1、Designation: F 2550 06Standard Practice forLocating Leaks in Sewer Pipes Using Electro-Scan-theVariation of Electric Current Flow Through the Pipe Wall1This standard is issued under the fixed designation F 2550; the number immediately following the designation indicates the year oforiginal adoption
2、or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONInfiltration of groundwater into a sewer through defects in the pipe can con
3、siderably increase theoperation and capital costs of a sewer system. Exfiltration of sewage out of a sewer pipe may causedegradation of aquifers and shoreline waters. Accurate location, measurement, and characterization ofall potential pipe leak defects are essential inputs for cost-effective design
4、 of pipe renewal orremediation. Commonly used sewer leak assessment methods either do not detect a significant numberof large potential pipe leak defects, particularly those caused by faulty joints or service connections,or are too slow or costly or both for widespread application.2, 31. Scope1.1 Th
5、is practice covers procedures for using the electro-scan method4to detect and locate potential pipe leak defectsthat are potential sources of leaks in pipes fabricated fromelectrically nonconductive material such as plastic, clay, andconcrete (reinforced and non-reinforced). The electro-scanmethod u
6、ses the variation of electric current flow through thepipe wall to locate defects that are potential water leakagepaths either into or out of the pipe.1.2 This practice applies to mainline and lateral gravity flowstorm sewers, sanitary sewers, and combined sewers withdiameters between 3 and 60 in. (
7、75 and 1500 mm). The pipesmust be free of obstructions that prevent the sonde passingthrough the pipe.1.3 The use of the electro-scan requires access to sewers,filling sewers, and operations along roadways that are safetyhazards. This standard does not describe the hazards likely tobe encountered or
8、 the safety procedures that must be carriedout when operating in these hazardous environments. (7.1.3)There are no safety hazards specifically associated with the useof an electro-scan apparatus that complies with the specifica-tions provided in this standard. (6.7 and 6.10.)1.4 The use of electro-s
9、can requires the insertion of variousitems into a sewer. There is always a risk that due to unknownstructural conditions in the sewer such items may becomelodged in the pipe or may cause the state of a sewer in poorstructural condition to further deteriorate. This standard doesnot describe methods t
10、o assess the structural risk of a sewer.1.5 The values stated in inch/pound units are to be regardedas the standard. The values in parentheses are for informationonly.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of
11、the user of this standard to establish appro-priate safety and health practices and to determine theapplicability of regulatory limitations prior to use.2. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 lateral, nsewer pipe connecting the common sewercollection system to the use
12、r.2.1.2 mainline, npipe that is part of the common sewercollection system.2.1.3 maintenance hole, n(MH) vertical shafts intersect-ing a sewer that allows entry to the sewer for cleaning,inspection and maintenance.2.1.4 owner, nentity holding legal rights to, and respon-sible for the operation and ma
13、intenance of the sewer pipe.2.1.5 sliding pipe plug, ndevice that blocks the flowthrough a pipe and at the same time can be pulled through thepipe.1This practice is under the jurisdiction of ASTM Committee F36 on Technologyand Underground Utilities and is the direct responsibility of Subcommittee F3
14、6.20on Rehabilitation of Sewers Using Chemical Grouting Techniques.Current edition approved Feb. 1, 2006. Published February 2006.2Water Environmental Research Foundation (WERF), An Examination ofInnovative Methods Used in the Inspection of Wastewater Systems. December, 2004.3Harris, R.J et al, Sewe
15、r Leak DetectionElectro-Scan Adds a New Dimension:Case Study, City of Redding, California, ASCE. August, 2004.4The sole source of supply of the electro-scan methodapparatus known to thecommittee at this time is Metrotech Corporation. If you are aware of alternativemanufacturers, please provide this
16、information to ASTM International Headquar-ters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.1.6 sonde, n
17、electro-scan electrode placed in a pipe.3. Significance and Use3.1 The testing of sewers for leaks is a regular practicenecessary for the maintenance and optimal performance ofsewer collection systems so remedial action can be prioritized,designed, and carried out to reduce infiltration and exfiltra
18、tion.3.2 This practice serves as a means to detect and locate alltypes of pipe defects that are potential sources of water leakseither into or out of electrically non-conducting pipes. Leakingjoints and defective service connections are detected that oftenmay not show as a defect when viewed from in
19、side the pipe.The electro-scan data maybe processed and analyzed to pro-vide some information on the size and type of pipe defect.(8.4.1)3.3 This practice applies to mainline and lateral gravity flowstorm sewers, sanitary sewers, and combined sewers fabricatedfrom electrically non-conducting materia
20、l with diameters be-tween 3 and 60 in. (75 and 1500 mm). The pipes must be freeof obstructions that prevent the sonde passing through the pipe.4. Contract Responsibilities4.1 Apart from the provisions generally included in a testingservices contract, electro-scan testing contracts should defineor af
21、fix responsibility for or make provisions for the followingitems:4.1.1 Access to the site of work is to be provided to theextent that the owner is legally able to so provide or, if not soable, a written release from responsibility for the performanceof work at sites where access cannot be made avail
22、able;4.1.2 Clearances of blockages or obstructions in the sewersystem;4.1.3 Location and exposure of all maintenance holes (MH);4.1.4 MH numbering system for all areas of the project andMH invert elevations and depths;4.1.5 Shutdown or manual operation of certain pump sta-tions if such becomes neces
23、sary for performance of the work;4.1.6 Permission to use water from fire hydrants at the worksite, or other suitable designated sources within a reasonabledistance from the work areas, which is necessary for contractedwork performance;4.1.7 Authorization to perform work that must be performedduring
24、nighttime hours, weekends, or holidays; and4.1.8 Traffic control by uniformed officers or contract per-sonnel when the safety of workers or the public requires suchprotection.5. Electro-scan: Principle of Operation5.1 Most sewer pipe materials such as clay, plastic, con-crete, reinforced concrete, a
25、nd brick are poor conductors ofelectrical current.Adefect in the pipe wall that leaks water willalso leak electrical current, whether or not water infiltration orexfiltration is occurring at the time of the test.5.2 The electro-scan test is carried out by applying anelectrical potential of 9 to11 Vo
26、lts rms with a frequency of 500Hz to 30 kHz between an electrode in the electrically noncon-ductive pipe and an electrode on the surface, which is usuallya metal stake pushed into the ground. A simplified electricalcircuit for this procedure is shown in Fig. 1. The water in thepipe is at a level tha
27、t ensures that the pipe is full at the electrodelocation. Provided electrical current is prevented from flowingalong the inside of the pipe, the electrical resistance of thecurrent path between the electrode in the pipe and the surfaceelectrode is very low except through the electrically noncon-duct
28、ive pipe wall. The high electrical resistance of the pipewall allows only a very small electrical current to flow betweenthe two electrodes unless there is a defect in the pipe such asa crack, defective joint, or faulty service connection. Thegreater the electric current flow through the pipe defect
29、, thelarger the size of the defect.6. Apparatus6.1 The electro-scan method requires a means of preventingthe electric current from the electrode in the electricallynonconductive pipe from traveling along the inside of the pipebefore reaching the ground electrode. Such a means is athree-electrode arr
30、ay, known as a sonde. The sonde is con-structed in such a way that when equal voltages are applied toall three electrodes, the electric fields of the outer electrodesprevent electrical current from the center electrode flowingalong the pipe. This also causes the electric field of the centerelectrode
31、 to be focused into a disk about 1 in. (25 mm) wide.FIG. 1 Electro-scan Electrical SchematicF2550062This electric field projects onto the pipe wall as a circumfer-ential band with a width of about 10 % of the pipe diameter.The center of the band is located at the center of the sonde. Asa result, the
32、 electrical current flow through the center electrodeof the sonde, called the focused current, is dependant on theelectrical resistivity of the pipe wall within the area of the bandaround the circumference of the pipe.6.2 The essential components of the electro-scan apparatusare: a controlled voltag
33、e source; the sonde; an insulated cableto connect the sonde to the voltage source and move the sondethrough the pipe; a system to measure the position of the sondein the pipe; a system to measure the focused current; a systemto measure the electrical current flowing through all threeelectrodes in th
34、e sonde, called the total current; and a surfaceelectrode. When a sliding pipe plug (7.1.6.2) is used, a systemto measure the water pressure in the pipe at the location of thesonde, called the water head, is required.6.3 The geometric dimensions of the sonde shall be suchthat the change of focused c
35、urrent as a result of a hole in thepipe with a diameter of 0.5 % of the pipe diameter will bedetected and defects separated by more than 25 % of the pipediameter will be resolved. That is for a 10 in. (250 mm)diameter pipe a hole with a diameter of 0.05 in. (1.3 mm) willbe detected and defects more
36、than 2.5 in. (62 mm) apart will beshown as two separate defects.6.4 The focused current and the total current flowing be-tween the surface electrode and the sonde and the water headshall be measured and recorded at not less than 0.40 in. (10.0mm) intervals along the pipe while the sonde is pulled th
37、rougha pipe at a speed of 32.8 ft/min (10.0 m/min).6.5 The accuracy of the sonde position measurement systemshall be within 60.5 % with a resolution 0.05 %. That is for apipe test section that is 100.00 ft long the length of pipemeasured by the system shall be 100.00 6 0.5 ft and thesmallest distanc
38、e readout unit will be 0.05 ft or less6.6 The resolution of the current measurements shall beequal to or less than 0.1 % of the maximum current. That is ifthe maximum current is 40 mA then the smallest currentreadout unit will be 0.04 mA6.7 The applied voltage between the sonde and the surfaceelectr
39、ode shall have a frequency between 500 and 30 000 Hzand a voltage range of 9 to 11 volt rms. The maximum currentbetween the sonde and the surface electrode shall be 0.04 Arms. These parameters prevent the occurrence of sparks orelectric shock to humans during normal operation or in theevent of a sho
40、rt circuit.6.8 The measurement of the sonde location, total current,focused current, and water head shall be stored in real time asdigital data in an electronic device.6.9 The sonde position, total current, focused electrodecurrent, and the water head shall be displayed in real time onan electronic
41、device on the surface when the system isactivated.6.10 The design of the electrical circuits shall prevent theoccurrence of sparks or electrical shock to humans if faults ordamage occur such as a severed cable.6.11 Power cable winches shall have an automatic slipclutch to prevent overstrain of the s
42、onde cable that may occurif the sonde becomes stuck in the pipe.7. Procedure7.1 Sewer Preparation7.1.1 The electro-scan test is usually carried out by movingthe sonde through the sewer at approximately 30 ft/min (10m/min). For the average MH interval of 300 ft (100 m), thistakes about 10 min. The ti
43、me to set up and dismantle the testequipment and fill the sewer in the region of the sonde usuallytakes up most of the field time. Appropriate selection of thesewer section test sequence, establishment of a setup routine,and ready availability of suitable equipment can considerablyreduce the test pr
44、eparation time.7.1.2 Generally, electro-scan testing does not require anypipe preparation. However, the sewer must be clear of obstruc-tions that prevent the sonde passing through the pipe such assevere root intrusion or protruding service connections. Inabil-ity to pass the haul line (7.1.5) throug
45、h the pipe will indicatethe presence of such obstructions and should be reported(7.2.4).7.1.3 Person-Entry into Sewer MHsElectro-scan fieldoperations should not require person-entry of MHs. Person-entry is hazardous and requires additional time to carry out thesafety checks and set up safety equipme
46、nt. However, unfore-seen situations may occur that require person-entry of a MH.Suitably trained personnel and safety equipment should be onhand just in case person entry is required. Prior to a personentering a MH the atmosphere in the MH must be evaluated fortoxic or flammable gases and oxygen dep
47、letion in accordancewith local, state or federal safety regulations and must becarried out in accordance with the owners person-entry of MHprocedures.7.1.4 Sewer FlowElectro-scan testing can be carried outin all conditions of sewer flow, from dry to surcharged.7.1.5 Haul Line7.1.5.1 A line is requir
48、ed to pull the sonde between theMHs of the pipe section to be tested. The haul line is flushedbetween the MHs at each end of the pipe section to beelectro-scanned using either water or air.7.1.5.2 An effective haul line is a jet cleaner hose.7.1.6 Filling the Sewer at the Sonde LocationWater in thep
49、ipe provides the electrical connection between the sonde andthe pipe wall (Fig. 1). To electro-scan the complete circumfer-ence of a electrically nonconductive pipe, it must be full ofwater at the location of the sonde, otherwise pipe defects not incontact with water will not be detected, that is, the top part ofthe pipe. Filling the sewer at the sonde location can beachieved by using a sliding pipe plug or a conventional sewerplug. Situations may arise where filling the pipe at the sondelocation is not feasible. In such cases electro-scanning may becarried out as long as
