1、Designation: D7877 14Standard Guide forElectronic Methods for Detecting and Locating Leaks inWaterproof Membranes1This standard is issued under the fixed designation D7877; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f 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 guide describes standard procedures for usingelectrical conductance measurement methods to locate leaks inexpos
3、ed or covered waterproof membranes.1.2 This guide addresses the need for a general technicaldescription of the current methods and procedures that are usedto test and verify the integrity of waterproof membranes.1.3 This guide is not intended to replace visual, infrared, orother methods of inspectio
4、n. It is to be used in conjunction withother methods of roof inspection when specified.1.4 This guide recommends that the leak locationequipment, procedures, and survey parameters used are cali-brated to meet established minimum leak detection sensitivity.The leak detection sensitivity calibration s
5、hould be verified ona regular basis according to the manufacturers recommenda-tions.1.5 Leak location surveys can be used on waterproofingmembranes installed in roofs, plaza decks, pools, waterfeatures, covered reservoirs and other waterproofing applica-tions.1.6 The procedures are applicable for me
6、mbranes made ofmaterials such as polyethylene, polypropylene, polyvinylchloride, bituminous material, and other electrically insulatingmaterials.1.7 This guide provides a general description of the equip-ment and methods for locating membrane breaches usingelectric conductance. Refer to the manufact
7、urers instructionsfor the proper operation and use of the equipment described inthis guide.1.8 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 practi
8、ces and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1079 Terminology Relating to Roofing and WaterproofingD5957 Guide for Flood Testing Horizontal WaterproofingInstallationsD6747 Guide for Selection of Techniques for ElectricalDetec
9、tion of Leaks in Geomembranes2.2 NFPA Standard:3NFPA 70 National Electric Code3. Terminology3.1 For definitions of terms, see Terminology D1079.3.2 Definitions of Terms Specific to This Standard:3.2.1 breachas defined for this guide, a membrane breachis a defect in the membrane that allows surface w
10、ater to reachthe substrate below.3.2.2 conductancethe ability of a material to pass elec-trons. The unit of conductance is the Siemens (S), the relation-ship that exists between resistance (R) and conductance (G) isa reciprocal one. In terms of resistance and conductance:R 5 1G ohms, G 5 1R Siemens
11、(1)3.2.3 deckthe structural surface to which the roofing orwaterproofing system (including insulation) is applied.3.2.4 electric currentthe flow of electric charge. Theelectric charge that flows is carried by mobile electrons in aconductor measured in amps.3.2.5 electric gradientthe potential differ
12、ence betweentwo points measured in volts.3.2.6 high voltagefor purposes of this guide, the UnitedStates 2005 National Electrical Code (NEC) defines highvoltage as any voltage over 600 V (article 490.2).3.2.7 leakany unintended opening, perforation, slit, tear,puncture, crack, hole, cut, or similar b
13、reaches through an1This guide is under the jurisdiction of ASTM Committee D08 on Roofing andWaterproofing and is the direct responsibility of Subcommittee D08.22 on Water-proofing and Dampproofing Systems.Current edition approved Aug. 1, 2014. Published August 2014. DOI: 10.1520/D7877-14.2For refere
14、nced 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.3Available from National Fire Protection Association (NFPA), 1 Batteryma
15、rchPark, Quincy, MA 02169-7471, http:/www.nfpa.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1installed waterproofing membrane which may allow the pas-sage of liquid. Scratches, gouges, or other aberrations that donot completely
16、penetrate the membrane are not considered tobe leaks as the term is used in this guide although they may bedefects requiring attention.3.2.8 leak detection sensitivitythe smallest size liquidwater leak that the leak location equipment and survey meth-odology are capable of detecting under a given se
17、t of condi-tions. The leak detection sensitivity specification is usuallystated as the minimum electrical leakage current that can bedetected and is directly related to the area of the smallest liquidwater leak that can be reliably detected.3.2.9 low voltagefor purposes of this guide, the UnitedStat
18、es 2005 National Electrical Code (NEC) defines lowvoltage as 0 49 volts.3.2.10 potentialelectrical voltage measured relative to areference point.3.2.11 sensitive voltmetera voltmeter that is capable ofreading voltage levels in the millivolt or microvolt range.3.2.12 substratethe surface upon which t
19、he roofing orwaterproofing membrane is placed (structural deck or insula-tion).3.2.13 waterproof membranean element of the exteriorenclosure of a building intended to provide a continuous barrierto prevent the passage of water under hydrostatic pressure.NOTE 1Waterproof membranes tested by electrica
20、l conductancemethods may be horizontal, sloped, or vertical.NOTE 2Examples of waterproof membranes included in this guideare: below-grade waterproofing membranes, above-grade waterproofingmembranes, waterproof membranes covered by wearing courses, vegeta-tive roof membranes, planter waterproofing me
21、mbranes, protected roofmembranes, and roofing membranes.4. Significance and Use4.1 The failure to correct membrane defects during and assoon as possible after its installation can cause prematurefailure of the membrane. Problems include design deficiencies,faulty application of the membrane system,
22、and damage bysubsequent trades.4Roof designs incorporating a waterproofmembrane under overburden such as a vegetative roof, insu-lation layer, wear-course, or topping slab greatly exacerbate theproblem of leak locating.4.2 This guide describes methods for using electric conduc-tance testing to locat
23、e breaches in waterproof membranes.5Themethods described include testing procedures designed toprovide a part of the construction quality control of membraneinstallations.4.3 The methods described in this guide may also be usedfor integrity or forensic testing of existing waterproofmembranes, specif
24、ic limitations apply.4.4 The electric conductance methods described in thisguide require a conductive substrate under the membrane toserve as a ground return path for the test currents. In roofassemblies where the membrane is installed over electricinsulating material such as insulating foam or a pr
25、otectionboard, or both, the electric path to any conductive deck isinterrupted. The situation can be remedied by placing aconductive material directly under the membrane. The conduc-tive material provides the return path for the test currents.5. Summary of Conductance Leak Location5.1 The principle
26、of the conductance leak location method isthe establishment of an electrical potential between the elec-trically insulating waterproof membrane and the underlyingsubstrate.5.2 For methods employing low voltage electrical potential,a controlled covering of water on the surface forms theconductive pat
27、h horizontally across the membrane to anymembrane breach.At a breach location, an electrical path to thedeck is formed through the water leaking to the deck below. Asensitive receiver detects the leakage current and alerts theoperator.5.3 For methods using a high voltage potential, an electrodeis sw
28、ept across the surface of the membrane. The electrode ischarged to a high potential relative to the deck below. At abreach location an electrical arc occurs from the electrode tothe deck below. The arc discharge is electronically detected andthe operator alerted.5.4 The leak-locate methods in this g
29、uide describe theelectrical conductance techniques used to detect and locatemembrane breaches. These methods while accurate and effec-tive are subject to noted limitations.5.5 Electric conductance leak location requires that the deckmaterial directly below the membrane be sufficiently conduc-tive fo
30、r the test method employed. In most instances, a concretesubstrate is sufficiently conductive to allow this method. Incertain membrane assemblies, where the substrate isnonconductive, it may be possible to install a conductivematerial directly under the membrane to facilitate testing.6. Low Voltage
31、Horizontal Membrane Scanning Platform6.1 The principle of the scanning platform method is toestablish a voltage potential between the platform and the roofdeck and track any leakage current passing through themembrane. This is accomplished by wetting the surface of themembrane under test, generating
32、 a voltage with respect to thedeck and then locating areas where electrical current flowsfrom the platform through membrane breaches to the deck.6.2 The basic circuit and application of a dual sweepscanning platform is shown in Fig. 1. The platform is con-structed with two sets of metal sweeps which
33、 make continuous4Bailey, David M., et al, “Survey of Passive Leak Location Technologies,” USArmy Corp of Engineers Construction Engineering Research Laboratories, USAC-ERL Technical Report FM-94/04.5Vokey, David and Townsend, Duncan, “Electrical Conductance Methods forLocating Leaks in Roofing and W
34、aterproof Membranes,” Journal of ASTMInternational, Vol 8, No. 9.D7877 142electrical contact with the membrane surface. The outer sweepforms a continuous perimeter around the platform with theinner sweep contained within the perimeter of the outersweep.66.3 The positive terminal of the voltage sourc
35、e is attached tothe building electrical ground or the roof (concrete or metal)deck/substrate and the negative terminal connects to theconductive sweep of the platform through the measuring andindicator unit. Since the majority of roofing/waterproofingmembranes are non-conductive (excluding high carb
36、on blackloaded materials such as certain types of EPDM) the electricalpotential applied to the platform sweeps is provided a paththrough the water over the wetted area of the membrane to anybreach thus completing the circuit to the substrate and back tothe generator.6.4 During the membrane scan, a l
37、ight spray of water isapplied to the membrane in front of the advancing platform(Fig. 2). The outer sweep responds to and displays any leakagecurrent in the test area. The inner sweep, which is electricallyshielded by the outer sweep, will detect a leakage current whenthe sweep platform is directly
38、over the membrane defect. Thiswill result in a noticeable deflection on the inner sweep meteraccompanied by an audible alert. This is precisely the locationwhere moisture is penetrating the membrane.6.5 LimitationsThe conductance leak locate method usingthe scanning platform cannot be carried out on
39、 conductivemembranes such as EPDM. The deck material directly belowthe membrane must be sufficiently conductive for purposes ofthis test method (concrete decks typically meet this criterion).Drains and other grounding penetrations can cause a falsereading if not isolated from the applied water spray
40、. Thismethod is not suited to scanning membranes with overburden.The equipment manufacturers instructions provide recommen-dation for addressing these issues.NOTE 3Certain scanning equipment designs provide built-in isolationof the sweep from drains and other grounds thereby lowering the potentialfo
41、r false readings.7. Low Voltage Membrane Electric Field Vector Mapping7.1 The electric field vector mapping technique employs anelectric potential gradient across the membrane surface alongwith a sensitive voltmeter and probes to locate membraneleaks. As illustrated in Fig. 3, a conductor cable loop
42、 isinstalled around the perimeter of the area to be tested. A signalgenerator is connected to the loop cable and the buildingground. The area within the loop is covered with a spray ofwater to form a continuous conductive surface in the test area.Since most roofing/waterproofing membranes are non-co
43、nductive the electrical signal from the perimeter cable looplooks for an electrical path over the wet area of the roof to anybreach within the wetted area thus completing the circuit to thesubstrate. The resulting current from the breach location to theperimeter cable sets up a voltage gradient in t
44、he water withinthe perimeter.7.2 A sensitive voltmeter and a pair of hand held electricalprobes long enough to reach the membrane surface are used todetect, measure, and track the leakage current to its source atthe breach.7.3 A signal generator is connected to the building ground,or concrete roof d
45、eck and the perimeter cable that is placedaround the area to be tested. Metal penetrations and drainsmust be isolated by looping a separate cable around them andthen connecting these isolating cables to the perimeter cable.The meter response is read at an initial location within theperimeter area an
46、d the operator carefully moves the pair ofprobes left or right while reading the signal level (Fig. 4). Theprobe positions that result in the maximum meter reading, and,if equipped, the strongest audio response points toward thebreach. The probes are then repositioned towards the indicateddirection
47、and the process repeated. The location of maximumsignal strength will coincide with the breach location.7.4 Electric Field Vector mapping can be used to locatemembrane breaches through overburden within the limitationsdescribed in 7.5.6The (name of material, product, process, apparatus and may inclu
48、de the patentnumber for reference) is covered by a patent. Interested parties are invited to submitinformation regarding the identification of an alternative(s) to this patented item tothe ASTM International Headquarters. Your comments will receive careful consid-eration at a meeting of the responsi
49、ble technical committee, which you may attend.FIG. 1 Basic Circuit and Application of the Membrane Scanning PlatformD7877 1437.5 LimitationsThe proper operation of the electric fieldvector mapping system requires a continuous layer of water onthe membrane within the test perimeter and must always reachfrom any breach to the conductor cable. Gaps in the watercoverage can result in missed areas and possibly missedbreaches. This limitation is particularly apparent on new cleanmembranes where water beading occurs thereby impeding theformation of a continuous we
