Oxford-100-Manual.pdf - 第234页
OIPT Systems Oxford Instruments Plasma Technology System Manual 7. Liquid Nitrogen WARNING IF LIQUID NITROGEN FACILITIES ARE NOT INSTALLED, OPERATED AND MAINTAINED CORRECTLY, DANGEROUS SITUATIONS CAN RESULT. THESE INTROD…
System
Manual
Oxford
Instruments
Plasma
Technology
OIPT Systems
6.1.2
Installation
of
low
vapour
pressure gases
(e.g.
SiCI
4
•
BCI
3
•
C
4
F
s
)
The
low
vapour
pressure can lead
to
condensation in
the
gas supply lines,
particularly
at
cold
points
or
when
the
gas
passes
into
a cooler region. This condensation can result
in
a
build
up
of
liquid
in
the
gas pipe, usually
at
the
low
points
or
u-bends in
the
gas line,
often
leading
to
instability
of
gas
flow,
especially
if
liquid
condenses
or
flows
into
the
MFC.
The
low
vapour
pressure can also result in very
low
gas pressure
if
the
gas cylinder
is
very
cold, e.g.
if
it
is
kept
outdoors
in
the
winter.
Therefore,
it
is
important
to
adhere
to
the
following
guidelines:
(A)
It
is
necessary
to
keep
the
gas cylinder indoors (in an extracted gas cabinet)
to
avoid
loss
of
line
pressure
when
the
outside
temperature
is
cold.
However,
do
NOT
heat
the
gas cylinder
with
a heated
jacket
as
this can cause
condensation problems
when
the
gas
passes
into
the
cooler gas lines. Room
temperature
is
warm
enough
to
provide
sufficient
vapour
pressure.
(B)
It
is
important
to
maintain
a positive
temperature
gradient
from
the
cylinder
to
the
MFC,
or
at
least keep
them
at
the
same
temperature.
The simplest
method
is
to
position
the
gas cabinet close
to
the
gas pod,
minimising
the
chances
of
temperature
differences, reducing
the
length
of
the
gas pipe, and hence
minimising
the
chances
of
condensation.
If
this
is
not
possible,
then
it
is
necessary
to
heat
the
gas lines by
the
use
of
heater
tape.
The
MFC
will
also need
to
be heated.
OIPT
offers
a heated
MFC
kit
for
these
gases.
Alternatively,
heater
tape
can be
wrapped
around
the
MFC.
However, in this
case,
it
may
also
be
necessary
to
detach
the
MFC
from
the
backing
plate
to
avoid
heat
loss
through
the
plate, and
to
cover
the
MFC
in insulation material
to
avoid
cooling
from
air
flow
within
the
gas
pod
(from
the
gas
pod
exhaust).
It
will
then
be necessary
to
set
the
MFC
temperature
hotter
than
the
gas line
temperature,
which
in
turn
is
hotter
than
the
gas cylinder
temperature.
A typical set-
up
might
be
MFC
40
·C
or
above, gas line 30-40 ·C, and gas cylinder
at
room
temperature.
(C)
If
condensation problems are suspected,
it
will
be necessary
to
pump
out
the
gas
lines completely, and optimise
the
heater
tape
arrangement
and
temperature
setpoints
before
refilling
the
gas line.
(0) For
SiCI
4
it
is
important
to
use a dedicated
SiCI
4
MFC
as
this
is
designed specifically
for
low-pressure condensable
SiCI
4
operation.
Printed: 6-Jan-06, 8:44
Services Specifications
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05
OIPT
Systems
Oxford
Instruments
Plasma
Technology
System Manual
7.
Liquid
Nitrogen
WARNING
IF LIQUID NITROGEN FACILITIES ARE NOT INSTALLED, OPERATED
AND
MAINTAINED
CORRECTLY, DANGEROUS SITUATIONS
CAN
RESULT.
THESE
INTRODUCE RISKS
OF:
A)
HAZARDOUS
PRESSURE
BUILD-UP CAUSED
BY
THE
BOIL·OFF
OF
LIQUID
NITROGEN, WHICH
CAN
RESULT
IN
AN
EXPLOSION.
B) PERSONAL INJURY FROM TOUCHING PIPEWORK
OR
OTHER SYSTEM
COMPONENTS CARRYING LIQUID NITROGEN. THIS RISK
CAN
REMAIN
EVEN
AFTER VENTING
THE
CHAMBER.
C)
ASPHYXIATION CAUSED BY
THE
BOILED-OFF LIQUID NITROGEN REPLACING
OXYGEN IN
THE
SYSTEM ENVIRONMENT.
7.1
Mandatory
Requirements
for
Liquid
Nitrogen
systems
•
Ensure
that
the
Liquid
Nitrogen
installation
is
carried
out
in
accordance
with
local
safety
regUlations.
This
includes
the
following:
(a)
No
part
of
the
Liquid
Nitrogen
circuit
can
become
blocked
with
ice
or
other
contaminants.
(b)
Adequate
precautions,
e.g.
pressure
relief
valves,
are
fitted
to
prevent
hazardous
pressure
build-up
from
boil-off
of
the
Liquid
Nitrogen.
(c)
All
system
components
carrying
liqUid
Nitrogen
are
adequately
insulated,
and
covered
to
prevent
personnel
touching
exposed
components.
•
Ensure
that
the
installation
is
inspected
by
a
Specialist
to
confirm
that
it
is
safe
to
use.
Inspections
must
be
carried
out
before
the
system
is
commissioned
and
at
regular
intervals
throughout
its
life.
•
Pipework
from
the
Dewar
to
the
system
must
be
adequately
insulated
and
connected
to
the
system
via
a
3/
8
"
SwaQelok
connector.
Issue
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05
Services Specifications
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System
Manual
Oxford
Instruments
Plasma
Technology
OIPT
Systems
8. Extraction
The
following
mandatory
requirements
describe
the
extraction
systems
recommended
by
OIPT.
While
these
recommendations
may
be
regarded
as
"good
practice",
they
are
not
a
complete
definition
of
the
safety
standards
required
when
handling
toxic,
corrosive
or
otherwise
hazardous
gases.
It
is
the
customer's
responsibility
to
ensure
that
the
installation
meets
all
relevant
local
safety
regulations
and
OIPT
accepts
no
responsibility
in
this
respect.
For
detailed
information
about
the
safety
aspects
of
gas
handling
and
pumping
systems,
the
customer
should
consult
the
relevant
manufacturer/supplier
of
the
gases
and
pumps
to
be
used.
8.1
Mandatory
requirements
for
Rotary
Pump
extraction
The
installation
must
provide
a
rotary
pump
exhaust
extraction
system
which
matches
the
rotary
pump
exhaust
and
which
conforms
to
local
safety
standards.
In
particular,
all
fittings
and
pipework
connected
to
the
rotary
pump
exhaust
must
be
made
from
industry
standard
stainless
steel
in
accordance
with
local
safety
regulations.
Specialised
equipment
such
as
scrubbers
and
furnaces
may
be
needed
to
dispose
of
hazardous
gases.
The
routing
of
the
pump
exhaust
line
must
be
arranged
so
that
condensates
cannot
flow
back
into
the
pump.
Note
that
there
is
a
risk
of
damage
from
cross-contamination
if
rotary
pumps
share
one
exhaust
system.
This
applies
whether
the
pumps
are
on
the
same
system
or
on
different
systems.
Damage
caused
by
any
cross-contamination
is
not
covered
by
the
system
warranty.
Care
must
be
taken
to
route
mutually
incompatible
exhaust
gases
through
separate
exhaust
ducts.
In
particular,
oxygen
enriched
exhaust
gases
should
not
be
mixed
with
exhausts
from
mineral
oil
pumps,
otherwise,
an
explosion
may
occur.
8.2
Mandatory
requirements
for
Gas
Pod
extraction
The
gas
pod
must
be
connected
to
the
customer's
gas
extraction
system
via
a
100
mm
diameter
pipe
collar
to
provide
cabinet
extraction
with
a
minimum
flow
rate
of
1 m
3
/hour
(6-line
gas
pod)
or
3 m
3
/hour
(12-line
gas
pod),
i.e.
an
extraction
vacuum
of
approximately
500
Pa
relative
to
local
atmospheric
pressure
is
required.
It
is
the
customer's
responsibility
to
ensure
that
the
gas
extraction
system,
including
any
necessary
gas
sensors,
meets
local
safety
regUlations.
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Services Specifications
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