1、Designation: D7703 11Standard Practice forElectrical Leak Location on Exposed Geomembranes Usingthe Water Lance System1This standard is issued under the fixed designation D7703; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear 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 standard is a performance-based practice using thewater lance system, a electrical method for detecting le
3、aks inexposed geomembranes. For clarity, this document uses theterm “leak” to mean holes, punctures, tears, knife cuts, seamdefects, cracks and similar breaches in an installed geomem-brane.1.2 This standard can be used for geomembranes installed inbasins, ponds, tanks, ore and waste pads, landfill
4、cells, landfillcaps, canals, and other containment facilities. It is applicablefor geomembranes made of materials such as polyethylene,polypropylene, polyvinyl chloride, chlorosulfonated polyethyl-ene, bituminous geomembrane, and any other electricallyinsu-lating materials. This standard may not be
5、applicable forlocating geomembrane leaks where the proper preparationshave not been made during the construction of the facility.1.3 WarningThe electrical methods used for geomem-brane leak location could use high voltages, resulting in thepotential for electrical shock or electrocution. This hazard
6、might be increased because operations might be conductedin or near water. In particular, a high voltage could existbetween the water or earth material and earth ground, orany grounded conductor. These procedures are potentiallyVERY DANGEROUS, and can result in personal injury ordeath. The electrical
7、 methods used for geomembrane leaklocation should be attempted only by qualified and experi-enced personnel. Appropriate safety measures must betaken to protect the leak location operators as well as otherpeople at the site.1.4 This standard does not purport to address all of thesafety concerns, if
8、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 to use.2. Referenced Documents2.1 ASTM Standards:2D4439 Terminology for GeosyntheticsD6747 Guide f
9、or Selection of Techniques for ElectricalDetection of Potential Leak Paths in GeomembranesD7007 Practices for Electrical Methods for Locating Leaksin Geomembranes Covered with Water or Earth Materials3. Terminology3.1 For general definitions used in this document, refer toD4439.3.2 Definitions of Te
10、rms Specific to This Standard:3.2.1 artificial leak, nan electrical simulation of a leak ina geomembrane.3.2.2 current, nthe flow of electricity or the flow ofelectric charge.3.2.3 electrode, nthe conductive plate that is placed inearth or in the material under the geomembrane or a conductiveelement
11、 typically placed inside the water reservoir.3.2.4 electrical leak location, na method which useselectrical current or electrical potential to detect and locateleaks.3.2.5 leak, nfor the purposes of this document, a leak isany unintended opening, perforation, breach, slit, tear, punc-ture, crack, or
12、 seam breach. Significant amounts of liquids orsolids may or may not flow through a leak. Scratches, gouges,dents, or other aberrations that do not completely penetrate thegeomembrane are not considered to be leaks. Leaks detectedduring surveys have been grouped into five categories:holesround shape
13、d voids with downward or upward pro-truding rims.tearslinear or areal voids with irregular edge borders.linear cutslinear voids with neat close edges.1This practice is under the jurisdiction of ASTM Committee D35 on Geosyn-thetics and is the direct responsibility of Subcommittee D35.10 on Geomembran
14、es.Current edition approved June 1, 2011. Published July 2011. DOI: 10.1520/D770311.2For 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 p
15、age onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.seam defectsarea of partial or total separation betweensheets.burned through zonesvoids created by melting polymerduring welding.3.2.6 leak detection sensitivity,
16、 nthe smallest leak that theleak location equipment and survey methodology are capableof detecting under a given set of conditions. The leak detectionsensitivity specification is usually stated as a diameter of thesmallest leak that can be reliably detected.3.2.7 water stream, nfor the purposes of t
17、his document, acontinuous stream of water between the water lance and thegeomembrane that creates a conduit for current to flow throughany leaks.3.2.8 water lance, nfor the purposes of this document, aprobe (lance) incorporating two electrodes that directs a solidstream of water through a single noz
18、zle mounted at the end.4. Summary of Practice4.1 The Principle of the Electrical Leak Location MethodUsing the Water Lance System:4.1.1 The principle of the electrical leak location method isto place a voltage across a geomembrane and then locate areaswhere electrical current flows through leaks. AS
19、TM StandardD6747 is a guide for the selection of the various implementa-tions of the method.4.1.2 Fig. 1 shows a diagram of the electrical leak locationmethod of the water lance system for exposed geomembranes.One output of an electrical excitation power supply is con-nected to an electrode placed i
20、n the water reservoir; a pumpsends this charged water to the water lance (Fig. 2) that jets thewater in a solid stream on top of the geomembrane. The otheroutput of the power supply is connected to an electrode placedin electrically conductive material under the geomembrane.4.2 Leak Location Surveys
21、 of Exposed Geomembrane Usingthe Water Lance System:4.2.1 The water lance detection system usually consists of asingle nozzle mounted at the end of a probe (lance) (Fig. 2) thatdirects a solid stream of water onto a geomembrane, and anelectronic detector assembly as shown in Fig. 3. A pressurizedwat
22、er source, usually from a small reservoir on top of the liner,or from a tank truck isolated from ground parked at higherelevation, is connected to the water lance using a plastic orrubber hose.4.2.2 Direct current power supplies (often a 12 or 24 voltbattery) have been used for leak location surveys
23、.4.2.3 For leak location surveys of exposed geomembrane,the solid water stream (not a spray) is moved systematicallyover the geomembrane area to locate the points where theelectrical current flow increases as the charged water from thewater lance contacts the oppositely charged conductive mediaunder
24、 the geomembrane through a hole.4.2.4 The voltage drop signal between the two electrodes inthe water column in the water lance is typically connected to anelectronic detector assembly that converts the electrical signalto an audible signal that increases in pitch and amplitude as theleak signal incr
25、eases (Fig. 3).4.2.5 When a leak signal is detected, the location of the leakis then marked or located relative to fixed points.4.2.6 The leak detection sensitivity can be very good for thistechnique. Leaks smaller than 1 mm in diameter are routinelyfound, including leaks through seams in the geomem
26、brane.4.3 Preparations and Measurement Considerations:4.3.1 Proper field preparations and other measures must beimplemented to assure an electrical connection to the conduc-tive material directly below the geomembrane is in place.4.3.2 There must be a conductive material directly belowthe geomembran
27、e being tested. Typically a properly-preparedsubgrade will have sufficient conductivity. Under proper con-ditions and preparations, geosynthetic clay liners (GCLs) canbe adequate as conductive material. There are some conductivegeotextiles with successful field experience which can beinstalled benea
28、th the geomembrane to facilitate electrical leaksurvey (that is, on dry subgrades, or as part of a planar drainagegeocomposite).4.3.3 Measures should be taken to perform the leak locationsurvey when geomembrane wrinkles are minimized.FIG. 1 Diagram of the Electrical Leak Location Method for Surveys
29、with Water Lance on Exposed GeomembraneD7703 112NOTE 1The leak location survey could be conducted at night or earlymorning when wrinkles are minimized. Sometimes wrinkles can beflattened by personnel walking or standing on them as the surveyprogresses. Condensation may provide a conductive layer und
30、er thegeomembrane.4.3.4 Conversely, surveys should not be made in areas withbridging geomembrane. The survey of areas with minorbridging might be accomplished when the geomembrane iswarmer.FIG. 2 Typical water lanceFIG. 3 Photographs of Water Lance Electronic Detector AssemblyD7703 1134.3.5 For lini
31、ng systems comprised of two geomembraneswith only a geonet or geotextile/geonet/geotextile composite(geocomposite) between them, to make the method feasible aconductive layer such as a conductive geotextile must beinstalled under the geomembrane or integrated into the geo-composite.4.3.6 For best re
32、sults, conductive paths such as metal pipepenetrations, pump grounds, and batten strips on concreteshould be isolated or insulated from the water lance on thegeomembrane. These conductive paths conduct electricity andmask nearby leaks from detection.4.3.7 Depending on specific construction practices
33、 and siteconditions, other preparations and support may still be neededto successfully perform the leak location survey.4.3.8 The system characteristics are presented in Table 1.5. Significance and Use5.1 Geomembranes are used as barriers to prevent liquidsfrom leaking from landfills, ponds, and oth
34、er containments. Forthis purpose, it is desirable that the geomembrane have as littleleakage as practical.5.2 The liquids may contain contaminants that if releasedcan cause damage to the environment. Leaking liquids canerode the subgrade, causing further damage. Leakage can resultin product loss or
35、otherwise prevent the installation fromperforming its intended containment purpose.5.3 Geomembranes are often assembled in the field, eitherby unrolling and welding panels of the geomembrane materialtogether in the field, or unfolding flexible geomembranes in thefield.5.4 Geomembrane leaks can be ca
36、used by poor quality ofthe subgrade, poor quality of the material placed on thegeomembrane, accidents, poor workmanship, and carelessness.D7007 describes the electrical methods for locating leaks inGeomembranes Covered with Water or Earth Materials.5.5 Electrical leak location methods are an effecti
37、ve andproven quality assurance measure to locate previously unde-tected leaks and check the integrity of a liner.6. Procedure6.1 A realistic test of the leak detection sensitivity shall beperformed and documented as part of the leak location survey.An actual or artificial leak can be used. The leak
38、locationequipment and procedures should demonstrate the ability todetect the artificial or actual leak when the water stream ispassed over the leak in the geomembrane.6.2 Artificial LeakAn artificial leak may consist of the cutend of an insulated solid core wire, or an exposed metal discmounted on a
39、 plastic plate and connected to a wire (Fig. 4). Theassembly is placed on the surface of the liner. The wire isconnected to an electrode in the subgrade such that current willflow through the subgrade for a distance equivalent to thedistance between the center of the liner and the negative(ground) a
40、pplied potential electrode.6.3 Actual LeakIf an actual leak is used, which is techni-cally preferred, it shall be constructed by drillinga1mmdiameter hole in the installed geomembrane that is to be tested.For double geomembranes, measures must be taken to ensurethat the secondary geomembrane is not
41、damaged. The holemust be drilled at least 600 mm away from the edge of thegeomembrane. The distance between the hole and the electrodein contact with the conductive media under the geomembraneshould be greater than the distance between the center of theliner and the electrode in contact with the con
42、ductive mediaunder the geomembrane. The hole should be drilled, and thedrill bit reciprocated in the hole so the geomembrane materialis removed rather than displaced.6.4 The excitation power supply and the water supply shallbe turned on, and the water stream shall be moved over theartificial or actu
43、al leak at a speed equal to the desiredTABLE 1 Characteristics of the Water Lance Leak Detection Techniquegeomembranes Bituminous, CSPE, CPE, EIA, fPP, HDPE, LLDPE, LDPE, PVC,VLDPE,applicableEPDM, GCL not applicableexposed applicablecovered not applicableGCL GCL not applicablecharacteristics set up
44、time and leak detection sensitivity test 1 to 3 hmeasurement time Instantaneousaverage survey speed (horizontal surface) 900 m2per hour per operatorseams all types: welded, tape, adhesive, glued and other applicability is project specificSeams of patches not usually applicablejunctions at synthetic
45、pipes and accessories applicability is project specificat permanent structure applicability is project specificsurvey during construction phase (installation of GM) applicableafter installation (exposed) applicableafter soil covering not applicablepresence of large wrinkles and waves not applicables
46、lopesduring the service life (if exposed) applicableelectrical isolated conductive structures applicablepresence of bridging not applicableclimate sunny, temperate, warm applicablerainy weather, freezing weather not applicableleak detected size of 1 mm and larger applicablediscrimination between mul
47、tiple leaks applicableD7703 114production survey speed. Ideally testing shall progress fromareas of lower elevation to areas of higher elevation6.5 The resulting signal as the stream passes over the holeshall be distinctly and consistently greater than the backgroundlevel. The applied potential acro
48、ss the liner and the signalmeter controls shall be adjusted to achieve such a signal.6.6 The leak location survey shall be conducted using thesame water distribution speed as that used for the leakdetection sensitivity test. The survey shall not be performedany farther from the electrode in contact
49、with the conductivemedia under the geomembrane than the distance between theleak detection sensitivity test and the electrode in contact withthe conductive media under the geomembrane.6.7 Periodic testing of the integrity of the electrical circuit isrecommended. It is recommended to check the integrity of theelectrical circuit every 15 to 20 minutes by contacting theconductive media under the geomembrane with the waterstream or by using an extra electrical cable well-connected tothe conductive media under the geomembrane. At a minimum,this check shall be conducte
