ASTM_G_18_-_07_2013.pdf

Designation:G1807(Reapproved 2013)Standard Test Method forJoints,Fittings,and Patches in Coated Pipelines1This standard is issued under the fixed designation G18;the number immediately following the designation indicates the year of originaladoption or,in the case of revision,the year of last revision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method describes determination of the com-parative corrosion preventative characteristics of materialsused for applications to joints,couplings,irregular fittings,andpatched areas in coated pipelines.The test method is applicableto materials whose principal function is to act as barriersbetween the pipe surface and surrounding soil environment.1.2 The test method described employs measurements ofleakage current,capacitance,and dissipation factor to indicatechanges in the insulating effectiveness of joint and patchingmaterials.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.4 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 practices and determine the applica-bility of regulatory limitations prior to use.1.5 The values stated in SI units to three significant deci-mals are to be regarded as the standard.The values given inparentheses are for information only.2.Referenced Documents2.1 ASTM Standards:2G12 Test Method for Nondestructive Measurement of FilmThickness of Pipeline Coatings on Steel(Withdrawn2013)33.Summary of Test Method3.1 The test method consists of an immersion test wherecoated pipe specimens,each containing a simulated joint,tee,or patched area,are suspended in an electrolyte and placedunder cathodic protection by connecting the specimens to thenegative()terminal of a 6-V d-c power supply(see Fig.1).An anode,also immersed in the electrolyte and connected tothe positive(+)terminal of the power supply,completes thetest circuit.Joint or patch performance is followed throughperiodic determinations of leakage current measured as voltagedrops across a calibrated resistor in the anode-to-cathodecircuit.3.2 Capacitance and dissipation factor measurements areused to supplement the periodic leakage current determina-tions.4.Significance and Use4.1 The exposed metal surfaces at joints,fittings,anddamaged areas in an otherwise coated pipeline will be sub-jected to corrosion if allowed to come in contact with the soilenvironment.The performance of joint and patching materialsdesigned to function as protective coverings will depend uponsuch factors as the ability of the material to bond to both thepipe coating and exposed metal surfaces,the integrity of themoisture seal at lapped joints,and the water absorptioncharacteristics of the joint material.4.2 The existence of substantial leakage current through thecoating joint,patch,or fitting is reliable evidence that thematerial has suffered a significant decrease in its performanceas a protective barrier.In a similar manner,measured changesin joint capacitance and dissipation factor are useful becausethey are related to the water absorption rate of the jointmaterial.Water permeating an insulating barrier increases itscapacitance and its progress can be measured through the useof a suitable impedance bridge.5.Apparatus5.1 Test Vessel,nonconducting,shall be used to contain thetest specimens.Dimensions of the vessel shall permit thefollowing requirements:5.1.1 The test vessel shall be large enough to allow forsuspension of the specimens in a vertical position and equidis-tant from a centrally located anode.The specimens shall nottouch either each other,the walls,or bottom of the test vessel.5.1.2 The test vessel shall be deep enough to allow forimmersion of the specimens in the electrolyte to the lower edge1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.48 on Durability of Pipeline Coating and Linings.Current edition approved June 1,2013.Published June 2013.Originallyapproved in 1971.Last previous edition approved in 2007 as G18 07.DOI:10.1520/G0018-07R13.2For referenced 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 of the upper moisture shield(see Fig.2).NOTE1A commercially available,42 L(11-gal)waste container ofhigh-density polyethylene can be conveniently used as a test vessel andwill accommoda