1、Designation: F2550 06F2550 13Standard Practice forLocating Leaks in Sewer Pipes Using Electro-Scan-the ByMeasuring the Variation of Electric Current Flow Throughthe Pipe Wall1This standard is issued under the fixed designation F2550; the number immediately following the designation indicates the yea
2、r 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.INTRODUCTIONInfiltration of groundwater into a sewer through defect
3、s in the pipe can considerably 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 c
4、ost-effective design of pipe renewal orremediation. Commonly design, testing, and certification of pipe repairs, renewal, and newconstruction. While commonly used sewer leak assessment methods either do not detect a significantnumber of large potential pipe leak defects, particularly those caused by
5、 faulty joints or serviceconnections, or are too slow or costly or both for widespread application.methods, such as air andwater pressure testing, represent cost effective methods to provide overall Pass/Fail pipe assessments,their inability to provide accurate location and size of leaks, particular
6、ly at individual joints andservice connection, limit their use in remediation and rehabilitation decision support.2,31. Scope1.1 This practice covers procedures for usingmeasuring the electro-scan methodvariation of electric current flow to detect andlocate potential pipe leak defects that are poten
7、tial sources of leaks in pipes fabricated from electrically nonconductivematerialmaterials such as plastic,brick, clay, and concrete (reinforced concrete, and plastic pipes (that is, reinforced andnon-reinforced). The electro-scan method uses the variation of electric current flow through the pipe w
8、all to locate defects that arepotential water leakage paths either into or out of the pipe.1.2 This practice applies to mainline and lateral gravity flow storm sewers, sanitary sewers, and combined sewers with diametersbetween 3 and 60 in. (75 and 1500 mm). The pipes must be free of obstructions tha
9、t prevent the sondeprobe passing through thepipe.1.3 The use of the electro-scan scanning process requires access to sewers, filling sewers, and operations along roadways thatare safety hazards. This standard does not describe the hazards likely to be encountered or the safety procedures that must b
10、ecarried out when operating in these hazardous environments. (7.1.3) There are no safety hazards specifically associated with theuse of an electro-scan apparatus that complies with the specifications provided in this standard. (6.7 and 6.10.)1.4 The use of electro-scan measurement of the variation o
11、f electric current requires the insertion of various items into a sewer.There is always a risk that due to unknown structural conditions in the sewer such items may become lodged in the pipe or maycause the state of a sewer in poor structural condition to further deteriorate. This standard does not
12、describe methods to assess thestructural risk of a sewer.1.5 The values stated in inch/poundinch-pound units are to be regarded as the standard. The values given in parentheses are forinformation only. mathematical conversions to SI units that are provided for information only and are not considered
13、 standard.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatorylimitations prior to use.1 Th
14、is practice is under the jurisdiction of ASTM Committee F36 on Technology and Underground Utilities and is the direct responsibility of Subcommittee F36.20 onInspection and Renewal of Water and Wastewater Infrastructure.Current edition approved Feb. 1, 2006Nov. 1, 2013. Published February 2006Novemb
15、er 2013. Originally approved in 2006. Last previous edition approved in 2006 asF255006. DOI: 10.1520/F2550-06.10.1520/F2550-13.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Beca
16、useit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 B
17、arr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12. Terminology2.1 Definitions of Terms Specific to This Standard:2.1.1 lateral, nsewer pipe connecting the common sewer collection system to the user.2.1.2 mainline, npipe that is part of the common sewer collection syste
18、m.2.1.3 maintenance hole, n(MH) vertical shafts intersecting a sewer that allows entry to the sewer for cleaning, inspection andmaintenance.2.1.4 owner, nentity holding legal rights to, and responsible for the operation and maintenance of the sewer pipe.2.1.5 probe, nscan electrode placed in a pipe.
19、2.1.6 sliding pipe plug, ndevice that blocks the flow through a pipe and at the same time can be pulled through the pipe.2.1.6 sonde, nelectro-scan electrode placed in a pipe.3. Significance and Use3.1 The testing of sewers for leaks is a regular practice necessary for the maintenance and optimal pe
20、rformance of sewercollection systems so remedial action can be prioritized, designed, and carried out to reduce infiltration and exfiltration.3.2 This practice serves as a means to detect and locate all types of pipe defects that are potential sources of water leaks eitherinto or out of electrically
21、 non-conducting pipes. Leaking joints and defective service connections are detected that often may notshow as a defect when viewed from inside the pipe. The electro-scanscan data maybe may be processed and analyzed to providesome information on the size and type of pipe defect. (8.4.1)3.3 This prac
22、tice applies to mainline and lateral gravity flow storm sewers, sanitary sewers, and combined sewers fabricatedfrom electrically non-conducting material with diameters between 3 and 60 in. (75 and 1500 mm). The pipes must be free ofobstructions that prevent the sondeprobe passing through the pipe.4.
23、 Contract Responsibilities4.1 Apart from the provisions generally included in a testing services contract, electro-scan testing contracts testing contractsfor measuring the variation in electric flow through a pipe wall should define or affix responsibility for or make provisions for thefollowing it
24、ems:4.1.1 Access to the site of work is to be provided to the extent that the owner is legally able to so provide or, if not so able,a written release from responsibility for the performance of work at sites where access cannot be made available;4.1.2 Clearances of blockages or obstructions in the s
25、ewer system;4.1.3 Location and exposure of all maintenance holes (MH);4.1.4 MH numbering system for all areas of the project and MH invert elevations and depths;4.1.5 Shutdown or manual operation of certain pump stations if such becomes necessary for performance of the work;4.1.6 Permission to use w
26、ater from fire hydrants at the work site, or other suitable designated sources within a reasonabledistance from the work areas, which is necessary for contracted work performance;4.1.7 Authorization to perform work that must be performed during nighttime hours, weekends, or holidays; and4.1.8 Traffi
27、c control by uniformed officers or contract personnel 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, concrete, reinforced concrete, and brick are poor conductors of electricalcurrent. A defe
28、ct in the pipe wall that leaks water will also leak electrical current, whether or not water infiltration or exfiltrationis occurring at the time of the test.5.2 The electro-scan test is carried out by applying an electrical potential of 9 to11 to 11 Volts rms with a frequency of 500 Hzto 30 kHz bet
29、ween an electrode in the electrically nonconductive pipe and an electrode on the surface, which is usually a metalstake pushed into the ground.Asimplified electrical circuit for this procedure is shown in Fig. 1. The water in the pipe is at a levelthat ensures that the pipe is full at the electrode
30、location. Provided electrical current is prevented from flowing along the insideof the pipe, the electrical resistance of the current path between the electrode in the pipe and the surface electrode is very lowexcept through the electrically nonconductive pipe wall. The high electrical resistance of
31、 the pipe wall allows only a very smallelectrical current to flow between the two electrodes unless there is a defect in the pipe such as a crack, defective joint, or faultyservice connection. The greater the electric current flow through the pipe defect,opening, the larger the size of the defect.le
32、ak.6. Apparatus6.1 The electro-scan method method for measuring the variation in electric flow through a pipe wall requires a means ofpreventing the electric current from the electrode in the electrically nonconductive pipe from traveling along the inside of the pipebefore reaching the ground electr
33、ode. Such a means is a three-electrode array, known as a sonde.probe. The sondeprobe isF2550 132constructed in such a way that when equal voltages are applied to all three electrodes, the electric fields of the outer electrodesprevent electrical current from the center electrode flowing along the pi
34、pe. This also causes the electric field of the center electrodeto be focused into a disk about 1 in. (25 mm) wide. This electric field projects onto the pipe wall as a circumferential band witha width of about 10 % of the pipe diameter. The center of the band is located at the center of the sonde.pr
35、obe. As a result, theelectrical current flow through the center electrode of the sonde,probe, called the focused current, is dependant on the electricalresistivity of the pipe wall within the area of the band around the circumference of the pipe.6.2 The essential components of the electro-scanscanni
36、ng apparatus are: a controlled voltage source; the sonde;probe; aninsulated cable to connect the sondeprobe to the voltage source and move the sondeprobe through the pipe; a system to measurethe position of the sondeprobe in the pipe; a system to measure the focused current; a system to measure the
37、electrical currentflowing through all three electrodes in the sonde,probe, called the total current; and a surface electrode. When a sliding pipe plug(7.1.6.2) is used, a system to measure the water pressure in the pipe at the location of the sonde,probe, called the water head, isrequired.6.3 The ge
38、ometric dimensions of the sondeprobe shall be such that the change of focused current as a result of a hole in thepipe with a diameter of 0.5 % of the pipe diameter will be detected and defects potential leaks separated by more than 25 % ofthe pipe diameter will be resolved. That is for a 10 in. (25
39、0 mm) diameter pipe a hole with a diameter of 0.05 in. (1.3 mm) willbe detected and defectsopenings more than 2.5 in. (62 mm) apart will be shown as two separate defects.leaks.6.4 The focused current and the total current flowing between the surface electrode and the sondeprobe and the water head sh
40、allbe measured and recorded at not less than 0.40 in. (10.0 mm) intervals along the pipe while the sondeprobe is pulled through apipe at a speed of 32.8 ft/min (10.0 m/min).6.5 The accuracy of the sondeprobe position measurement system shall be within 60.5 % with a resolution 0.05 %. That is fora pi
41、pe test section that is 100.00 ft long the length of pipe measured by the system shall be 100.0060.5 ft and the smallest distancereadout unit will be 0.05 ft or less6.6 The resolution of the current measurements shall be equal to or less than 0.1 % of the maximum current. That is if themaximum curre
42、nt is 40 mA then the smallest current readout unit will be 0.04 mA6.7 The applied voltage between the sondeprobe and the surface electrode shall have a frequency between 500 and 30 000 Hzand a voltage range of 9 to 11 volt rms. The maximum current between the sondeprobe and the surface electrode sha
43、ll be 0.04 Arms. These parameters prevent the occurrence of sparks or electric shock to humans during normal operation or in the event ofa short circuit.6.8 The measurement of the sondeprobe location, total current, focused current, and water head shall be stored in real time asdigital data in an el
44、ectronic device.6.9 The sondeprobe position, total current, focused electrode current, and the water head shall be displayed in real time on anelectronic device on the surface when the system is activated.6.10 The design of the electrical circuits shall prevent the occurrence of sparks or electrical
45、 shock to humans if faults or damageoccur such as a severed cable.6.11 Power cable winches shall have an automatic slip clutch to prevent overstrain of the sondeprobe cable that may occur ifthe sondeprobe becomes stuck in the pipe.FIG. 1 Electro-scan Electrical SchematicSchematic of a Simplified Ele
46、ctrical Scanning Circuit in a Non-Conductive PipeF2550 1337. Procedure7.1 Sewer PreparationPreparation:7.1.1 The electro-scan test is usually carried out by moving the sondeprobe through the sewer at approximately 30 ft/min (10m/min). For the average MH interval of 300 ft (100 m), this takes about 1
47、0 min.The time to set up and dismantle the test equipmentand fill the sewer in the region of the sondeprobe usually takes up most of the field time.Appropriate selection of the sewer sectiontest sequence, establishment of a setup routine, and ready availability of suitable equipment can considerably
48、 reduce the testpreparation time.7.1.2 Generally, electro-scan testing does not require any pipe preparation. However, the sewer must be clear of obstructionsthat prevent the sondeprobe passing through the pipe such as severe root intrusion or protruding service connections. Inability topass the hau
49、l line (7.1.5) through the pipe will indicate the presence of such obstructions and should be reported (7.2.4).7.1.3 Person-Entry into Sewer MHsElectro-scan field Field operations should not require person-entry of MHs. Person-entryis hazardous and requires additional time to carry out the safety checks and set up safety equipment. However, unforeseensituations may occur that require person-entry of a MH. Suitably trained personnel and safety equipment should be on hand justin case person entry is required. Prior to a person entering a MH the atmosphere in the MH must be
