atmospheres
containing
even
minute
amounts
of
trichloroethylene
or
perchioroethylene.
C.
Fire
and
Explosion
Prevention
Causes
of
fire
and
explosion
are:
combustibles
reached
by
the
arc,
flame,
flying
sparks,
hot
slag
or
heated
mate
rial;
misuse
of
compressed
gases
and
cylinders;
and
short
circuits.
BE
AWARE
THAT
flying
sparks
or
falling
slag
can
pass
through
cracks,
along
pipes,
through
windows
or
doors,
and
through
wall
or
floor
openings,
out
of
sight
of
the
goggled
operator.
Sparks
and
slag
can
fly
35
feet.
To
prevent
fires
and
explosion:
Keep
equipment
clean
and
operable,
free
of
oil,
grease,
and
(in
electrical
parts)
of
metallic
particles
that
can
cause
short
circuits.
If
combustibles
are
in
area,
do
NOT
weld
or
cut.
Move
the
work
if
practicable,
to
an
area
free
of
combustibles.
Avoid
paint
spray
rooms,
dip
tanks,
storage
areas,
venti
lators.
If
the
work
cannot
be
moved,
move
combustibles
at
least
35
feet
away
out
of
reach
of
sparks
and
heat;
or
protect
against
ignition
with
suitable
and
snug-fitting,
fire-resistant
covers
or
shields.
Walls
touching
combustibles
on
opposite
sides
should
not
be
welded
on
(or
cut).
Walls,
ceilings,
and
floor
near
work
should
be
protected
by
heat-resistant
covers
or
shields.
Fire
watcher
must
be
standing
by
with
suitable
fire
extin
guishing
equipment
during
and
for
some
time
after
weld
ing
or
cutting
if:
a.
appreciable
combustibles
(including
building
construction)
are
within
35
feet
b.
appreciable
combustibles
are
further
than
35
feet
but
can
be
ignited
by
sparks
c.
openings
(concealed
or
visible)
in
floors
or
walls
within
35
feet
may
expose
combustibles
to
sparks
d.
combustibles
adjacent
to
walls,
ceilings,
roofs,
or
metal
partitions
can
be
ignited
by
radiant
or
conducted
heat.
Hot
work
permit
should
be
obtained
before
operation
to
ensure
supervisors
approval
that
adequate
precautions
have
been
taken.
After
work
is
done,
check
that
area
is
free
of
sparks,
glowing
embers,
and
flames.
An
empty
container
that
held
combustibles,
or
that
can
produce
flammable
or
toxic
vapors
when
heated,
must
never
be
welded
on
or
cut,
unless
container
has
first
been
cleaned
as
described
in
AWS
Standard
A6.O,
listed
7
in
Standards
Index.
This
includes:
a
thorough
steam
or
caustic
cleaning
(or
a
solvent
or
water
washing,
depending
on
the
combusti
bles
solubility)
followed
by
purging
and
inerting
with
ni
trogen
or
carbon
dioxide,
and
using
protective
equip-
ment
as
recommended
in
A6.O.
Waterfilling
just
below
working
level
may
substitute
for
inerting.
A
container
with
unknown
contents
should
be
cleaned
(see
preceding
paragraph).
Do
NOT
depend
on
sense
of
smell
or
sight
to
determine
if
it
is
safe
to
weld
or
cut.
Hollow
castings
or
containers
must
be
vented
before
welding
or
cutting.
They
can
explode.
Explosive
atmospheres.
Never
weld
or
cut
where
the
air
may
contain
flammable
dust,
gas,
or
liquid
vapors
(such
as
gasoline).
D.
Compressed
Gas
Equipment
Standard
precautions.
Comply
with
precautions
in
this
manual,
and
those
detailed
in
CGA
Standard
P-i,
SAFE
HANDLING
OF
COMPRESSED
GASES
IN
CYLIN
DERS,
listed
ii
in
Standards
Index.
1.
Pressure
Regulators
Regulator
relief
valve
is
designed
to
protect
only
the
regulator
from
overpressure;
it
is
not
intended
to
protect
any
downstream
equipment.
Provide
such
protection
with
one
or
more
relief
devices.
Never
connect
a
regulator
to
a
cylinder
containing
gas
other
than
that
for
which
the
regulator
was
designed.
Remove
faulty
regulator
from
service
immediately
for
re
pair
(first
close
cylinder
valve).
The
following
symptoms
indicate
a
faulty
regulator:
Leaks-if
gas
leaks
externally.
Excessive
Creep-if
delivery
pressure
continues
to
rise
with
downstream
valve
closed.
Faulty
Gauge-if
gauge
pointer
does
not
move
off
stop
pin
when
pressurized,
nor
returns
to
stop
pin
after
pressure
release.
Repair.
Do
NOT
attempt
to
repair.
Send
faulty
regulators
for
repair
to
manufacturers
designated
repair
center,
where
special
techniques
and
tools
are
used
by
trained
personnel.
2.
Cylinders
Cylinders
must
be
handled
carefully
to
prevent
leaks
and
damage
to
their
walls,
valves,
or
safety
devices:
Avoid
electrical
circuit
contact
with
cylinders
including
third
rails,
electrical
wires,
or
welding
circuits.
They
can
produce
short
circuit
arcs
that
may
lead
to
a
serious
acci
dent.
(See
1-3C.)
ICC
or
DOT
marking
must
be
on
each
cylinder.
It
is
an
assurance
of
safety
when
the
cylinder
is
properly
han
dled.
Identifying
gas
content.
Use
only
cylinders
with
name
of
gas
marked
on
them;
do
not
rely
on
color
to
identify
gas
content.
Notify
supplier
if
unmarked.
NEVER
DEFACE
or
alter
name,
number,
or
other
markings
on
a
cylinder.
It
is
illegal
and
hazardous.
Empties:
Keep
valves
closed,
replace
caps
securely;
mark
MT;
keep
them
separate
from
FULLS
and
return
promptly.
OM-113
336
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2