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lnternaonal

lnstute

ol

Ammona efrigraon

iiCIr.

Chapter

I

Welding

Procedures

lntroduction

Ammonia

refrigerating system

piping is

usuaily

joined

by welding.

This

chapter

lists

applicable

standads,

denes

cornmon

terms,

and gives

examples

of

typical

welding

procedures.

Pertinent

ANSI

Codes

and

Standards

for Welding

The

list below

briefly

describes the scope

of

the

referenced stardad. The most recent

revlqion applies.

1.

ASME

Boiler

and Pressure

Vessel

Code,

Seclon

tr Material

Specifications,

Part A

-

Ferous.

Specifies

all

ferrous materials approved

for

use

with ASME

Codes.

2.

ASME

Boiler

an d

Pressure

Vessel

Code,

Seclon

II

Material

Specifications,

Part C

-

Welding

rods,

Electrodes

and

Filler Metals.

Specifies

all welrling

rods, electrodes

and

filler

metals approved

for

use

with

ASME

Codes.

3.

A,SME Boiler

and Pressure

Vessel

Code,

Seclon

V Nondestructive

Examination.

Contains

requirements

and

methods

for

nondestructive examinations

required

in

other

Code

Sections.

Intended to

detect

surface

and

internal

discontinuances

in

materials, welds,

and

fabricated

parts

and

components,

meods

include radiographic examination, ultrasonic

examinis,

quid

penetrant

examination, magnetic

particie

examination,

eddy

curent

exminis,

sual

saminfi6, and leak testing.

4.

ASIvIE

Boiler

and,

Pressure Vessel

Code,

Secion

D(

Welding

and Brazing

Quaiifications.

Covers

qualication

of

welders,

welding operators, brazers,

brazing

operators,

and the

procedures

employed in

welding

or brazi:rg

in

accordance

with

the

ASME

Code.

NME

831 Codefor Pressure Piping,831.5

Refrigeration Piping.

Contais

requirements

for

refrigerant

and secondary

coolant

piping.

Heat

exchanger

coils

to be added

in tle near

future.

AWS

82.1

Stanlardfor Welding Procedure

and Performance

Qualificar'ore

Contains

requirements welding

procedure

qualication

and

for

performance qualification

of

welders

and

welding

operators.

Covers

manual,

semi-u1s6rtic, machine,

and

automatic

wslding,

when

referenced

by

a

product

code, standard,

or

specifi.cation.

ASME

Section

D(

permits

referencing is

standard

fs

\ryslding

qualification

i contract documents when no

product

standard appes.

AWS

82.1-)0{

StandardforWelding

Procedure

Specifications

(WPS)

for

(various

methods

and

materials). Provides

information for producing

acceptable welds

using various

conditions

and

variables.

The user needs a signifisan knowledge

sf

\/slding

and

accepts

fuIl responsibity

for

all aspects of e work.

AWS

AilO{

Nanous)

Filler Metal

Specificaions.

Provides

standard classification

systems

for the

purchase

and distribution

of

filler

metals

without

consideration

of trade or brand

n?mes.

5.

7.

Ammonia

Refrigeration

Piping

Handbook

@

llAR 2000

8-1

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Chapter

8,

Welding

Procedures

Jurisdictional

Acceptance

of

Standards

Jurisdictional

Acceptance

of

Standards

The

American

Sociery

of

Mechanical

Engineers

(ASME) develops

voluntary

consensus

standads

under

the

rules

of

the

Ameican

National

standads

Institute

(ANSI)'

ANSI

provides procedurai oversight

for

standards-development;

it

does

not

develop

or

support

standards.

For

pressure

coritainment

technology,

ASME

Section

D(

of

the

Boiler

and

pressure

Vessel

Code

defines

weiding

and

other

general

requirements,

procedure

qualifications,

performance

qualifications

and

welding

data.

ASME

does

not

publish

specifi

c Welding

Procedure

Specifi

cations

(WPS's)'

The American

Welding

Society

(AWS)

also

develops

voluntary

consensus

standards

in

accordance

with

the

rules

of

ANSI.

For

pressure

containment

welding'

AWS

Bulletin

B2'1

uses

similar

welding

information

as

at

contained

in

ASME

Section

D('

Both

publications

use

the

same

ASTIvI

references

and

groupings

for

base

metals'

They

both

include

AWS

Specif,cation

and

classification

numbers

for

electrodes'

welding

rods

and

filier

metals.

In

addition,

AWS

publishes

marry

welding

Procedure

specification's

flMPS',s)

for

pressure vessels,

piping,

*

,t

o t*es._These

procedures

are

pre-qualified

so

that

piping

contractors

*

urol

the

expense

of continuously

qualifying

welded

joints.

ASME

and

some

jurisdictions

maditionally

do

not

accept

other-than-ASME

welding

qualications

for

use

under

ASME

codes.

some

fabricators

traditionally

use

AV/S

or

other

qualifi.cations

for

ammonia

system

piping;

ir

some

areas

this

is

accepted'

In

the

Model

Uupr ,

concerning

fabricatitn

approved

for

e

ASME

831

Piping

Codes'

other-than-ASME

Procedure

qurincations

are

allowed

to

avoid

duplication

of

effort'-

WPS,s

qualified

by

a

technically

competent

glouP

or

agency

may

be

used,

provided

all

of

the

following

are

met:

l.ThegrouporagencyqualifyingtheW?smeetsalloftheWPSqualificationrequirements

of

the

ASME

Code.

2.Theweldingemployeracceptsresponsibiryforthenon-ASMEW?sbysigninge

required

euancatitn

Recoids,

which

show the date

and

results of

WPS

and

performance

qualifications,

the

welders

and/or

welding

operators

used,

and

the

identification

symbol

assigned

to

each.

3.Theemployerhasqualifiedatleastonewelderorweldingopefatorusingenon.ASME

WPS.

I

a

I

t

t

it

I

t

t

t

t

I

I

rl

Definitions

of

Terms

welding

Procedure

specification

(wPS):

a

document

which

delineates

or

references

all

welding

variables

required

to

provide

direction

for

welding'

Procedure

Quatification

Record

(PQR):

a

document

providing

the

actual

welding

variables

or

to produce

an acceptable

test

weld,

and

the

results

of

qualication

tests

conducted

on

the

test

weld.

The

wPS

and

the

PQR

deterrnine

that

e

proposed

weldment

hry

the

required

properties

for

its

intended

application

if

consucted

by

iqualified

welder'

The

welding

procedure

qualification

test

estbshes

the

properties

of

the

weldment,

not

the

skill

of

the

welder

or

welding

operator.

8-2

@

llAR

2000

ffiPipingHandbook

8/10/2019 IIAR_ProcedimientodeSoldadura.pdf

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Chapter

8,

Welding

Procedures

Welding

Processes

Record

of

Welder

or

Welding

Operator

Qualification

Tests

(Performance

Qualification

Test

Record):

a

record

of

welder

or

welding

operator tests

that qualify

a

welder

to

perform

manual

or

semi-automatic

welding, or

qualify

a welding

operator

to

perform

machine or

automatic

welding.

The welder

or

welding

operator

performs

the

test

with

a

specific WPS.

The record

includes

guided

bend

test results,

radiographic

results,

and

fillet

weld

test

results

where

applicable.

Qualified

Welding

Procedure:

a

welding

procedure

which

meets

qualication

requirements.

Documents

qualification

tests

of

weldments

made

in

accordance with

the

WPS and

recorded

on a

PQR.

Qualified

welding

procedwes

are

of

two types:

1.

Procedues

ildependently

qrlifisd

by an employer

for his own

use.

2.

Standard

procedures

permitted

for

use

without

further

qualification.

Welding

Frocesses

Typical

Welding

Machines

A

variety

of

single-purpose and

muiti-purpose

welding

machines are

available,

both

electric

and

gas-engine

powered.

Portable

macbjnes

have

input

capacities up to 10kW,

whiie fixed

machines range

uP to 30kW.

pical

multi-purpose

shop

machines

can

handle

Stick,

MIG, AC TIG, DC

TIG,

and

Flux

Core

welding.

Typical

Pipe

Welding

Procedures

A typical

pipe

butt-weld

procedure

for carbon

steel

pipe,

without

the

use

of backing

bands

(or

chill rings),

makes one

pass

using

Stick

(SMAV/)

with

86010

electrodes and

two

more

with

E7018

eiectrodes.

A

cleaner procedure

when

not using

backing

bands

is

a MIG

(GMAID

root pass

withB7?

tungsten

wie

foliowed

by two

or more cover

passes

using

Stick

(SMAW)

with

87018

electrodes. A

typical

butt-welding

procedure

with

backing

bands makes

tlree

passes

with

Stick using

E7018 electrodes. Socket

fillet

welds

use

procedures

simila

to that

for

buft welds with

backing

bands.

Shielded

Metal

Arc

Welding

(SMAW,

or

Stick Welding)

This

process

uses

a

consumable

electrode,

or stick,

to

forrn

an arc

between the

electrode

and the

workpiece.

As

the

weld bead

forms,

the

stick

contributes

molten

metal

to

the

weld

puddle.

Eventually,

the

electrode

must

be

replaced.

1'lo

preserve

the

integdty

of

the weld,

the

electrode

is

coated

with

a flux

that vaporizes

to

form

a

protective

atnosphere

around

the ac. The

flux

forrns

a

slag

blanket which

must be

removed

after

the

weld

has

cooled.

Stick

is

a

relatively

slow

process

that requires

a

moderately

high

level

of

skiIl.

It is

suitable

for

steel and

stainless,

1/8 inch

and

thicker.

Gas Metal

Arc Welding

(GMAW,

or

MtG

Wetding)

This

ac

welding

process

uses

a continuous

wire electrode

to

forrn

the arc and add

molten

metal

to the

weld puddle.

A feeding

system

drives

wire

constantly

through

the gun.

Unlike

Stick welding,

electrodes need

not

be

constantiy

replaced.

An

atmosphere

of

shielding

gas,

also

delivered

through

the

welding

gun,

protects the

puddie.

A

short-circuit

MIG

process

delivers pellets

of

molten

electrode

into

the

weld

puddle,

reducing

spatter,

providing gfeater

control,

and

producing

very

clean

welds

with

no

slag blanket.

Ammonia

Flefrigeration

Piping

Handbook

o ltAR

2000

8-3

8/10/2019 IIAR_ProcedimientodeSoldadura.pdf

4/12

Chapter

8,

Welding

Procedures

Sample

Specifications for

Welding

of

Ammonia

Piping

Flux

Cored

Arc

Welding

(FCAW)

Similar to MIG

Welding,

FIux

Cored

Arc

Welding

CAV/)

uses

a

wire

wi a central core

of

protective

flux

wtrich

may

eliminate

the

need

for

gas

shielding.

Both

MIG

and

FCAW

are

very

fast

processes

which

require a

moderate

level of skill. They

are

suitable fo

steel,

stainless

and aluminum,

20

gauge

(0.036

inch)

and

icker.

Gas

Tungsten

Arc Welding

(GTAW)

Also known as

TIG

Weiding,

is

process uses

a

virrually non-consumable

tungsten alloy

electrode to

forrn

the arc

between

the

power source and the

weldment.

If

additional

material

is

needed

in

the

puddle,

the operator

normally

hand-feeds

a

metal

rod

into

the arc.

TIG

uses

different

electrode

types

to

control

e

arc

configuraon

and welding

action

with

remarkable

precision.

Greater

ampege

means

more

power,

and

more

power

aliows

the

welding of

thicker

metals.

An inert

gas,

fed

through

the

welding torch,

protects the

weld

from atmospheric

contamitation.

TIG

is

a

very slow

process,

and it requires

a

high

level of

skill.

It

is suitable

for

all

weldable

metals,

22

gauge

(0.033

inch)

and

thicker.

Gas

Welding

(FGW)

Also known

as Oxyfuel

Gas

Weiding

(OFG),

Oxyacerylene

GAS

Welding

(OA V/),

and

Oxyhydrogen

Welding

(OHW).

In

ttris

gas

welding

process,

a

gas

flame

or

flames

(with

or

without the

application

of

pressure and with

or without

fil1er metal)

produce coalescence

of

the

base

metal.

lh

E

]U

j

17

AE

-

a7

a7

?

a}

a>

e

J7

e

a,

AF

a)

C

a-

a

f

a

aF

a2

a

a

en

an

a

J

ap

ar;

a-,

J

J2

,r

Sample

Specifications

for

Welding

of

Ammonia

Piping

Scope

This

basic practice governs

weiding qualifications

for

e

welding of:

.

Materials

used

in

the

construction

of

piping

assemblies,

pressure

containing

equipmenl

and attachments

welded

thereto.

.

Any

other

component

when

referenced

by

an

appcable

purchase

document.

Table 8-1

Applicable

Codes

and

Specifications

ASME

Boiler and

Pressure

Vessel Codes

Section

ll

Material Specifications,

Part A

-

Ferrous

Materials

Section

ll

Material Specifications,

Part

C

-

Welding

Rods,

Electrodes

and

Filler Metal

Section

Vlll

Pressure

Vessels,

Division

1

Section

lX

and

Brazing Qualifications

ASME Piping Code

831.5

Refrigerant

Piping

AS.>

Filler Metal

Specif

ications

B,2.1

Standard

Welding Procedure

and

Qualification,

when applicable

Welding Procedure Specifications,

when applicable

ANSUAWS

Specifications

82.1.rc