Handbook of Weld Inspection

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION This note is prepared to give some idea about the requirements of pipe line welding in accordance with the code ASME sect. IX, API 1104, ASME B31.3/31.4/31.8 & additional requirements by SAUDI ARAMCO. Use this note for engineering education purposes only.

TEJAS V. ROOWALA Project Inspector Welding AWS-CWI Certificate No. 08111791 [email protected]

TEJAS ROOWALA

Digitally signed by TEJAS ROOWALA DN: cn=TEJAS ROOWALA, o=OM, ou=INSPECTION, [email protected], c=IN Date: 2010.01.04 11:17:13 +03'00'

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION WELDING REQUIREMENTS Procedure Qualification 

Either as per ASME sect. IX (or API 1104 for pipeline welding) with additional limitations as per governing code B31.3, 31.4 or 31.8 and requirements of SAES-W-011/012/016.



Hardness testing of WPQ is required for hydrogen services, sour service applications and all services requiring PWHT.



Only Vicker test method (in accordance with ASTM E92) is acc eptable, with max. load of 10 Kg.



The location of the HAZ indents nearest the fusion line can be demonstrated to be within 0.2 mm of the fusion line. The max. allowable hardness is VHN 250. (for pipeline 250 VHN for sour services & 300 VHN for offshore non sour services).



For procedure qualified to API 1104, the tensile test results shall be considered acceptable if the specimen breaks in the base metal outside of the weld/fusion line, provided the strength is not more than 5% below the specified min. tensile strength of the base metal.



Following are the max. tolerance limit for procedure qualified in accordance with sect. 9 (automatic welding) of API 1104; Travel speed:

±20% of the actual PQR value

Voltage:


Current:


Performance Qualification 

Either as per ASME sect. IX (or API 1104 for pipeline welding) with additional limitations as per governing code B31.3, 31.4 or 31.8 and requirements of SAEP-321.



The test coupon shall be secured in the test position at a height of 18” above the flo or of the test

booth. 

Grinding, filing or mechanical dressing of the cap pass is not permitted.



Weld reinforcement and root penetration shall not exceed the given values in table-1. Table-1 Test coupon wall thickness (mm) t≤6.4 6.4


Maximum weld reinforcement/root penetration 1.6 3.2 4 5

Undercut up to the depth of 0.8 mm shall be permitted for a total length of 2” max. Undercut

exceeding 0.8 mm in depth is not permitted. 

Under fill up to 1.6 mm in depth shall be permitted f or a total length of 2” max. Under fill exceeding 1.6 mm in depth is not permitted.

2

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION WELDING REQUIREMENTS Procedure Qualification 

Either as per ASME sect. IX (or API 1104 for pipeline welding) with additional limitations as per governing code B31.3, 31.4 or 31.8 and requirements of SAES-W-011/012/016.



Hardness testing of WPQ is required for hydrogen services, sour service applications and all services requiring PWHT.



Only Vicker test method (in accordance with ASTM E92) is acc eptable, with max. load of 10 Kg.



The location of the HAZ indents nearest the fusion line can be demonstrated to be within 0.2 mm of the fusion line. The max. allowable hardness is VHN 250. (for pipeline 250 VHN for sour services & 300 VHN for offshore non sour services).



For procedure qualified to API 1104, the tensile test results shall be considered acceptable if the specimen breaks in the base metal outside of the weld/fusion line, provided the strength is not more than 5% below the specified min. tensile strength of the base metal.



Following are the max. tolerance limit for procedure qualified in accordance with sect. 9 (automatic welding) of API 1104; Travel speed:


Voltage:


Current:


Performance Qualification 

Either as per ASME sect. IX (or API 1104 for pipeline welding) with additional limitations as per governing code B31.3, 31.4 or 31.8 and requirements of SAEP-321.



The test coupon shall be secured in the test position at a height of 18” above the flo or of the test

booth. 

Grinding, filing or mechanical dressing of the cap pass is not permitted.



Weld reinforcement and root penetration shall not exceed the given values in table-1. Table-1 Test coupon wall thickness (mm) t≤6.4 6.4


Maximum weld reinforcement/root penetration 1.6 3.2 4 5

Undercut up to the depth of 0.8 mm shall be permitted for a total length of 2” max. Undercut

exceeding 0.8 mm in depth is not permitted. 

Under fill up to 1.6 mm in depth shall be permitted f or a total length of 2” max. Under fill exceeding 1.6 mm in depth is not permitted.

2

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION 

Lack of penetration is not permitted.



Lack of fusion is not permitted.



Unremoved arc strikes on the base metal are not acceptable.



Guided bend testing; Table-2 Test coupon thickness (mm) t≤9.5 9.519.05

No. & Type 2F & 2R 2F & 2R or 4S 4S

Test piece Shall be taken from the location shown in QW-463 of ASME IX. Testing shall be done in accordance with ASME IX. 

The repair rates shall be calculated on a lineal basis. The max. weekly repair rate for each welder should not exceed 2%.

%RR = (Lr/Lw) X 100

Lr = welder’s total length of repair in one week, mm Lw = welder’s total length of weld r adiographed in one week, mm

Processes 

Except for ASME P-No. 1 through P-No.5A/5B/5C base material, all manual GTAW shall use a high frequency start and post purge gas flow for the torch.



Filler metal must always be added (i.e. autogeneous process is not permitted) unless specified.



The GTAW process shall be used for the root pass of butt welds without backing in piping and set in fittings of 50.8 mm nominal pipe size or less, except for vent and drain piping open to the atmosphere.



The GTAW process shall be used for the root pass of single sided groove welds without backing made with SS or Ni based consumables.



GMAW/FCAW shall not be used for single sided tee or corner joints (i.e. branch/nozzle welds)



The GMAW dip mode (STT mode) shall not be used except for, Structural attachments to the outside surface of the pipe, including seal welds. Tacking that will be completely removed by back gouging go uging and back welding. The root pass and hot pass only for butt welds in P-No.1 CS.



FCAW Gas shielded process shall not be used for root pass on full penetration groove joints that are welded from one side only without backing.



FCAW Self shielded process shall not be used unless specified.

3

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION Consumables 

Low hydrogen consumables may be used. The root pass of single sided groove welds without backing in P-No.1 CS may be made with an EXX10 electrode.



For welding P-No.1 CS, the weld deposit shall meet the A-No.1 analysis classification for normal applications or A-No.10 for low temp. applications unless specified.



Filler metal or deposit chemistries conforming to A-No.2,i.e. C-0.5% Mo (E7010-A1 or E7018-A1) shall not be used for sour services applications without PWHT unless specified.



SAW Fluxes: Active flux shall not be used unless specified. Flux that uses recrushed slag is not acceptable. SAW Flux that the manufacturer recommended for single pass shall not be used for multi pass welding.



SMAW Elect.: F-No.1 & 2 elect. shall not be used on material requiring impact tests and pressure retaining welds.



Shielding Gases:

Shall confirm to the AWS A5.32 specifications for welding shielding gas.

Joint Details 

All pressure containing welds shall be made with multiple pass.



All nozzles, branch and T-connections shall be made with full penetration groove welds only.



Internal misalignment of butt joints shall not exceed 1.5 mm.



Permanent backing strips or rings shall not be used. Temporary back up strips in weld joints may be used if the backing m/t is of a composition similar to the base/weld metal. Under no circumstances shall rebar or galvanized steel be used. Temporary back up shoes made of non-metallic, non-fusing m/t may be used.



Consumable inserts may be used for all applications providing the composition matches the weld metal composition.



Full penetration groove joint included angles less than 30° shall not be used unless specified.



All holes cut for set-on nozzles, bosses or branch connections shall be ground smooth and the dia. of the hole shall be ±1.6 mm of the inside dia. of the set-on member.



A min. of 1.5 mm depth shall be removed by grinding or machining from thermally cut or gouged surface.



Fittings that are re-cut or re-beveled shall have the cut surface examined for laminations before welding.



SS and non ferrous m/t shall be cleaned with grinding wheels or SS brushes not previously used on other metals.

4


Buttering/weld build up on the prepared surfaces shall not exceed the lesser of 1/3 of the base metal thk. or 10 mm unless specified. If it exceeds it shall be inspected by RT, PT/MT after completion of the buildup but before final welding of the joint.

Tack Welds 

Tack welds shall be of sufficient size to maintain joint alignment. The recommended tack thk. is 3.24.8 mm and length is 12.5-25.4 mm.



The min. no. of tack welds are,

pipe dia D≤4” D>4”



-

3 equally spaced min. 4 equally spaced

Tack welds that are to be incorporated into the final weld shall be thoroughly cleaned, prepared at each end and inspected for cracks. Any cracked tacks shall be removed before welding the joint.



If the tack welds are to be incorporated into the final root pass weld and are made with different process or elect. than the root pass, then the tack weld process and elect. shall have been used as the root pass for an appropriate procedure qualification.



Bridge tacks (located above the root area) are acceptable but such tacks must be made completely within weld groove and shall be completely removed prior to completion of weld.

Back Purging 

An inert backing gas shall be used for GTAW/GMAW root passes on a single sided groove welds for m/t of ASME P-No.5 and higher.



For P-No.5 and higher m/t, any back purging shall be maintained until at least 10 mm of the weld deposit thk. has been completed.



The use of Nitrogen as a backing gas for austenitic SS is prohibited.



The back purge for low alloy steel shall reduce the oxygen level below 1%. The back purge for SS & Ni alloys shall reduce the oxygen level below 0.05%. An oxygen analyzer should be used to determine the oxygen content inside the pipe during purging. The below formula is used to achieve the required purging time: PT

=

(V/PGFR) x 4

V = vol. of pipe sect. to be purged, ft3 PGFR = purging gas flow rate, ft3/hr

Pre heating 

The min. preheat shall not be less than the greater of 10°C or recommended in ASME B31.3. Whenever ambient temp. is below 0°C then the recommendations given in particular code become requirements.



CS having a carbon content in excess of 0.32% or a CE>0.65% shall be preheated to the temp. indicated by the procedure.

5


If a weld joint is wet or has surface moisture or condensation, it shall be dried by heating for a dist. of 100 mm from the weld joint and shall be warm to the hand before welding unless a greater preheat is required.



Pipe that has been used in sour gas services shall be heated for at least 20 min at 400°F or higher to drive off any hydrogen in the metal. Heating shall be done just prior to welding. This heating should be in addition to and immediately preceding any pre heating specified in the we lding procedure.



Temp. indicating crayons, thermocouples or calibrated contact pyrometers shall be used to measure pre heat and interpass temp. Temp. indicating crayons shall not be used on any weld joint that is to be coated or that will have a heat shrink sleeve installed on it.



The preheat temp. shall be established over a min. distance of 75 mm on each side of weld.



If wall thk. exceeds 25 mm then preheating shall be done from the same side as the welding, and the heat source shall be removed for 1 min. to allow for temp. equalization prior to measuring the temp.

Welding 

Dissimilar metal welds (DMW) are defined as any weld joint (excluding weld overlays/strip lining) between ferritic steel and either austenitic SS, duplex SS or Ni based alloys. They shall be restricted as follows, Are not permitted for pressure containing welds in sour services. Are permitted for non-sour hydrogen services if made with Ni based consumables. Austenitic SS may be used only for following applications and if max. temp. is below 300°C, External structural attachments Non-sour, non-hydrocarbon (e.g. water) services Ni based consumables may not be suitable for direct exposure to sulfur or hydrogen-sulfur reducing environment at temp. exceeding 400°C due to possible sulfidation attack.



Any GMAW elect. to be used for procedures with impact toughness requirements and any SAW flux or FCAW elect. shall be restricted to the specific brand, type and max. size as used for PQR.



A change in filler metal or deposit chemistry from A-No.1 to A-No.2 and vice-versa is not permitted without approval. A change from A-No.1 to A-No.2 is not permitted for sour services applications without requalification.



The direction of welding for the vertical position shall be an essential variable. If the procedure is not qualified in the vertical position, then the direction of the welding shall be vertical up.



Procedure using any consumable with a “G” designation shall be restricted to the brand and type of elect. used for the PQR.



Deletion of backing in a single sided groove weld shall be c onsidered an essential variable.

6


Deletion of a backing gas purge or a change in the backing gas composition for a joint welded from a one side without backing m/t shall require requalification.



Special requirements for procedures requiring impact testing, The min. charpy impact value of P-No.1 Gr.1 m/t (including API 5L Gr B through X52) shall be 34/27 J and for Gr.2 shall be 40/32 J. If the PQR thk. exceeds 12 mm and multiple processes or consumables are used, separate impact test specimens shall be conducted for each process or consumable. The Heat input of each production weld must be calculated, if notch toughness tests are specified; HI (J/cm)





=

(V*I*60)/travel speed (cm/min)

The max. allowable SMAW elect. size that can be used are, Low hydrogen elect.

5 mm for 1G/1F position & 4 mm for all other position

Non low hydrogen elect.

5 mm for all position

The socket weld shall be at least two pass weld and with SMAW the max. permissible size of elect. is 3.2 mm.



Peening is not allowed unless specified. When peening is specified, the WPS shall include details of how it will be performed. Peening is prohibited on root and final (cap) pass.



Adjacent beads of a weld shall be staggered and not started in the same location.



GTAW, GMAW and Gas shielded FCAW shall not be used for field or yard fabrication unless adequate windshields are used. The wind velocity in the weld area for such applications shall not exceed 8 kph.



The min. distance between parallel butt welds and pressure containing welds (e.g. nozzles and other attachments) from other pr. containing welds by no less than 20 mm or three times the WT of the joint, whichever is greater. Radiography of butt welds is required for situations in which the min. separation is not achieved. These restrictions do not apply if one of the welds has been PWHTed prior to making the second weld or both welds have been PWHTed and inspected.



API Gr. X70 and higher require special stress corrosion cracking tests for sour services applications.



The min. distance (circumferential offset) between longitudinal welds (including spiral weld seams) of adjacent pipe joints shall be 100 mm.



For pipelines the working clearance shall not be less than 900 mm all around the pipe.



An internal line-up clamp shall be used if the pipe dia. is 16” or larger, except for tie-in welds or cements lined pipe. Special shoes must be used for internally coated pipe to ensure the coating is not damaged. For pipelines less than 16” dia., either internal or e xternal clamps may be used.



External line-up clamps may be used for pipe dia 16” or larger if approved by welding engr. with a condition that 100% radiography is performed to the production welds.



The internal clamps shall not be removed before completion of root bead. For external clamps, the root bead must be at least 50% complete prior to removal.



For pipelines greater than 16” dia. at least 2 welders shall be used, operating simultaneously and in

opposite quadrants.

7


For pipeline welding the second/hot pass shall be added as soon as possible after the completion of the root pass, but shall not exceed 5 min. for vertical down welding with cellulosic elect. or 15 min. for vertical up welding. If a production joint exceeds the specified time lapse, then MPI of the root pass shall be conducted and the joint preheated to 60°C min or the preheat specified in the procedure, whichever is greater, prior to making the hot pass. If the joint has been completed without MT of the root pass, then supplemental NDT of the joint, as specified by inspection, shall be conducted.



The hot pass shall be made while the pipe is still fully supported by the side boom tractor or supports.



The pipe shall not be lifted or moved or lowered into the ditch during partially welded joints .



The weld joint shall be completed within 24 hrs of starting. (for pipeline welding)



If welding is interrupted, the rate of cooling shall be controlled or other means shall be used to prevent detrimental effects in piping. The preheating specified in WPS shall be applied before welding is resumed.



Unless specified otherwise, the max. interpass temp. shall be 177°C for P-No.8, 315°C for P-No.1,3,4 & 5, 149°C for P-No. 6 and 177-232°C 177 -232°C for P-No. 10I (27 Cr steel).



When backing rings are used, they shall conform to t he following; Ferrous metal backing rings shall be of weldable quality. Sulfur content shall not excee d 0.05%. If there is a m/t difference between backing m/t and metal to be welded i.e. one of them is ferritic and another is austenitic then the satisfactory use of such m/t shall be demonstrated by PQR. Non ferrous and non metallic backing rings may be used provided the welding procedure using them is qualified.



The welding machine should be calibrated every 6 months.

PWHT 

The PWHT heating and cooling rates above 316°C shall not exceed 222°C/hr divided by weld thk. in inches, but in no case shall it be more than 222°C/hr.



The specified PWHT shall be applied over an area extending at least 3 times the thk. of m/t being welded from each edge of the weld but not less than 25 mm from each edge of weld whichever is greater.



For PWHT that are not permitted in a furnace, insulation shall be applied a min. of 300 mm on either side of the weld that is to be PWHTed. The insulation shall not be removed before the temp. has cooled to below 150°C. The ends of open lines shall be closed off in order to eliminate drafts or air circulation that could lowered the temp. on the inside surface of the joint unless the internal surface is also insulated.



Code exemptions for PWHT of ferritic m/t based on the use of austenitic or Ni-based elect. are not permitted.



Code exemptions for PWHT of P.No-4 & 5 m/t are not permitted for applications involving either sour service or m/t exceeding 1.5% nominal Cr content.



Any reduction in the PWHT below the normal holding temp. listed in B31.3 are not permitted.

8


The min. PWHT soak time shall be 1 hr. If hardness limits are specified, the soak time for production welds shall not be less than 80% of the PQR soak time unless specified.



All temp. within the heated zone for furnace or localized PWHT shall exceed the specified min. holing temp.



The actual temp. range for the soak period, as recorded by thermocouples shall not have a spread of more than 40°C.



The thk. for PWHT temp. is the thk. of the thicker component at the joint, except as follows; The thk. of reinforcement in the case of branch connection shall not be taken into account. Heat treatment is required however, when the thk. through the weld in any plane through the branch is greater than twice the min m/t thk. requiring heat treatment, even though the thk. of the components at the joint is less than the min. thk. In the case of fillet welds at slip-on and socket welding flanges and piping connections DN50 and smaller, for seal welding of threaded joints in piping DN50 and smaller, and for attachment of external non pr. parts in all pipe sizes heat treatment is required when thk. through the weld in any plane through the branch is greater than twice the min m/t thk. requiring heat treatment, even though the thk. of the components at the joint is less than the min. thk. But heat treatment is not required for P-No.1 m/t when weld throat thk. is 16 mm or less, regardless of base metal thk. and not required for P-No. 3, 4, 5 & 10A m/t when weld throat thk. is 13 mm or less, regardless of base metal thk., provided that not less than the recommended pre heat is applied, and the base m/t is of min tensile strength less than 71 ksi.



Welding or heating after the final PWHT is not permitted.



Welding or heating to joints that have been PWHTed requires re-PWHT prior to any hydro test. tes t.



For P-No. 10 (Cr-Cu Steel) cool as rapidly as possible after the hold period. For P-No. 10I cooling rate to 649°C shall be less then 56°C/hr, thereafter the cooling rate shall be fast enough to prevent embrittlement.



For P-No. 62 PWHT shall be applied within 14 days after welding.



PWHT shall be carried out using one or more of the following types of heat sources: Permanent or semi permanent furnaces using gas or oil or electric heaters. Electrical resistance heaters. Induction heaters.



If localized PWHT is used, the following min. no. of equally spaced recording T/C shall be used; D≤12”

1

12”
2

D>24”

4



Temp. recorders shall be calibrated every 3 months.



Only type K (Chromel – Alumel) or type J (Iron – Constantan) T/C are permitted.



CS having a carbon content in excess of 0.32% or a CE>0.65% or welds in all CS shall be stress relieved when the nominal WT>31.75 mm.



Stress relieving shall be performed at a temp. of 1100°F or greater for CS and 1200°F or greater for ferritic alloy steels.



Temp. recorders shall be calibrated every 3 months.

9

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION Inspection 

The hardness indentation shall be made at or near the middle of the deposited weld bead by the Brinel Hardness test method. 10% of the welds shall be sampled. The max. allowed hardness is 200 BHN. For pipeline welding the max. hardness for P-No.1 material is 225 BHN for non sour services and 200 BHN for sour services. If any reading exceeds the specified limit by no more than 10 BHN, then a min. of 3 additional indentations shall be made near the original high reading. If all 3 retests are below the specified limits, then the joint is acceptable. If any of the retest readings are found to exceed the specified limits, then the weld shall be considered unacceptable. If any welds are found unacceptable, then two additional welds from the same lot shall be tested. If more than one weld in a lot is found to be unacceptable, then all welds in that lot shall be tested.



Inspection of all welds shall include a bend of base metal at least 25 2 5 mm wide on each side of weld.



For P-No. 3, 4 & 5 m/t, examination shall be performed after completion of any heat treatment.



For a welded branch connection the examination of and any necessary repairs to the pr. containing weld shall be completed before any reinforcing pad or saddle is added.



For RT, fluorescent intensifying screens shall not be used. Only fluorescent metallic screens are permitted.



If the joint is required to be radiographed and radiography is not feasible, then UT & MT may be used in lieu of RT after getting approval. This does not apply if radiography r adiography is required by B31.3 or 31.8.



In MPT, permanent magnet yokes are not permitted. Prods are not permitted for use on air hardenable m/t or on m/t with impact testing requirements or on the fluid side surface of components in sour services.



All pr. containing welds, other than butt welds (including branch connections such as weldolets, sockolets and welding boses) shall be 100% examined.



All attachment welds on pressurized components that are not hydrotested after making the attachment weld shall be 100% examined.



Wire penetrameter in accordance with ASTM E747 may be used.



For B 31.8, the acceptance criteria is as per API 1104 for onshore, and API 1104 or ASME sect. VIII Div. 1 for sour services and offshore pipeline facilities.



For B 31.3, the acceptance criteria is as per given in table 341.3.2 in B 31.3. Any type of crack, LF, LOP & surface porosity or exposed slag is not allowed.



The max. height of reinforcement or internal protrusion for piping welding shall be; Wall thk. (mm)

Max. reinforcement (mm)

≤6

≤1.5

>6 , ≤13

≤3

>13, ≤25

≤4

>25

≤5

10


The max. root reinforcement acceptance criteria for pipeline welding shall be;

General

Internally coated



Max. reinforcement

Acceptable length

3mm or less

any

3 to 6 mm

25 mm max

Over 6 mm

none

2.5 mm or less

any

Over 2.5 mm

none

Onshore A min of 10% of the weld joints made each day shall be radiographed. If any joint found unacceptable then additional 10% is performed. If again any joint is found unacceptable then 100% radiography shall be done. An increase percentage of radiography is required if a higher percentage of radiographic coverage is established by either of the following methods: a) Lineal basis %RAD =

(318 x L)/(N x D)

L = total length of repairs, mm N= total no. of weld joints radiographed in one day D = pipe dia, mm The amount of RAD shall be rounded to the nearest amount divisible by 10. Any value ending in 5 shall be rounded up. b) Joint basis The following repair rates are calculated on a joint basis, i.e., the no. of joints requiring repairs divided by the total no. of joints radiographed that day. (i)

An increase to 50% RAD is required when the repair rate exceeds 30%. This increase shall be required for both the same day’s and the next day’s

production. (ii)

An increase to 100% RAD is required when the repair rate exceeds 50%. This increase shall be required for both the same day’s and the next day’s

production.

11


Offshore All welds on submarine and offshore pipelines, risers and associated spool pieces require 100% radiographed, except for open-non pr. vents and drains which shall be radiographed 10%.



Branch connections Welds shall be inspected by MPT. The min inspection rate shall be 10%, except for the clauses a to j (as per given for additional radiography) which shall be inspected 100%.



Additional radiography If additional radiography is required by these provisions, these radiographs shall not count towards the required radiographic coverage for the remaining joints of that day’s production. However, all of

the joints radiographed that day shall be used in calculating the repair rate and the required radiographic coverage for the following day. a) All welds of the first day’s production for a particular job or a min of the first 40 production joints, whichever is greater. b) The joint preceding and the joint succeeding a repaired weld, if previously not radiographed. c) The ten preceding and ten succeeding welds of a cracked weld, if previously not radiographed. d) All welds within 60 m of paved road, rail road and airport crossing. e) All welds over water, over tidal flats or within 30m of the shoreline. f)

All welds that can’t be hydrostatically tested.

g) All hook-up or tie-in welds. h) All expansion loop fitting welds.



i)

All repair welds

j)

All welds in class 3 or 4 locations.

PMI (Positive Material Identification): o

For welding consumables, one consumable from each lot shall be PMI tested.

o

PMI testing of weld is an acceptable alternative to PMI testing of consumable provided it is conducted immediately prior to or during welding.

o

X-Ray Fluorescence Spectrometer is quite often used for PMI. But because of inherent limitations of XRF, it is not possible to detect all elements. Elements lighter than sulfur can not be detected using portable XRF spectrometers. Therefore this technique can’t be used to

detect carbon. o

Optical Emission Spectrograph may be used to check for all the required elements, including carbon. A hot work permit may be required before using this equipment. Any burn damage resulting from the usage of the emission spectrograph shall be removed by grinding.

o

Acceptance criteria: alloys shall be acceptable if the alloying elements are each within 10% of specified range of values. Welds with consumables that match, or nearly match, the base metal composition shall be within 12.5% of the ranges allowed in ASME sect . II part C.

Repair 

Welds may be repaired twice at any defect location.

12


Repair of cracks that are fabricated related or welding consumables or base metal and are of less than 8% of total weld length shall require the approval. Crater cracks do not require special repair and shall be ground out only.



In process repairs (i.e. repairs performed prior to completion of the joint using the same welding procedure as for the original fabrication) during production do not require a separate repair procedure except for cracks.



For offshore pipeline girth welding the repair criteria is limited as,



full thk. repair openings shall be limited in length to 25% of the pipe dia. Partial thk. repair excavations less than 50% of the WT shall be limited in length to 30% of the pipe dia.

Welding of Special Corrosion Resistance Materials 

This is defined as SS and Ni based alloys for piping in severe corrosion and high temp. service (above 427°C).



The WPQ and production welds for austenitic SS, except type 310, shall include a determination of the Fettire No. in the as-welded condition. The Ferrite no. shall be between 3 to 10.



The GTAW process shall be used for the following applications; The root pass of single sided groove welds without backing. For all passes for piping, tubes and nozzles of 1 ” nominal dia or less. For all passes for wall thk. less than 9.5 mm for duplex SS or for WT less than 6.5 mm for other corrosion rest. alloys.



All manual GTAW shall use a high frequency start and post-purge gas flow for the torch.



For all GTAW welding, filler metal shall be used.



The max. interpass temp shall not exceed 100°C.



The purge time for the backing gas shall be calculated to give a theoretical volume charge of 6 times the enclosed pipe vol. The purge shall achieve actual oxygen levels inside or existing the joint (via the vent) no greater than 0.05% prior to and during welding.



A min of 4 equi-spaced tacks around a pipe circumference shall be used. Either root tacks or bridge tacks are permitted. Root tacks must be either feathered or ground out prior to making the root pass.



The continuous feed technique shall be used for the root pass.



Stringer beads shall be used. Minor arc oscillations to ensure sidewall fusion is permitted.



Whenever the welder stops welding, the welding current shall be gradually decreased by use of the remote current control. The torch shall be held in position close to the weld pool until the gas shielding post purged flow is completed.



Grinding of all starts/stops is required.

13


Ferrite content of the weld metal shall be measured, unless the weld metal is Ni based. The ferrite range must be within 35 to 60% as measured by metallographic methods. Min ferrite content should be 50% for service that have potential for chloride stress cracking. The fabricator shall establish a correlation between the % ferrite and FN (as measured using AWS 4.2). Ferrite measurements using both methods shall be recorded on the PQR.



Corrosion testing to ASTM G48, using method A (pitting test) at 35°C for 72 hrs shall be performed. No pitting or crevice corrosion in either the weld metal or HAZ is permitted.



Charpy impact testing shall be conducted on the weld metal and HAZ at a test temp of -20°C. The min charpy impact value shall be 34/27 J for full size (10mm x 10mm) specimen.



The heat i/p shall be restricted to a min and max. value. If a single PQR is used the WPS heat i/p shall be limited to ±10% of actual PQR value.

STORAGE, CONDITIONING AND EXPOSURE OF CONSUMABLES

DRYING STORAGE EXPOSURE

RE DRYING

LOW HYDROGEN ELCT. (A 5.1) 260°-430°C for 2 hrs. min 120°C min May not be exposed to atmosphere more than 4 hrs. The exposure may be extended to 8 hrs. if the elect. are continuously stored in a portable oven at 65°C min

Elect. exposed in excess of the permitted time period must be re dried. Elect. may be re dried only

LOW HYDROGEN ELCT. (A 5.5) 370°-430°C for 2 hrs. min 120°C min May not be exposed to atmosphere more than 2 hrs for E70XX & E80XX and 30 min for any higher strength elect. The exposure may be doubled (to 4 hrs and 1 hr respectively) if the elect. are continuously stored in a portable oven at 65°C min Elect. exposed in excess of the permitted time period must be re dried. Higher strength elect.

14

SS & NON FERROUS ELECT. 120°-250°C for 2 hrs. min 120°-200°C May not be exposed to atmosphere more than 4 hrs. The exposure may be extended to 8 hrs. if the elect. are continuously stored in a portable oven at 65°C min

Elect. exposed in excess of the permitted time period must be re dried. Elect. may be re dried only

NON LOW HYDROGEN ELECT. The elect. shall be stored in dry environment.

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION once.

must be re dried once. after any atmospheric exposure. Elect. may be re dried only once. RE CONDITIONING Elect. exposed to Elect. exposed to Elect. exposed to atms. for less than atms. for less than atms. for less than permitted time permitted time permitted time may be returned may be returned may be returned to a oven to a oven to a oven maintained at maintained at maintained at 120°C min. After a 120°C min. After a 120°C min. After a min. holding min. holding min. holding period of 4 hrs. at period of 4 hrs. at period of 4 hrs. at 120°C the elect. 120°C the elect. 120°C the elect. may be re used. may be re used. may be re used. The drying steps for E70XX and E80XX may be deleted if the elect. are supplied in the dried condition in hermetically sealed metal can/vacuum sealed package. Electrode that have become wet or moist shall not be used and shall be discarded. The consumables for SAW, GTAW, GMAW/FCAW shall be stored in a dry place.

15


Welding Inspection Check list Points Pre welding inspection a) Review of drawings & specifications. b) Check qualification of procedures and personnel to be used. c) Review of material test certificates. d) Check for base metal discontinuity. e) Weld no. is marked adjacent to the weld joint and verified to confirm with the weld map. f)

An approved WPS to be used is available at the weld site.

g) Weld joint confirms with the weld joint details of the approved WPS. (Base m/t, thk., bevel type, root gap) h) Internal misalignment of butt welds shall not exceed 1.5 mm. i)

Oil, moisture, scale, rust, paint or other foreign matter has been removed from the weld surface and at least 25 mm of the adjacent base metal surface prior to welding.

j)

Irregular edges/thermal cut surfaces are ground or machined to bright metal prior to welding.

k) Thermally cut or gouged surfaces for all m/t have been power brushed or ground prior to welding. l)

A min of 1.5 mm depth has been removed by grinding/machining from thermally cut or gouged surface for air hardenable m/t (Cr Mo steels).

m) SS and non ferrous m/t have been cleaned with grinding wheels or SS brush not previously used on other m/t. n) Re-cut or re-beveled fittings, have surfaces examined for laminations before welding. o) Temporary attachments or back-up strips have been made from compatible m/t. No rebar or galvanized steel is used. p) Tack welds are made by qualified welder.

16

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION q) All tacks or temporary welds shall be performed with the same care, m/t, elect, min preheat and procedures that are used for permanent weld. r)

Tack welds shall be of sufficient size to maintain joint alignment; 3.2-4.8 mm thk. and 12.5-25.4 mm long

s)

t)

Min no. of tack welds are,

D≤4”

3 equally spaced

D>4”

min four equally spaced

Tack welds that are to be incorporated into the final weld shall be thoroughly cleaned, prepared at each end and inspected for cracks. Any cracked tack shall be removed before welding the joint.

u) Bridging tacks (located above the root area) are made completely within the weld groove and shall be completely removed prior to completion of the weld. v) As the thumb rule the min dist. between adjacent butt welds is 1D or 1 ½” whichever is greater to prevent the overlapping of HAZ. And min dist. between circumferential welds between centerlines shall not be less than 4 times the WT or 25 mm whichever is greater. w) Calibration of equipments; General purpose equipments:

all parameters should be ±10%

For automatic or automated equipment parameters should be ±2.5% for current and wire feed speed, ±5% for voltage and temp. reading equipments i.e. thermocouples, ±20% for gas flow rate.

In process welding inspection 1. Joint Preparation & Cleanliness

The same points a, b, e, & i that of pre weld inspection. Furthermore coated and clad or overlaid surfaces are protected from the welding arc, associated weld spatter and damaged from ground clamps or other associated equipments. 2. General

a) Wind velocity in weld area for GTAW, GMAW or Gas shielded FCAW shall not exceed 8 kph. b) For field welding remote current control shall be used if the welding is more than 30 m from the welding power source or when the welders are working in ‘remote’ locations (e.g. on an elevated

pipe rack). c) Filler metal size, type and classification confirms with the approved WPS. d) Storage, handling of consumables are done as per recommendation. 3. Pre heat

a) Wet or damp weld joints are dried by heating to a dist. of 100 mm from the toe, and are hand warm before welding. b) The pre heat temp. shall be established over a min dist of 75 mm on each side of weld. c) Min pre heat temp. is 10°C or specified by code.

17

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION d) On WT exceeding 25 mm, preheat is done from the same side as the welding and heat source removed for 1 min prior to measuring the temp. 4. Back Purging & Shielding Gas

a) Inert gas is used for GTAW or GMAW root pass on single sided groove welds, on ASME P-No.5 and higher. b) For P-No.5 and higher m/t back purging is maintained until at least 10 mm of the weld deposit thk. is completed. c) Nitrogen as a backing gas for austenitic SS is prohibited. d) Back purge for carbon and low alloy steel has reduced the oxygen level to below 1% and for SS & Ni based alloys below 0.05%. 5. Root pass

a) The direction of welding conforms with WPS. b) The GTAW process shall be used for the root pass of butt welds without backing in piping and nozzles of 50.8 mm nominal dia. and less. GTAW shall also be used for root pass when the consumables are SS or Ni based alloys. 6. Hot pass & Weld out

a) The direction of welding conforms with the WPS. b) Each weld, weld pass is thoroughly cleaned and all slag or other foreign matter removed before the next pass is deposited. c) SAW flux fused during welding shall not be reused. d) The max allowable SMAW elect. size that can be used are; Low hydrogen elect.

-

5 mm for 1G/1F position, 4 mm for all other positions

Non low hyd. elect.

-

5 mm for all positions

e) The heat i/p of each production weld is calculated. f)

Adjacent weld beads shall be staggered and not started from the same location.

g) Unless specified otherwise the max interpass temp.; 177°C for P-No.8 315°C for P-No.1 to 5 7. During the entire welding process the checking of variables i.e. current, voltage & welding speed.

Post welding inspection 1. General

a) All slag, flux and spatter is removed from the completed weld and surrounding weld. b) All arc strikes, gouges and other surface imperfections are removed by grinding. c) Temporary attachments have been cut off no closer than 3 mm to the base metal, then ground flush. d) Grinding does not reduce the base metal thk. than the design thk.

18

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION e) Where temporary welds were removed, base metal repairs made, or arc strikes repaired by grinding, examined by MT or PT has been carried out. f) All weld joints are marked for identification by a weld no. and a welder symbol. g) Surface irregularities, including weld reinforcement, which inhibit accurate interpretation of the specified method of NDT (including VT) are ground out. h) Inspection of all welds include a band of base metal at least 25 mm wide on each side of the weld. i) Visually inspection finished weld for weld appearance and to confirm that ht. and width of reinforcement and technique of cap (multi pass or weave) comply with WPS. 2. PWHT

a) Post Weld Heat Prior to the start of work the contractor or fabricator has prepared a table listing each joint or component requiring heat treatment. b) The table includes the following information for each joint or component: location, drawing number, diameter, wall thickness, material, heating rate, cooling rate, soak temperature, and soak time. c) PWHT heating and cooling rates > 316 degrees C shall not exceed 222 degrees C/hr. divided by the weld thickness in inches, but in no case is it > 222 degrees C/hr. d) The specified PWHT is applied over an area extending at least three times the thickness of the material being welded from the weld toe, but not < 25mm from the weld toe, which ever is greater. e) If localized PWHT is used, the following minimum numbers of equally spaced thermocouples (T/C) are used: Pipe diameter of 305mm or less: 1(T/C). Pipe diameter > 305mm and up to and including 610 mm: 2 (T/C). Pipe diameter > 610mm: 4(T/C). f) Temperature recorders are calibrated every three months. Current calibration sticker details are maintained. g) Only Type K (Chromel - Alumel) or Type J (Iron-Constantan) thermocouples are used. h) Prior to the start of PWHT, components are checked to ensure all restraints are removed, and that the component is free to expand and contract and that suitable and sufficient supports are used. i) Machined surfaces such as flange faces, threaded bolt holes, threads, etc., are protected from oxidation during the heat treatment process by coating with deoxaluminite, or other approved suitable material. j) When PWHT is not performed in a furnace, a minimum of 300 mm insulation is applied on either side of the weld. The insulation is not removed before the temperature has cooled below 150 degrees C. The ends of open lines are closed off to eliminate drafts. k) The min soak time for PWHT is 1 hr/inch. Hold time shall be increased by each ½ hr for each 25 mm increase after 25 mm WT. l) After PWHT all thermocouples are removed, the attachment is ground smooth to clean sound metal. m) The PWHT shall be applied within 14 days after welding.

19


ACCEPTANCE CRITERIA FOR INSPECTION OF BARE LINE PIPES AS PER API 5L Brief description of this specification is explained here; Scope:

Applicable to Petroleum & Natural gas systems, sour & offshore services

Two basic levels of standard technical requirements for line pipes: PSL (Product Specification Level) 1: provides a standard quality levels for line pipe PSL 2: has additional mandatory requirements for chemical composition, notch toughness and strength properties and additional NDE.

Inspection

Pipe length Cold expansion Skelp width for helical seam pipe Undercuts

11.7-12.7 mtr 0.5-3.0% X OD 0.3-1.5 X OD

Laminations in bevel face Straightness Weld reinforcement

Exceeding 6.4 mm is defect

Misaligned welds

Not cause for rejection provided within: t≤20 mm: 3 mm

a) depth≤0.4 mm acceptable – any length b) 0.8>d>0.4 mm acceptable with indiv. length ≤0.5t & max 2 in 300 mm – removed by grinding

Not to exceed 0.2% length & ≤4 mm within 1m from pipe end t≤13 mm: 0-3.5 mm t>13 mm: 0-3.5 mm ID & 0-4.5 mm OD

20

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION t>20mm : 4 mm & provided NDT confirms complete penetration and fusion Radial offset of strip/plate edges

t≤15 mm: 1.5 mm 25≥t>15: 0.1 t t>25 : 2.5 mm

Burn through RT density

Not allowed Density of radiograph shall not be less than 2.0 and the density through the thickest portion of the weld shall not be less than 1.5 Destructive testing TS ≥ min TS for grade The test piece shall not, a) Fracture completely b) Weld crack/rupture>3.2 mm long & any depth c) Parent metal/HAZ/fusion line crack/rupture>3.2 mm long & >12.5%t deep though edge cracks>6.4 mm long

Tensile test Bend test

CVN test DWTT

Essential Variables

27 J at temp. 0°C or lower & average shear area≥85% for each test Average shear area≥85%/test unit at temp. 0°C or lower Manufacturing process qualification Test per Table-18 of API 5L as applicable at start of production

Welding process Pipe material

∆ process ∆ method ∆grade category

a) ≤X42 b) X65≥Gr>X42

c) 0.03% of material qualified ∆ filler metal classification Welding materials: ∆ consumable brand name (if CVN required) ∆ electrode dia. ∆ composition of shielding gas ∆ shielding gas flow rate ∆ SAW flux designation Welding parameters: ∆ current type (AC to DC) ∆ polarity ∆I>10%, ∆V>7%, ∆Speed>10% ∆ weld bead width>50% ∆ Pre/post-weld heat treatment

Welder qualification

Qualification by API 5L or ASME IX Operator qualified on one grade is qualified on any lower grade provided same weld process

21

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION Tests Repair weld procedure qualification

all tests as per given in inspection with same acceptance criteria Repair of weld per API 5L or ASME IX Repair length<5% of total weld length Weld defects separated by less than 100 mm shall be repaired as a continuous single weld repair Each single repair shall be carried out with a min of two layers/passes over a min length of 50 mm.

BRIEF DISCRIPTION ABOUT CODES: ASME IX, VIII & API 1104 ASME SECT . IX Welding qualifications to ASME 9 are for use with the ASME boiler and pressure vessel code or the ASME pipe work codes. Advantages of ASME welding procedures are: 1) All joint types approved each other, i.e., a double sided weld approves a single sided weld and vice versa. 2) No limits on dia. approval for pipe. A plate procedure can be used to weld any dia. of pipe. 3) Any butt weld will qualify all fillet weld sizes on any parent metal thk. 4) A welding procedure qualified in one position approves all positions unless impact tests are required then only a vertical up approves all positions. Advantages of ASME welder approval tests are: 1) There is no min parent metal thk., only max., and they are applied to the deposited thk. of the weld not the parent metal thk. 2) There is no upper limit on dia. approval for pipe, only a lower limit. 3) Any butt weld approval will qualify all fillet weld sizes on any parent metal thk. o

P - NUMBER GROUPING: P1 TO P11

STEEL & STEEL ALLOYS

P21 TO P25 AL & AL BASE ALLOYS P31 TO P35 CU & CU BASE ALLOYS P41 TO P47 NI & NI BASE ALLOYS P51 TO P53 TI & TI BASE ALLOYS P61 TO P62 ZI & ZI BASE ALLOYS

22

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION P No.

Base Metal

Carbon Manganese Steels, 4 Sub Groups 

1

  

Group 1 up to approx 65 ksi Group 2 Approx 70ksi Group 3 Approx 80ksi Group 4 ?

2

Not Used

3

2 Sub Groups:- Typically 1/2Mo and 1/2Cr-1/2Mo

4

2 Sub Groups:- Typically 1Cr-1/2Mo and 1 1/4Cr-1/2Mo

5A

Typically 2 1/4Cr-1Mo

5B

3 Sub Groups:- Typically 5Cr-1/2Mo, 7Cr-1/2Mo & 9Cr-1Mo

5C

5 Sub Groups:- Chrome moly vanadium

6

6 Sub Groups:- Martensitic Stainless Steels Typically Grade 410

7

Ferritic Stainless Steels Typically Grade 409 Austenitic Stainless Steels, 4 Sub groups 

8

  

9A, B, C

Group1 Typically Grades 304, 316, 347 Group 2 Typically Grades 309, 310 Group 3 High manganese grades Group 4 Typically 254 SMO type steels

Typically two to four percent Nickel Steels

10A,B,C,F,G Mixed bag of low alloy steels, 10G 36 Nickel Steel 10 H 10J

Duplex and Super Duplex Grades 31803, 32750 Typically 26 Chrome one moly

11A Group 1 9 Nickel Steels 11 A Groups Mixed bag of high strength low alloy steels. 2 to 5 11B 12 to 20

10 Sub Groups:- Mixed bag of high strength low alloy steels. Not Used

21

Pure Aluminium

22

Aluminium Magnesium Grade 5000

23

Aluminium Magnesium Silicone Grade 6000

24

Not Used

25

Aluminium Magnesium Manganese Typically 5083, 5086

26 to 30

Not used

23

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION 31

Pure Copper

32

Brass

33

Copper Silicone

34

Copper Nickel

35

Copper Aluminium

36 to 40

Not Used

41

Pure Nickel

42

Nickel Copper:- Monel 500

43

Nickel Chrome Ferrite:- Inconel

44

Nickel Moly:- Hastelloy C22, C276

45

Nickel Chrome :- Incoloy 800, 825

46

Nickel Chrome Silicone

47

Nickel Chrome Tungstone

47 to 50

Not Used

51, 52, 53

Titanium Alloys

61, 62

Zirconium Alloys

F – NUMBER GROUPING:

o

F General Description Number 1

Heavy rutile coated iron powder electrodes :- A5.1 : E7024

2

Most Rutile consumables such as :- A5.1 : E6013

3

Cellulosic electrodes such as :- A5.1 : E6011

4

Basic coated electrodes such as : A5.1 : E7016 and E7018

5

High alloy austenitic stainless steel and duplex :- A5.4 : E316L-16

6

Any steel solid or cored wire (with flux or metal)

2X

Aluminium and its alloys

3X

Copper and its alloys

4X

Nickel alloys

5X

Titanium

6X

Zirconium

7X

Hard Facing Overlay

o

A – NUMBER GROUPING:

24


A1

Plain unalloyed carbon manganese steels.

A2 to A5 Low alloy steels containing Moly and Chrome Moly A6

Chrome- Martensitic

A7

Chrome- Ferritic

A8 to A9 Chrome – Ni (Austenitic stainless steels such as type 316) A10

Ni upto 4%

A11

Mn – Mo

A12

Ni – Cr - Mo

o

PROCEDURE Q UALIFICATION FOR GROOVE WELDS – PLATE THE TEST PLATE WELDING IS USUALLY CARRIED OUT IN THE FLAT POSITION ONLY . A BUTT OR GROOVE WELD APPROVES BRANCH AND FILLET WELDS BUT NOT THE VICE VERSA

.

PRESSURE RETAINING BRANCH WELDS MUST BE QUALIFIED BY GROOVE WELDS . A TEST IN ONE P -NO . APPROVES ALL M /T LISTED UNDER THAT P-NO ., EXCEPT WHERE IMPACT TESTS ARE REQUIRED THEN APPROVAL IS RESTRICTED TO M /T LISTED IN THE GROUP NO. WITHIN P -NO . NOTE P 5,

9 & 10 ARE DIVIDED INTO SUB GROUPS I .E. 5A, 5B, ETC . TREAT EACH SUB GROUP LIKE A SEPARATE P -

NO . NOTE S -NO . ARE FOR PIPE WORK TO B -31. A P- NO . COVERS AN S -NO . BUT NOT VICE VERSA . WHEN IMPACT TESTS ARE REQUIRED THE MIN THK . APPROVED IS RESTRICTED . THE THK .’ t ’ OF DEPOSITED WELD METAL FOR EACH PROCESS INVOLVED IS APPROVED FROM

0 TO 2t EXCEPT ;

MIG /MAG (GMAW/FCAW ) DIP TRANSFER WELD OF DEPOSITED THK . LESS THAN ½” APPROVES MAX . THK . OF

1.1 t ONLY. IF ANY PASS IN A SINGLE OR MULTI PASS WELD>1/2” THAN THE THK . APPROVED EQUALS TO

1.1t.

FOR DISSIMILAR THICKNESS THE THICKER AND THINNER PART MUST BE QUALIFIED , EXCEPT P 8 AND P4X THE THINNER PART CAN BE QUALIFIED IF NO IMPACTS AND TEST COUPONS >6 MM .

WHEN MORE THAN ONE WELDING PROCESS OR FILLER METAL IS USED TO WELD A TEST COUPON , THE DEPOSIT WELD METAL THICKNESS OF EACH PROCESS AND FILLER METAL WOULD BE RECORDED .

PREPARATION OF TEST JOINT : METHOD OF TAKING TEST SPECIMENS FROM PLATE & PIPE:

25


26


T HE RECOMMENDED PIPE SIZE IS 5” IN DIAMETER AND 9.57 MM IN WT, ALTHOUGH LARGER PIPE SIZE MAY BE USED .

SMALLER PIPE SIZE MAY BE USED , BUT IN SUCH CASES THE PROCEDURE MUST BE QUALIFIED FOR

THICKNESS BET

½ AND TWO TIMES THE WT OF TEST PIPE , BUT NOT OVER 19.05 MM .

T HE TYPE AND NUMBER OF TEST SPECIMENS , RANGE OF THICKNESS QUALIFIED FOR PROCEDURE QUALIFICATION ARE SHOWN IN FOLLOWING TABLES ;

T HICKNESS ( T) OF TEST COUPON

(MM ) LESS THAN 1.58 1.58 TO 9.57 INCLUSIVE OVER 9.57 & LESS THAN 19.05 19.05 TO LESS THAN 38.01 38.01 & OVER

T HICKNESS ( T) OF TEST COUPON

(MM ) LESS THAN 1.58 1.58 TO 9.57 INCLUSIVE OVER 38.01

RANGE OF THICKNESS Q UALIFIED (MM ) MAX . MIN . (6) (1,3,6) T 2T 1.58 2T (2)

TYPE AND NUMBER OF TESTS REQUIRED TENSION 2 2

TRANSVERSE BEND TESTS (4) SB FB RB 2 2 2 2

4.76

2T

2

-

2

2

4.76 4.76

2T 8

2 2

4 (4) 4

-

-

”

RANGE OF THICKNESS Q UALIFIED (MM ) MAX . MIN . (6) (1,3,6) T 2T 1.58 2T 4.76 2T

TYPE AND NUMBER OF TESTS REQUIRED TENSION 2 2 2

LONGITUDINAL BEND TESTS (5) FB RB 2 2 2 2 2 2

THE NOTES TO TABLES ARE ESSENTIAL TO THE USE OF THE TABLES . THE APPLICABLE NOTES ARE : 1) THE MAXIMUM THICKNESS QUALIFIED IN GAS WELDING IS THE THICKNESS OF THE TEST PLATE OR PIPE .

27

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION 2) THE MAX . THICKNESS QUALIFIED FOR PIPE SMALLER THAN 5” IS TWO TIMES THE THICKNESS OF THE PIPE WALL BUT NOT MORE THAN

19.05MM.

3) FOR SAW AND GMAW, THE THICKNESS LIMITATION FOR PRODUCTION WELDING , BASED ON PLATE THICKNESS T , SHALL BE AS FOLLOWS ;

(a)

FOR SINGLE PASS WELDING WITH NO BACKING STRIP OR AGAINST A METAL OR CERAMIC ( FLUX ) BACKING , THE MAXIMUM THICKNESS WELDED IN PRODUCTION SHALL NOT EXCEED THE THICKNESS OF THE TEST PLATE OR PIPE WALL .

(b)

IF THE TEST PLATE IS WELDED BY A PROCEDURE INVOLVING ONE PASS FROM EACH SIDE , THE MAXIMUM THICKNESS THAT MAY BE WELDED IN PRODUCTION SHALL BE 2T, WHERE 2 T SHALL NOT EXCEED 2”. IF SECTION HEAVIER THAN 2” ARE TO BE WELDED IN PRODUCTION , A SEPARATE TEST PLATE SHALL BE PREPARED WITH THE THICKNESS NOT LESS THAN THE THICKNESS TO BE USED IN PRODUCTION .

(c)

FOR MULTIPLE PASS WELDING , THE THICKNESS LIMITATIONS IN TABLES ARE APPLY .

4) EITHER FACE AND ROOT BENDS OR SIDE BENDS MAY BE USED FOR THICKNESSES FROM 9.57 MM TO 19.05 MM .

5) LONGITUDINAL BEND TESTS MAY BE USED IN LIEU OF TRANSVERSE BEND TESTS ONLY FOR TESTING MATERIAL COMBINATIONS DIFFERING MARKEDLY IN MECHANICAL BENDING PROPERTIES BETWEEN

(A) THE TWO BASE

MATERIALS OR (B ) THE WELD METAL AND BASE MATERIALS .

6) FOR QUENCHED AND TEMPERED STEELS (TENSILE STRENGTH 95,000 PSI OR HIGHER ) OF THICKNESSES LESS THAN

15.87 MM, THE THICKNESS OF TEST PLATE OR PIPE IS THE MINIMUM THICKNESS QUALIFIED . F OR TEST

PLATES OR PIPE RECEIVING A

PWHT IN WHICH THE LOWER CRITICAL TEMP . IS EXCEEDED , THE MAXIMUM

THICKNESS QUALIFIED IS THE THICKNESS OF THE TEST PLATE OR PIPE .

Tensile test:

28


TENSION – REDUCED SECTION FOR PLATE/PIPE

The tensile strength must not be less than, 1) THE MINIMUM STRENGTH SPECIFIED FOR THE BASE MATERIAL . 2) THE MINIMUM SPECIFIED FOR THE WEAKER OF THE TWO , IF MATERIAL OF DIFFERENT SPECIFIED MIN . TENSILE STRENGTHS ARE USED .

3) THE MIN . SPECIFIED FOR THE WELD METAL WHERE THE WELD METAL HAS LOWER ROOM TEMP . STRENGTH THAN THE BASE METAL .

29

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION IF THE SPECIMEN BREAKS IN THE BASE METAL , THE TEST SHALL BE ACCEPTABLE IF THE TENSILE STRENGTH IS NOT MORE THAN

5% BELOW THE MIN . SPECIFIED FOR THE BASE METAL .

BEND TEST :

30


BEND SPECIMEN PASSES IF ANY CRACK OR OTHER OPEN DISCONTINUITY DOES NOT EXCEED 3.17 MM AFTER BENDING THROUGH AN ANGLE OF

180°. CRACKS AT CORNERS ARE NOT CONSIDERED unless there is evidence

of slag inclusions or other internal discontinuities. THE TESTING REQUIREMENTS FOR FILLET WELDS ON PLATE IS

5 MACRO SECT . ONLY. FOR PIPE FILLET WELDS 4

MACRO SECT . NO FRACTURE TEST REQUIRED .

Brief summary of variables: Legends:

Ø Change

> Increase

+ Addition

- Deletion

Uphill

Downhill

1) QW-402 (J OINT DESIGN ) Ø -

GROOVE DESIGN

ALL ARE NON ESSENTIAL VARIABLES

BACKING

(+ BACKING ONLY FOR GTAW) Ø

ROOT SPACING

+

RETAINERS

31


2) QW-403 (B ASE METAL ) NON ESSENTIAL VARIABLES : Ø

DIAMETER IN THE CASE OF PIPE

ESSENTIAL VARIABLES : Ø

T QUALIFIED ( REFERENCE : TABLE 451.1 & 451.2)

Ø

P NO .

>1/2” T (INCREASE IN WELD DEPOSITION THICKNESS BEYOND 13 MM)

SUPPLEMENTARY ESSENTIAL VARIABLES : Ø

GROUP NO.

3) QW-404 (F ILLER METAL ) NON ESSENTIAL VARIABLES : +

CONSUMABLES /I NSERT (ONLY FOR GTAW)

E SSENTIAL VARIABLES : Ø

F NO .

Ø

A NO .

Ø

T (REFERENCE : TABLE

+

FILLER (ONLY FOR GTAW)

451.1 & 451.2)

Ø>10% MORE THAN 10% CHANGE IN VOLUME OF FILLER METAL Ø

RECRUSHED SLAG


AWS CLASSIFICATION

Ø>6 MM DIAMETER ( CHANGE IN DIA. MORE THAN 6MM ONLY FOR SMAW)

4) QW-405 (P OSITION ) NON ESSENTIAL VARIABLES : +

POSITION VERTICAL WELDING


POSITION (A CHANGE FROM ANY POSITION TO THE VERTICAL POSITION

PROGRESSION E .G. 3G,

5G OR 6G)

5) QW-406 (P REHEAT )

32

UPHILL

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION NON ESSENTIAL VARIABLES : Ø

TEMP . FOR PREHEAT MAINTENANCE

ESSENTIAL VARIABLES : <100°F DECREASE IN PRE HEAT TEMP . GREATER THAN 100°F SUPPLEMENTARY ESSENTIAL VARIABLES : >100°F INCREASE IN PRE HEAT TEMP . GREATER THAN 100°F 6) QW-407 (PWHT) ESSENTIAL VARIABLES : Ø

TEMP . OF PWHT

7) QW-408 (G AS ) NON ESSENTIAL VARIABLES : Ø

FLOW RATE

+/Ø

BACKING FLOW


SINGLEMIXTURE

8) QW-409 (E LECTRICAL CHARACTERISTIC ) NON ESSENTIAL VARIABLES : Ø

CURRENT & POLARITY (AC DC, DC+V EDC-VE)

Ø

I & E RANGE (CHANGE WITHIN RANGE I .E. + 15%)


TRANSFER MODE (S PRAY/GLOBULAR /PULSE ARC SHORT CIRCUIT )

SUPPLEMENTARY ESSENTIAL VARIABLES : >10%

HEAT INPUT (I NCREASE IN MORE THAN 10%)

9) QW-410 (T ECHNIQUE ) NON ESSENTIAL VARIABLES :

33

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION Ø

STRING WEAVE

Ø

METHOD OF CLEANING

Ø

METHOD OF BACK GOUGE

Ø

MANUAL AUTOMATIC

Ø

PEENING

Ø

TUBE -WORK DISTANCE

Ø

ELECTRODE SPACING


CLOSED TO OUT OF CHAMBER (ONLY FOR

GTAW)


SINGLEMULTIPLE ELECT .

Ø

SINGLEMULTI PASS

(B OTH ARE NOT APPLICABLE IN CASE OF PWHT WHERE LOWER CRITICAL TEMP . EXCEEDED )

o

PERFORMANCE Q UALIFICATION TEST FOR GROOVE WELDS NOTE A SINGLE SIDED WELD IS CLASSED AS A WELD WITHOUT BACKING AND A DOUBLE SIDED WELD OR WELD WITH SEALING RUN IS CLASSED AS A WELD WITH BACKING. THE F- NO. CAN’T BE CHANGED WITHOUT REQUALIFICATION EXCEPT THAT FOR PERFORMANCE QUALIFICATION ONLY USING SMAW F-NO. UP TO AND INCLUDING 4 APPROVES ALL LESSER FNO FOR DOUBLE SIDED OR WELDS WITH BACKING ONLY. NOTE ‘A’ NO . DO NOT APPLY TO WELDER APPROVAL TESTS.

THE THK. LIMIT ONLY APPLIES TO THE DEPOSITED WELD METAL THK. NOT THE PLATE THK. AND ANY GROOVE WELD APPROVES ALL FILLET WELD SIZES. FOR T>13 MM THERE IS NO RESTRICTION ON THE SIZE THAT CAN BE WELDED. (PROVIDING THE TEST WELD DEPOSIT CONTAINS AT LEAST 3 LAYERS OF WELD) JOINT GEOMETRY, A DOUBLE V (OR U) IS CONSIDERED THE SAME AS A JOINT WITH BACKING AND DOES NOT QUALIFY A SINGLE V (OR U) WITHOUT BACKING, BUT A SINGLE FULL PENETRATION JOINT WITHOUT BACKING QUALIFIES ALL JOINT CONFIGURATION.

THE

CODE PROVIDES THAT THE WELDER WHO PREPARES THE WELDING PROCEDURE QUALIFICATION TEST

SPECIMENS MEETING THE REQUIREMENTS OF THE CODE IS THEREBY QUALIFIED WITHOUT FURTHER TESTING.

WELDERS THICKNESS .

QUALIFIED ON GROOVE WELDS ARE AUTOMATICALLY QUALIFIED FOR FILLET WELDS IN ALL

WELDERS QUALIFIED ON FILLET WELDS ONLY ARE QUALIFIED TO MAKE FILLET WELDS ONLY .

34

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION THE BASE MATERIAL FOR THE TEST SPECIMENS MAY BE EITHER PLATE OR PIPE. THE MINIMUM NOMINAL DIA . OF

5” IS RECOMMENDED FOR PIPE USED AS BASE MATERIAL.

THE

DIMENSIONS OF THE WELDING GROOVE FOR THE TEST JOINT USED IN MAKING WELDER

QUALIFICATION TESTS , ON DOUBLE WELDED BUTT JOINTS AND SINGLE WELDED BUTT JOINTS WITH BACKING STRIP, SHALL BE SAME AS THOSE FOR PROCEDURE QUALIFICATION.

35


Q UALIFICATION ON A SINGLE WELDED PLATE WITH A BACKING STRIP SHALL ALSO QUALIFY FOR PIPE WITH A BACKING STRIP AND VICE VERSA IN POSITION

1G AND 2G ONLY.

Q UALIFICATION ON A SINGLE WELDED PLATE WITHOUT A BACKING STRIP SHALL ALSO QUALIFY FOR SINGLE WELDED PIPE WITHOUT A BACKING STRIP AND VICE VERSA IN POSITIONS

1G AND 2G ONLY.

FOR ALL OTHER POSITIONS QUALIFICATION ON PIPE SHALL QUALIFY FOR PLATE BUT NOT VICE VERSA . T HE METHOD FOR REMOVING TEST SPECIMENS AND ACCEPTANCE CRITERIA ARE THE SAME AS FOR PROCEDURE QUALIFICATION TEST . T HE TYPE , NUMBER OF TEST SPECIMENS ARE GIVEN IN FOLLOWING TABLE ;

THICKNESS (T) OF TEST COUPON (3) (MM ) 1.58 TO 9.57 INCLUSIVE OVER 9.57 & LESS THAN 19.05 (4) OVER 9.57 & LESS THAN 19.05 (4) 19.05 & OVER

TYPE AND NUMBER OF TESTS REQUIRED (1) TRANSVERSE BEND TESTS (4) SB FB RB 1 1 -

1

1

2

-

-

2(4)

-

-

TYPE AND NUMBER OF TESTS REQUIRED LONGITUDINAL BEND TESTS (5) FB RB 1 1 1 1 THE NOTES TO TABLES ARE ESSENTIAL TO THE USE OF THE TABLES . T HE APPLICABLE NOTES ARE : THICKNESS (T) OF TEST COUPON (3) (MM ) 1.58 TO 9.57 INCLUSIVE OVER 9.57

1) A TOTAL OF FOUR SPECIMENS ARE REQUIRED TO QUALIFY FOR POSITION 5G.

36

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION 2) THE MAXIMUM THICKNESS QUALIFIED IN GAS WELDING IS THE THICKNESS OF TEST PLATE OR PIPE . 3) THE BASE MATERIAL MAY CONSIST OF EITHER PLATE OR PIPE . THE MINIMUM NOMINAL DIA . OF 5” IS RECOMMENDED FOR PIPE USED AS BASE MATERIAL .

4) EITHER FACE AND ROOT BENDS OR SIDE BENDS MAY BE USED FOR THICKNESSES FROM 9.57 TO 19.05 MM . 5) LONGITUDINAL BEND TESTS MAY BE USED IN LIEU OF THE TRANSVERSE BEND TESTS ONLY FOR TESTING MATERIALS COMBINATIONS DIFFERING MARKEDLY IN MECHANICAL BENDING PROPERTIES BETWEEN TWO BASE MATERIALS OR (B ) THE WELD METAL AND BASE MATERIALS .

OD LIMITS FOR WPQ

POSITION & OD LIMITATIONS FOR WPQ

37

(A) THE

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION RADIOGRAPHIC ACCEPTANCE CRITERIA FOR Q UALIFYING WELDERS /W ELDING OPERATORS : RADIOGRAPHY IS OPTIONAL AND MUST BE SUPPLEMENTED BY BEND TESTS WHEN USING GMAW WITH DIP TRANSFER OR WHEN WELDING SOME SPECIAL M /T . UT IN LIEU OF RT IS NOT PERMITTED . A LENGTH OF AT LEAST 6” MUST BE EXAMINED FOR PLATE OR THE ENTIRE CIRCUMFERENCE FOR PIPE

.

ANY IMPERFECTION IN EXCESS OF SPECIFIED BELOW SHALL BE JUDGED UNACCEPTABLE : a) LINEAR INDICATIONS : ANY TYPE OF CRACK /LF/LOP IS NOT PERMITTED . ANY ELONGATED SLAG INCLUSION WHICH HAS A LENGTH GREATER THAN ; 3 MM

T ≤10 MM T >10 MM

& T ≤57 MM

T >57 MM

T/3 MM

19 MM

ANY GROUP OF SLAG INCLUSIONS IN LINE THAT HAVE AN AGGREGATE LENGTH GREATER THAN T IN A LENGTH OF

12 T, EXCEPT WHEN THE DIST . BETWEEN SUCCESSIVE IMPERFECTIONS EXCEEDS 6L WHERE L IS THE

LENGTH OF THE LONGEST IMPERFECTION IN THE GROUP .

b) ROUNDED INDICATIONS : T HE MAX. PERMISSIBLE DIMENSION FOR ROUNDED INDICATION SHALL BE 20% OF T OR 3 MM , WHICHEVER IS SMALLER .

FOR WELDS IN M /T LESS THAN 3 MM IN THK ., THE MAX . N O. OF ACCEPTABLE ROUNDED INDICATIONS SHALL NOT EXCEED

12 IN A 6” LENGTH.

FOR WELDS IN M /T 3 MM OR GREATER THK ., THE CHARTS IN APP .I REPRESENTS THE MAX . ACCEPTABLE CRITERIA .

ROUNDED INDICATIONS LESS THAN 0.8 MM IN MAX . DIA SHALL NOT BE CONSIDERED IN

RADIOGRAPHIC ACCEPTANCE TESTS OF WELDERS /OPERATORS IN THESE RANGE OF M /T THK .

Brief summary of essential variables: 1) QW-402

-

Backing

2) QW-403 Ø Pipe dia. (reference: table 452) Ø P no. 3) QW-404 Ø F no. Ø t + Inserts Ø Solid/Metal cored

Flux cored

38

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION 4) QW-405 + Position (The addition of other welding position than qualified) Vertical welding 5) QW-408

-

Deletion of Inert gas backing

Ø

Metal transfer mode

Ø

Current/Polarity

6) QW-409

o

Following tables should be need to remembered for sect. IX;

QW-416 QW-422

: :

WELDING VARIABLES FOR WPQ BASE M/T P-NO. GROUPING

QW-432

:

F-NO. GROUPING FOR FILLER M/T

QW-433

:

F-NO. RANGE QUALIFIED FOR WPQ

QW-442

:

A-NO. GROUPING FOR DEPOSITED WELD METAL

QW-451

:

QUALIFIED THK. LIMITS & REQUIRED NO. OF TEST SPECIMENS FOR PQR

QW-452.1(A):

NO. OF TEST SPECIMENS REQUIRED FOR WPQ

QW-452.1(B):

RANGE OF THK. QUALIFIED FOR WPQ

QW-461.9 :

RANGE OF QUALIFIED DIA & POSITIONS FOR WPQ

QW-462

GRAPHICAL REPRESENTATION FOR TEST SPECIMENS

:

39

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION API 1104 o

PROCEDURE Q UALIFICATION TEST Table shows the type and number of butt weld test specimens required for procedure qualification;

Pipe Size, Outside Dia. (mm)

Tensile

Under 60.3 60.3 to 114.3 inclusive Over 114.3 to 323.9 inclusive Over 323.9

0 0

114.3 and smaller Over 114.3 to 323.9 inclusive Over 323.9

Number of Specimens NB RB FB Wall Thickness ≤12.7 mm 2 2 0 2 2 0

2

SB

Total

0 0

4 4

2

2

2

0

8

4

0

16

0 2

4 4 4 Wall Thickness >12.7 mm 2 0 0 2 0 0

2 4

4 8

4

4

8

16

0

BELOW IS SHOWN THE ORDER OF REMOVAL FOR TEST SPECIMENS ;

40

0


TENSILE TEST :

T HE TENSILE STRENGTH OF THE WELD , INCLUDING THE FUSION ZONE, SHALL BE EQUAL TO OR GREATER THAN THE MINIMUM SPECIFIED TENSILE STRENGTH OF THE PIPE MATERIAL .

41

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION NICK BREAK TEST:

I N THE NICK BREAK TEST , THE EXPOSED SURFACES OF EACH SPECIMEN SHALL SHOW COMPLETE PENETRATION AND FUSION , WITH THE GREATEST DIMENSION OF ANY GAS POCKET NOT TO EXCEED AREA OF ALL GAS POCKETS SHALL NOT EXCEED THAN

1.6 MM AND THE COMBINED

2% OF THE EXPOSED AREA . SLAG INCLUSIONS SHALL NOT BE MORE

0.8 MM IN DEPTH NOR 3 MM OR ½ THE NOMINAL WT IN LENGTH, WHICHEVER IS SHORTER , AND THERE

SHALL BE AT LEAST ½” OF SOUND WELD BETWEEN ADJACENT INCLUSIONS .

BEND TEST :

42


T HE BEND TESTS SHALL BE CONSIDERED ACCEPTABLE IF NO CRACK OR OTHER DISCONTINUITY EXCEEDING 3.2 MM OR

½ THE NOMINAL WT, WHICHEVER IS SMALLER , IN ANY DIRECTION IS PRESENT IN THE WELD OR BETWEEN

THE WELD AND THE FUSION ZONE AFTER BENDING .

CRACKS WHICH ORIGINATE ALONG THE EDGES OF THE

SPECIMEN DURING TESTING , AND WHICH ARE LESS THAN

6.35 MM MEASURED IN ANY DIRECTION , SHALL NOT BE

CONSIDERED UNLESS DISCONTINUITIES ARE OBSERVED .

BRIEF SUMMARY OF ESSENTIAL VARIABLES : CHANGE IN WELDING PROCESS CHANGE IN BASE MATERIAL GROUP , I . E., A)

MIN . YS≤42,000 PSI

B)

42,000
C)

YS≥65,000

MAJOR CHANGE IN JOINT DESIGN, I . E., FROM V TO U GROOVE A CHANGE IN POSITION FROM ROLL FIX A CHANGE IN WT GROUP, I . E.,

A) WT<4.8 MM B) 4.8≤WT≤19.1 C) WT>19.1

A CHANGE IN DIA. GROUP, I.E.,

A)OD<60.3 MM B)60.3≤OD≤323.9 MM

C)OD>323.9 MM CHANGE IN FILLER METAL GROUP , I .E., A) GROUP 1: A 5.1 (E6010, E6011) & A 5.5 ( E7010, E 7011) ( ONLY FOR SMAW IS GIVEN HERE )

B) GROUP

2: A 5.5 (E8010, E8011, E9010)

C) GROUP

3: A 5.1/A 5.5 (E 7015/16/18, E 8015/16/18, E 9018)

43

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION CHANGE IN ELECTRICAL CHARACTERISTICS , I . E., CHANGE MORE THAN 10% IN AMPERAGE & SPEED , MORE THAN 7% IN VOLTAGE TIME BETWEEN PASSES CHANGE IN DIRECTION OF WELDING CHANGE IN SHIELDING GAS & FLOW RATE CHANGE IN SPEED OF TRAVEL DECREASE IN SPECIFIED MIN . PREHEAT TEMP . ADDITION OF PWHT OR A CHANGE FROM THE RANGES o

PERFORMANCE Q UALIFICATION TEST THERE ARE TWO TYPES OF WELDER QUALIFICATION IN API 1104: SINGLE QUALIFICATION & MULTIPLE QUALIFICATION .

1) SINGLE QUALIFICATION : SHALL BE IN

WHEN THE WELDER IS QUALIFYING IN THE FIXED POSITION , THE AXIS OF THE PIPE

HP, IN VP OR INCLINED FROM HP AT AN ANGLE OF NOT MORE THAN 45°.

2) MULTIPLE QUALIFICATION : FOR MULTIPLE QUALIFICATION , WELDER SHALL SUCCESSFULLY COMPLETED THE TWO TESTS , USING QUALIFIED PROCEDURES. FOR FIRST TEST , THE WELDER SHALL MAKE A BUTT WELD IN THE FIXED POSITION WITH THE AXIS OF THE PIPE EITHER IN THE MORE THAN LEAST

H.P. OR INCLINED FROM H.P. AT AN ANGLE NOT

45°. THIS BUTT WELD SHALL BE MADE ON PIPE WITH AN OD OF AT LEAST 6” AND WITH A WT AT

6.4 MM WITHOUT BACKING STRIP . FOR THE SECOND TEST , THE WELDER SHALL WELD A FULL SIZE BRANCH ON PIPE CONNECTION . T HIS

TEST SHALL BE PERFORMED WITH A PIPE DIA . OF AT LEAST 6” AND WITH THE RUN PIPE AXIS IN THE

WT 6.4 MM. THE WELD SHALL BE MADE

H.P. & THE BRANCH PIPE AXIS EXTENDING VERTICALLY DOWNWARD FROM

THE RUN .

THE WELD SHALL EXHIBIT COMPLETE PENETRATION AROUND THE ENTIRE CIRCUMFERENCE , COMPLETED ROOT BEADS SHALL NOT CONTAIN ANY BURN THROUGH OF MORE THAN

6 MM . T HE SUM OF MAX

DIMENSION OF SEPARATE UNREPAIRED BURN THROUGH IN ANY 12” LENGTH WELD SHALL NOT EXCEED

13

MM .

S COPE:

A WELDER WHO QUALIFIED FOR MULTIPLE QUALIFICATION ON PIPE DIA . GREATER THAN

323.9

(12”) MM SHALL BE QUALIFIED TO WELD IN ALL POSITIONS , ALL WT, JOINT DESIGNS & FITTING AND ALL PIPE DIA .

A WELDER QUALIFIED ON DIA . LESS THAN 323.9 SHALL BE QUALIFIED TO WELD IN ALL POSITIONS , ALL

WT, JOINT DESIGNS & FITTING AND ALL PIPE DIA. LESS THAN OR EQUAL TO OD USED IN THE QUALIFICATION TEST .

44

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION LOCATION OF TEST SPECIMENS :

45


46

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION I N PRODUCTION WELDS ; o

The pipe must be aligned carefully using internal pneumatically or hydraulically operated clamps. The alignment must not be altered during the welding or the root pass and the internal clamps shall not be removed until the root welding is finished and for external clamps weld shall be completed more than 50%.

o

Any misalignment of abutting ends of pipe of the same nominal thickness should not exceed 1.6 mm.

o

It is convenient practice to preheat joints to approximately 100°C particularly when ambient temp. is below 5°C or if the WT of the pipe exceeds 12.5 mm. This reduces the risk of martensite formation in the HAZ, which is the main cause for hydrogen induced cracking.

o

The second or hot weld pass is deposited immediately after the root pass has been completed, before the temp. of the pipe in the weld zone drops to less than 100°C.

o

The weld bead height at no point shall neither fall below the outside surface of pipe nor shall be raised above the parent metal by more than 1.6 mm.

o

Two beads shall not be started at same location. The face of the completed weld shall be approximately 3 mm wider than the width of original groove.

o

In order to evaluate the weldability of these line pipe steels, sometimes slot weldability test is conducted to as a field test. This test is done when welding problems are encountered especially during site welding. The test involves creating a through thickness slot of 90 mm length on a sample test piece of 250 mm length. Welding is carried out to fill up the groove with a pre qualified welding procedure. After aging for 24 hrs the sample is reheated to 500°C to arrest further cracking. The sample is heat treated at 300°C for 10 min and the sample is broken up by hammering from the other side. The c/s is examined for the development of hydrogen induced cracks. In case of doubt, welding procedures are suitable modified and adopted for the site welding.

o

Acceptance criteria in production welds:

WITH MPT

WITH LPT

ANY INDICATION GREATER THAN 1.6 MM IN ANY DIRECTION SHALL BE TREATED AS RELEVENT AND SHALL B E CONFIRMED BY LPT OR ONETHER NDE TESTING. ANY LINEAR INDICATION EVALUTED AS C RATER CRACK EXCEED IN DIMENSION GREATER THAN 4 MM SHALL BE CONSIDERED DEFECT. LINEAR INDICATION OTHER THAN C RACK SHALL BE CONSIDERED DEFECT. LINEAR INDICATION EVALUTED AS LF AND EXCEED 1” IN CONTINUOUS 12” WELD LENGTH OR 8% OF TOTAL WELD LENGTH IN THE CASE OF WELD LENGTH LESS THAN 12” SHALL BE CONSIDERED AS DEFECT. THE ACCEPTANCE CRITERIA FOR ROUNDED INDICATIONS IS SAME AS PER GIVEN FOR RT. ANY INDICATION GREATER THAN 2 MM IN ANY DIRECTION SHALL BE TREATED AS RELEVENT AND SHALL BE

47


WITH UT

WITH RT/VISUAL INSPECTION DEFECT TYPE

REINFORCEMENT (H EIGHT ) REINFORCEMENT (A PPEARANCE ) INCOMPLETE FILLING SLAG INCLUSIONS

UNDERCUT

POROSITY

CRACKS LACK OF FUSION

CONFIRMED BY LPT OR ONETHER NDE TESTING. ACCEPTANCE STANDARD FOR LINEAR/ROUNDED INDICATIONS IS SAME AS PER MPT. ANY DEFECT INTERPRETETED AS CRACK IS CONSIDERED AS DEFECT. LINEAR BURIED INDICATIONS (OTHER THAN CRACK) NOT OPEN TO THE ID/OD AND EXCEED 2” IN CONTINUOUS WELD LENGTH OF 12” OR 8% OF TOTAL WELD LENGTH. LINEAR SURFACE INDICATIONS (OTHER THAN CRACK) OPEN TO THE ID/OD AND EXCEED 1” IN CONTINUOUS WELD LENGTH OF 12” OR 8% OF TOTAL WELD LENGTH. TRANSEVERSE INDICATIONS HAVE SAME ACCEPTANCE CRITERIA AS PER GIVEN FOR V OLUMETRIC INDICATIONS. VOLUMETRIC CLUSTER INDICATIONS ARE CONSIDERED TO BE DEFECT WHEN DIMENSION EXCEED 13 MM. VOLUMETRIC INDIVIDUAL INDICATIONS ARE CONSIDERED TO BE DEFECT WHEN DIMENSION EXCEED 3 MM. ACCEPTANCE CRITERIA IS AS PER GIVEN BELOW; MAX ALLOWANCE WELD FACE 3 MM SMOOTH NOT ALLOWED ESI : 1.6 MM WIDTH & 50 MM LENGTH IN ANY 12” WELD LENGTH ISI : 3 MM WIDTH & 13 MM LENGTH IN ANY 12” WELD LENGTH MAX 4 ISI IN ANY 12” WELD LENGTH THE AGGREGATE LENGTH OF ESI & ISI 8% OF WELD LENGTH IN THE CASE OF WHEN WELD LENGTH IS LESS THAN 12” ≤0.4 MM OF ANY LENGTH >0.4<0.8 MM OF 50 MM LENGTH >0.8 MM NOT ACCEPTABLE OF ANY LENGTH FOR SCATTERED PORO. DIA . OF INDIVIDUAL PORO . UP TO 25% OF WT OR 3 MM WHICHEVER IS SMALLER FOR CLUSTER PORO. MAX. DIA OF CLUSTER 13 MM AND AGGREGATE LENGTH IS 13 MM IN ANY CONTINUOUS 12” WELD LENGTH NOT ALLOWED ACCEPTING CRATER CRACK UP TO 4 MM INDIVIDUAL & AGGREGATE LENGTH 25 MM (OR 8% IN THE CASE OF WELD LENGTH LESS THAN 12”) IN ANY CONTINUOUS 12” WELD LENGTH

LF DUE TO COLD LAP ARC STRIKE MECHANICAL DAMAGE MISALIGNMENT

INDIVIDUAL AND AGGREGATE LENGTH UP TO 50 MM NA NA 3 MM

48

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION WELD ROOT

MISALIGNMENT REINFORCEMENT (HEIGHT ) LACK OF ROOT PENETRATION WITHOUT HIGH - LOW LACK OF ROOT PENETRATION DUE TO HIGH - LOW LACK OF ROOT FUSION ROOT CONCAVITY

3 MM 1.6 MM INDIVIDUAL & AGGREGATE LENGTH UP TO 25 MM IN ANY CONTINUOUS 12” WELD LENGTH. INDIVIDUAL LENGTH UP TO 50 MM & AGGREGATE LENGTH UP TO 75 MM IN ANY CONTINUOUS 12” WELD LENGTH . SAME AS FOR WELD FACE ANY LENGTH IS ACCEPTABLE BUT THE DENSITY OF THE RADIOGRAPH IMAGE OF INTERNAL CONCAVITY SHALL NOT EXCEED THAT OF THE THINNEST ADJACENT PARENT MATERIAL . IN SUCH CASES CRITERIA FOR

ROOT UNDERCUT MECHANICAL DAMAGE POROSITY BURN THROUGH

BT IS APPLICABLE . SAME AS FOR WELD FACE NA SAME AS FOR WELD FACE INDIVIDUAL LENGTH UP TO 6 MM OR THINNER OF THE NOMINAL WT WHICHEVER IS SMALLER

AGGREGATE LENGTH UP TO 13 MM IN ANY CONTINUOUS 12” WELD LENGTH .

49

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION ACCEPTANCE CRITERIA AS PER ASME SECT. VIII DIV. I 1. LPT (Appendix 8) 

Reference given in sect. V, article 6.



Relevant indications:

only indications with major dimensions greater than 1.5 mm shall

be considered as relevant. 

A linear indication is one having a length greater than 3 times the width.



A rounded indication is one of circular or elliptical shape with the length equal or less than 3 times the width.



Acceptance criteria: All surfaces to be examined shall be free of; a) Relevant linear indications b) Relevant rounded indications greater than 5 mm. c) Four or more rounded indications in a line separated by 1.5 mm or less (edge to edge).

2. MPT (Appendix 6) 




All evaluations of indications and acceptance criteria are same as for LPT.

3. UT (Appendix 12) 




Indications which produce a response greater than 20% of the reference level shall be investigated to the extent that the operator can determine the shape, identity and location of all such imperfections and evaluate them in terms of the acceptance standard given below; a) Indications characterized as cracks, LF or LOP are unacceptable regardless of length. b) Other imperfections are unacceptable if the indication exceeds the reference level amplitude and have lengths which exceeds: 6 mm for t up to 19 mm. 1/3t for t from 19 mm to 57 mm. 19.05 mm for t over 57 mm. Where t is the thickness of the thinnest member excluding any allowable reinforcement.

50

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION 4. RT 




Acceptance criteria for linear indications:

o

Cracks, LF & LOP are not acceptable.

o

Other imperfections are unacceptable if length exceed; 6 mm for t up to 19 mm. 1/3t for t from 19 mm to 57 mm.

o

19.05 mm for t over 57 mm. Where t is the thickness of the thinnest member excluding any allowable reinforcement. For fillet welds with full penetration throat thk. (th) is included in t.

o

Any group of aligned indications in which aggregate length exceeds t in a weld length of 12 t, except when the distance between two edges of adjacent indication exceeds 6L, where L is the dimension of the longest indication.



Acceptance criteria for rounded indications:

o

Appendix 4

o

Rounded indications which exceed the following dimension shall be considered relevant; 1/10t for t less than 3 mm 0.4 mm for t 3 to 6 mm. 0.8 mm for t 6 to 50 mm. 1.6 mm for t>50 mm.

o

Max. size of rounded indications; The max permissible size of any indication shall be 1/4t or 4 mm, whichever is smaller, except that an isolated indication separated from an adjacent indication by 1” or more may be 1/3t or 6 mm whichever is less. For t greater than 2” the max permissible size of

isolated indication shall be 10 mm. Aligned rounded indications are acceptable when the summation of the dia. of the indications is less than (t) in a length of 12t. (fig 4-1 to 4-2 in App. 4) For t less than 3 mm, the max no. of rounded indications shall not exceed 12 in a 6” weld

length. For t greater than 3 mm, follow chart 4-3 through 4-8 of App. 4. The length of acceptable cluster rounded indications shall not exceed the lesser of 1” or 2t. Where more than one cluster is present, the sum of the lengths of the clusters shall not exceed 1” in a 6” weld length.

51

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION WELD JOINT DETAILS (Ref: ASME B 31.3, 31.4/31.8)

Joint preparation for un equal wall thickness

52


Branch connections 

Branch connections which abut the outside surface of the run pipe shall be contoured for groove welds which meet the WPS requirements (fig-a & b).



Branch connections which are inserted through a run opening shall be inserted at least as far as the inside surface of the run pipe at all points (fig-c).



Lateral transition of branches and connections from the centerline of the run shall not exceed ±1.5 mm.



Branch connections, including branch connection fittings, which abut the outside of the run or which are inserted in an opening in the run shall be attached by fully penetrated groove welds. The welds shall be finished with cover fillet welds having a throat dimension not less than tc. (fig-1&2)

The nomenclature used here are; Tb = nominal thickness of branch

53

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION Th = nominal thickness of header Tr = nominal thickness of reinforcing pad or saddle tc = lesser of 0.7Tb or 6 mm (1⁄4 in.) tmin = lesser of Tb or Tr 

A reinforcing pad or saddle shall be attached to the branch pipe by either; a) A fully penetrated groove weld finished with a cover fillet weld having a throat dimension not less than tc b) A fillet weld having a throat dimension not less than 0.7tmin.



The outer edge of a reinforcing pad or saddle shall be attached to the run pipe by a fillet weld having a throat dim not less than 0.5Tr.



The corners of the pad shall be rounded corners.

For Fillet & Socket welds 

The max size of socket welded joints in hazardous services shall be 1.5” for new construction. Max 2”

may be used in hazardous service for maintenance, minor field modifications of existing piping systems, and when necessary to match existing equipment connections. 

For sour services socket welded joints should be avoided. In case they could not be avoided the max. size of socket welded joints shall be 1”.



Generally, socket welded joints should be avoided in any services where crevice corrosion, severe erosion, or cyclic loading may occur.



The axial gap between male and female component shall be max of 3 mm and min of 1.5 mm. This gap is required prior to welding.

DETAILS FOR DOUBLE WELDED SLIP-ON & SOCKET WELDING FLANGE

54


MIN WELDING DIMENSIONS FOR SOCKET WELDING OF COMPONENTS OTHER THAN FLANGE

55

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION SERVICE CODES Line material:

CA

Impact tested carbon steel

CB

Killed CS

CC

Low carbon CS

CS

Carbon steel

CG

Galvanized CS

CJ

1-1/4 Cr ½ Mo alloy steel

CK

2-1/4 Cr 1 Mo alloy steel

CL

5 Cr ½ Mo alloy steel

CM

9 Cr 1 Mo alloy steel

BC

Copper tubing

BD

90-10 Cu-Ni

DC

Cast Iron Grey

SC

304H SS

SD

316/316L SS

SJ

321 SS

SX

Duplex SS

NM

Monel 400

PV

PVC

Corrosion allowance:

0

Zero corrosion allowance

1

1.6 mm

2

3.2 mm

3

4.8 mm

4

6.4 mm

9

Corrosion allowance as noted

Pressure rating:

1

150

3

300

4

400

6

600

9

900

15

1500

25

2500

Services:

A

Acid

C

Caustic

56

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION D

Drain, sewer

H

Hydrogen

P

Process (General hydrocarbon)

Q

Chlorination gas

T

Well head piping

U

Utility

W

Water

Y

Chlorine gas

Ex.

6”-FG-123-1CS9P 6” fuel gas line no. 123 and m/t specification;

1

Pressure rating (150#)

CS

Carbon steel

9

Corrosion allowance (corrosion allowance as noted)

P

Process (General hydrocarbon) services

57

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION PIPE LINE WELDING PRACTICES DOWNHILL WELDING VS UPHILL WELDING DOWNHILL WELDING IS USED PRIMARILY TO WELD THIN WALL MS PIPE HAVING A WT OF

3.17 TO 9.5 MM. THE

RELATIVELY THIN WALL OF THE PIPE RETAINS THE HEAT LONGER THAN THICK METAL WOULD . WHEN WELDING MS PIPE , THE SLOWER COOLING RATE OF THE THIN WALLED PIPE DOES MAKE IT POSSIBLE TO DEPOSIT THE WELD AT A FASTER RATE WITHOUT HARMFUL EFFECTS TO THE WELDED JOINT . ALSO DOWNHILL WELDING TECHNIQUE ALLOWS FASTER WELDING SPEEDS WITH LESS TENDENCY TO BURN THROUGH THE ROOT OF THE JOINT . DOWNHILL WELDING REQUIRES THE USE OF FAST -FREEZING , LIGHTLY COATED ELECTRODES (F3 GROUP) SUCH AS

6010, 6011 THAT PRODUCE MINIMUM SLAG . THE USE OF THE HEAVIER ELECT . SUCH AS 7024 AND THE IRON

POWDER LOW HYDROGEN TYPES ARE NOT SUITABLE IN DOWNHILL WELDING AS THE PROBLEMS OF SLAG ENTRAPMENT , POROSITY AND COLD LAPPING BECOME INSURMOUNTABLE . SUCH ELECT . WILL ALSO REQUIRE HIGHER OPERATING CURRENTS THUS INCREASING THE CHANCE OF BURN THROUGH . UPHILL WELDING IS PREFERRED FOR WELDING HEAVY WALL PIPE AND PIPE MADE OF ALLOY STEEL . THE THICKER PIPE WALL ACTS AS A ‘HEAT SINK ’ BY WITHDRAWING THE HEAT MORE RAPIDLY FROM THE WELD AREA THAN DOES A THIN WALL PIPE . THE FASTER COOLING RATE CAUSES THE METAL IN THE WELD AREA TO BECOME MORE BRITTLE IN MS PIPE . IN ALLOY STEEL PIPE THE TENDENCY TOWARD BRITTLENESS IS GREATLY INCREASED . TO OVERCOME THIS TENDENCY THE COOLING RATE IN THE WELD AREA MUST BE REDUCED . THIS CAN BE ACCOMPLISHED BY DECREASING THE WELDING SPEED AND BY DEPOSITING A HEAVIER BEAD . BOTH OF THESE OBJECTIVES ARE ACHIEVED BY UPHILL WELDING. VERTICAL DOWN WELDING WITH CELLULOSIC ELECT . IS NORMALLY DONE WITH HIGH CURRENTS AND HIGH TRAVEL SPEED . CELLULOSIC ELECT . HAVE A THIN COATING CONTAINING A LARGE AMOUNT OF ORGANIC CELLULOSE . WHEN THE ELECT . IS BURNED , THE COATING FORMS A PROTECTIVE GAS COATING FOR THE MOLTEN METAL . BECAUSE OF THE ORGANIC M /T AND MOISTURE CONTENT OF THESE ELECT . THEY HAVE A VERY STRONG ARC FORCE BUT AT THE SAME TIME THE WELD METAL FREEZES VERY QUICKLY . THIS METHOD OF WELDING IS FAST AND ECONOMICAL , CONSEQUENTLY MOST CROSS COUNTRY PIPELINES ARE WELDED WITH THE PROGRESSION VERTICALLY DOWNWARD . HOWEVER IT IS RECOMMENDED PRACTICE TO USE UPHILL TECHNIQUE WITH LOW HYDROGEN ELECT . (F 4 GROUP ) FOR WELDING THE ROOT BEAD AND THE SUCCESSIVE BEAD WELDING SHOULD BE CARRIED OUT WITH DOWNHILL TECHNIQUE FOR WELDING OF HIGH PR ., HIGH TEMP ., LOW TEMP . PIPELINES WHICH DEMANDS FOR MORE STRICT RADIOGRAPHY REQUIREMENTS . THE REASON IS THAT WITH UPHILL TECHNIQUE WITH RELATIVELY LOW CURRENT AND LOW TRAVEL SPEED PRODUCES JOINTS RELATIVELY FEW , BUT LARGE BEADS WHICH GIVES GREATER HEAT INPUT SO LESS CHANCE OF LF OR LOP IN THE ROOT BEAD . ALSO WITH LOW HYDROGEN ELECT . WITH VERTICAL UPHILL WELDING WELDS MAY BE MADE VIRTUALLY FREE OF ANY SLAG ENTRAPMENT AND POROSITY . ALSO WITH UPHILL WELDING THE DEPOSITED BEAD IS SOMEWHAT OF CONVEX PROFILE WHICH PUTS THE DEPOSITED BEAD IN CONTRACTION STRESSES SO LESS SUSCEPTIBLE TO STRESS INDUCED CRACKING . IT IS DESIRABLE NOT TO FINISH A WELD IN EXACTLY THE BOTTOM OF THE PIPE BECAUSE THE TIE - IN CAN BE MORE DIFFICULT . SIMILARLY IT IS BEST TO AVOID STARTING AT EXACTLY THE TOP OF PIPE

58

.

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION WHEN THE ARC IS STRUCK , IT SHOULD NOT BE SHORTENED IMMEDIATELY . TIME SHOULD BE ALLOWED TO STABILIZE THE ARC AND TO ALLOW THE GASEOUS SHIELD TO FORM .

WELDING OF ROOT BEAD : KEYHOLE IS AN ESSENTIAL PART IN WELDING THE ROOT BEAD . IT IS A TEARDROP SHAPED ENLARGEMENT OF THE ROOT OPENING AHEAD OF THE BEAD AND IT SHOULD BE ABOUT

1 1/3 TIMES THE DIA . ACROSS THE ELECT . COATING IN SIZE .

THE KEYHOLE HELPS TO INSURE THAT THE DEPOSITED BEAD WILL PENETRATE TO THE ROOT AS EVIDENCED BY THE SMALL CROWN AT THE BACK OF THE BEAD . THIS CROWN SHOULD RISE ABOUT

1.6 MM ABOVE THE INSIDE SURFACE OF

THE PIPE . WHILE WELDING , THE WELDER SHOULD WATCH THE KEYHOLE CONSTANTLY . IF IT BECOMES ENLARGED , OVER PENETRATION WILL RESULT . THIS CAN BE CORRECTED BY REDUCING THE WELDING CURRENT OR , IN SOME CASES , BY INCREASING THE WELDING SPEED. IF THE KEYHOLE IS TOO SMALL , THE PENETRATION OF THE ROOT BEAD WILL BE INSUFFICIENT . WHILE SLOWING THE SPEED OF WELDING OR THE ELECT . ANGLE SHOULD BE DECREASED SLIGHTLY BY POINTING THE ELECT . MORE DIRECTLY TOWARD THE KEYHOLE WILL HELP IN SOME CASES , USUALLY IT IS NECESSARY TO INCREASE THE WELDING CURRENT TO CORRECT THIS CONDITION . THE ARC SHOULD BE STRUCK IN THE JOINT AND NEVER ON A TACK WELD . A LONG ARC LENGTH SHOULD BE MAINTAINED FOR A SHORT PERIOD AFTER THE ARC HAS BEEN STRUCK . DURING THIS TIME WEAVE THE ELECT . BACKWARD AND FORWARD TO PREHEAT THE BEVEL OF THE WELD . IN ADDITION TO PREHEATING THE BEVEL MAINTAINING THE LONG ARC LENGTH STABILIZES THE ARC AND ALLOWS THE GASEOUS SHIELD TO FORM . NO FILLER METAL IS TRANSFORMED FROM THE ELECT . TO THE WORK PIECE WHEN THE LONG ARC IS MAINTAINED IN THE OVERHEAD POSITION . AFTER THE ARC HAS BEEN STABILIZED AND THE GASEOUS SHIELD HAS FORMED , THE ELECT . IS BROUGHT BACK TO THE ACTUAL START POSITION FOR THE ROOT BEAD . WITH THE ELECT . HELD AT THE CORRECT ANGLE, IT IS CAREFULLY MOVED TOWARD THE ROOT BEAD UNTIL THE CORRECT ARC LENGTH IS ESTABLISHED

.

THE WHIPPING PROCEDURE MUST ALWAYS BE USED WHEN WELDING IN THE VERTICAL UPHILL PORTION OF THE PIPE . IT IS CONTINUED UNTIL THE WELD IS STOPPED AT THE

12 O ’CLOCK POSITION . THE OBJECTIVE OF WHIPPING IS TO ALLOW

THE MOLTEN POOL OF METAL TO COOL SUFFICIENTLY TO LOSE OF ITS FLUIDITY . WHEN THE MOLTEN METAL IN THE PUDDLE IS SOMEWHAT MUSHY , A FURTHER DEPOSIT OF FILLER METAL FROM THE ELECT . WILL NOT CAUSE IT TO OVERFLOW . THE LENGTH OF THE STROKE WHEN WHIPPING SHOULD NOT BE EXCESSIVE . IF IT IS EXCESSIVE , THE HOT LIQUID METAL IN THE PUDDLE WILL BE EXPOSED TO THE ATMOSPHERE AS A RESULT OF THE REMOVAL OF THE GASEOUS SHIELD . RAPID OXIDATION WILL RESULT , WHICH LEADS TO POROSITY IN THE WELD . EXCESSIVE WHIPPING CAN ALSO CAUSE SLAG ENTRAPMENT . TO STOP THE WELD , THE ARC IS BROKEN BY MAKING A QUICK STAB THROUGH THE KEYHOLE WITH ELECT AND THEN BY WITHDRAWING IT QUICKLY TO CLEAR THE WORK . BY THIS PROCEDURE A FULL SIZE KEYHOLE IS LEFT SO THAT COMPLETE PENETRATION CAN BE OBTAINED WHEN RESTARTING THE WELD OR WHEN MAKING A TIE - IN AT THIS POINT . FOR RE STARTING THE WELD STRIKE THE ARC SOMEWHAT AHEAD OF THE KEYHOLE AND MAINTAIN LONG ARC TO STABILIZE IT AND TO FORM GASEOUS SHIELD . AFTER STABILIZATION CAREFULLY DECREASE THE ARC LENGTH WITH MOVEMENT UPTO THE KEYHOLE AND GRADUALLY CLOSE THE KEYHOLE AND START WELD FROM HERE .

WELDING THE ROOT BEAD WITH L OW HYDROGEN ELECT .:

ROOT BEADS ARE SELDOM WELDED WITH LOW -

HYDROGEN ELECT . BECAUSE THE DIA . ACROSS THE COATING FOR THE LOW HYDROGEN ELECT . IS SOMEWHAT MORE THAN FOR SAME SIZE CELLULOSIC ELECT . THE HEAVIER COATING OF THE LH ELECT . DOES NOT ALLOW THE ARC TO BE

59

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION TAKEN CLOSE ENOUGH TO THE ROOT FACE , THEREBY MAKING IT DIFFICULT TO ESTABLISH THE CORRECT ARC LENGTH . WELDING WITH AN ARC THAT IS TOO LONG CAN CAUSE SUCK -IN . FURTHERMORE , THE HEAVIER COATING INTERFERES WITH THE MANIPULATION OF THE ELECT WHEN MAKING A WEAVE . A HIGHER CURRENT SETTING IS ALWAYS USED FOR WELDING WITH LOW - HYDROGEN ELECT . AND THEREFORE MORE HEAT IS LIBERATED . THE ARC CHARACTERISTIC IS ALSO DIFFERENT . THE LH ELECT . PRODUCES AN ARC THAT IS RELATIVELY SMOOTH BUT LACKS THE PENETRATING POWER OF THE MORE LIGHTLY COATED ELECT

.

A HEAVY COATING WILL FORM A HEAVY BLANKET OF SLAG OVER THE LIQUID PUDDLE OF MOLTEN METAL , WHICH CAUSES THE COOLING RATE TO BE SLOWER AND THE METAL TO REMAIN LIQUID FOR A LONGER PERIOD . THE VISCOSITY OF THE MOLTEN SLAG AND WELD METAL IS LOWER ; I. E., IT WILL FLOW MORE READILY THAN A LIQUID HAVING A HIGHER VISCOSITY . THE COMBINED EFFECT OF THE SLOWER COOLING RATE AND THE LOWER VISCOSITY OF THE LIQUID WILL CAUSE THE MOLTEN PUDDLE TO DRIP READILY . FOR THIS REASON , DIFFICULTY IS EXPERIENCED WHEN WELDING IN THE OVERHEAD AND VERTICAL POSITIONS WITH LH ELECT . A VERY SHORT ARC SHOULD BE USED AT ALL TIMES WHEN WELDING WITH LH ELECT . TO OBTAIN ADEQUATE PENETRATION . ALSO WHEN WELDING WITH LH ELECT ., PINHOLES CAN BE CAUSED BY INCORRECT ARC STRIKING , CHIPPED FLUX COATING , MOISTURE IN THE WELD JOINTS , OR WET ELECT . TO AVOID PINHOLES WHILE STRIKING THE ARC , STRIKE JUST AHEAD OF THE STARTING POINT AND SHORTEN THE ARC AS QUICKLY AS POSSIBLE TO THE PROPER LENGTH . THEN BACK - UP THE ARC TO THE STARTING POINT AND PROCEED TO WELD AS SOON AS THE MOLTEN POOL OF METAL HAS FORMED . THE WHIPPING PROCEDURE SHOULD NEVER BE USED WHEN WELDING WITH LH ELECT . A V- SHAPED WEAVE , MUST BE USED FOR WELDING THE ROOT BEAD ENTIRELY , AROUND THE PIPE WHEN USING THE LH ELECT . THE OBJECTIVE OF THIS WEAVE IS TO ALLOW THE MOLTEN SLAG AND METAL IN THE PUDDLE TO COOL AND TO LOSE SOME OF ITS FLUIDITY IN ORDER TO PREVENT DRIPPING . USING THIS WEAVE ALSO PREHEATS THE METAL AHEAD OF THE WELD .

WELDING THE ROOT BEAD WITH GTAW:

USUALLY , ONLY THE ROOT BEAD IS WELDED BY THE GTAW PROCESS .

HOWEVER , SOMETIMES THE SECOND PASS IS ALSO MADE BY THIS PROCESS BECAUSE GTAW WELDED ROOT BEADS TEND TO SOMEWHAT THIN . SS AND HIGH ALLOY STEEL PIPES , AS WELL AS MS PIPES , ARE WELDED BY THE GTAW PROCESS , ESPECIALLY FOR HIGH PR . PIPE JOINT THAT REQUIRES HIGH QUALITY WELDS . THE OUTSTANDING FEATURES OF THE GTAW PROCESS ARE :

1) WELDS OF EXCEPTIONAL QUALITY CAN BE MADE IN ALMOST ALL METALS 2) PRACTICALLY NO PWHT IS REQUIRED . 3) THE ARC AND THE POOL OF MOLTEN METAL ARE READILY VISIBLE BY THE WELDER . 4) NO FILLER METAL IS TRANSPORTED ACROSS THE ARC STREAM ; THUS THERE IS NOT SPATTER . 5) WELDING IS POSSIBLE IN ALL POSITIONS . 6) THERE IS NO SLAG WITH MIGHT BE TRAPPED IN THE WELD .

60

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION THE PROCEDURE FOR PREPARING THE WELD JOINT IS THE SAME AS FOR PREPARING THE JOINT WHEN WELDING BY SMAW . THE PRINCIPAL DIFFERENCE IS IN THE DIMENSIONS OF THE JOINT . THE WIDTH OF THE ROOT FACE IS REDUCED TO

1.6 MM AND THE ROOT OPENING IS NARROWED TO 1.6 TO 2.4 MM .

FOR THE ELECT . TI P, THE INCLUDED ANGLE OF THE POINT SHOULD BE ABOUT GROUND BACK TO A DIST . EQUAL TO ABOUT

2-1/2 ELECT. DIA . IT IS IMPORTANT TO BLUNT THE TIP SLIGHTLY BY

GRINDING IT FLAT AT THE END FOR A DIST . SLIGHTLY LESS THAN WHEN THE PIPE IS IN THE

22 TO 23°, OR THE LENGTH SHOULD BE

0.4 MM FROM THE POINT .

5G POSITION , THE TACK WELDS SHOULD BE MADE IN THE 8:30, 4:30, 1:30 AND 11:30

POSITIONS . THE REGULAR ROOT BEAD IS STARTED IN THE

6 O ’CLOCK POSITION .

THE ARC SHOULD NOT BE STRUCK IN A MANNER SIMILAR TO THE PROCEDURE USED FOR SMAW WITH CONSUMABLE ELECT . AS THIS PROCEDURE WOULD SERIOUSLY DAMAGE THE TUNGSTEN ELECT . TO START THE WELD , THE CURRENT AND THE INERT GAS SUPPLY TO THE WELDING TORCH MUST BE SHUT OFF . AFTER POSITIONING THE TORCH AND FILLER METAL , THE WELDER SWITCH ON THE WELDING CURRENT USING THE FOOT SWITCH OR THE SWITCH ON THE WELDING TORCH . SLOWLY AND CAREFULLY HE WILL STRAIGHTEN THE WELDING TORCH THEREBY REDUCING THE ELECT . ANGLE AND BRINGING THE TIP OF THE ELECT . INTO THE GROOVE . AFTER THE ARC HAS BEEN ESTABLISHED , THE WELDING TORCH IS HELD IN PLACE UNTIL A PUDDLE OF MOLTEN METAL HAS APPEARED . AFTER THE PUDDLE IS ESTABLISHED , THE FILLER ROD IS DIPPED INTO THE MOLTEN METAL . THE WELDER THEN BEGINS TO OSCILLATE THE WELDING TORCH FROM SIDE TO SIDE , ALLOWING THE ARC TO TRAVEL SLIGHTLY BEYOND THE EDGES OF THE PIPE . WHEN THE PUDDLE HAS BEEN BUILT UP TO THE REQUIRED SIZE BY THE ADDITION OF FILLER METAL , THE WELDING TORCH IS THEN MOVED ON BY SLOWLY AND STEADILY GLIDING IT OVER THE BEVEL WHILE AT THE SAME TIME THE TORCH IS OSCILLATED FROM SIDE TO SIDE. FILLER IS ADDED CONTINUOUSLY TO THE MOLTEN PUDDLE FROM THE END OF THE ROD WHICH IS HELD IN THE PUDDLE . TO STOP THE WELD , THE WELDING CURRENT IS SIMPLY SWITCHED OFF . IF THE FILLER ROD IS TO BE REPLACED OR IF THE WELD BEAD IS FINISHED , THE FILLER ROD SHOULD BE WITHDRAWN BEFOREHAND . HOWEVER , IF THE BEAD IS TO BE CONTINUED , THE FILLER ROD IS LEFT IN THE PUDDLE TO SOLIDIFY AGAINST THE END OF THE BEAD

.

THE PROCEDURE FOR RESTARTING THE WELD AGAINST A LAYER OF WELD METAL IS SIMILAR TO THE STARTING PROCEDURE AS PREVIOUSLY DESCRIBED . FOR MAKING A TIE - IN , WHEN THE WELD APPROACHES ANOTHER BEAD , THE NORMAL GTAW WELDING PROCEDURE IS CONTINUED UNTIL THE WELD IS APP .

1.6 MM FROM THE BEAD . AT THIS POINT THE FILLER ROD IS WITHDRAWN , BUT

THE WELDING TORCH IS SLOWLY MOVED ON ; IT IS TILTED AS NECESSARY TO PREVENT THE ELECT . FROM COMING IN CONTACT WITH THE WELD METAL . WHEN A SMOOTH BEAD BETWEEN THE BEADS HAS BEEN OBTAINED THE CURRENT IS SWITCHED OFF . WHEN A SECOND PASS WITH THE GTAW TORCH MUST BE MADE , THE PROCEDURE IS SAME AS THAT USED IN WELDING THE ROOD BEAD . HOWEVER THE LENGTH THAT THE ELECT . PROTRUDES FROM THE END OF THE NOZZLE MUST BE SHORTENED SO THAT IT WILL NOT COME IN CONTACT WITH THE ROOT BEAD OR THE MOLTEN POOL OF METAL

.

WELDING OF INTERMEDIATE AND COVER PASSES HOT PASS :

AFTER THE ROOD PASS IS WELDED , THE ROOT BEAD IS GENERALLY VERY CONVEX . THE NORMAL

PROCEDURE IS TO GRIND THE ROOT PASS TO ELIMINATE THE EXCESSIVE CONVEXITY . NORMALLY , THE ENTIRE WELD IS NOT GROUND OUT RATHER ONLY ENOUGH TO EXPOSE “ WAGON TRACKS ”. THESE ARE LINES OF SLAG THAT ARE ON EITHER SIDE OF THE BUILT UP CONVEX REGION .

61

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION THE PURPOSE OF THE HOT PASS IS PRIMARILY TO BURN OUT THE “ WAGON TRACKS ”. TO DO THIS , A HIGH CURRENT IS NORMALLY USED . FILL PASS :

FOR LIGHT COATED ELECT ., THE ARC LENGTH SHOULD BE ABOUT

2.3 TO 3.2 MM. THIS WILL

PROVIDE ENOUGH HEAT SO THAT THE PUDDLE OF MOLTEN METAL WILL BE LARGE ENOUGH TO ACCEPT THE GLOBULES OF FILLER METAL WITHOUT EXCESSIVE BUILD -UP . IF A SHORT ARC IS USED , THE SIZE OF THE PUDDLE OF MOLTEN METAL IS DECREASED CONSIDERABLY . IN THIS CASE THE SIZE OF THE POOL OF MOLTEN METAL IN WHICH THE FILLER METAL CAN BE DEPOSITED IS LIMITED . WHEN THE GLOBULE ENTERS THE SMALLER BODY OF LIQUID METAL , IT WILL RISE AND , AT THE SAME TIME , COOL MORE RAPIDLY CAUSING THE BEAD TO HAVE A HIGH CROWN AND , PERHAPS , LACK OF GOOD EDGE FUSION . EACH LAYER SHOULD BE START IN A DIFFERENT POSITION ON THE JOINT . FOR EX ., THE ROOT BEAD WAS STARTED IN THE

6:30 POSITION ; THUS THE SECOND LAYER SHOULD THEN NOT START IN THIS POSITION BUT IN THE 6 O’CLOCK

POSITION . IN CRITICAL APPLICATIONS FOR LOW TEMP . SERVICES , IT MAY BE NECESSARY TO MAXIMIZE THE IMPACT TOUGHNESS PROPERTIES OF A WELD . IN THIS CASE , ONE TECHNIQUE IS TO SPLIT THE LAYERS INTO TWO PASSES . THE OBJECTIVE IS TO ALIGN FINE GRAINED REHEATED ZONES ALONG THE CENTERLINE OF THE WELD , FROM WHERE THE TEST SAMPLES ARE TAKEN . WHEN THE END OF A BEAD IS REACHED OR WHEN THE ELECT . IS CONSUMED , THE WELD MUST BE STOPPED . THIS IS DONE BY SIMPLY REVERSING THE DIRECTION OF THE ELECT . TRAVEL FOR A SHORT DIST . AND THEN BREAKING THE ARC WITH A QUICK MOVEMENT . THE PROCEDURE FOR RESUME OF WELDING IS SAME AS FOR ROOT BEAD . CAP PASS :

NORMALLY THE COVER BEAD SHOULD OVERLAP THE EDGES OF THE BEVEL FOR APP . 1.6 MM .

IF THE PIPE IS TOO HOT THE MOLTEN METAL WILL SOLIDIFY MORE SLOWLY AND IT WILL BE VERY DIFFICULT TO CONTROL THE PUDDLE . AS A RESULT THERE WILL BE A ROUGH -LOOKING WELD WHICH IS UNSATISFACTORY AS A COVER PASS . THE REMEDY WOULD BE TO ALLOW THE PIPE TO COOL UNTIL IT IS WARM

(ABOUT 200 TO 300 F) BEFORE

STARTING TO WELD . THE CAP PASS SHOULD BE WELDED AT LOWER CURRENTS THAN THE FILL PASSES .

GENERALLY , 1)

THE CURRENT RANGE SHOULD BE ,

PASS

ROOT

HOT

FILL

160-200 160-190 THE RANGE IS GIVEN IN THE REFERENCE TO THE 4” DIA. ELECT . CURRENT RANGE

125-165

STRIPPER

CAP

150-180

150-180

2) AS A RULE OF THUMB , FOR A 4 MM ELECT THE WELDING TIME FOR ONE ELECT SHOULD BE APPROXIMATELY 1 MIN AND THE LENGTH OF WELD SHOULD BE APPROXIMATELY SAME AS THE LENGTH OF THE ELECT CONSUMED . THIS WOULD PRODUCE A TRAVEL SPEED OF APP . 12”/MIN , BUT THIS IS EXTREMELY SENSITIVE TO JOINT PREPARATION AND EXACT WELDING CONDITIONS .

62

GUIDE BOOK FOR PIPING/PIPE LINE WELDING INSPECTION 3) NO . OF PASSES REQUIRED , PIPE WT ( MM )

NO . OF PASSES (WITH

7.9 9.5 12.7

4 5 7

4) RECOMMENDED JOINT DESIGN AS PER API 1104, DOWNHILL WELDING,

UPHILL WELDING,

63

4 MM DIA . OF ELECT .)

Handbook of Weld Inspection

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