35、ment Considerations:6.4.1 Spark testing must be performed on conductive-backed geomembranes that are generally clean and dry.6.4.2 For geomembranes covered by water or soils, othertest procedures such as those described in Guide D6747 may bepossible for testing electrically isolated conductive-backe
36、dgeomembrane installations.6.5 Practices for Surveys With the Spark Testing Method:6.5.1 Before beginning a leak survey, the equipment mustbe checked to ensure it is in working order. The power sourceshould have a range of voltage from 15 000 to 35 000 V. Awider voltage range is acceptable, but the
37、maximum practicalvalue is typically 35 000 V.6.5.2 The test wand may be up to 2 m wide with aconductive wand. The coupling pad should be connected asshown in Fig. 1.6.5.3 Once the equipment has been checked and wiredproperly, a trial test must be performed. A puncture (deliberatedefect) should be in
38、troduced in a test piece of geomembrane.The deliberate defect should be no greater than 1 mm indiameter. The test piece of geomembrane must be of sufficientsize to enable movement of the test wand at normal testingspeed over the deliberate defect without touching the edges ofthe test piece or the co
39、upling pad. If a deliberate defect isintroduced in the geomembrane installation, it should be doneoutside the limits of the containment area and with permissionof the owner of the installation.6.5.4 Place the test piece on a large scrap of geomembraneor on the installed geomembrane with the conducti
40、ve sidedown. The deliberate defect and the coupling pad should bothbe on the test piece.6.5.4.1 Turn on the test unit and adjust the voltage andsensitivity to maximum settings.6.5.4.2 Sweep the test piece with the wand, ensuring that thetest wand remains in contact with the geomembrane surface. Itis
41、 important this be done at normal speeds.6.5.4.3 Ensure the audible alarm sounds when the wandpasses over the deliberate defect. If the alarm does not sound,recheck the connections and retest. If the alarm sounds prior topassing over the damage, turn the sensitivity down and retestthe area. The mini
42、mum voltage required is site specific and willvary with atmospheric and other site conditions.6.5.4.4 At a minimum, the equipment should be checkedbefore testing begins and after any shutdown of an hour ormore. In the event a test reveals the equipment is not workingproperly, the entire area spark t
43、ested since the last passingcheck of the equipment must be retested to ensure it was sparktested with working equipment.6.5.5 Field testing may be performed by marking a prede-termined grid, or another acceptable method, and performingthe survey within that grid at the same speed as the trial testwa
44、s performed.6.5.6 The leak location survey shall be conducted usingprocedures whereby the test wand brushes every point on thesurface of the geomembrane being surveyed for leaks, neglect-ing the edge and other ground effects.6.5.7 For typical conductive-backed geomembraneinstallations, the spark tes
45、t on a given geomembrane panelmust be performed with the coupling pad over the surface ofthat panel. When crossing over panel overlaps, care must betaken to ensure that the neoprene pad is on the panel beingtested.6.5.8 In the case of conductive paths through the geomem-brane such as metal pipe pene
46、trations, pump grounds, andbatten strips on concrete, the geomembrane can be tested up tothe conductive feature but not including the conductive feature.The conductive feature should produce a false positive.6.6 Safety:6.6.1 WarningThe electrical methods used for geomem-brane leak location use high-
47、voltage, low-current powersupplies, resulting in the potential for electrical shock. Theelectrical methods used for geomembrane leak location shouldFIG. 1 Diagram of the Spark Testing MethodD7240 183be attempted only by qualified and experienced personnel.Appropriate safety measures must be taken to
48、 protect the leaklocation operators as well as other people at the site.7. Report7.1 The leak location survey report shall contain the follow-ing information:7.1.1 Description of the survey site,7.1.2 Weather conditions,7.1.3 Type and thickness of geomembrane,7.1.4 Liner system layering,7.1.5 Descri
49、ption of the electrical leak location method,7.1.6 Survey methodology,7.1.7 Identification of equipment and operators,7.1.8 Results of the trial test,7.1.9 Specific conditions of survey,7.1.10 Location, type, and size of detected leaks, and7.1.11 Map of the surveyed areas showing the approximatelocations of the leaks.8. Keywords8.1 arc testing method; bare geomembrane survey;conductive-backed geomembrane; damage; electrical leak de-tection method; electrical leak location; electrical leak locationmethod; exposed geomembrane survey; geoelectric leak loca-tion; geomembrane;
