This necessary pipeline modification and repair method requires the expertise of a
CWI at every step to make it safer and meet the standards
Hot tapping is a method used inpipeline repairs, or for attaching abranch outlet to existing pipelines for
the purpose of additional service capabilities,without disrupting service. Inmany cases, the hot tap is done to repairlines and systems damaged ordeemed unsafe by inspectors and operatorsdue to anomalies discovered
during an in-line inspection (ILI). Hottapping often creates risky and dangeroussituations; however, pipeline
operators, contractors, and inspectioncompanies who specialize in themethod have acquired enough experienceand expertise over the years toaccomplish the process safely — Fig. 1.American Welding Society (AWS) CertifiedWelding Inspectors (CWIs) planningto work in hot tapping should betrained by CWIs experienced in theprocess to understand the many importantsteps and safety aspectsrequired.
Hot Tapping and CWIs
Hot tapping can be done with a varietyof methods, including split-T fittings,reinforced forgings, sleeves, or
specialized fittings. These specializedproducts must meet strict inspectionstandards and undergo rigorous materialand statistical analysis in their development,from the billet to the finalforging, well before being placed in useby tapping contractors.
AWS CWIs play an instrumentalrole in the visual testing (VT) and nondestructiveexamination (NDE) of
these fittings and devices prior to implementationin the field. Quality assuranceof the integrity of these fixturesis mandatory before being placedin pressurized, production situations.CWIs ensure the safety of the operatorsand the workers who are contractedto complete a hot tapping procedure,but their work starts long beforethe welding or even before the excavations.The CWI must ensure the fabricationof the components of the particularhot tap follow the exact standardsneeded to ensure quality, safecompletion, and long duration of safeworking conditions. Without theexperienced, observing eyes of theinspector, substandard materials andworkmanship can lead to unsafeconditions.
Common accidents can be traced toimproper techniques or material imperfections.The CWI is an essential elementin the cycles of the productionand implementation of a hot tap andmust be involved early in the processto remove any potential threats tosafety, environment, or production.Often, production companies and finalusers of the hot tap product decline tobring a CWI into the process becauseof the costs associated with having aninspector on site. These costs can beminuscule compared to the costs of repair,replacement, or failure.
Fig. 1 — Hot tapping allows for a pipeline for be repaired or modified without interrupting service.
Duties of the CWI as theEngineer of Record (EOR)Representative
Before beginning work, the inspectioncrew should be involved in the examination of the proposed workers
and their operator qualification (OQ)status. Workers, including CWIs, musthave current OQs that can be demonstratedwith field verification reports(FVRs). These reports are issued fromthe training and registering agenciesor an individual production company.Those tapping and contracting employeeswho will be involved in thework must show their respective operatorqualifications are up to date andvalid for the work they are going toperform. Rejection of these documentsbefore the work starts can createa sizable delay. CWIs work withtheir contracted employers to helpmake this part of the hot tap go quicklyand smoothly. A good CWI will oftenwork well ahead of the beginning workdate to ensure this sort of interruptiondoes not occur.
A CWI should also be involved inthe qualifying of the materials early onto avoid discrepancies after the parts
have been manufactured. One examplecould be an appliance that has beenmanufactured with a material that
does not meet the Charpy impact testingminimums for high-pressurebranch work where the appliance must
be installed above ground, in an areasubject to very low temperatures.Some operating companies require
these low-temperature impact valuesas per their respective safety operatingprocedure (SOP) manuals. If an essentialtapping component is manufacturedwith a material that does notmeet those requirements, a substantialdelay can be incurred. An experiencedCWI could ensure the requirementwould be met, and if the CWI isbrought into the early productionphase of that process, most delayscould be averted.
Emphasis on positive material identification(PMI) has become an essentialpart of the inspector’s duty and
generally is done at this front load partof the project. More companies are requiringcertified chemical identificationto ensure the materials specifiedare the materials supplied. This is alsoan integral part of the primary stepsof the inspection process for tappingprojects. Often, tapping parts arrivewith documentation that gives the inspectora readout of the fabricating facility’smetallurgical makeup of theparts.
A secondary test, usually done onsite,can determine the validity of thesupplier’s submission. These are done
with portable spectroanalyzers thatcan give a reliable readout of thechemical makeup. Although not as accurateas an in-lab spectroanalyzer,these portable units are used to verifyand release the tapping apparatus sentby the contractors to fabrication andinstallation. Once again, an experiencedCWI with a background in metallurgyand an understanding of specificationsand standard operating procedurescan be an invaluable asset atthis stage of the process — Fig. 2.
Fig. 2 — Billet markings on tap segments showing material specifications.
CWI Duties withDocumentation
The next step in this detailedprocess is to be sure the welding proceduresare accurate and in order. Once
again, it is helpful to receive the weldingdocumentation well before thecrews and equipment arrive on site, as
this seems to be the area where manydelays arise. When contracted to inspecta hot tap, the CWI must begin
with getting the welding documentationto check the parameters and personnel.Beginning with the welding
procedure specification (WPS) and followingthrough to the procedure qualificationrecord (PQR), the contractedcompany that is hired to do the installationwelding must produce these tothe EOR or his or her designated representative— usually a CWI.
Once these documents have beenexamined and determined to be accurateand proper for the operation, the
attention then turns to the weldingpersonnel. The welders must be qualifiedto the proper procedures and havethe appropriate welder qualificationrecord (WQR).
Welding rod must also be inventoriedand documented by size, type,brand, date opened, and hours since
opened, for the welding consumable tobe monitored and verified when used.Welding rod supply companies mustsupply manufacturer technical reports(MTRs) to the contractor and theEOR’s representative for the weldingrod used to be adequately documentedbefore the welding operations. TheseMTRs must be determined by the actuallot number on the cans and not bythe general MTRs given by the local
supplier. The document presented bythe supplier is usually only an electrode-type MTR and too general to be
considered for hot tap work. Thechemistry of the actual lot must be determinedand documented.
Depending on the diameter of thepipe and the particular company specifications,in many cases at least two
welders are needed to be qualified andon site to do the job. Most companiesrequire two welders to work in unisonon a weld on opposite sides of theworkpiece. This is done so that thermal input is balanced and does notcreate undue stress and heat issueswith the mainline pipe or the hot tapappliance. It is good practice to alwayshave a third qualified welder on site toserve as a backup because the operationrequires at least two welders atthe same time.
The welding procedures and thewelders qualified to that procedure arecovered in Appendix B of American PetroleumInstitute (API) Standard1104, Standard for Welding Pipelinesand Related Facilities. There is also API RP 2201, Safe Hot Tapping Practices inthe Petroleum and PetrochemicalIndustries, which gives specific guidelines
when conducting a hot tap procedure.Depending upon the particulartype of tapping project to be done, the welders must be tested to API 1104Appendix B “In Service” testing, whichinvolves conducting the welding whilea simulated product media is flowingthrough the test pipe setup — Fig. 3.Most often, this is water or oil flowingat a specified volume-per-time unitthrough the test setup, and is flowingcontinuously to simulate a productthat removes the heat input from thewelding process. The detrimental effectof heat removal in this way canhave severe effects on the integrity ofthe completed weld. If heat input islost too rapidly, the resulting weld willcontain an elevated hardness, whichcan cause weld failures at pressure. If the heat input is too high, the possibilityof pipe wall failure can occur andhave catastrophic results. It is for
these reasons that an experienced andattentive CWI should be employed inthe tapping process. CWIs who havebeen trained in welding heat input calculations,voltage and amperage management,metallurgy, and visual weldanomaly recognition are needed to thesuccessful completion of any tappingoperation.
Fig. 3 — Welder testing for in-service welding.
The first step in a hot tap operationis to locate the exact place on the pipethe tap is to occur. If the tapping is tobe done in a plant setting, the exact locationmust be determined, markedappropriately, and prepared. If the tapis to be executed in the field in a remotelocation, survey crews can determinethe precise location by GPS coordinatesand then it be verified andagreed upon by company representatives,NDE personnel, and inspectionparties before the actual work can begin.Once this has been done and allparties agree to that location, the crewmust sandblast the exact areas to beworked to “near white” conditions,and made ready for the NDE crew tocomplete its job. Before the sandblastingoperation, a visual examinationmust be done to the entire surface tobe blasted to locate any anomaly thatmight interfere with the location ofthe tapping work to be done.
NDE personnel must then performultrasonic testing (UT) examining theareas on the pipe where the actualwelding will be done. This is to makesure the welding heat input occurs onpipe wall that can sustain the high energyinput, and the pipe wall containsno discontinuity that has not otherwisebeen detected. Pipe defects such as laminations,dents or wall thinning, internalporosity, corrosion, or damage canlead to compromises in the process thatmight curtail the tapping being done inthat location. After these essential UTexams are performed, defects can beuncovered that require additional attentionand a relocation of the tap to anadjacent location to ensure tap integrity.Smart pigging and ILI examinationsoften miss some of these problems. Anydiscontinuities within the proposedwelding areas for tapping must ultimatelybe dealt with promptly andmade inert to the overall pipeline safetyand integrity.
CWI Monitoring of Preheat
Preheating takes place at this point,and the inspector must be satisfied byexamination using temperaturecrayons or temperature pyrometersshowing the appropriate preheat temperaturehas been reached beforewelding may begin. Depending on thegrade of the pipe to be worked, thispreheat is crucial to setting the propermetal temperature before the actualwelding. The preheat process is also instrumentalin driving off any water,water vapor, oil, or grease that mayhave accumulated on the line or fixture.The presence of these substancescan severely degrade the wholeprocess, creating defects in the weld orbase pipe material during the weldingprocedure.
Weld Monitoringby the CWI
When the preheat has been metand the welders have been determinedto be qualified, the actualwelding can begin. Using precise calculationformulas to determine heatinput, the welders begin welding underthe watchful eyes of the CWI.These calculations use product type,pipe pressure, velocity of productflow, volume of product per time unitfor the diameter of pipe involved, amperage,voltage, electrode diameter,and pipe wall thickness as input variables,and let the inspector and thewelder know how many inches perminute must be welded for the properamount of heat input to be applied sothat martensite creation is held tozero and enough heat input is generatedso the weld material has integritywith an absence of discontinuities.The area where the pipe is to be weldedis usually marked off in 1-in.marks so the welder and the inspectorcan monitor and make sure thosecalculated values are met; too muchheat or too little heat can fail thewelding or the overall success of thetap project. While the welding is takingplace, the inspector is also continuously
monitoring the voltage andamperage of the welding equipmentto ensure the target values are beingutilized. It is an intensive operationthat requires continuous attention bythe CWI and the tapping contractorpersonnel. Quite often, the owner oroperator of the pipeline is in continuouscontact via phone or computer toassist in the monitoring of the parametersof the process, advising theon-site crew of pressure or velocity
fluctuations. These changes can alterthe in./min speed that the weldersmust employ at any given moment.These real-time values are determinedand recorded with every weldingminute, per welder, per electrode.
NDE of the CompletedWelding
Fig. 4 — Magnetic particle testing (MT) of completed fillet welds on hot tap split sleeve.
Once the necessary welding iscompleted, the NDE crew conductspenetrant testing (PT) on the girthfillet welds and on the longitudinalwelds of the split-T groove welds.Magnetic particle testing (MT) canalso be used for these fillet weld examinationsat the discretion of theEOR — Fig. 4.
In some cases, the EOR requeststhe welds be tested using acousticvolumetric methods to ensure thesoundness of the girth welds. Welddiscontinuities, which may be uncoveredin the NDE process, most often
involve undercutting, underfill,porosity, or slag inclusion that mustbe addressed. Typically, welding onhot taps is done by highly skilled individualswith many years of experienceand the ability to make multiple,
high-quality welds with a minimumof weld blemishes — Fig. 5.
Fig. 5 — Completed hot tap ready forbackfill.
Real-time monitoring occasionallyfinds issues that must be corrected inprocess and in-situ. One of the morecritical weld problems that arises isundercut. It is critical that any undercutis immediately removed by repair
and any discrepancies present mustbe analyzed to determine how theypropagated, then removed andrepaired.
Future of Hot Tapping
As the welding and pipeline industriesmove further into the twentyfirstcentury, the demand for hot tapping
will likely increase to keep upwith the demands of various other industries.The role of CWIs and other
engineering and inspection personnelwill continue to expand along withtechnological research and new equipmentbeing pioneered by a host ofsuppliers.
JEFFRY STRAHAN is an instructor atWeber State University. He is an AWSCWI, CRI, CWE, and API 1169 CWI. Hehas a BS and MS from Utah StateUniversity, and extensive experience onhot tap projects.