Miller MT-20-25 Owner's manual

MT-20-25
Miller
Brand
Miller
Model
MT-20-25
Category
Welding System
Type
Owner's manual

This manual is also suitable for

Millerfi
May
1993
Form:
OM-1562B
Effective
With
Style
No.
KB-8
OWNERS
MANUAL
MT-20-1
2,
MT-20-25,
MT-20V-1
2,
And
MT-20V-25
Torches
U
U
U
Read
and
follow
these
instructions
and
all
safety
blocks
carefully.
Have
only
trained
and
qualified
persons
install,
operate,
or
service
this
unit.
Call
your
distributor
if
you
do
not
understand
the
directions.
U
Give
this
manual
to
the
operator.
1I~fl
U
For
help,
call
your
distributor
U
or:
MILLER
ELECTRIC
Mtg.
1079,
Appleton,
WI
54912
Co.,
P.O.
Box
414-734-9821
~IIII~
~
Water-Cooled
Torch
For
GTAW
Welding
Rated
At
250
Amperes
100%
Duty
Cycle
Using
Argon
Shielding
Gas
.020
Thru
1/8
in
(0.5
Thru
3.2
mm)
Tungsten
Size
Capacity
U
Includes
12-1/2
Or
25
ft
(3.8
m
Or
7.6
m)
Cable
Available
With
Or
Without
A
Gas
Valve
U
Tungsten
Electrode
And
Consumables
Needed
cove,
8/92
ST-800
152
PRINTED
IN
USA
J
-I_u
MILLERS
TRUE
BLUETM
LIMITED
WARRANTY
Effective
January
1,
1992
(Equipment
with
a
serial
number
preface
of
KC
or
newer)
This
limited
warranty
supersedes
sit
previous
MILLER
warranties
end
is
exclusive
with
no
other
guarantees
or
wsrrsnties
expressed
or
implied.
LIMITED
WARRANTY
Subject
to
the
terms
snd
conditions
below,
MILLER
Electric
Ml
g.
Co..
Appleton.
Wisconsin,
warrsnts
10
its
origlnsl
retail
purchaser
that
new
MILLER
equipment
sold
after
the
effective
dste
of
this
limited
warranty
is
free
of
de
tects
in
msterisl
and
workmanship
at
the
lime
it
is
shipped
by
MILLER.
TIllS
WAR
RANT?
IS
EXPRESSLY
IN
LIEU
OF
ALL
OTHER
WARRANTIES.
EXPRESS
OR
IMPLIEO.
INCLUDING
THE
WARRANTIES
OF
MERCHANTABILITY
AND
FIT
NESS.
Within
the
warranty
periods
listed
below.
MILLER
will
repair
or
replace
any
wer
ranted
parts
or
components
that
fail
due
to
such
defects
in
material
or
workmanship.
MILLER
must
be
notified
in
writing
within
thirty
(30)
days
of
such
defect
or
failure,
at
which
time
MILLER
will
provide
instructions
on
the
warranty
claim
procedurea
to
be
followed.
MILLER
shall
honor
warranty
claims
on
warranted
equipment
listed
below
in
the
event
of
such
a
taiture
within
the
warranty
time
periods.
All
warranty
time
periods
start
on
the
date
that
the
equipment
was
delivered
to
the
original
retail
purchaser,
or
one
year
after
the
equipment
is
sent
to
the
distributor.
1.
5
Yearn
Parts
3
Years
Labor
*
Original
main
power
rectifiers
2.
3
Years
Parts
and
Labor
*
Transtormer/Rectifier
Power
Sources
*
Plasma
Arc
Cutting
Power
Sources
Semi-Automatic
and
Automatic
Wire
Feeders
Robots
3.
2
Years
Parts
and
Labor
Engine
Driven
Welding
Generators
(NOTE:
Engines
are
warrants
separately
by
the
engine
manufacturer.)
Air
Compressors
Remote
Controls
Accessory
Kits
*
Replacement
Parts
MILLERS
True
Blue
Limited
Warranty
shall
not
apply
to:
1.
Items
furnished
by
MILLER,
but
manutactured
by
others,
such
as
engines
or
trade
accessories.
These
items
are
covered
by
the
manufacturers
warranty,
if
any.
2.
Consumable
components:
such
as
contact
tips,
cuBing
nozzles.
contaclors
and
relays
or
parts
that
fail
due
to
normal
wear.
3.
Equipment
that
has
been
modified
by
any
party
other
than
MILLER,
or
equip
ment
that
has
been
improperly
installed,
improperly
operated
or
misused
based
upon
industry
standards,
or
equipment
which
has
not
had
reasonable
and
necessary
maintenance,
or
equipment
which
has
been
used
for
operalion
outside
of
the
specifications
for
the
equipment.
MILLER
PRODUCTS
ARE
INTENDED
FOR
PURCHASE
AND
USE
BY
COMMER
CIAL/INDUSTRIAL
USERS
AND
PERSONS
TRAINED
AND
EXPERIENCED
IN
THE USE
AND
MAINTENANCE
OF
WELDING
EQUIPMENt
In
the
event
of
a
warranty
claim
covered
by
this
warranty,
the
exclusive
remedies
shall
be.
at
MILLERS
option:
(1)
repair,
or
(2)
replacement;
or,
where
authorized
in
writing
by
MILLER
in
appropriate
cases.
(3)
the
reasonable
cost
of
repair
or
replace
ment
at
an
authorized
MILLER
service
alalion;
or
(4)
payment
of
or
credit
for
the
pur
chase
price
(less
reasonable
depreciation
based
upon
actual
use)
upon
return
of
the
goods
at
customers
risk
and
expense.
MILLERS
option
of
repair
or
replacement
will
be
FOB.,
Factory
at
Appleton.
Wisconsin,
or
FOB,
at
a
MILLER
authorized
ser
vice
facility
as
determined
by
MILLER.
Therefore
no
compensation
or
reimburxa
ment
for
transportation
costa
of
any
kind
will
be
allowed.
TO
THE
EXTENT
PERMItTED
BY
LAW,
THE
REMEDIES
PROVIDED
HEREIN
ARE
THE
SOLE
AND
EXCLUSIVE
REMEDIES.
IN
NO
EVENT
SHALL
MILLER
BE
LIABLE
FOR
DIRECT,
INDIRECt
SPECIAL,
INCIDENTAL
OR
CONSEOUENTIAL
DAMAGES
(INCLUDING
LOSS
OF
PROFIT).
WHETHER
BASED
ON
CON
TRACt
TORT
OR
ANY
OTHER
LEGAL
THEORY.
ANY
EXPRESS
WARRANT?
NOT
PROVIDED
HEREIN
AND
ANY
IMPLIED
WAR
RANT?,
GUARANTY
OR
REPRESENTATION
AS
TO
PERFORMANCE.
AND
ANY
REMEDY
FOR
BREACH
OF
CONTRACT
TORT
OR
ANY
OTHER
LEGAL
THEORY
WHICH,
BUT
FOR
THIS
PROVISION.
MIGHT
ARISE
BY
IMPLICATION,
OPERATION
OF
LAW,
CUSTOM
OF
TRADE
OR
COURSE
OF
DEALING.
IN
CLUDING
ANY
IMPLIED
WARRANT?
OF
MERCHANTABILITY
OR
FITNESS
FOR
PARTICULAR
PURPOSE.
WITH
RESPECT
TO
ANY
AND
ALL
EOUIPMENT
FURNISHED
BY
MILLER
IS
EXCLUDED
AND
DISCLAIMED
BY
MILLER.
Some
stales
in
the
U.S.A.
do
not
allow
limitations
of
how
long
an
implied
warranty
lasts,
or
the
exclusion
of
incidental.
indirect,
special
or
consequential
damages,
so
the
above
limilalion
or
exclusion
may
not
apply
10
you.
This
warranty
provides
ape
citic
legal
rights,
and
other
rights
may
be
available,
but
may
vary
from
slale
10
slate.
In
Canada.
legislation
in
some
provinces
provides
br
certain
additional
warranties
or
remedies
other
than
as
slated
herein,
and
to
the
extent
that
they
may
not
be
waived,
the
limitations
and
exclusions
set
out
above
may
not
apply
This
Limited
Warranly
provides
specific
legal
rights,
and
other
rights
may
be
available,
but
may
vary
from
province
to
province.
I
S
4.
1
Year
Parts
and
Labor
Motor
Driven
Guns
Process
Controllers
Water
Coolant
Systems
HF
Units
Grids
Spot
Welders
*
Load
Banks
SDX
Tranatormers
Running
Gear/Trailers
*
Field
Options
(NOTE:
Field
options
are
covered
under
True
Blue
for
the
remaining
warranty
period
of
the
product
they
are
installed
in,
or
for
a
minimum
of
one
year
whichever
is
greater.)
5.
6
Months
Batteries
6.
90
Days
Parts
and
Labor
*
M113
Guns/TIG
Torches
*
Plasma
Cutting
Torches
1_U
RECEIVING-HANDLING
Before
unpacking
eqUipment,
check
carton
for
any
damage
that
may
have
occurred
during
shipment.
Fi(e
any
C)aimS
for
loss
or
damage
with
the
delivering
carrier.
Ass(stance
for
filing
or
sett)irig
claims
may
be
obtained
from
distributor
and/or
equipment
manufacturers
Transportation
Department.
When
requesting
information
about
this
equipment,
always
provide
Mode)
Designation
and
Seria(
or
Sty(e
Number.
Use
the
fol(owing
spaces
to
record
Model
Designation
and
Serial
or
Style
Number
of
your
unit.
The
information
is
)ocated
on
the
rating
(abel
or
namep(ate.
Model
_________
Serial
or
Style
No.
Date
of
Purchase
.
miller
5193a
/
/
/GTAW
SAFETY
PRECAUTIONS
ELECTRIC
SHOCK
can
kill.
Touching
live
electrical
parts
can
cause
fatal
shocks
or
severe
burns.
The
electrode
and
work
circuit
is
electrically
live
whenever
the
output
is
on.
The
input
power
circuit
and
machine
internal
circuits
are
also
live
when
power
is
on.
Incorrectly
installed
or
improperly
grounded
equipment
is
a
hazard.
1.
Do
not
touch
live
electrical
parts.
2.
Wear
dry,
hole-free
insulating
gloves
and
body
protection.
3.
Insulate
yourself
from
work
and
ground
using
dry
insulating
mats
or
covers
big
enough
to
prevent
any
physical
contact
with
the
work
or
ground.
4.
Do
not
touch
torch
parts
if
in
contact
with
the
work
or
ground.
5.
Turn
off
power
before
checking,
cleaning,
or
changing
torch
parts.
6.
Disconnect
input
power
or
stop
engine
before
installing
or
servicing
this
equipment.
Lockout/tagout
input
power
according
to
OSHA
CFR
1910.147
(see
Safety
Standards).
WELDING
can
cause
explosion
or
fire.
Welding
on
closed
containers,
such
as
tanks,
drums,
or
pipes,
can
cause
them
to
blow
up.
Sparks
can
fly
off
from
the
welding
arc.
The
flying
sparks,
hot
workpiece,
and
hot
equipment
can
cause
fires
and
burns.
Accidental
contact
of
electrode
to
metal
objects
can
cause
sparks,
explosion,
overheating,
or
fire.
Check
and
be
sure
the
area
is
safe
before
doing
any
welding.
Protect
yourself
and
others
from
flying
sparks
and
hot
metal.
Do
not
weld
where
flying
sparks
can
strike
flammable
material.
Remove
all
flammables
within
35
ft
(10.7
m)
of
the
welding
arc.
If
this
is
not
possible,
tightly
cover
them
with
approved
covers.
7.
Properly
install
and
ground
the
welding
power
source
orwelding
generator
according
to
its
Owners
Manual
and
national,
state,
and
local
codes.
8.
Turn
oft
input
power
on
all
equipment
not
in
use.
9.
Do
not
use
worn,
damaged,
undersized,
or
poorly
spliced
cables.
10.
Inspect
and
replace
any
worn
or
damaged
torch
cable
leads.
11.
Do
not
wrap
torch
cable
around
your
body.
12.
If
earth
grounding
of
the
workpiece
is
required,
use
a
separate
connection
do
not
use
work
cable.
13.
Do
not
touch
electrode
if
in
contact
with
the
work
or
ground.
14.
Use
only
well-maintained
equipment.
Repair
or
replace
damaged
parts
at
once.
Wear
a
safety
harness
if
working
above
floor
level.
Keep
all
panels
and
covers
securely
in
place.
Clamp
work
cable
with
good
metal-to-metal
contact
to
workpiece
or
worktable
as
near
the
weld
as
practical.
4.
Be
alert
that
welding
sparks
can
easily
go
through
small
cracks
and
openings
to
adjacent
areas.
5.
Watch
for
fire,
and
keep
a
fire
extinguisher
nearby.
6.
Be
aware
that
welding
on
a
ceiling,
floor,
bulkhead,
or
partition
can
cause
fire
on
the
hidden
side.
7.
Do
not
weld
on
closed
containers,
such
as
tanks,
drums,
or
pipes,
unless
they
are
properly
prepared
according
to
AWS
F4.
1
(see
Safety
Standards).
8.
Connect
work
cable
to
the
work
as
close
to
the
welding
area
as
practical
to
prevent
welding
current
from
traveling
long,
possibly
unknown
paths
and
causing
electric
shock
and
fire
hazards.
9.
Wear
oil-free
protective
garments.
10.
Remove
any
combustibles,
such
as
a
butane
lighter
or
matches,
from
your
person
before
doing
any
welding.
11.
Allow
work
and
equipment
to
cool
before
handling.
FUMES
AND
GASES
can
be
hazardous
5.
Work
in
a
confined
space
only
if
it
is
well
ventilated,
or
while
to
your
health.
Welding
produces
fumes
and
gases.
Breathing
these
fumes
and
gases
can
be
hazardous
to
your
health.
I
Keep
your
head
out
of
the
fumes.
Do
not
breathe
the
fumes.
wearing
an
air-supplied
respirator.
Always
have
a
trained
watchperson
nearby.
Welding
fumes
and
gases
can
displace
air
and
lower
the
oxygen
level
causing
injury
or
death.
Be
sure
the
breathing
air
is
safe.
6.
Do
not
weld
in
locations
near
degreasing,
cleaning,
or
spraying
operations.
The
heat
and
rays
of
the
arc
can
react
with
vapors
to
inside,
ventilate
the
area
and/or
use
exhaust
at
the
arc
to
form
highly
toxic
and
irritating
gases.
remove
welding
fumes
and
gases.
7.
Do
not
weld
on
coated
metals,
such
as
galvanized,
lead,
or
ventilation
is
poor,
use
an
approved
air-supplied
respirator.
cadmium
plated
steel,
unless
the
coating
is
removed
from
the
Read
the
Material
Safety
Data
Sheets
(MSDSs)
and
the
weld
area,
the
area
is
well
ventilated,
and
if
necessary,
while
manufacturers
instruction
for
metals,
consumables,
coatings,
wearing
an
air-supplied
respirator.
The
coatings
and
any
metals
cleaners,
and
degreasers.
containing
these
elements
can
give
off
toxic
fumes
if
welded.
ARC
RAYS
can
burn
eyes
and
skin;
ARC
RAYS
NOISE
can
damage
hearing.
2.
Wear
a
welding
helmet
fitted
with
a
proper
shade
of
filter
(see
Arc
rays
from
the
welding
process
produce
intense
visible
and
invisible
(ultraviolet
and
infrared)
rays
that
can
burn
eyes
and
skin.
Noise
from
some
processes
can
damage
hearing.
ANSI
Z49.
I
listed
in
Safety
Standards)
to
protect
your
face
and
eyes
when
welding
or
watching.
3.
Wear
approved
safety
glasses
with
side
shields.
4.
Use
protective
screens
or
barriers
to
protect
others
from
flash
and
glare;
warn
others
not
to
watch
the
arc.
5.
Wear
protective
clothing
made
from
durable,
flame-resistant
Use
approved
ear
plugs
or
ear
muffs
if
noise
level
is
high.
material
(wool
and
leather)
and
foot
protection.
/
GTAW
WELDING
can
be
hazardous.
PROTECT
YOIY~SELF
AND
OTHERS
FROM
POSSIBLE
SERIOUS
INJURY
OR
DEATH.
KEEP
CHILDREN
AWAY.
PACI~V~&KER
WEARERS
KEEP
AWAY
UNTIL
CONSULTING
YOUR
DOCTOR.
In
welding,
Is
in
most
jobs,
exposure
to
certain
hazards
occurs.
Welding
is
safe
when
precautions
are
taken.
The
safety
infc/nation
given
below
is
only
a
summary
of
the
more
complete
safety
information
that
will
be
found
in
the
Safety
~ndards
listed
on
the
next
page.
Read
and
follow
all
Safety
Standards.
See
also
Safety
Precautions
in
powe~.iource
manual.
HAVE
ALL
INSTALLATION,
OPERATION,
MAINTENANCE,
AND
REPAIR
WORK
PERFORMED
ONLY
BY
Ql~ALlFlED
PEOPLE.
/
/
15.
16.
17.
1.
2.
3.
sr3
2/93
FLYING
SPARKS
AND
HOT
METAL
can
cause
injury
and
start
fires.
Grinding
the
tungsten
electrode
causes
flying
metal.
1.
Shape
tungsten
electrode
only
on
a
grinder
with
proper
guards
in
a
safe
location.
2.
Keep
flammables
away.
3.
Wear
approved
face
shield
or
safety
goggles
with
side
shields.
4.
Wear
gloves
and
proper
body
protection
to
protect
skin
and
hands.
PRINCIPAL
SAFETY
STANDARDS
Safety
in
Welding
and
Cutting,
ANSI
Standard
Z49.1,from
American
Welding
Society,
550
NW.
LeJeune
Rd,
Miami
FL
33126
Safety
and
Health
Standards,
OSHA
29
CFR
1910,
from
Superinten
dent
of
Documents,
U.S.
Government
Printing
Office,
Washington,
D.C.
20402.
Recommended
Safe
Practices
for
Gas
Shielded
Arc
Welding,
Ameri
can
Welding
Society
Standard
A6.1,from
American
Welding
Society,
550
NW.
LeJeune
Rd.
Miami,
FL
33126
Recommended
Safe
Practices
for
the
Preparation
for
Welding
and
Cutting
of
Containers
That
Have
Held
Hazardous
Substances,
Ameri
can
Welding
Society
Standard
AWS
F4.1,from
American
Welding
So
ciety,
550
NW.
LeJeune
Rd.
Miami,
FL
33126
National
Electrical
Code,
NFPA
Standard
70,
from
National
Fire
Pro
tection
Association,
Batterymarch
Park.
Quincy,
MA
02269.
Safe
Handling
of
Compressed
Gases
in
Cylinders,
CGA
Pamphlet
P-i.
from
Compressed
Gas
Association,
1235
Jefferson
Davis
High
way,
Suite
501,
Arlington,
VA
22202.
Code
for
Safety
in
Welding
and
Cutting,
CSA
Standard
W117.2,
from
Canadian
Standards
Association,
Standards
Sales,
178
Rexdale
Bou
levard,
Rexdale,
Ontario,
Canada
M9W
1
R3.
Safe
Practices
For
Occupation
And
Educational
Eye
And
Face
Protec
tion.
ANSI
Standard
Z87.1,
from
American
National
Standards
Institute.
1430
Broadway.
New
York,
NY
10018.
Cutting
And
Welding
Processes,
NFPA
Standard
SiB,
from
National
Fire
Protection
Association,
Batterymarch
Park,
Quincy,
MA
02269.
..
.
r~..j
CYLINDERS
can
explode
if
damaged.
4.
Never
allow
electrical
contact
between
a
Gas
Tungsten
Arc
.~
~
..
.
.
.
torch
and
a
cylinder.
Shielding
gas
cylinders
contain
gas
under
high
-~
~-
pressure.
If
damaged,
a
cylinder
can
explode.
Since
5.
Use
only
correct
shielding
gas
cylinders,
regulators,
hoses,
and
~,:;
gas
cylinders
are
normally
part
of
the
welding
fittings
designed
for
the
specific application;
maintain
them
and
process,
be
sure
to
treat
them
carefully.
associated
parts
in
good
condition.
g
T,
rn
fnrn
n,n,n,,
frnm
,,nI,,n
ni
tint
,nhon
nnoninn
r,,iinrlar
,,ni,,o
1.
Protect
gas
cylinders
from
excessive
heat,
mechanical
shocks,
slag,
open
flame,
sparks,
and
arcs.
7.
Keep
protective
cap
in
place
over
valve
except
when
cylinder
is
2.
Install
and
secure
cylinders
in
an
upright
position
by
chaining
in
use
or
connected
for
use.
them
to
a
stationary
support
or
equipment
cylinder
rack
to
8.
Read
and
follow
instructions
on
compressed
gas
cylinders,
prevent
falling
or
tipping.
associated
equipment,
and
CGA
publication
P-i
listed
in
Safety
3.
Never
drape
a
welding
torch
over
a
gas
cylinder.
Standards.
sr3
2/93
EMF
INFORMATION
TABLE
OF
CONTENTS
SECTION
1
SAFETY
INFORMATION
SECTION
2
SPECIFICATIONS
2-1.
Duty
Cycle
2
SECTION
3INSTALLATION
3-1.
Torch
Parts
And
Consumables
2
Assembling
Torch
Body
Installing
Gas
Supply
Coolant.Guidelines
3-5.
Connecting
Torch
6
SECTION
4OPERATING
THE
TORCH
7
SECTION
5
MAINTENANCE
&
TROUBLESHOOTING
5-1.
Routine
Maintenance
8
5-2.
Troubleshooting
Table
9
SECTION
6
TUNGSTEN
ELECTRODE
6-1.
Selecting
Tungsten
Electrode
6-2.
Preparing
Tungsten
SECTION
7
PARTS
LIST
Figure
7-1.
Complete
Torch
Assembly
Table
7-1.
Consumable
Parts
And
Cross
Reference
Chart
NOTE
LII~=
Considerations
About
Welding
And
The
Effects
Of
Low
Frequency
Electric
And
Magnetic
Fields
The
following
is
a
quotation
from
the
General
Conclusions
Section
of
the
U.S.
Congress,
Office
of
Technology
Assessment,
Biological
Effects
of
Power
Frequency
Electric
&
Magnetic
Fields
Background
Paper,
OTA-BP-E-53
(Washington,
DC:
U.S.
Government
Printing
Office,
May
1989):
.
.
.
there
is
now
a
very
large
volume
of
scientific
findings
based
on
experiments
at
the
cellular
level
and
from
studies
with
animals
and
people
which
clearly
establish
that
low
frequency
magnetic
fields
can
interact
with,
and
produce
changes
in,
biological
systems.
While
most
of
this
work
is
of
very
high
quality,
the
results
are
complex.
Current
scientific
understanding
does
not
yet
allow
us
to
interpret
the
evidence
in
a
single
coherent
framework.
Even
more
frustrating,
it
does
not
yet
allow
us
to
draw
definite
conclusions
about
questions
of
possible
risk
or
to
offer
clear
science-based
advice
on
strategies
to
minimize
or
avoid
potential
risks.
To
reduce
magnetic
fields
in
the
workplace,
use
the
following
procedures:
1.
Keep
cables
close
together
by
twisting
or
taping
them.
2.
Arrange
cables
to
one
side
and
away
from
the
operator.
3.
Do
not
coil
or
drape
cables
around
the
body.
4.
Keep
welding
power
source
and
cables
as
far
away
as
practical.
5.-
Connect
work
clamp
to
workpiece
as
close
to
the
weld
as
possible.
About
Pacemakers:
The
above
procedures
are
among
those
also
normally
recommended
for
pacemaker
wearers.
Consult
your
doctor
for
complete
information.
modlO
1
4/9~
3-2.
3-3.
3-4.
3
4
5
10
11
12
14
OM-1562B
-
6/93
.
SECTION
1
-
SAFETY
IN
FORMATION
modl.1
2/93
Read
all
safety
messages
throughout
this
manual.
Obey
all
safety
messages
to
avoid
injury.
Learn
the
meaning
of
WARNING
and
CAUTION.
I
I~
ELECTRIC
SHOCK
can
kilI.~~
~
~\
S
Do
not
touch
live
electrical
parts,
Disconnect
input
power
before
L,
installing
or
servicing,
Figure
1-1.
Safety
Information
SECTION
2
SPECIFICATIONS
Table
2-1.
Welding
Torch
1
2 2
\
a
CAUTION
/
5
MOVING
PARTS
can
injure.
Kee~
away
from
moving
parts.
Keep
all
panels
and
covers
closed
when
operating.
6
1
Safety
Alert
Symbol
2
Signal
Word
WARNING
means
possible
death
or
serious
injury
can
happen.
CAUTION
means
possible
minor
injury
or
equipment
damage
can
happen.
3
Statement
Of
Hazard
And
Result
4
Safety
Instructions
To
Avoid
Hazard
5
Hazard
Symbol
(If
Available)
6
Safety
Banner
Read
safety
blocks
for
each
sym
bol
shown.
7
NOTE
Special
instructions
for
best
oper
ation
not
related
to
safety.
READ
SAFETY
BLOCKS
at
start
of
_____
Section
3-1
before
proceeding.
H
NOTE
~
Turn
Off
switch
when
using
high
frequency.
Specification
Model
Description
Description
MT:
Miller
Torch;
20:
250
Ampere
Rating;
12:
12-1/2
ft
(3.8
m)
Cable;
25:
25
ft
(7.6
m)
Cable;
V:
Gas
Valve
Example:MT-20-12
Miller
Torch,
250
Ampere
Rating,
12-1/2
ft
Cable
250
A
With
Argon
Gas
And
Gas
Lens
Collet
Body
Installed
(see
Section
3-1)
Ampere
Rating
At
100%
Duty
Cycle
DCEN,
ACHF
Cooling
Method
Coolant
Requirements
Tungsten
Size
Capacity
Options
And
Accessories
Torch
Body
Dimensions
And
Weight
Water
1
qtlmin
(0.94
L/min)
.020
Thru
1/8
in
(0.5
Thru
3.2
mm)
See
Section
7
And
Rear
Cover
Length:
7-1/2
in
(191
mm);
Handle
Diameter:
3/4
in
(19
mm);
Weight:
2.5
oz
(71
g)
Total
Weight
Net:
1-1/2
lb
(0.7
kg);
Ship:
2
lb
(0.9
kg)
12-1/2
ft
Cable
25
ft
Cable
Net:
2-1/2
lb
(1.1
kg);
Ship:
3
lb
(1.4
kg)
OM-1562
Page
1
3-2.
Assembling
Torch
Body
I
Torch
Body
2
Heat
Shield
3
Collet
Body
4
Cup
-4
5
Backcap
(Long
Backcap
Shown)
6
0-Ring
7
Standard
Collet
8
Reverse
Coltet
Reverse
collet
improves
electrical
contact
of
tungsten
electrode.
9
Installing
Tungsten
10
Tungsten
Electrode
To
adjust
tungsten
position,
loosen
backcap.
Keep
connections
tight.
Replace
cup,
heat
shield,
backcap,
and
0-rings
if
cracked.
Distance
about
same
as
diameter
of
tungsten
5
3
4
Install
Check
9
Ttghten
Figure
3-2.
Installing
Torch
Body
5T-800
153
OM-1562
Page
3
3-3.
Installing
Gas
Supply
a
WARNING
CYLINDERS
can
explode
if
damaged.
Keep
cylinders
away
from
welding
and
other
electrical
circuits.
Never
touch
cylinder
with
welding
electrode.
Always
secure
cylinder
to
running
gear,
wall,
or
other
stationary
support.
BUILDUP
OF
SHIELDING
GAS
can
harm
health
or
kill.
Shut
off
shielding
gas
supply
when
not
in
use.
6
Flow
Adjust
Typical
flow
rate
is
20
cfh
(cubic
feet
per
hour).
Check
wire
man
ufacturers
recommended
flow
rate.
This
flowmeter
can
be
adjusted
between
5
and
40
cfh.
7
CO2
Adapter
8
0-Ring
Install
adapter
with
0-ring
between
regulator/flowmeter
and
CO2
cylinder.
Figure
3-3.
Typical
Regulator/Flowmeter
Installation
F.
S
warn4.1
9/91
2
Obtain
gas
cylinder
and
chain
to
running
gear,
wall,
or
other
station
ary
support
so
cylinder
cannot
fall
and
break
off
valve.
1
Cap
2
Cylinder
Valve
Remove
cap,
stand
to
side
of
valve,
and
open
valve
slightly.
Gas
flow
blows
dust
and
dirt
from
valve.
Close
valve.
3
Cylinder
4
Regulator/Flowmeter
Install
so
face
is
vertical.
5
Gas
Hose
Connection
Fitting
has
5/8-18
right-hand
threads.
Obtain
and
install
gas
hose.
3
Argon
Gas
6
5
4
OR
2
7
8
3
Tools
Needed:
~::=::::::::r
1-1/8,5/Bin
CO2
Gas
ssb3.1
12/92
ST-158
697-A
OM-1562
Page
4
3-4.
Coolant
Guidehnes
a
WARNING
ELECTRIC
SHOCK
can
kill.
Do
not
touch
live
electrical
parts.
Turn
Oft
welding
power
source,
and
disconnect
input
power
before
working
on
torch.
FAILURE
TO
PROPERLY
MAINTAIN
COOLANT
SYSTEM
can
cause
damage
to
the
coolant
system
and
torch.
Circulate
and
flush
clear
water
through
entire
system,
and
replace
coolant
everj
six
months.
INCORRECT
COOLANT
will
damage
unit.
Use
plain
distilled
or
deionized
water,
or
use
high
quality
tap
water.
In
freezing
temperatures
use
only
a
mix
of
pure
ethylene
glycol
and
distilled
or
deionized
water
such
as
MILLER
coolant
Part
No.
128
705
or
equivalent.
DO
NOT
USE
AUTOMOTIVE
ANTIFREEZE.
2
Figure
3-4.
Coolant
Guidelines
This
torch
is
rated
at
a
I
qt/min
(0.94
L/min)
coolant
flow
rate.
Changes
in
flow
rate
will
affect
operating
temperature
of
torch.
Follow
these
guidelines
to
de.
crease
corrosion
in
torch.
Material
in
contact
with
coolant
can
only
be
brass,
copper,
silver
solder,
300
Series
stainless
steel,
or
plas
tic.
I
Coolant
See
table
for
coolant
mixture
need
ed
for
operating
temperature.
2
Coolant
Supply
See
coolant
supply
Owners
Manual
for
installation
instructions.
Ref.
ST-137
225-0
OM-1562
Page
5
3-5.
Connecting
Torch
A
Torch
Without
A
Gas
Valve
To
A
Welding
Power
Source
With
A
Gas
Valve
Figure
3-5.
Connecting
A
Torch
Without
A
Gas
Valve
To
A
Welding
Power
Source
With
A
Gas
Valve
B.
Connecting
A
Torch
With
A
Gas
Valve
To
A
Welding
Power
Source
Without
A
Gas
Valve
Figure
3-6.
Connecting
A
Torch
With
A
Gas
Valve
To
A
Welding
Power
Source
Without
A
Gas
Valve
OM-1562
Page
6
I
~
READ
SAFETY
BLOCKS
at
start
of
Section
3
before
proceeding.
.
8
a
Tools
Needed:
~
5/8,
7/8
in
1
Torch
2
Welding
Power
Source
3
Coolant
Hose
(Customer
Supplied)
Obtain
correct
length
with
5/8-18
left-hand
fittings.
4
Coolant
System
5
Coolant
In
Fitting
6
Coolant
Out
Fitting
7
Regulator/Flowmeter
8
Gas
Cylinder
9
Gas
Hose
(Customer
Supplied)
Obtain
correct
length
with
5/8-18
right-hand
fittings.
10
Power
Cord
11
Gas
Valve
Ret.
ST-120
503
12
Power
Cable
Adapter
13
Torch
Gas
In
Hose
14
Torch
Coolant
In
Hose
15
Torch
Power
Cable/Coolant
Out
Hose
Connect
torch
power
cable/coolant
out
hose
to
power
cable
adapter,
and
connect
adapter
to
weld
output
terminal.
16
Work
Clamp
READ
SAFETY
BLOCKS
at
start
of
Section
3
before
proceeding.
Tools
Needed:
14
13
12
11
10
5/8,
7/Bin
Ret
ST-120
503
1
Torch
6
Coolant
In
Fitting
12
Power
Cable
Adapter
2
Gas
Valve
7
Coolant
Out
Fitting
13
Torch
Coolant
In
Hose
3
Welding
Power
Source
8
Regulator/Flowmeter
14
Torch
Power
Cable/Coolant
Out
Hose
4
Coolant
Hose
(Customer
Supplied)
Obtain
correct
length
with
5/8-18
left-hand
fittings.
9
10
Gas
Cylinder
Torch
Gas
In
Hose
Connect
torch
power
cable/coolant
out
hose
to
power
cable
adapter,
and
connect
adapter
to
weld
output
terminal.
5
Coolant
System
11
Power
Cord
15
Work
Clamp
.
SECTION
4-
OPERATING
THE
TORCH
a
WARNING
ELECTRIC
SHOCK
can
kill.
Always
wear
dry
insulating
gloves.
Insulate
yourself
from
work
and
ground.
Do
not
touch
live
electrical
parts.
Keep
all
covers
and
handle
securely
in
place
FUMES
AND
GASES
can
be
hazardous
to
your
health.
Keep
your
head
out
of
the
fumes.
Ventilate
area,
or
use
breathing
device.
Read
Material
Safety
Data Sheets
(MSDSs)
and
manufacturers
instructions
for
material
used.
WELDING
can
cause
fire
or
explosion.
Do
not
weld
near
flammable
material.
Watch
for
fire;
keep
extinguisher
nearby.
Do
not
locate
unit
over
combustible
surfaces.
Do
not
weld
on
closed
containers.
Allow
work
and
equipment
to
cool
before
handling.
,~
~
.
ARC
RAYS
can
burn
eyes
and
skin;
NOISE
can
damage
hearing.
Wear
welding
helmet
with
correct
shade
of
filter.
Wear
correct
eye,
ear,
and
body
protection.
~
I
~
.~_
~
MAGNETIC
FIELDS
FROM
HIGH
CUR
RENTS
can
affect
pacemaker
operation.
Pacemaker
wearers
keep
away.
Wearers
should
consult
their
doctor
before
going
near
arc
welding,
gouging,
or
spot
welding
opera
tions.
Figure
4-1.
Safety
Equipment
Figure
4-3.
Gas
Valve
(Optional)
See
Safety
Precautions
at
beginning
of
manual
for
ba
sic
welding
safety
information.
Swam6.1
10/91
3
12
1
Insulating
Gloves
2
Safety
Glasses
With
Side
Shields
3
Welding
Helmet
Wear
dry
insulating
gloves,
safety
glasses
with
side
shields,
and
a
welding
helmet
with
a
correct
shade
of
filter
(see
ANSI
Z49.1).
sb3.1
10/91
1
Work
Clamp
Connect
work
clamp
to
a
clean,
paint-free
location
on
workpiece,
as
close
to
weld
area
as
possible.
Tools
Needed:
Use
wire
brush
or
sandpaper
to
clean
metal
at
weld
joint
area.
sb4.1
2/93
Figure
4-2.
Work
Clamp
1
Gas
Valve
Use
valve
to
control
gas
preflow
and
postfiow
at
torch.
Posifiow
pre
vents
electrode
from
oxidizing,
or
becoming
contaminated
with
a
black
surface.
Open
valve
just
before
welding.
If
welding
power
source
and
torch
have
gas
valves,
open
both
valves
before
welding.
After
welding,
leave
valve
open
about
10
seconds
for
every
100
amperes
of
weld
current.
Close
valve
when
postflow
is
finished.
ST-800
152
OM-1562
Page
7
a
WARNING
r
BUILDUP
OF
SHIELDING
GAS
can
harm
health
or
kill.
Shut
off
shielding
gas
supply
when
not
in
use
warnl.1
9/91
1
Shielding
Gas
Cylinder
2
Valve
3
3
Foot
Control
Open
valve
on
cylinder
just
before
_____________
welding.
Foot
control
turns
weld
output
and
gas
flow
on
and
off.
Close
valve
on
cylinder
when
fin
ished
welding.
sb5.3
6/92
S.062i-C
Figure
4-4.
Shielding
Gas
SECTION
5
MAINTENANCE
&
TROUBLESHOOTING
a
WARNING
Figure
5-1.
Maintenance
Schedule
.
Connect
High-Frequency
~
)
Tungsten Tungsten
Per
________________
Unit
))
(See
Section
6)
Into
Torch
D)
Equipment
J~Source
Install
Install
&
Connect\
Selec~~))
Insert
Put
O~~\
Set
Controls
sonal
Safety
)
On
Welding
J
Equipment
_________________
________________
________________
________________
Turn
On
))
Turn
On
))
Turn
On
Turn
On
)
Shielding
Gas
Coolant
Supply
High-Frequenc
Welding
Pow~~)
Begin
Weldin~
Unit
Source
ssb8
1*9/92
Figure
4-5.
Sequence
Of
Gas
Tungsten
Arc
Welding
(GTAW)
E
LECTRIC
SHOCK
can
kill.
HOT
PARTS
can
cause
se
vere
burns.
Do
not
touch
live
electrical
parts.
Allow
cooling
period
before
maintaining
or
.
Turn
Off
welding
power
source,
and
input
power
before
working
on
torch.
.
disconnect
~stt((S~li,l~l~
servicing.
Maintenance
and
troubleshooting
only
by
qualified
persons.
to
be
performed
swarn8.i~
2/93
5-1.
Routine
Maintenance
40
Hours
Replace
Cracked
Parts
Torch
Body
~
ST-Boo
152
Gas
Hose
Torch
Cable
I
OM-1562
Page
8
5-2.
Troubleshooting
Table
Table
5-1.
Welding
Trouble
Decreased
coolant
flow
rate.
-.
*
See
welding
power
source
Owners
Manual.
**
See
coolant
supply
Owners
Manual.
Add
coolant
Check
for
clogged
hoses
or
coolant
strainer.
I
Section
-~
6-1
-a
*
---
--
---
--
-
*
3-3
Figure
4-3
6-1
6-2
--a
--
Figure
4-3
-~
3-3,3.5
-..
6-2
-~
7
.~
3-4
-~
**
-~
3.4
-~
**
OM-1562
Page
9
Trouble
Lack
of
high
frequency;
difficulty
in
es-
 
-~
tablishing
arc.
Remedy
Select
proper
size
tungsten.
Check
High
Frequency
control
on
welding
power
source.
Be
sure
that
electrode
holder
cable
is
not
close
to
any
grounded
metal.
Check
cables
and
torch
for
cracked
insulation
or
bad
connections.
Repair
or
replace
necessary
parts.
Check
and
adjust
spark
gaps
in
welding
power
source,
if
neces
sary.
Wandering
arc
poor
control
of
direc-
-~
tion
of
arc.
Reduce
gas
flow
rate.
Select
proper
size
tungsten.
Tungsten
electrode
oxidizing
and
not
re-
-~
maining
bright
after
conclusion
of
weld.
Properly
prepare
tungsten.
Shield
weld
zone
from
drafts.
Increase
postflow
time.
Check
and
tighten
all
gas
fittings.
Properly
prepare
tungsten.
No
coolant
flow.
1
-.
Replace
torch
parts
if
water
has
leaked
into
torch.
Add
coolant.
Check
for
clogged
hoses
or
coolant
strainer.
SECTION
6-
TUNGSTEN
ELECTRODE
Typical
argon
shielding
gas
flow
rates
are
15
to
35
cfh
(cubic
feet
per
hour).
Not
Recommended.
The
figures
listed
are
intended
as
a
guide
and
are a
composite
of
recommendations
from
American
Welding
manufacturers.
mod2,1
3/93
.
NOTE
~
For
additional
information,
see
your
distributor
fora
handbook
on
the
Gas
Tungsten
Arc
Welding
(GTAW)
process.
Wear
clean
gloves
to
prevent
contamination
of
tungsten
electrode.
6-1.
Selecting
Tungsten
Electrode
Table
6-1.
Tungsten
Size
Electrode
Diameter
Amperage
flange
-
Gas
Type
-
Polarity
DC
Argon
Electrode
DC
Argon
Electrode
AC
Argon
Using
AC
Argon
Balanced
Negative/Straight
Polarity
Positive/Reverse
Polarity
High
Frequency
Wave
Using
High
Freq.
Pure
Tungsten
(Green
Band)
.010
.020
.040
1/16
3/32
1/8
5/32
3/16
1/4
Uptol5
5-20
15-80
70-150
125-225
225-360
360-450
450-720
720-950
*
*
*
10-20
15-30
25-40
40-55
55-80
80-125
Uptol5
5-20
10-60
50-100
100-160
150-210
200-275
250-350
325-450
UptolO
10-20
20-30
30-80
60-130
100-180
160-240
190-300
250-400
2%
Thorium
Alloyed
Tungsten
(Red
Band)
.010
.020
.040
1/16
3/32
1/8
5/32
3/16
1/4
Up
to
25
15-40
25-85
50-160
135-235
250-400
400-500
500-750
750-1000
*
*
*
10-20
15-30
25-40
40-55
55-80
80-125
Up
to
20
15-35
20-80
50-150
130-250
225-360
300-450
400-500
600-800
Up
to
15
5-20
20-60
60-120
100-180
160-250
200-320
290-390
340-525
Zirconium
Alloyed
Tungsten
(Brown
Band)
.010
.020
040
1/16
3/32
1/8
5/32
3/16
1/4
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
Upto2O
15-35
20-80
50-150
130-250
225-360
300-450
400-550
600-800
Uptol5
5-20
20-60
60-120
100-180
160-250
200-320
290-390
340-525
Society
(AWS)
and
electrode
S
-0009
OM-1562
Page
10
SECTION
7
PARTS
LIST
Figure
7-1.
Complete
Torch
Assembly
.
9
4
Table
7-1
Table
7-1
2
5
11
18
i~12
19
18
ST-120
502
OM-1562
Page
12
Item
Stock
Model
No.
No.
No.
OPTIONAL
Description
BE
SURE
TO
PROVIDE
MODEL
AND
SERIAL
NUMBER
WHEN
ORDERING
REPLACEMENT
PARTS.
Figure
7-1.
Complete
Torch
Assembly
Quantity
TUNGSTEN,
electrode
(consult
your
welding
supply
distributor)
CUP,
(see
Table
7-1)
COLLET
BODY,
(see
IbIe
7-1)
116
223
TORCH
BODY,
wlheat
shield
(consisting
of)
1
116
222
TORCH
BODY,
w/heat
shield
and
valve
(consisting
of)
1
5
...
116
279
.
300VK
....
VALVE
KNOB,
with
0-rings
(consisting
of)
I
6
...
116254
..
100R
0-RING
2
7
200HS
....
HEAT
SHIELD,
std
1
7
2GHS
HEAT
SHIELD,
gas
lens
I
8
COLLET,
(see
Table
7-1)
9
...
116
224
...
200L
BACK
CAP,
medium
(consisting
of)
1
9
..
116
225
..
200M
BACK
CAP,
long
(consisting
of)
1
9
..
116
226
.
.
.
200S
BACK
CAP,
short
(consisting
of)
1
10
..
116227
..
200R
...
0-RING
1
11
..
117585
HANDLE
1
11
..
118516
HANDLE,
models
w/valve
1
12
.
116
228
..
2PCA
POWER
CABLE
ADAPTER
1
13
..
116
205
.
212TF
CABLE,
Tn-Flex
12-1/2ft
(consisting
of)
1
13
..
116
206
.
225TF
CABLE,
Tn-Flex
25ft
(consisting
of)
1
14
..
116
267
.
212AH
....
GAS
HOSE,
12-1/2ft
(consisting
of)
1
14
..
116
268
.
225AH
....
GAS
HOSE,
25ft
(consisting
of)
1
15
.
118
512
HOSE,
black
2
series
1/8
in
ID
(order
by
ft
as
required)
16
.
116
266
...
2AN
GAS
NUT
1
17
.
116
269
...
3HF
HOSE
FITTING
1
18
..
116231
.
212PC
...
POWER
CABLE,
w/fittings
12-1/2ft
1
18
.
116
230
.
225PC
...
POWER
CABLE,
w/fittings
25ft
1
19
.
116
232
.
212WH
...
WATER
HOSE,
12-1/2ft
(consisting
of)
1
19
.
116
233
.
225WH
...
WATER
HOSE,
25ft
(consisting
of)
1
20
.
116
269
...
3HF
HOSE
FITTING
1
21
.
116236
..
2WN
WATER
NUT
1
22
.
118
512
HOSE,
black
2
series
1/8
in
ID
(order
by
ft
as
required)
OM-1562
Page
13
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OM-1562
Page
14
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Miller MT-20-25 Owner's manual

MT-20-25
Miller
Brand
Miller
Model
MT-20-25
Category
Welding System
Type
Owner's manual
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