ASTM G18-07(2013)
(Test Method)Standard Test Method for Joints, Fittings, and Patches in Coated Pipelines
Standard Test Method for Joints, Fittings, and Patches in Coated Pipelines
SIGNIFICANCE AND USE
4.1 The exposed metal surfaces at joints, fittings, and damaged areas in an otherwise coated pipeline will be subjected to corrosion if allowed to come in contact with the soil environment. The performance of joint and patching materials designed to function as protective coverings will depend upon such factors as the ability of the material to bond to both the pipe coating and exposed metal surfaces, the integrity of the moisture seal at lapped joints, and the water absorption characteristics of the joint material.
4.2 The existence of substantial leakage current through the coating joint, patch, or fitting is reliable evidence that the material has suffered a significant decrease in its performance as a protective barrier. In a similar manner, measured changes in joint capacitance and dissipation factor are useful because they are related to the water absorption rate of the joint material. Water permeating an insulating barrier increases its capacitance and its progress can be measured through the use of a suitable impedance bridge.
SCOPE
1.1 This test method describes determination of the comparative corrosion preventative characteristics of materials used for applications to joints, couplings, irregular fittings, and patched areas in coated pipelines. The test method is applicable to materials whose principal function is to act as barriers between the pipe surface and surrounding soil environment.
1.2 The test method described employs measurements of leakage current, capacitance, and dissipation factor to indicate changes in the insulating effectiveness of joint and patching materials.
1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.5 The values stated in SI units to three significant decimals are to be regarded as the standard. The values given in parentheses are for information only.
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: G18 − 07 (Reapproved 2013)
Standard Test Method for
Joints, Fittings, and Patches in Coated Pipelines
ThisstandardisissuedunderthefixeddesignationG18;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope or patched area, are suspended in an electrolyte and placed
under cathodic protection by connecting the specimens to the
1.1 This test method describes determination of the com-
negative (−) terminal of a 6-V d-c power supply (see Fig. 1).
parative corrosion preventative characteristics of materials
An anode, also immersed in the electrolyte and connected to
used for applications to joints, couplings, irregular fittings, and
the positive (+) terminal of the power supply, completes the
patchedareasincoatedpipelines.Thetestmethodisapplicable
test circuit. Joint or patch performance is followed through
to materials whose principal function is to act as barriers
periodicdeterminationsofleakagecurrentmeasuredasvoltage
between the pipe surface and surrounding soil environment.
drops across a calibrated resistor in the anode-to-cathode
1.2 The test method described employs measurements of
circuit.
leakage current, capacitance, and dissipation factor to indicate
3.2 Capacitance and dissipation factor measurements are
changes in the insulating effectiveness of joint and patching
used to supplement the periodic leakage current determina-
materials.
tions.
1.3 The values stated in SI units are to be regarded as the
standard. The values given in parentheses are for information
4. Significance and Use
only.
4.1 The exposed metal surfaces at joints, fittings, and
1.4 This standard does not purport to address all of the
damaged areas in an otherwise coated pipeline will be sub-
safety concerns, if any, associated with its use. It is the
jected to corrosion if allowed to come in contact with the soil
responsibility of the user of this standard to establish appro-
environment. The performance of joint and patching materials
priate safety and health practices and determine the applica-
designed to function as protective coverings will depend upon
bility of regulatory limitations prior to use.
such factors as the ability of the material to bond to both the
1.5 The values stated in SI units to three significant deci-
pipe coating and exposed metal surfaces, the integrity of the
mals are to be regarded as the standard. The values given in
moisture seal at lapped joints, and the water absorption
parentheses are for information only.
characteristics of the joint material.
2. Referenced Documents
4.2 The existence of substantial leakage current through the
2 coating joint, patch, or fitting is reliable evidence that the
2.1 ASTM Standards:
material has suffered a significant decrease in its performance
G12Test Method for Nondestructive Measurement of Film
as a protective barrier. In a similar manner, measured changes
Thickness of Pipeline Coatings on Steel (Withdrawn
3 in joint capacitance and dissipation factor are useful because
2013)
they are related to the water absorption rate of the joint
material. Water permeating an insulating barrier increases its
3. Summary of Test Method
capacitance and its progress can be measured through the use
3.1 The test method consists of an immersion test where
of a suitable impedance bridge.
coated pipe specimens, each containing a simulated joint, tee,
5. Apparatus
This test method is under the jurisdiction of ASTM Committee D01 on Paint
5.1 Test Vessel, nonconducting, shall be used to contain the
and Related Coatings, Materials, andApplications and is the direct responsibility of
Subcommittee D01.48 on Durability of Pipeline Coating and Linings.
test specimens. Dimensions of the vessel shall permit the
Current edition approved June 1, 2013. Published June 2013. Originally
following requirements:
approved in 1971. Last previous edition approved in 2007 as G18–07. DOI:
5.1.1 The test vessel shall be large enough to allow for
10.1520/G0018-07R13.
suspension of the specimens in a vertical position and equidis-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tant from a centrally located anode. The specimens shall not
Standards volume information, refer to the standard’s Document Summary page on
touch either each other, the walls, or bottom of the test vessel.
the ASTM website.
3 5.1.2 The test vessel shall be deep enough to allow for
The last approved version of this historical standard is referenced on
www.astm.org. immersionofthespecimensintheelectrolytetotheloweredge
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
G18 − 07 (2013)
NOTE 1—A commercially available, 42 L (11-gal) waste container of
high-density polyethylene can be conveniently used as a test vessel and
will accommodate up to six test specimens of a size indicated in 7.2.
5.2 Support Plate, fabricated from a nonconductive
material, to suspend the specimens in the test vessel. The
support plate shall contain an access hole for the reference
electrode. A typical test cell is illustrated in Fig. 3.
5.3 Anode, fabricated from 9.525 mm (0.375-in.) diameter
300seriesstainlesssteelrod,609.6mm(24.00in.)long.Other
inert anodes such as carbon or platinum may be used.
5.4 D-C Voltmeter, to serve the dual purpose of (1)
measuringleakagecurrentasapotentialdropacrossa1,000-Ω
shunt in the measuring circuit and (2) measuring the potential
of the test specimen with reference to a Cu-CuSO half cell.
The instrument characteristics for these functions shall be:
5.4.1 Voltage Range—50 µV full scale to 10 V full scale in
overlapping 1× and 3× ranges.
5.4.2 Accuracy—63 percent of full scale on all ranges.
5.4.3 Input Resistance—Greater than 10 MΩ on all ranges.
FIG. 1 Test Circuits
5.5 Thickness Gage—Measurements of coating thickness
will be required for this test. Any instrument suitable for use
of the upper moisture shield (see Fig. 2). with Test Method G12 can be used. However, the choice of
measuring gage shall be compatible with the joint coating
thickness that will be encountered in the test.
5.6 Ohmmeter—Measurements for end-cap integrity shall
be made with a suitable ohmmeter capable of reading resis-
tance to an upper limit of 1000 MΩ 65%.
5.7 Reference Electrode—ACu-CuSO half cell of conven-
tional glass or plastic tube with porous plug construction, but
preferably not over 19.05 mm ( ⁄4 in.) in diameter, having a
potential of−0.316 V with respect to the standard hydrogen
electrode.
NOTE 2—Asaturated calomel half cell may be used, but measurements
made with it shall be converted to the Cu-CuSO reference for reporting
NOTE 1—All dimensions are in millimetres with inches in parentheses.
FIG. 2 Joint Test Specimen FIG. 3 Joint Test Cell
G18 − 07 (2013)
by adding−0.072 V to the observed reading.
coating may be removed by power brushing or any other
suitable device that will remove all of the coating in the area
5.8 Voltage Source—A battery or rectifier-type power sup-
indicated and leave a clean metal surface behind.
plyshallbeusedtomaintainapotentialdifferenceof6.0 60.1
V dc between each of the test specimens and the Cu-CuSO
4 7.4 The lower end of the test specimen shall be plugged
half cell. Where multiple specimens are tested, a suitable
flush with a stopper and sealed or capped with a material
voltage-dividing circuit will be required for individual control
meeting the requirements of 6.2.
of the voltage applied to each specimen.
7.5 When used, the primer shall be applied to the test
5.9 Circuit Wiring from the anode to specimen shall be of
specimen in sufficient quantity to coat the test specimen from
No. 18Awg insulated copper.Aswitch for disconnecting each
a point 88.9 mm (3.50 in.) below its upper end and ending at
specimen from its voltage source shall be included in the
apoint317.5mm(12.5in.)fromtheupperend.Thiswillallow
circuit. A1000 Ω 61 percent, 1-W (minimum) precision
for a 12.7-mm (0.5-in.) band of excess primer beyond each
resistor shall be placed in the anode-to-cathode circuit as a
tape margin.
shunt for current. A diagram illustrating the test cell wiring
7.6 The joint material to be tested shall be applied to the
appears as Fig. 1.
prepared pipe specimen (using a spiral wrap for tapes) and
5.10 Capacitance Bridge—Measurements of specimen ca-
starting from a point 101.6 mm (4.0 in.) below the upper end
pacitance and dissipation factor shall be made with a low-
of the pipe section and ending at a point 304.8 mm (12.0 in.)
voltage a-c, resistive ratio arm-type bridge having the follow-
from the upper end. The 203.2 mm (8.0 in.) of joint material
ing characteristics:
thus applied should overlap the bared section of pipe by 50.8
5.10.1 Oscillator Frequency, 1 kHz 62% tolerance.
mm (2.0 in.) at each end. This distance represents the typical
5.10.2 Series Capacitance Range, 100 pF to 1100 pF
cut-back distance encountered in the field joining, through
accuracy 61% 61 pF, whichever is larger.
welding, of coated pipe in 60.325 mm (2.375 in.) outside
5.10.3 Dissipation Factor Range, 0.002 to 1.0 at 1 kHz
diameter size.Adiagram of the joint specimen appears as Fig.
accuracy 65%or 6 0.001 dissipation, whichever is larger.
2.
5.11 Connectors—Miniature, pin-type, insulated jacks shall
7.7 The manner of applying the joint material shall be done
be used at the point of connection to each test specimen. The
in accordance with the manufacturer’s specifications. The
jacks serve two important functions: (1) they permit the
supplier of the joint material should specify the desired time
disconnection of the specimen from the voltage source when
interval between the application of the material and the start of
the impedance bridge is in use, and (2) disconnection of the
the test.
specimen from the test circuit also removes the effect of stray
NOTE 3—Materials that are intended for use as a field-applied patch
capacitance due to excessive lead length that may introduce
over damaged areas on coated pipelines can be tested using the same
error into impedance bridge measurements.
procedures, with the patching compound applied, instead, to the bared
area of the simulated joint.
5.12 Foil Shield—As an additional safeguard agai
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