1、Designation: D7703 15Standard Practice forElectrical Leak Location on Exposed Geomembranes Usingthe Water Lance Method1This 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 practice is a performance-based standard for anelectrical method for locating leaks in exposed geomembrane
3、s.For clarity, this practice uses the term “leak” to mean holes,punctures, tears, knife cuts, seam defects, cracks, and similarbreaches in an installed geomembrane (as defined in 3.2.5).1.2 This practice can be used for geomembranes installed inbasins, ponds, tanks, ore and waste pads, landfill cell
4、s, landfillcaps, canals, and other containment facilities. It is applicablefor geomembranes made of materials such as polyethylene,polypropylene, polyvinyl chloride, chlorosulfonatedpolyethylene, bituminous geomembrane, and any other electri-cally insulating materials. This practice is best applicab
5、le forlocating geomembrane leaks where the proper preparationshave been made during the construction of the facility.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address all of thesaf
6、ety 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 to use.2. Referenced Documents2.1 ASTM Standards:2D4439 Terminology for Geosynthe
7、ticsD6747 Guide for Selection of Techniques for Electrical LeakLocation of Leaks in GeomembranesD7002 Practice for Electrical Leak Location on ExposedGeomembranes Using the Water Puddle MethodD7953 Practice for Electrical Leak Location on ExposedGeomembranes Using the Arc Testing Method3. Terminolog
8、y3.1 Definitions:3.1.1 For general definitions used in this practice, refer toTerminology D4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 artificial leak, nan electrical simulation of a leak ina geomembrane.3.2.2 conductive-backed geomembrane, na specialitygeomembrane manufactured usi
9、ng coextrusion technology fea-turing an insulating layer in intimate contact with a conductivelayer.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 potential to locate leaks in ageomembrane.3.2
10、.5 leak, nfor the purposes of this practice, a leak is anyunintended opening, perforation, breach, slit, tear, puncture,crack, or seam breach. Significant amounts of liquids or solidsmay or may not flow through a leak. Scratches, gouges, dents,or other aberrations that do not completely penetrate th
11、egeomembrane are not considered to be leaks. Type of leaksdetected during surveys include, but are not limited to: burns,circular holes, linear cuts, seam defects, tears, punctures, andmaterial defects.3.2.6 leak detection sensitivity, nthe smallest leak that theleak location equipment and survey me
12、thodology are capableof detecting under a given set of conditions. The leak detectionsensitivity specification is usually stated as a diameter of thesmallest leak that can likely be detected.3.2.7 poor contact condition, nfor the purposes of thispractice, a poor contact condition means that a leak i
13、s not inintimate contact with the conductive layer above or underneaththe geomembrane to be tested. This occurs on a wrinkle orwave, under the overlap flap of a fusion weld, in an area ofliner bridging and in an area where there is a subgradedepression or rut.1This practice is under the jurisdiction
14、 of ASTM Committee D35 on Geosyn-thetics and is the direct responsibility of Subcommittee D35.10 on Geomembranes.Current edition approved Jan. 1, 2015. Published February 2015. Originallyapproved in 2011. Last previous edition approved in 2011 as D770311. DOI:10.1520/D770315.2For referenced ASTM sta
15、ndards, 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 website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
16、PA 19428-2959. United States13.2.8 probe, nfor the purposes of this practice, any con-ductive rod that is attached to a power source.3.2.9 water stream, nfor the purposes of this practice, acontinuous stream of water between the water lance and thegeomembrane that creates a conduit for current to fl
17、ow throughany leaks.3.2.10 water lance, nfor the purposes of this practice, aprobe (lance) incorporating one or two electrodes that directs asolid stream of water through a single nozzle mounted at theend.4. Significance and Use4.1 Geomembranes are used as barriers to prevent liquidsfrom leaking fro
18、m landfills, ponds, and other containments. Forthis purpose, it is desirable that the geomembrane have as littleleakage as practical.4.2 The liquids may contain contaminants that, if released,can cause damage to the environment. Leaking liquids canerode the subgrade, causing further damage. Leakage
19、can resultin product loss or otherwise prevent the installation fromperforming its intended containment purpose.4.3 Geomembranes are often assembled in the field, eitherby unrolling and welding panels of the geomembrane materialtogether in the field, unfolding flexible geomembranes in thefield, or a
20、 combination of both.4.4 Geomembrane leaks can be caused by poor quality ofthe subgrade, poor quality of the material placed on thegeomembrane, accidents, poor workmanship, manufacturingdefects, and carelessness.4.5 Electrical leak location methods are an effective andproven quality assurance measur
21、e to detect and locate leaks.5. Summary of Exposed Geomembrane Electrical LeakLocation Methods5.1 Principles of the Electrical Leak Location Methods forExposed Geomembranes:5.1.1 The principle of the electrical leak location methods isto place a voltage across a geomembrane and then locate areaswher
22、e electrical current flows through leaks in the geomem-brane.5.1.2 Currently available methods include the water puddlemethod (Practice D7002), the arc testing method (PracticeD7953), and the water lance method.5.1.3 All of the methods listed in 5.1.2 are effective atlocating leaks in exposed geomem
23、branes. Each method hasspecific site and labor requirements, survey speeds,advantages, and limitations. A professional specializing in theelectrical leak location methods can provide advice on theadvantages and disadvantages of each method for a specificproject.5.1.4 Alternative ASTM Standard Practi
24、ces for electricalleak location survey methods should be allowed when mutuallyagreeable and warranted by adverse site conditions, clearlytechnical superiority, logistics, or schedule.6. Water Lance Method6.1 A summary of the method capabilities and limitations ispresented in Table 1.6.2 The Principl
25、e of the Water Lance Method:6.2.1 Fig. 1 shows a diagram of electrical leak locationusing the water lance method for exposed geomembranes. Oneoutput of an electrical excitation power supply is connected toan electrode placed in the water reservoir; a pump sends thischarged water to the water lance t
26、hat jets the water in a solidstream on top of the geomembrane. The other output of thepower supply is connected to an electrode placed in electricallyconductive material under the geomembrane.6.2.2 The water lance method can also be set up with thesame configuration as the water puddle method, as sh
27、own inFig. 2, if the detector electronics are capable of measuringcurrent and converting that to an audible alarm.6.3 Leak Location Surveys of Exposed Geomembrane Usingthe Water Lance Method:TABLE 1 Summary of Water Lance MethodGeomembranes Bituminous, CSPE, CPE, EIA, fPP, HDPE, LLDPE,LDPE, PVC, VLD
28、PE,U applicableConductive-backed Geomembrane U applicableASeams All types: welded, tape, adhesive, glued, and other U applicable: project specificJunctions At synthetic pipes and accessories U applicable: project specificAt grounded conducting structures X not applicableSurvey During construction ph
29、ase (installation of GM) U applicableAfter installation (exposed) U applicableSlopes U applicable: project specificInsufficiently conductive subgrade X not applicableDuring the service life (if exposed) U project specificClimate Sunny, temperate, warm U applicableRainy weather X not applicableFrozen
30、 conditions X not applicableLeaks detected Discrimination between multiple leaks U applicableAIf used, conductive-backed geomembrane must be installed per the manufacturers recommendations in order to allow it to be tested using all of the available electricalleak location methods. In particular, th
31、ere must be some means to break the conductive path through the fusion welds along the entire lengths of the welds, the undersidesof adjacent panels (and patches) should be electrically connected together, and a means of preventing unwanted grounding at the anchor trenches or other unwanted earthgro
32、unds should be provided.D7703 1526.3.1 The water lance leak location method usually consistsof a single nozzle mounted at the end of a probe (lance) thatdirects a solid stream of water onto a geomembrane, and anelectronic detector assembly, as shown in Figs. 1 and 2.Apressurized water source, usuall
33、y from a reservoir on top of theliner, or from a tank truck isolated from ground parked athigher elevation, is connected to the water lance using a plasticor rubber hose.6.3.2 Direct current power supplies (often a 12 to 36 voltbattery or series of batteries) have been used for water lanceleak locat
34、ion surveys.6.3.3 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
35、 mediaunder the geomembrane through a hole.6.3.4 The voltage drop signal between the two electrodes inthe water column in the water lance (or the current flowthrough the detector electronics) is connected to an electronicdetector assembly that converts the electrical signal to anaudible signal that
36、increases in pitch and amplitude as the leaksignal increases.6.3.5 When a leak signal is detected, the location of the leakis then marked or located relative to fixed points.6.3.6 The leak detection sensitivity can be very good for thistechnique. Leaks smaller than 1 mm in diameter are routinelyfoun
37、d, including leaks through seams in the geomembrane.6.4 Preparations and Measurement Considerations:6.4.1 Proper field preparations and other measures must beimplemented to assure an electrical connection to the suffi-ciently conductive material directly below the geomembrane isin place to successfu
38、lly complete the leak location survey.6.4.2 There shall be a sufficiently conductive material di-rectly below the geomembrane being tested. A properly-prepared subgrade typically will have sufficiently conductivity.Under proper conditions and preparations, geosynthetic clayliners (GCLs) can be adequ
39、ate as conductive material. Thereare some other conductive layers such as conductive geotex-tiles and aluminum foils with successful field experience whichcan be installed beneath the geomembrane to facilitate electri-cal leak survey (that is, on dry subgrades, or as part of a planardrainage geocomp
40、osite).6.4.3 Measures should be taken to perform the leak locationsurvey when geomembrane wrinkles are minimized. If a hole isFIG. 1 Diagram of the Water Lance Method Using Voltage MeasurementFIG. 2 Diagram of the Water Lance Method Using Current MeasurementD7703 153located on a wrinkle, then this p
41、oor contact condition mayresult in an undetected leak. The leak location survey should beconducted at night or early morning when wrinkles areminimized. Sometimes wrinkles can be flattened by personnelwalking or standing on them as the survey progresses.6.4.4 Conversely, surveys should not be made i
42、n areas withbridging geomembrane. The survey of areas with minorbridging might be accomplished when the geomembrane iswarmer.6.4.5 For lining systems comprised of two geomembraneswith only a geonet or geonet/geocomposite between them, tomake the method feasible a sufficiently conductive layer suchas
43、 a conductive geotextile, conductive geocomposite, alumi-num foil, or any appropriate conductive material shall beinstalled under the geomembrane or integrated into the geonetgeocomposite. Conductive-backed geomembrane can also beused as the primary geomembrane to enable the method. SeeGuide D6747.6
44、.4.6 For best results, 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.6.4.7 The water stream applied to
45、the geomembrane shouldnot be allowed to flow out of the survey area, connecting thewater to the ground of the power supply. The results in a falsepositive signal and will compromise survey sensitivity.6.4.8 Depending on specific construction practices and siteconditions, other preparations and suppo
46、rt may still be neededto successfully perform the leak location survey.6.5 Practices for Surveys with the Water Lance Method:6.5.1 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 lea
47、k locationequipment and procedures should demonstrate the ability todetect the artificial or actual leak when the water stream ispassed over the leak in the geomembrane.6.5.2 Artificial LeakAn artificial leak may consist of thecut end of an insulated solid core or standard wire, with a crosssection
48、no larger than 1.0 mm diameter, IEC 0.75 mm2or 18AWG.6.5.3 Actual LeakIf an actual leak is used, which istechnically 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 sec
49、ondary geomembrane is not damaged. The holemust be drilled at least 600 mm away from the edge of thegeomembrane. The hole should be drilled, and the drill bitreciprocated in the hole so the geomembrane material isremoved rather than displaced.6.5.4 The excitation power supply and the water supplyshall be turned on, and the water stream shall be moved overthe artificial or actual leak at a speed equal to the desiredproduction survey speed.6.5.5 The resulting signal as the stream passes over the holeshall be distinctly and consistently greater than the backgroundlevel.
