repair welding

8/18/2019 Repair Welding

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PRE - ASSEMBLY AND WELDING OF CEILING GIRDERS

PRE-ASSEMBLY FIT UP & ALIGNMENT :

Do pre-assembly fit up and alignment of girder pieces following shop match marks. Use„L‟ clamps and wedges (Tack welds are not permitted on the weld joints ) for webalignment to keep the joint free during welding of flange joints to facilitate weldshrinkage.

Check, measure and record the following for the pre-assembly before welding (Sketch-2A/ Sketch 2B) (Also to measure & record after welding & PWHT)

- Sweep by piano wire on bottom flange (max 3mm at joints & 10mm for assy)- Camber by water level on bottom flange (max 3mm at joint & 10mm for assy)- Length between girder pin bolt hole centers (overall max 15 mm)

- Diagonal difference (max 15 mm)- Root gap (Flange=4 to 6mm; Web=6 to 8mm)- Web verticality by plumb (To monitor distortion before & after welding)- Distance between punch marks at weld joints (To monitor weld shrinkage)

NOTE: Flange root gap will be absorbed during welding as weld shrinkage.Tolerances given above are indicative.To accommodate weld shrinkage, ensure web root gap 3-4 mm more than flange root gapLength before welding = Drg length + root gap of flange jointsEnsure temporary locking & welding of the pre-assembly before start of girder welding(Sketch-3) with provision for longitudinal movement during welding to avoidaccumulation of thermal stresses & facilitates controlled weld shrinkage

NON-DESTRUCTIVE EXAMINATION (NDE ):

FLANGE BUTT JOINT:

Root Back grinding : 100% LPI Intermediate radiography for thickness > 80mm (desired)

On completion of weld 100 % RT for thickness >32mm & < 80mm

100 % UT for thickness > 80mm100 % MPI for thickness > 25mm (after PWHT)

WEB BUTT JOINT: Root Back grind ing: 100% LPIOn completion of weld Spot RT for thickness 32mm

FILLET WELDS : Between flange and web: 100% MPI (after PWHT)


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PRE-HEATING, POST HEATING & PWHT REQUIREMENTS:

PWHT CYCLE:

Weld thermocouples on top & bottom flange and web joints (as per sketch-4). ArrangePWHT of flange and web joints with electric resistance coil heaters. Issue PWHT jobcard. (Refer Exhibit) Select midpoint of temperature range and control cycle within atolerance of 15°C. Record PWHT cycle with a calibrated temperature recorder

Identify PWHT chart with chart No & date and PWHT cycle with weld joint number.Review the cycle and record observations / acceptance on chart .

FINAL INSPECTION (AFTER PWHT):

Grind / buff the Flange Butt & Fillet joints (site welds) and conduct MPI.

Clean all Site welds and paint with two coats of red oxide primer.Repeat all checks under section B and record measurements (Sketch – 2A / 2B).Punch centre line of girder on flange thicknesses and top surface of top flange

OTHER PREPARATORY WORKS FOR ERECTION:

Blue match girder pin bottom piece with column and complete support lugs welding in position. Subsequently blue match girder pin top piece with girder, tack weld supportlugs in position, remove and complete lugs welding. Conduct LPI & maintain record.

Open the girder pin assembly, buff clean the pin and seating surfaces, apply grease, re-assemble and lock the pin with pin assembly by tack welding of lock plates.Mount the girder pin assembly on ceiling girder for easiness of erection of girder

pins. Buff Clean Cement wash in the HSFG bolt area and cleat angles at WB‟slocation


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WELDING SEQUENCE FOR CEILING GIRDER

Sl. No.

SEQ. No.

WELDING SEQUENCE

1 1 Pre heat and weld root run at flange

2 2 Weld root run at flange

3 Repeat step 1 and 2 and weld three runsPost heat and cool to room temperature

4 Back grind and do LPI (at flange)

5 3 Pre heat and weld Root + Three runs (at other side of the flange)

6 Follow steps 1, 2 and 3 alternatively and welding upto 60% of the thickness of the

7 Correct the mismatch and check the root gap of the web and grind if required

8 4 Weld root run (at web)

9 5 Weld root run (at web)

10 4 Weld two run (at web)

11 5 Weld two run (at web), post heat and cool to room temperature

12 Back grinding and do LP (at web)

13 Grind the flange welding and take intermediate RT if required

14 6 Root run (at other side of the web)

15 7 Root run (at other side of the web)

16 6 Weld two run at web17 7 Weld two run at web

18 1,2 Weld three run at flange

19 3 Weld three run at flange

20 Follow steps 1,2 and 3 alternatively and complete the flange welding21 4 Weld three run at web22 5 Weld three run at web

23 6 Weld three run at web

24 7 Weld three run at web

25 Follow steps 4, 5,6,7 alternatively and complete the web welding26 8 Weld root +two run (at flange +web) - Fillet weld

27 9 Weld root +two run (at flange +web) - Fillet weld

28Follow step 8 and 9 alternatively(each three run and complete flange +web fillet

welding)


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ERECTION WELDING PRACTICE FOR SA335 P91 MATERIAL

Color Code: Brown & RedHard Stamping: Specification, Heat No, Size.

Paint / Stencil: WO DU, as per the relevant drg & document.

When any defect like crack, lamination, and deposit noticed during visual examination the same shall be confirmed by Liquid Penetrant Inspection. If confirmed, it shall be referred to unit.

The fit-up shall be as per drawing. Root gap shall be 2 to 4 mm; root mismatchshall be within 1-mm. Suitable Reference punch marks shall be made on both the pipes (at leaston three axis).At 200 mm from the EP for UT.At 1000 mm from the EP for identifying weld during PWHT.

No Preheating is required for fixing T / C with resistance spot weldingFollowing are the equipment / facilities for heating cycles.Heating methods: Induction heating

Thermocouples: Ni-Cr / Ni-Al of 0.5 mm gauge size.Temp.Recorders : 6 Points / 12 Points.

ARRANGEMENT FOR PURGING:

Argon gas of 99.99% conforming to Gr 2 IS 5760 –1998 shall be used for purging the root side

of weld.

The flow rate is to be maintained during purging is 10 to 26 litres/minute and for shielding during GTAWis 8 to14 litres/minute.(A minimum flow rate as per welding Procedure specification shall bemaintained).

Start purging from inside of pipe when root temperature reaches 220deg C. Provide continuous andadequate Argon Gas to ensure complete purging in the root area.The minimum pre-flushing time for purging before start of welding shall be 5 minutes,irrespective of the pipe size.

Wherever possible, solid purging gas chambers are to be used which can be removed after welding. Ifnot possible, only water-soluble paper is to be used. Plastic foils that are water- soluble are NOTacceptable.

USING ALUMINIUM DAM ARRANGEMENT:The Aluminum discs shall be firmly secured with a thin wire rope. After completion of the rootwelding followed by two filler passes, the disc may be pulled outwards softly.


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CAUTION : ENSURE REMOVAL OF PURGE DAM ARRANGEMENT AFTER WELDING

USING OF WATER SOLUBLE PAPER:

The dams can be made of water-soluble paper for creating the purgingchamber. The advantage in such dam arrangement is that dissolving in watercan flush the dams. The following are different methods used.


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WELDING / WELDERS QUALIFICATION:

The drying Temp shall be 200 - 300 deg C for two hours if it is not specified by the manufacturer.Portable flasks shall be used by the welders for carrying electrodes to the place of use. The electrodesshall be kept at minimum100 deg C in the flask. Welding shall be carried out with short arc and stringer

bead technique only.

The inter-pass temperature shall not exceed 350 deg C. After completion of Welding bring down thetemp to 80 - 100 deg C and hold it at this temp for one hour minimum. The PWHT shall commenceafter completing one hour of soaking.

CAUTION: - No LPI / Wet MPI shall be carried out on weld before PWHT.


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POST WELD HEAT TREATMENT:

Arrangements: - A minimum of four thermocouples shall be placed such that at least two are on theweld and the other two on the base material on either side of the weld within the heating band at 180degrees apart about 50mm from the weld joint. Two stand by thermocouple shall also be provided on

the weld in case of any failure of the thermocouple

The PWHT temp for P91 with P91 material shall be 760 + 10 deg C and the soaking timeShall be 2.5 minutes per mm of weld thickness, subject to a MINIMUM OF TWO HOURS. All recordsshall be reviewed by Welding Engineer prior to PWHT clearance. Heating shall be done by Inductionheating only.

The rate of heating / cooling :- Thickness up to 50mm - 110 deg C / hr.(max)(above 350 deg C) Thickness 50 to 75mm - 75 deg C / hr.(max)Thickness above 75mm - 55 deg C / hr.(max)Thickness = Actual thickness as measured.

INSULATION: The width of the insulation band beyond the heating band shall be at least two timesthe heating band width on either side of the weldment.

PREVENTIVE MEASURES DURING POWER FAILURE AND NON-FUNCTIONING OFEQUIPMENT'S:

During start of preheating :

In case of any power failure/interruption during preheating, the weld fit-up shall be insulated and broughtto room temperature. After the electric supply resumes the joint shall be preheated

During GTAW / SMAW:

Use gas burner arrangement to maintain the temperature at 80 deg - 100 deg C up to a length of 50mmon either side from weld centerline along the complete circumference of the pipe. Root welding shall

be continued after power is restored and preheating temperature is raised to 220 deg C. During theabove period temperature shall be recorded through contact type Thermometer.


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During cooling cycle after SMAW welding to holding temperature at 80 to 100 deg C for one hour.Care shall be taken to avoid faster cooling rate by adequate insulation. The required temp 80- 100 deg C shall be maintained by gas burner arrangements till power resumes / start o f PWHT.

RT

Power Failure during cooling / holding

220 350

80

Time

Temp in deg c

100

Theoretical curve

Actual curve

During power cut

After power resumesMaintain 80 - °C for a min period100 One hour by immediate insulation and

heating by gas

Fig - 5


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During post weld heat treatment; the following shall be followed:

During heating cycle, the whole operation to be repeated from the beginning.

2) During soakingHeat treat (soak) subsequently for the entire duration. (Complete period).

3) During cooling (above 350 deg C).Reheat to soaking temperature and cool at the required rate.Temp should not be allowed to fall below 80 – 100 deg C. Gas burner arrangement shall be used tomaintain the temperature.

RT

220

350

80

Time

100

10 760 ±

Temp

in deg c

Theoretical curve

Actual curve

Power cut

T

T1 =T

T1


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THE PWHT TEMP. SHALL NOT DEVIATE FROM THE VALUES SPECIFIED IN THE CHARTRANGE SINCE ANY DEVIATIONS TO THE SPECIFIED HOLDING TEMPERATURE RANGE,WILL ADVERSLY AFFECT THE MECHANICAL PROPERTIES OF THE WELDMENT ANDMAY LEAD TO REJECTION OF THE WELDMENT. THE WELD JOINTS SHOULD BE KEPTDRY.UNDER NO CIRCUMSTANCES ANY WATER/LIQUID IS ALLOWED TO COME INCONTACT WITH WELD AS WELL AS PREHEATED PORTION OF PIPE.


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NONDESTRUCTIVE EXAMINATION:

The calibration blocks used shall be of same material specification (P91) dia & thickness.

The UT equipment shall be calibrated prior to use and should be of „digital type‟ – Krautkramer ModelUSN 50 or equivalent or higher version, capable of storing calibration data as well as ultrasonic testresults as per UT-21

All record able indications will be stored in memory of – either the digital flaw detector or aPC for review at a later period.

HARDNESS SURVEY:

The max allowable hardness at weld and parent metal shall be 300 HV10. Joints havinghardness above 300 HV shall be reheat treated and hardness shall be checked again. Ifhardness is still more refer to unit.

PM 1 WELD

PM 2 0

270 90

180

Figure – 10

LOCATION WELDREADINGS 1 2 3 AVE 1 2 3 AVE 1 2 3 AVE

090

180270

PM: PARENT MATERIAL AVE: AVERAGE

COMBINATION WELDING:

SOAKING TIME FOR COMBINATION WELDING:

WPS N0. Material1035 P91+P22MS W0454. P91+X22

Temp.,745 15 C750 10 C

Soaking time2.5mts / mm minimum one hour2.5mts / mm minimum two hour for thickness upto50 mm and minimum four hours for thicknessabove 50 mm.

However the precautions as required for P91shall be fully taken care of.


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DO‟s and DON‟T‟s during P 91 welding, heat treatment and NDE at construction site:

DO‟S: a) Cutting by Band saw/Hack saw/Machining.

b) Pipes Edge Preparation by machining. Machining shall be done without excessive pressure to

prevent heating up of pipe

c) Grinding may be done on exceptional cases after approval and taking adequate care to preventoverheating.

d) Thermocouple wire (hot/Cold junctions) shall be welded with condenser discharge portablespot-welding equipment.

e) Reserve Thermocouples shall be made available, in case of failure of connected thermocoupleelements.

f) Ensure adequate Argon Gas for complete purging of air inside the pipe before starting GTAWroot welding.

g) Ensure Preheating at 220 Deg.C minimum before GTAW root welding.

h) Start preheating only after clearance from Welding engineer / Quality assurance engineer forweld fit-up and alignment of the joint as well as fixing of Thermocouple connections ( forInduction heating)

i) Do visual inspection on root weld maintaining weld preheating temp.

j) Continue Argon purging until the GTAW root welding followed by minimum two filler passes of SMAW, is completed.

k) Perform partial root welding to facilitate fit-up if necessary.

l) Ensure that only one layer of root welding using TGS 2CM filler wire (2 ¼ Cr 1 Mo) isdeposited. (Wherever specified).

m) Ensure proper use of TIG wires as identified by color coding or suitable hard punching.

n) Keep the GTAW wires in absolutely clean condition and free from oil, rust, etc.

o) Dry the SMAW electrodes before use.

p) Ensure the interpass temperature is less than 350 Deg.C.

q) Hold at 80-100 Deg.C for a period of Minimum 1 hour before the start of PWHT.

r) Record entire heating cycle on Chart through recorders.

s) Exercise control during grinding of weld and adjoining base metal while removingsurface/sub-surface defects or during preparation for NDE.

t) Ensure no contact with moisture during preheat, welding, post heat and PWHT ofWeld Joints.

u) Ensure removal of argon purging arrangements after welding.v) Use short Arc o n l y . The maximum weaving shall be limited to 1.5 times the dia of

the electrode.


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DON‟T‟s: a) Avoid Oxy-Acetylene flame cutting.

b) Avoid Weld-build up to correct the weld end-d1 or to set right the lip of the weld bevel.

c)

Avoid Arc strike on materials at the time of weld fit up or during welding.d) Do not Tack weld the Thermocouple wires with Manual Arc/TIG welding?

e) NO GTAW root welding without thorough purging of root area.

f) Do not use Oxy-acetylene flame heating for any heating requirements.

g) Do not use Thermal chalks on the weld groove.

h) Do not stop argon purging till completion of GTAW root welding and two layers of SMAW.

i) No Tack welding or Bridge piece welding is permitted.

j) Do not use unidentified TIG wires or electrodes.

k) Do not exceed the maximum interpass temperature indicated in WPS

l) Do not allow moisture, rain, water, cold wind, cold draft etc. to come in contact with the weldzone or heating zone during the entire cycle from preheat to PWHT.

m) Do not exceed the limits of PWHT soaking temperature.

n) Do not Interrupt the Welding/heating cycle except for unavoidable power failureso) Do not use uncalibrated equipment for temperature measurement during heating, welding,

post weld, heat treating etc.,

WHAT IS ARGON? Argon is chemically-inert, monatomic gas, heavy and available in quantity at reasonable cost. Itschemical symbol is Ar. Atomic weight is 40. Molecular weight is 40.

The compressed argon is supplied in cylinders and liquid argon is supplied in tanks. The cylinder usedfor argon will have the body colour of BLUE without band, size of 25 cms dia. & 1.5 m length,capacity of 6.2 M3 and pressure when fully charged at 150C (approx) 137 Kg/Cm2 (1949 psi).

PURITY LEVEL OF ARGON

INDIAN STANDARD for ARGON, Compressed & Liquid Specification no. IS 5760: 1998 shall bereferred.There are 3 grades of argon, namely:Grade 1 : Ultra high purity argon for use in electronics and allied industries and indirect reading vacuumspectrograph,Grade 2 : High purity argon for use in lamp and allied industries and

Grade 3 : Commercial grade argon for use in welding industry and for other metallurgical operations.


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Accordingly the argon shall comply with the requirements given below:

Sl. No. CHARACTERISTIC

REQUIREMENT Grade 1 Grade 2 Grade 3

i. Oxygen, ppm, Max. 0.5 5.0 10.0

ii. Nitrogen, ppm, Max. 2.0 10.0 300iii. Hydrogen, ppm, Max. 1.0 2.0 5.0iv. Water vapours, ppm. Max. 0.5 4.0 7.0v. Carbon dioxide, ppm, Max. 0.5 0.5 3.0vi. Carbon monoxide, ppm, Max. 0.5 0.5 2.0vii. Hydrocarbons, ppm, Max. 0.2 0.5 -

PURCHASE SPECIFICATION FOR ARGON: “Argon as per Grade 3 of IS-5760: 1998 Rev 02 with Oxygen & Water Vapours restricted to max. 7

PPM each and with Argon purity level of min. 99.99%. The supply should accompany Test Certificatefor the batch indicating individual element „PPM‟ level and overall purity level.”


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GENERAL TOLERANCES FOR WELDED STRUCTURES - (FORM AND POSITION)

GENERAL:

Tolerance on form and position as defined in this standard are permissible variations from thegeometrically ideal form and position corresponding to the accuracies commonly obtained in workshops.

The standard covers tolerances on straightness, flatness and parallelism.

This standard is based on DIN 8570 Part 3 - 1987General tolerances for machined components arecovered in corporate standard AA 023 02 08.

Refer Corporate Standard AA 062 11 04 for general tolerances for lengths and angles of weldedcomponents, assemblies and structures.

TOLERANCES ON STRAIGHTNESS, FLATNESS AND PARALLELISM

Gradeof accu-

racy

Nominal Dimension Range (larger side length of surface) - mm

Above30 to120

Above120 to

315

Above315 to1000

Above1000

to2000

Above2000

to4000

Above4000

to8000

Above8000

to12000

Above12000

to16000

Above16000

to20000

Above20000

E 0.5 1 1.5 2 3 4 5 6 7 8F 1 1.5 3 4.5 6 8 10 12 14 16G 1.5 3 5.5 9 11 16 20 22 25 25H 2.5 5 9 14 18 26 32 36 40 40


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TESTING:

STRAIGHTNESS: The edge of the welded component and the straight edge can be arranged in relation to each other so thatthe end points of the measured length are the same distance apart from the ends of the straight edge. Thedistances between the edge and the straight edge should be measured.

FLATNESS:

A measuring plane can be set up outside the welded component parallel to the limiting planes at any desireddistance . For example this can be done with optical instruments, flexible tube liquid levels, tension wires,clamp plates, surface plates and machine beds.

PARALLELISM: Any of the measuring devices mentioned above can be used to set up a measuring plane outside the weldedcomponent parallel to its reference plane. The distance from the actual surface to the measuring plane ismeasured.The position of the reference surface (= surface after machining) is dimensionally determined.

Dimension a1

gives the required finished height of the foundation. Dimension a2

gives the minimumthickness of the support.

The distance between the reference plane and the measuring plane is greater than: h max by the minimum possible thickness of the machining allowance “b”. The variation of the actual surface (=surface beforemachining) from the reference plane must be within the tolerance on parallelism. Maximum variation ishmax - hmin t

Note: The tolerance on form and position as per this standard may be mentioned on the drawing in addition

to the linear tolerances as per AA 062 11 04 wherever required.


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REPAIR PROCEDURE FOR GREY CAST IRON CASTINGS IS 210 Gr. 20 & Gr.25

ELECTRODES: Low heat nickel iron electrodes (ENi CI and ENiFe-CI type) should be used. The following

brands are recommended for repairs:

ENi CI : 1) NFM (D&H Secheron) 2) CASTRON KALT ( Modi) 3) FERROLOID -4 (ESAB)

ENiFe-CI : 1) ESAB 802 2) 1111CI (D&H Secheron)


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WELDING PROCEDURE:

To ensure maximum freedom from porosity in weld deposits, nickel iron electrodes should be re-bakedfor at least one hour at 260˚C in a well ventilated electric oven and either used immediately or stored ina similar oven at 120˚C until used.

The welding current should be kept as slow as possible consistent with smooth operation and a goodwash at the sides of the joint.

Wherever possible the casting should be positioned for down hand welding operation. When extra-longwelds or several repair positions are involved it is preferable to stagger the welding operation to distributethe heat and to minimize the distortion.

Manipulation of the electrode:It is preferable to use stringer bead technique, with beads not > 50 to 75 mm in length, slight weaving ofthe electrode may be done to obtain better wash, but in no case the width of the deposit should be > 3times the nominal dia. of the electrode.

PREHEATING:

Preheating is normally not required. Where preheating is resorted to, the entire casting should be preheated. Interpass temperature should not exceed 250˚C.

Peening of the weldment after the weld cools down may be done to reduce the shrinkagestresses.

INSPECTION: In addition to visual examination, non-destructive tests like liquid penetrant inspection might beemployed on repaired areas to ensure freedom from cracks.


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SPECIAL INSTRUCTIONS FOR THE REPAIR OF STEAM TURBINE

1 Material specification : GS-C25, 422710, 422643, SA 216

WCB

2 Removal of defects : Defects shall be removed by grinding /

machining.

3 Inspection of pre-welding : Complete elimination of defects shall

be ensured by LPI / MPI /

Radiography.

4 Welding procedure :

a) Welder : Qualified as per ASME Sec.IX / IBR

b) Process : SMAW

c) Electrode : E7018-A1. Properly baked electrodes

to be used.

d) Position : The welding shall be done in the flat position as far as possible.

e) Arc current : Φ 2.50 mm (60-80 amps)

Φ 3.15 mm (90-130 amps)

Φ 4.00 mm (140-180 amps)

Φ 5.00 mm (190-240 amps)

f) Preheating : Up to 30 mm thickness } 10ºC

30-100 mm thickness } 100ºC

101-200 mm thickness } 150ºC

g) Inter pass temperature : 350ºC max.

5 Stress relief : Below 40 mm thickness no stress

relief is required.Above 40-200 mm thickness stress

relieve at 600-620ºC for 3 hours.

6 Inspection of Post welding : MPI followed by UT.


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REPAIR WELDING PROCEDURE

1 Material specification : GS-17CrMoV511, 21CrMoV57V,

21CrMoV57, 422731.1, 422743.1,

422744.1, 422745.1

2 Removal of defects : Defects shall be removed by grinding

or machining and ensure complete

removal by LPI / MPI.


a) Welder : Qualified as per ASME Sec.IX / IBR

b) Process : SMAW

c) Electrode : E9018B3. Properly baked electrodes to

be used.

d) Arc current : Φ 2.50 mm (60-80 amps)

Φ 3.15 mm (90-130 amps)

Φ 4.00 mm (140-180 amps)

Φ 5.00 mm (190-240 amps)

e) Preheating : 300ºC, continue this temp. Throughout

the welding operation.

f) Inter pass temperature : 375ºC max.

5 Post weld heat treatment : The casing has to be stress elieved as

per code of practice in welding

procedure specification.

6 Inspection after Post weld heat treatment : MPI followed by UT.


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REPAIR WELDING PROCEDURE

1 Material specification : GS-17CrMo55(P4), A182F12,

A217WC6, A387-12

2 Removal of defects : Defects shall be removed by grindingor machining and ensure complete

removal by LPI.


a) Welder : Qualified as per ASME Sec.IX

b) Electrode : E8018B2. Properly baked electrodes

to be used.

d) Arc current : Φ 4.00 mm (140-180 amps)

Φ 5.00 mm (190-240 amps)

e) Preheating : 250ºC, maintain this temp. throughout

the welding operation.

f) Inter pass temperature : 350ºC max.

5 Post weld heat treatment : Maintain the temp. at 300ºC for about

2-3 hours and allow it to cool under

asbestos.

6 Inspection after Post weld heat treatment : MPI followed by UT.

Note: If weld repair is extensive, i.e. thickness of weld metal is more than 10 mm,

the casing has to be stress relieved as per the code of practice.


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GENERAL

In GMAW the consumable is a wire spool, which is continuously fed by a motor. Thisconsumable as well as the shielding gas come out through a hand held torch and the torch ismoved manually.

The method has two commonly used variants:

(a)Metal Inert Gas (MIG) welding (an example is the welding of aluminum bus ducts at site)(b)Metal Active Gas (MAG) welding (an example is steel chimney fabrication at site)

While Argon is almost always used in MIG welding for shielding the arc, Carbon Dioxide orCarbon Dioxide with Argon is used for MAG welding.

ADVANTAGES OF GMAW

The advantages of GMAW over SMAW are:(a) High welding speed due to continuous feed of filler metal and high deposition rate(b) No slag removal and no slag inclusion(c) Higher deposition efficiency(d) Higher arcing time(e) Low hydrogen content in weld metal

VARIABLES AFFECTING WELD QUALITY

The variables which affect weld quality in GMAW ARE:(a) Welding current(b) Polarity(c) Arc Voltage(d) Travel speed(e) Electrode extension(f) Weld joint position(g) Electrode diameter(h) Shielding gas composition(i) Gas flow rate

Current range : 120 to 160 Amps

Voltage range : 19 to 22 VoltsElectrode consumed (cm / M) : 3 to 3.8 M / Min.Current AC or DC : DCPolarity : EPSize of reinforcement : 1.5 to 2 mmWhether removed : NoInspection and test schedules : As per IS 7307 PT-1


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WELDING PROCEDURE DATA SHEET

Welding Process : Semi-Auto

Material specification : IS 2062 Gr.A

ThicknessPlate : 8 mmPipe diameter : --

Filler metal specification : IS-6419 84-C504 (ER-7086)

Weld metal analysis : NA

FLUX OR SHIELDING GAS

Flux trade Name or composition : NA

Shielding gas composition : 99.7% CO 2

Trade Name : NA

Flow rate : 10-15 LPM

Backing strip used : NA

Pre-heat temperature range : 10 C Min.

Interpass temperature range : 265 C Max.

Post Weld Heat Treatment : NA

WELDING PROCEDURE

Single or Multi-pass : Multi-pass

Single or Multiple Arc : Single

Welding position(s) : Horizontal – Vertical

FOR INFORMATION ONLY

Electrode and filler wire diameter : 1.2 mm

Trade Name : CTTOFIL(ADVANI)

Type of backing : NA

Fore hand and back hand : NA


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WHAT IS ORBITAL WELDING

Definition

The term Orbital-Welding is based on the Latin word ORBIS = circle. This has been adopted

primarily by aerospace and used in terms of Orbit (n.) or Orbital (adj.) for the trajectory of a

man- made or natural satellite or around a celestial body.

The combination Orbital and Welding specifies a process by which an arc travels

circumferentially around a work piece (usually a tube or pipe).

The concept Orbital Welding is basically a loosely defined term that is usually used for

process only, where the arc travels at least 360 degrees around the work piece without

interruption.

Consequently, processes, which interrupt the full 360-weld sequence such as for better

puddle control (often used for MIG/MAG welding, using the down-hand welding sequence

in 2 half- circles), cannot truly be called orbital welding.

INSTRUCTIONS FOR CARRYING OUT CONDENSER PLATE AND NECK WELDING:

The welding of the condenser is performed by „step back seam method‟ i.e. from tack weld totack weld. Subsequent filling welds after tack welding are always performed in the oppositedirection.

repair welding

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