welding installation procedure

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installation instruction

Page: 1 (33)

Status: APPROVED

Table of contents

1. The danger of electricity ......................................................................................... 3 Example........................................................................................................................................... 4

2. Grounding of work piece ........................................................................................ 4

Avoid branch grounded current....................................................................................................... 5

Avoid series connection .................................................................................................................. 6

3. Hot welding sparks.................................................................................................. 7

Protect yourself and the environment.............................................................................................. 7

4. Noise.......................................................................................................................... 8

5. How to treat the welding equipment ................................................................... 10

Arc and gas arch welding equipment ............................................................................................ 10

Siting and cabling.......................................................................................................................... 10

Welding machines......................................................................................................................... 10

6. Welding methods................................................................................................... 10

7. Welders................................................................................................................... 11

8. Welding examples at site ......................................................................................11

9. Selection and use of welding consumables .......................................................... 15

Storage and drying of welding consumables................................................................................. 16

10. Welding requirements........................................................................................... 18

Compliance with next tables ......................................................................................................... 18

Acceptance levels for surface and internal defects and imperfect shape and defective geometry of

butt joints............................................................................................................................ 19

11. End preparation and cleaning.............................................................................. 23

11.1. Cleaning ...............................................................................................................23 11.2. Pipes.....................................................................................................................23

Doc. id: WDAAA116762 a



Wärtsilä Finland Oy

Doc id: WDAAA116762 a

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Bevelling ....................................................................................................................................... 23

Fitting 23

11.3. Elbows, reducers, caps, tees and valves with weld ends...............................23

11.4. Flanges.................................................................................................................23

Flanges for welding....................................................................................................................... 24

11.5. Joint preparations for butt welds ......................................................................26

Butt welds welded from one side .................................................................................................. 27

Butt welds welded from both sides ............................................................................................... 30

11.6. Branches ..............................................................................................................33

Edge preparation............................................................................................................................ 33 Fitting 33

12. Inspection of welds ................................................................................................ 33

Date: 25-Apr-2005





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Thedanger of electr icity

WARNING! Electricity can be mortal!

The intensity and effective time of the current as well as its frequency and path

contribute to the dangerousness of the electricity when leading through the human

body. Alternating current is more dangerous than direct current and the most

dangerous range is 15..100 Hz.

The current intensity depends on voltage and resistance in the circuit.

UI = R

where I= current

U=voltage

R=resistance

The total resistance of the human skin depends on voltage, the humidity of the skin,

wounds, etc. and there are a lot of individual variations in the total resistance. For

example, when the resistance of skin from one hand to the other, or from hand to

foot, is 1,400 W at a voltage of 230 V in 50% of the cases, it is even less than

1,000 W for 5%. Man’s entire resistance, skin resistance not included, is only some

500 W. In general, 500 W is regarded as calculated value for each limb (refer to

figure 1).

Figure 1. Resistance sketch





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Example

When arc welding, the electrode and the work piece can be touched simultaneously

and if that happens, the open circuit voltage will cause danger. If the open circuit

voltage of the welding power supply is 80 V and the current passage goes from the

left hand to the right foot, the circuit will be:

This is definitely a dangerous circuit. Safety can be improved by increasing

resistance, and sufficient insulation is the best protection for the welder:

• Dry rubber-souled boots without holes.

• Dry and not worn out leather gloves.

• Dry workplace.

• Insulating protective carpet under the welder, if necessary.

Gr oundingof wor kpiece

When grounding the work piece:

• The welding return current cable must always be attached directly to the workpiece or to the jointing point especially designed for the grounding clamp in thework piece treatment device.

• Paint and rust must always be removed from the fastening surface of theearthing press.

• The cable cross-sections of the two working cables and the earthing press mustbe sufficient for the current intensity used.

• The heating of the cable connections is an indication of a defective joint andthey must be repaired at the earliest possible convenience.

• The welding circuit must not be grounded (Suomensähköturvalisuusmääräykset). Do not place a grounded welding device or anyother electrical equipment on a work piece.





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Avoidbranchgroundedcurrent

The use of construction and equipment parts as return or current cable is definitelyprohibited. If welding current flows along the false path it may cause overheating

and fire in most unexpected places. Do not place the welding machine or the return

current clamp upon the welding power supply nor any other electrical device.

Figure 2. Incorrectly grounded work piece

Welding current can flow through the device protection cable. Net cables and their

grounding wires can be damaged, as they are not dimensioned for welding current.

This type of damages may also occur if, for instance, the work piece is in contact

with a grounded object during welding and if there is a defective electrical

connection in the welding return current circuit.

If the work piece is hanging in a hoisting device, the welding current may flow along

the hoisting conveyors or other parts transmitting electricity. The welding current

may cause fire or defects to the hoisting conveyors and lifting hooks. Damages also

occur in the hoist’s bearings and in grounded cables, when welding current is

transmitted through them. A defective hoist may on the other hand cause fatalinjuries to person.

If the wire feed unit hangs in the boom, it must always be electrically insulated from

the transport carriage. The wire end pushed forward from the filler wire winding may

feed welding current into the wire feed unit, thus causing dangerous situations as

described above.





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Figure 3. Incorrectly grounded work piece Avoidseriesconnection

When having several power supplies connected to one work piece you must be aware

of the risk of a possible series connection.

Never treat two welding machines simultaneously.

WARNING! There is voltage between two welding machines which is equivalent to the total open circuit voltage of these power supplies.

NOTE! As for welding transformers, the corresponding risk of series connection also occurs as a result of the connecting order of the transformer’s primary circuit.





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Hotweldingspar ks

WARNING! Welding sparks, hot waste metal and hot work pieces are always a risk of fire and burn injuries.

Protectyourselfandtheenvironment

• use fireproof dressing

• remember that the work piece is always hot

• clear the nearness from all flammable objects

• keep a foam extinguisher in the nearness

Figure 4. NEVER attempt to weld on or in a tank without to check for explosive gases first.





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Noise

Noise is produced from the welding arc during pulse MIG welding and at larger

current intensity when MIG welding.

The major sources of noise are the welding peripheral functions: slag-outs,

straightening and assembling hammering, disk cutting & bobbing and carbon arc

forming. Always use hearing protectors in such situations.

The A-noise level caused by the MMA and TIG welding is generally lower than 85

dB. MAG/MIG causes an A-noise level which exceeds 85 dB. The total A equivalent

level of the welding place often exceeds the limit of 85 dBA, therefore hearing

protectors are recommended.

The noise level caused by plasma cutting is generally 80-120 dB, therefore the use of

hearing protectors is always necessary.

According to regulation 191/82 set by Finnish authorities (Suomen

Työsuojeluhallitus), 8 hours daily exposure to noise may cause permanently impaired

hearing. The exposure will, as A equivalent (LAeq) level, when measured according

to SFS 4578 standards, exceed 85 dB. If the daily exposure is less than eight hours,

the time limits are the following:

Constant A-noise level

Hazardous exposure to

noise

85 dB 8 hours

88 dB 4 hours

91 dB 2 hours

94 dB 1 hours

97 dB 30 minutes

100 dB 15 minutes

103 dB 8 minutes

106 dB 4 minutes

109 dB 2 minutes

112 dB 1 minutes

115 dB < 1 minutes

Daily exposure to noise at different noise

levels that is hazardous to hearing

Table 1. Noise levels





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Safer working environment is granted by

a) use of approved hearing protectors

b) use of protective carpet under the welder

c) eliminating direct sources of noise.

The overall noise level can be lowered if the product itself, the methods and working

order are planned in such a way that noise generating stages are as few as possible or

fully omitted.

Figure 5. Incorrect working method

Figure 6. Correct working method





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Howtotr eattheweldingequipment

Arcandgasarchweldingequipment

Read and follow the operating instructions.Sitingandcabling

Follow the instructions given regarding the permitted siting and work places. Note

especially the limitations as to outdoor use.

Never use other cables than those recommended.Weldingmachines

• Never connect welding machines when current is on.

• Never use defective welding machines. They may cause fire and danger of life.Electrode holders, MIG pistols and Tig and plasma torches are designed toendure hard industrial use. They are, however, not designed to be used as slaghammers and their construction do not stand throwing or continuous dropping.

• Do not place welding apparatus upon power supplies or other electricaldevices.

Figure 7. Incorrect way of treating the welding machine

Weldingmethods

Electric welding or TIG-welding are recommended to used in welding of pipes, if

these are not available also MIG- or gas welding can used.





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Welder s

All welders that will be doing any kind of welding work at site must be qualified and

have valid welding certificates.

Likewise, welders employed by local subcontractors for erection and construction

work must be qualified and have valid welding certificates.

Weldingexamplesatsite

Figure 8-9 illustrates typical welding situations at site that must be avoided.

Figure 10-11 illustrates how the welding should be performed.

Figure 8. The welding current return cable is placed on the wrong side of the steel bellows.

Figure 9. There is no protection against welding sparks.





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Figure 10. Use steel sheets or leathers to protect the steel/rubber bellows against welding sparks.

Figure 11. Use steel sheets or leathers to protect the flexible hose against welding sparks





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The figures below illustrate typical welding situations during installation of equipment in the power plant.

Figure 12. Unit example under construction (wrong way)

Figure 13. Unit example under construction (wrong way)





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Figure 14. Unit example under construction (right way)

Figure 15. Unit example under construction (right way)





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Selectionanduseof weldingconsumables

As a rule, the filler metal for hot-rolled steel is chosen with a chemical composition

corresponding to that of the base metal. For steels of high strength and toughness, the

filler metal must be alloyed to a higher degree than the base metal in order to

produce a weld metal with strength and notch toughness equal to those of the base

material. In practice, the type of filler metal is dictated by the required strength level

and impact strength class. Silicon + manganese alloyed filler metals are suitable for

the steel grades JR, J0, J2, KR, K0, K2, LR, L0 and L2 (EN 10025), up to approx.

400 N/mm2 yield strength, giving an acceptable level of weld metal impact strength

at temperatures down to -20 °C (quality classes J2, K2 and L2). Weld metal

produced by silicon + manganese alloyed MIG/MAG wires generally remains toughat testing temperatures as low as -40 °C. For steels of higher strength and for

structures requiring greater notch toughness, filler metals of higher alloy content, for

example Ni, Ni + Cu, Mo or Ni + Mo, must be used.

For hot-rolled steel, filler metals of equal or only slightly (5 to 10 %) higher strength

than the base material are recommended. Filler metals for pressure vessels are,

however, required to produce a weld metal that meets the required strength factor.

The use of highly overmatching filler metals results in increased residual stresses and

a greater danger of distortion and cracking.

In welding steels of the highest strength levels, such as RAEX 560 HSF, RAEX 640

HSF and RAEX 700 HSF, it is advisable to avoid welded joints in locations where

the structure is under greatest stress so that under matching filler metals that are

softer than the base material can be used.

For welding pressure vessel steels, the consumables must be chosen from among

those approved by the proper authority or classification society.

Welding consumables for weathering steels must obviously be selected to ensure that

the welds will also be weather resistant. Consequently, the filler metal composition

must be similar to that of the base material. Nickel and copper are the most common

alloy elements in filler metals for welding weathering steels. Unalloyed filler metal

can be used where the form of joint preparation (square groove, fillet weld) and thedegree of penetration (submerged arc welding) are such that the base material amply

mixes with the weld metal. In that case the filler metal takes up the necessary

alloying elements from molten base material. In the multi-run welding of weathering

steels, the final runs should always be made with weather resistant filler metal.

The choice of filler metal for RAEX B boron steel depends on whether the welding is

carried out prior to heat treatments or only after hardening and, possibly, tempering.

The general idea is that non-alloy or low-alloy “low-strength” filler metals (e.g. OK

48.00, OK Autrod 12.51) should be preferred even for boron steels. Low-strength

filler metals make welds that are less sensitive to cracking and require less

preheating. Higher-alloyed filler metals (e.g. OK 75.75, OK Autrod 13.12) can beused if the weld metal must be easily hard enable and hardening is not followed by





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tempering, or if weld metal is required with high strength (hardness) in the as-welded

condition. Normally, the use of such high-alloy filler metals can be limited to the

surface passes. With low-strength filler metals, the surface of the weld metal

becomes as hard as with high-alloy materials, only the hardening depth remains

smaller.Storageanddryingofweldingconsumables

The proper storage and handling of welding electrodes, fluxes and wires is important

specially if these are meant for high-strength steels. Thus the hydrogen content of the

filler metal can be kept low and hydrogen cracking prevented. Welding consumables

must be stored in a dry and heated space so that the rate of moisture absorption by

electrodes and fluxes is kept to a minimum. The risk of corrosion is clearly reduced

for wires that are stored in dry space. Rust layers bind up moisture causing the

release of hydrogen into the molten weld pool. Welding consumables are best kept in

their unopened, original packages.

Coated electrodes and fluxes must be re-dried (preferably immediately before use) if

they have been exposed to moisture during storage or in transit, or if relevant

welding regulations provide for the special treatment of the filler materials to be

used.

In the storage and drying of filler materials, the specific instructions provided by

their manufacturer should always be observed. A re-drying system for basic covered

electrodes is presented in figure below. Table 2 summarizes the general

recommendations for the storage and drying of filler materials.





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Figure 16. The re-drying system for basic covered electrodes(ESAB recommendation)

Type of welding

consumablePredrying

1) Intermediate store,

package has been

opened and materials

taken3)

Storage on site4)

Re-drying5)

1. Unalloyed rutile

electrode

Not recommended Unopened package in main

store or sealed electrode

container (unheated)

In package or electrode

container (unheated) max. 1

week

80-100 °C, ca, 2 h

Do not over-dry

2. Basic covered unalloyed

and low-alloy electrodes.

Normal coating

drying

350 ± 25 °C

2-3 h2)

Storage cupboard

150 ± 25 °C

max. 3 months

In heated electrode container:

70-120 °C, max 4 h

In drying oven

350 ± 25 °C 2 h

max. 5 times



LMA coating

Normally not, un-

less prescribed.

Time and temperature as 2

Storage cupboard

150 ± 25 °C

max. 6 months

In heated electrode container:

70-120 °C, max 8 h

Same as 2



Hermetic packaging

(DRYPACK)

Not required Not suitable. Package only to

be opened on site before use.

In original package max. 8 h or

same as 3

Same as 2

5. MIG / MAG solid wire.

Metal-cored wire

Not suitable In main store or sheltered

against moisture and fouling in

site store.

Inspect the surface of wire

May be left sheltered against

dust, etc. In case of lengthy

breaks, return to store.

Not suitable

6. Flux-cored wire Not recommended In main store or under similar

conditions or in ageing oven:

40-50 °C, max. 3 months

In the welding unit, preferably

as covered. For breaks to last

over 8 h, return to store.

Not recommended

7. Submerged arc welding

flux. Agglomerated 100 %

basic fluxes

When used for high-strength

steel:

300 ± 25 °C

2-3 h2)

In closed bag in main store or

in flux container:


During welding, in flux

container. If the break is to last

over 4 h, return to heated flux

hopper.

In drying cupboard

300 ± 25 °C, 2-3 h

Thinly layered

8. Submerged arc welding

flux. Agglomerated LMA

basic fluxes, acid and

neutral fluxes

Not required In closed bag in main store or

in flux container:


During welding, in flux

container. If the break is to last

over 8 h, return to heated flux

hopper.

Same as 7

9. Metal flux for submerged

arc welding

Not recommended In closed bag in main store or

in ageing oven:40-50 °C

In flux container during

welding. For breaks of over 8h, return into ageing oven,

max. 3 months

Not recommended

Main store, original package:Temperature in store 15 °C and relative humidity max. 60 %.

Maximum storage time 3 years

Welding consumables of group 4 need no controlled climate, only a shelter against rain and snow.

1)Predrying refers to the drying of filler material after removal from the original package. For example, when extra reliability is

needed in welding critical structures or hardenable steels.

2)The need for predrying must be determined in each case se

Table 2. General recommendations for the storage and drying of welding consumables (ESAB).





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Weldingr equir ements

Next tables shows usual acceptance levels for different defects in cooling water,

starting air, lube- and fuel oil pipes. Welding of district heating, steam and gas pipes

shall be done according to local and national pressure vessel requirements.Compliancewithnexttables

With the aid of the detailed requirements specified in next tables for welding defects,

both with regard to their nature and extent, the description of a generally applicable

quality level for each quality class is attempted. However, a danger of such a system

is that it may be implemented too pedantically.

The dimensions in Tables refer to:

s Nominal thickness of parent metal. Where the weld going

together materials of different thicknesses, this refers to

the smaller nominal thickness.

d Shortest distance between defects.

l Length of individual defect.

h Largest height or depth of defect in weld thickness direction.

b Width of (weld face) reinforcement.





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Acceptancelevelsforsurfaceandinternal defectsandimperfectshapeanddefectivegeometryof buttjoints.

Water and air Oil

Crack (100)1)

Surface pores (2017) Extent of individual defect

≤ 0.2 s, in no case above 2

mm. Total surface area of pores ≤ 50 mm

2.

Extent of individual defect


mm. Total surface area of pores ≤ 25 mm

2.

Crater pipe (2024) Permitted when H ≤ 0.3 s, in no

case above 4 mm.

Permitted when H ≤ 0.2 s, in no

case above 3 mm.

Lack of fusion (401)

Incomplete penetration (402) When H ≤ 0.2 s, in no case

above 2 mm.

When H ≤ 0.1 s, in no case

above 1 mm.

Welding defect Flow media

Cracks that can be detected by conventional non destructive

testing methods are not permitted.

Incomplete fusion defect that can be detected by conventional

non destructive testing are not permitted.

1)

Figures within brackets are according to ISO 6520.





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Water and air Oil

Undercut (501) Permitted locally when H

≤ 0.2, s, in no case above

2 mm.

Permitted locally when H

≤ 0.1, s, in no case above

1 mm.

Excess weld metal on face side (502) H ≤ 1.5 + 0.15 B

Minor toe overlap permitted.

H ≤ 1.5 + 0.1 B

Toe overlap not permitted.

Excess weld metal on root side H ≤ 1.5 + 0.3 C H ≤ 1.5 + 0.2 C

Excessive penetration (504) Permitted locally. Permitted in isolation, if root

reinforement otherwise joins

parent metal gradually.

Misalignment, welding from one side (507)


The misalignment H on the outside of pipes must not exceed

0.5 s, and in no case be above 1 mm when the material

thickness is less than 5 mm. At a thickness of 5 mm £ s £ 10

mm, 0.2 s is permitted and if the thickness is more than 10 mm

0.1 s + 1 is permitted, but maximum 4 mm. The misalignment

H on the inside of the pipes must not exceed 0.5 s, and in nocase be above 1 mm when the material thickness is less than 5

mm. When the thickness is 5 mm or more, 0.05 (s-5) + 1 is

permitted, but maximum 2 mm.





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Water and air Oil

Incompletely filled groove (511) Permitted locally when H

≤ 0.2 s, in no case above

2 mm.



1 mm.

Root concavity (515) Permitted locally when H

≤ 0.2 s, in no case above2 mm.


≤ 0.1 s, in no case above1 mm.

Stray flash and spatter (601) (602) Isolated stray flash damage, if

without cracks, permitted.

Adhering spatter permitted.

Stray flash is not permitted.

Isolated adhering spatter drops

are permitted.

Stray flash and spatter,

possibly occurring, may be

removed by grinding.Crack (100) Internal crack permitted, when

H ≤ 0.2 s, in no case above 4

mm and when L ≤ s. Cracks in

heat affected zone are not

permitted.

Cracks that can be detected by

conventional non destructive

testing methods are not

permitted.

Gas pores1) 2)

(2011) Extent of individual pore ≤ 0.3

s, in no case above 5 mm.

Maximum porosity permitted

4 %.

Extent of individual pore


4 mm. Maximum porosity

permitted 2 %.


1) Elongated pores are assessed as slag inclusions.

2) Linear porosity may indicate incomplete fusion, incomplete penetration or a combination of

these.





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Water and air Oil

Clustered porosity1)

(2013) Maximum porosity permitted

12 %. Extent of individual pore


mm.

Maximum porosity permitted

8 %. Extent of individual pore ≤

0.25 s, in no case above

3 mm.

Shrinkage cavity (2021) Permitted Isolated cavities permitted if

without cracks.

Slag inclusion (301) (601) (602) Permitted Scattered slag inclusions

permitted.

Tungsten inclusion (3041) Permitted Scattered slag inclusions

permitted.

Incomplete fusion (401) Permitted when H ≤ 0.2 s, in no

case above 4 mm and when L

≤ s.

Lack of fusion defects that can

be detected by conventional

NDT methods are not

permitted.


1) With regard to spacing of pores, see information for guidance.





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Endpr epar ationandcleaning

Cleaning

Parts to be welded shall be properly cleaned on both sides of welding groove.

Grease, oil and rust shall be removed.Pipes

Bevelling

1. Bevelling of pipes shall be done as follows:

• if walls thickness of pipe is 3 mm or less I-groove shall be used

• if wall thickness is more than 3 mm V-groove shall be used

Pipe wallthickness (s)

Groove a b c Weldingmethod

3

0

2 - 3 mm

0 - 2 mm

E

TIG

3

50° - 70°

70° - 80°

2 - 4 mm

0 - 3 mm

0 - 2 mm

0 - 2 mm

E

TIG

b

b c

s

a

Table 3. Measures of grooves

E = Electric welding

TIG = TIG-weldingFitting

Pipes to be welded shall be fitted so that no step exists inside the pipe.

Figure 17.Elbows,reducers,caps,teesandvalves withweldends

Edge preparation and fitting as with pipes, valves with weld ends shall, aftertackwelding, be dismantled before final welding is done.

Flanges





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Figure 19. Welding neck flanges

Figure 20. Weld height

Figure 21. Incomplete weld

Pipes shall be prepared according to next table.

Preparation Butt weld

Asymmetry:

e < 0.15 × S1,

but less than 3 mm

s l o p e 1 : 4 £

s l o p e 1 : 4 £

s 2

s 2

e

e

s 1

s

1





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Jointpreparationsforbutt welds

The tables on the next pages specify the joint preparations and recommended

welding processes for butt welds.

All dimensions are given in millimetres.

Explanation of notes:

1) Angles are also larger and/or asymmetric for welding in position PC

according to ISO 6947 (horizontal position).

2) Dimensions given apply to the tacked condition.

3) The indication of the welding process does not mean that it is applicable for

the whole range of work piece thicknesses.4) Applicable for 111, 131, 135, 141.

5) Symbol not yet standardized in ISO 2553.





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Buttweldsweldedfromoneside





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Buttweldsweldedfrombothsides





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Branches

Edgepreparation

• Head of branch pipe shall be shaped to fit with main pipe.

• Angle of groove shall be 50 °.Fitting

• Branch pipe shall be fitted so that no step exists inside the pipe.

• Air gap (g) shall be 1 - 3 mm.

• Angle (α) shall be less than 90 °.

Figure 22.

Inspectionof welds

1. Visual examination shall be done to all welds before pressure tests.

2. In inspection special attention shall be paid to:

• Evenness of weld face.

• Height and width of reinforcement of weld.

• Pores in welds.

• Undercuts in welds.

• Stray flashes in welds.

• Complete penetration shall be checked where possible.

welding installation procedure

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