1、Designation: D7240 06 (Reapproved 2011)Standard Practice forLeak Location using Geomembranes with an InsulatingLayer in Intimate Contact with a Conductive Layer viaElectrical Capacitance Technique (ConductiveGeomembrane Spark Test)1This standard is issued under the fixed designation D7240; the numbe
2、r 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 standard is a performance-based practice for usingthe spark test to electrically locate leaks in exposed geomem-branes with an insulating layer that are in intimate contact witha conductive layer. For clarity, this document uses the termleak to mean holes, punctures, tears, cuts, cracks and s
4、imilarbreaches over the partial or entire area of an installed geomem-brane (as defined in 3.2.3).1.2 This test method can be used on exposed geomembranesinstalled in basins, ponds, tanks, ore and waste pads, landfillcells, landfill caps, and other containment facilities. Thisstandard is applicable
5、for geomembranes in direct and intimatecontact with a conductive surface or with a conductive layerintegrally included.1.3 SAFETY WARNING: The electrical methods used forgeomembrane leak location use high voltage, low currentpower supplies, resulting in the potential for electrical shock.The electri
6、cal methods used for geomembrane leak locationshould be attempted by only qualified and experienced person-nel. Appropriate safety measures must be taken to protect theleak location operators as well as other people at the site.1.4 This standard does not purport to address all of thesafety and liabi
7、lity concerns, if any, associated with its use. Itis the responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D4439 Terminology for Geosynthetic
8、sD6747 Guide for Selection of Techniques for ElectricalDetection of Potential Leak Paths in Geomembranes3. Terminology3.1 Definition of terms applying to this test method appearin Terminology D4439.3.2 Definitions:3.2.1 electrical leak location, na method which useselectrical current or electrical p
9、otential to detect and locateleaks.3.2.2 geomembrane, nan essentially impermeable mem-brane used with foundation, soil, rock, earth or any othergeotechnical engineering related material as an integral part ofa man made project, structure, or system.3.2.3 leak, nFor the purposes of this document, a l
10、eak isany unintended opening, perforation, breach, slit, tear, punctureor crack. Significant amounts of liquids or solids may or maynot flow through a leak. Scratches, gouges, dents, or otheraberrations that do not completely penetrate the geomembraneare not considered to be leaks.Leaks detected dur
11、ing surveys have been grouped into threecategories: Holes round shaped voids with downward or upwardprotruding rims Tears linear or circular voids with irregular edge borders Linear cuts linear voids with neat close edges3.2.4 intimate contact, nfor the purposes of this docu-ment, intimate contact i
12、s when a conductive layer is in directcontact with the insulating geomembrane, and there are nogaps between the two layers to prohibit the flow of current.3.2.5 leak detection sensitivity, nThe smallest size leakthat the leak location equipment and survey methodology arecapable of detecting under a
13、given set of conditions. The leakdetection sensitivity specification is usually stated as a diam-eter of the smallest leak that can be reliably detected.3.2.6 wand, nfor the purposes of this document, any rodthat has a conductive brush that is attached to a power sourceto initiate the spark test.1Th
14、is 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 June 1, 2011. Published July 2011 Originally publishedin 2006. Last previous edition approved 2006 as D724006 DOI: 10.1520/D7
15、240-06R11.2For 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 website.1Copyright ASTM International, 100 Barr Harbor Driv
16、e, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Practice4.1 The principle of this electrical leak location method is touse a high voltage pulsed power supply to charge a capacitorformed by the underlying conductive layer, the non-conductivelayer of the geomembrane and a
17、 coupling pad. The area is thenswept with a test wand to locate points where the capacitordischarges through a leak. Once the system senses the dis-charge current, it is converted into an audible alarm.4.2 General Principles4.2.1 Fig. 1 shows a wiring diagram of the coupling pad,power supply and tes
18、t wand for the electrical leak locationmethod of a geomembrane with a lower conductive layer. Onceall necessary connections are made, the pad is placed on theupper surface of the geomembrane. The nonconductive (insu-lating layer(s) of the geomembrane act as a dielectric in acapacitor which stores el
19、ectrical potential across the geomem-brane.FIG. 1 Wiring Diagram of the Equipment Required for Spark Testing Geomembrane in Intimate Contact With a Conductive Surface.D7240 06 (2011)24.2.2 A grid, test lanes or other acceptable system should beused to ensure that the entire area is tested with the t
20、est wand.4.2.3 Either a hand held wand or a larger wand mounted toan all terrain vehicle may be used. Generally a hand held wandis a more efficient method unless the area is quite large and flat.4.3 Preparations and Measurement Considerations4.3.1 Testing must be performed on geomembranes that arecl
21、ean and dry. For geomembrane covered by water or soils,other test procedures, such as described in Guide D6747 willhave to be used for testing the geomembrane.4.3.2 Fusion and extrusion welds must be tested using stateof the practice nondestructive methods such as air channel testand vacuum box test
22、, respectively. If the test wand gets tooclose to the edge of the conductive geomembrane, the electricalcharge can arc to the back side of the conductive geomembraneand may cause a false positive.5. Significance and Use5.1 Geomembranes are used as barriers to prevent liquidsfrom leaking from landfil
23、ls, ponds, and other 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 resulti
24、n product loss or 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 smaller flexible geomem-branes in the field.5.4
25、 In exposed geomembrane applications, geomembraneleaks can be caused by poor quality of the subgrade, accidents,poor workmanship, and carelessness.5.5 Electrical leak location methods are an effective finalquality assurance measure to locate previously undetectedleaks.6. Procedure6.1 Before beginnin
26、g a leak survey, the equipment must bechecked to ensure it is in working order. The power sourceshould have a range of voltage from 15,000 to 35,000 volts. Awider voltage range is acceptable but the maximum is typically35,000 volts. The test wand may be up to 6 feet wide with abrass brush. The coupl
27、ing pad should be connected as shown inFig. 1.6.2 Once the equipment has been checked and wired prop-erly, a trial test must be performed. A puncture (deliberatedefect) should be introduced in a test piece of geomembrane.The deliberate defect should be approximately 1 mm indiameter. The test piece o
28、f geomembrane must be of sufficientsize to enable movement of the brush at normal testing speedover the deliberate defect without touching the edges of the testpiece or the coupling pad.6.3 Place the test piece on a large scrap of geomembrane oron the installed geomembrane with the conductive side d
29、own.The deliberate defect and the coupling pad should both be onthe large scrap piece of geomembrane.6.3.1 Turn on the test unit and adjust the voltage andsensitivity to maximum settings.6.3.2 Sweep the test piece with the wand ensuring that thetest wand remains in contact with the geomembrane surfa
30、ce. Itis important this be done at normal speeds.6.3.3 Ensure the audible alarm sounds when the brushpasses 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. T
31、he minimum voltage required is site specific and willvary with atmospheric and other site conditions.6.3.4 At a minimum, the equipment should be checkedbefore testing begins and after any shut down of an hour ormore. In the event a test reveals the equipment is not workingproperly, the entire area s
32、park tested since the last passingcheck of the equipment will have to be retested to assure it wasspark tested with working equipment.6.4 Field testing may be performed by marking a pre-determined grid, using a two person team or another acceptablemethod.6.5 The leak location survey shall be conduct
33、ed usingprocedures whereby the test wand contacts every point on thesurface of the geomembrane being surveyed for leaks neglecting the edge effects.NOTE 1Welded seams cannot be tested using this method. They mustbe tested by test procedures appropriate for such items this standardpractice applies on
34、ly to the sections of geomembrane in between thewelded edges.NOTE 2Actual survey speed must be no greater than survey speedused during trial test.7. Reporting7.1 The leak location survey report shall contain the follow-ing information- Description of the survey site- Description of test apparatus- C
35、limatic conditions- Thickness of geomembrane- Survey methodology- Results of system functionality and calibration test- Location, type and size of leaks- Repair technique of detected leaks- Map of the surveyed areas8. Keywords8.1 geomembrane; leak detection; leak location; electricalleak location me
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