ASTM F2550-13(2018)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:F2550 −13 (Reapproved 2018)
Standard Practice for
Locating Leaks in Sewer Pipes By Measuring the Variation
of Electric Current Flow Through the Pipe Wall
This standard is issued under the fixed designation F2550; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Infiltration of groundwater into a sewer through defects in the pipe can considerably increase the
operation and capital costs of a sewer system. Exfiltration of sewage out of a sewer pipe may cause
degradation of aquifers and shoreline waters.Accurate location, measurement, and characterization of
all potential pipe leak defects are essential inputs for cost-effective design, testing, and certification of
pipe repairs, renewal, and new construction. While commonly used sewer leak assessment methods,
such as air and water pressure testing, represent cost effective methods to provide overall Pass/Fail
pipe assessments, their inability to provide accurate location and size of leaks, particularly at
individual joints and service connection, limit their use in remediation and rehabilitation decision
support.
1. Scope always a risk that due to unknown structural conditions in the
sewer such items may become lodged in the pipe or may cause
1.1 This practice covers procedures for measuring the varia-
the state of a sewer in poor structural condition to further
tion of electric current flow to detect and locate potential pipe
deteriorate. This standard does not describe methods to assess
leaks in pipes fabricated from electrically nonconductive
the structural risk of a sewer.
materials such as brick, clay, concrete, and plastic pipes (that
is, reinforced and non-reinforced). The method uses the varia-
1.5 The values stated in inch-pound units are to be regarded
tion of electric current flow through the pipe wall to locate
as standard. The values given in parentheses are mathematical
defects that are potential water leakage paths either into or out
conversions to SI units that are provided for information only
of the pipe.
and are not considered standard.
1.2 This practice applies to mainline and lateral gravity flow
1.6 This standard does not purport to address all of the
storm sewers, sanitary sewers, and combined sewers with
safety concerns, if any, associated with its use. It is the
diameters between 3 and 60 in. (75 and 1500 mm). The pipes
responsibility of the user of this standard to establish appro-
must be free of obstructions that prevent the probe passing
priate safety, health, and environmental practices and to
through the pipe.
determine the applicability of regulatory limitations prior to
1.3 The scanning process requires access to sewers, filling
use.
sewers, and operations along roadways that are safety hazards.
1.7 This international standard was developed in accor-
This standard does not describe the hazards likely to be
dance with internationally recognized principles on standard-
encountered or the safety procedures that must be carried out
ization established in the Decision on Principles for the
when operating in these hazardous environments. (7.1.3)There
are no safety hazards specifically associated with the use of an Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
electro-scan apparatus that complies with the specifications
provided in this standard. (6.7 and 6.10.) Barriers to Trade (TBT) Committee.
1.4 The measurement of the variation of electric current
2. Terminology
requires the insertion of various items into a sewer. There is
2.1 Definitions of Terms Specific to This Standard:
This practice is under the jurisdiction ofASTM Committee F36 on Technology
2.1.1 lateral, n—sewer pipe connecting the common sewer
and Underground Utilities and is the direct responsibility of Subcommittee F36.20
collection system to the user.
on Inspection and Renewal of Water and Wastewater Infrastructure.
Current edition approved Aug. 1, 2018. Published August 2018. Originally
2.1.2 mainline, n—pipe that is part of the common sewer
approved in 2006. Last previous edition approved in 2013 as F2550–13. DOI:
10.1520/F2550-13R18. collection system.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F2550−13 (2018)
2.1.3 maintenance hole, n—(MH) vertical shafts intersect- 4.1.3 Locationandexposureofallmaintenanceholes(MH);
ing a sewer that allows entry to the sewer for cleaning,
4.1.4 MH numbering system for all areas of the project and
inspection and maintenance.
MH invert elevations and depths;
2.1.4 owner, n—entity holding legal rights to, and respon-
4.1.5 Shutdown or manual operation of certain pump sta-
sible for the operation and maintenance of the sewer pipe.
tions if such becomes necessary for performance of the work;
2.1.5 probe, n—scan electrode placed in a pipe.
4.1.6 Permission to use water from fire hydrants at the work
site, or other suitable designated sources within a reasonable
2.1.6 sliding pipe plug, n—device that blocks the flow
distancefromtheworkareas,whichisnecessaryforcontracted
through a pipe and at the same time can be pulled through the
work performance;
pipe.
4.1.7 Authorizationtoperformworkthatmustbeperformed
3. Significance and Use
during nighttime hours, weekends, or holidays; and
3.1 The testing of sewers for leaks is a regular practice
4.1.8 Traffic control by uniformed officers or contract per-
necessary for the maintenance and optimal performance of
sonnel when the safety of workers or the public requires such
sewer collection systems so remedial action can be prioritized,
protection.
designed, and carried out to reduce infiltration and exfiltration.
3.2 This practice serves as a means to detect and locate all 5. Principle of Operation
types of pipe defects that are potential sources of water leaks
5.1 Most sewer pipe materials such as clay, plastic,
either into or out of electrically non-conducting pipes. Leaking
concrete, reinforced concrete, and brick are poor conductors of
joints and defective service connections are detected that often
electrical current.Adefect in the pipe wall that leaks water will
may not show as a defect when viewed from inside the pipe.
also leak electrical current, whether or not water infiltration or
The scan data may be processed and analyzed to provide some
exfiltration is occurring at the time of the test.
information on the size and type of pipe defect. (8.4.1)
5.2 The test is carried out by applying an electrical potential
3.3 This practice applies to mainline and lateral gravity flow
of 9 to 11 Volts rms with a frequency of 500 Hz to 30 kHz
storm sewers, sanitary sewers, and combined sewers fabricated
betweenanelectrodeintheelectricallynonconductivepipeand
from electrically non-conducting material with diameters be-
an electrode on the surface, which is usually a metal stake
tween 3 and 60 in. (75 and 1500 mm). The pipes must be free
pushed into the ground. A simplified electrical circuit for this
of obstructions that prevent the probe passing through the pipe.
procedure is shown in Fig. 1. The water in the pipe is at a level
4. Contract Responsibilities
that ensures that the pipe is full at the electrode location.
Provided electrical current is prevented from flowing along the
4.1 Apartfromtheprovisionsgenerallyincludedinatesting
inside of the pipe, the electrical resistance of the current path
services contract, testing contracts for measuring the variation
between the electrode in the pipe and the surface electrode is
in electric flow through a pipe wall should define or affix
very low except through the electrically nonconductive pipe
responsibility for or make provisions for the following items:
wall.The high electrical resistance of the pipe wall allows only
4.1.1 Access to the site of work is to be provided to the
a very small electrical current to flow between the two
extent that the owner is legally able to so provide or, if not so
able, a written release from responsibility for the performance electrodes unless there is a defect in the pipe such as a crack,
of work at sites where access cannot be made available; defective joint, or faulty service connection. The greater the
4.1.2 Clearances of blockages or obstructions in the sewer electric current flow through the pipe opening, the larger the
system; size of the leak.
FIG. 1Schematic of a Simplified Electrical Scanning Circuit in a Non-Conductive Pipe
F2550−13 (2018)
6. Apparatus electric shock to humans during normal operation or in the
event of a short circuit.
6.1 The method for measuring the variation in electric flow
6.8 The measurement of the probe location, total current,
through a pipe wall requires a means of preventing the electric
current from the electrode in the electrically nonconductive focused current, and water head shall be stored in real time as
digital data in an electronic device.
pipe from traveling along the inside of the pipe before reaching
the ground electrode. Such a means is a three-electrode array,
6.9 The probe position, total current, focused electrode
known as a probe. The probe is constructed in such a way that
current, and the water head shall be displayed in real time on
when equal voltages are applied to all three electrodes, the
an electronic device on the surface when the system is
electric fields of the outer electrodes prevent electrical current
activated.
from the center electrode flowing along the pipe. This also
6.10 The design of the electrical circuits shall prevent the
causes the electric field of the center electrode to be focused
occurrence of sparks or electrical shock to humans if faults or
intoadiskabout1in.(25mm)wide.Thiselectricfieldprojects
damage occur such as a severed cable.
onto the pipe wall as a circumferential band with a width of
about 10 % of the pipe diameter. The center of the band is 6.11 Power cable winches shall have an automatic slip
clutch to prevent overstrain of the probe cable that may occur
located at the center of the probe. As a result, the electrical
current flow through the center electrode of the probe, called if the probe becomes stuck in the pipe.
the focused current, is dependant on the electrical resistivity of
the pipe wall within the area of the band around the circum- 7. Procedure
ference of the pipe.
7.1 Sewer Preparation:
7.1.1 The test is usually carried out by moving the probe
6.2 The essential components of the scanning apparatus are:
a controlled voltage source; the probe; an insulated cable to through the sewer at approximately 30 ft/min (10 m/min). For
connect the probe to the voltage source and move the probe the average MH interval of 300 ft (100 m), this takes about 10
through the pipe; a system to measure the position of the probe min. The time to set up and dismantle the test equipment and
in the pipe; a system to measure the focused current; a system fill the sewer in the region of the probe usually takes up most
to measure the electrical current flowing through all three of the field time.Appropriate selection of the sewer section test
electrodes in the probe, called the total current; and a surface sequence, establishment of a setup routine, and ready avail-
electrode. When a sliding pipe plug (7.1.6.2) is used, a system ability of suitable equipment can considerably reduce the test
to measure the water pressure in the pipe at the location of the preparation time.
probe, called the water head, is required. 7.1.2 Generally, testing does not require any pipe prepara-
tion. However, the sewer must be clear of obstructions that
6.3 The geometric dimensions of the probe shall be such
prevent the probe passing through the pipe such as severe root
that the change of focused current as a result of a hole in the
intrusion or protruding service connections. Inability to pass
pipe with a diameter of 0.5 % of the pipe diameter will be
the haul line (7.1.5) through the pipe will indicate the presence
detected and potential leaks separated by more than 25 % of
of such obstructions and should be reported (7.2.4).
the pipe diameter will be resolved. That is for a 10 in. (250
7.1.3 Person-Entry into Sewer MH’s—Field operations
mm) diameter pipe a hole with a diameter of 0.05 in. (1.3 mm)
should not require person-entry of MH’s. Person-entry is
will be detected and openings more than 2.5 in. (62 mm) apart
hazardous and requires additional time to carry out the safety
will be shown as two separate leaks.
checks and set up safety equipment. However, unforeseen
6.4 The focused current and the total current flowing be-
situations may occur that require person-entry of a MH.
tween the surface electrode and the probe and the water head
Suitably trained personnel and safety equipment should be on
shall be measured and recorded at not less than 0.40 in. (10.0
hand just in case person entry is required. Prior to a person
mm) intervals along the pipe while the probe is pulled through
enteringaMHtheatmosphereintheMHmustbeevaluatedfor
a pipe at a speed of 32.8 ft/min (10.0 m/min).
toxic or flammable gases and oxygen depletion in accordance
with local, state or federal safety regulations and must be
6.5 The accuracy of the probe position measurement system
carried out in accordance with the owner’s person-entry of MH
shall be within 60.5 % with a resolution 0.05 %. That is for a
procedures.
pipe test section that is 100.00 ft long the length of pipe
7.1.4 Sewer Flow—Testing can be carried out in all condi-
measured by the system shall be 100.00 6 0.5 ft and the
tions of sewer flow, from dry to surcharged.
smallest distance readout unit will be 0.05 ft or less
7.1.5 Haul Line:
6.6 The resolution of the current measurements shall be
7.1.5.1 A line is required to pull the probe between the
equal to or less than 0.1 % of the maximum current. That is if
MH’s of the pipe section to be tested. The haul line is flushed
the maximum current is 40 mA then the smallest current
between the MH’s at each end of the pipe section to be scanned
readout unit will be 0.04 mA
using either water or air.
6.7 The applied voltage between the probe and the surface 7.1.5.2 An effective haul line is a jet cleaner hose.
electrode shall have a frequency between 500 and 30 000 Hz 7.1.6 Filling the Sewer at the Probe Location—Water in the
and a voltage range of 9 to 11 volt rms. The maximum current pipe provides the electrical connection between the probe and
between the probe and the surface electrode shall be 0.04 A the pipe wall (Fig. 1). To
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