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8/10/2019 IIAR_ProcedimientodeSoldadura.pdf
1/12
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
8/10/2019 IIAR_ProcedimientodeSoldadura.pdf
2/12
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
3/12
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