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Pressurization Hazards
❑
Large vacuum pumps and their components are
designed for vacuum service; they are not designed
to be pressurized which could cause them to burst
possibly expelling shrapnel at lethal velocities.
Serious accidents have been caused by intentional
pressurization of vacuum systems and their compo-
nents.
❑
Never pressurize any part of a vacuum system for
test or any other purpose.
❑
Always provide pressure relief when designing
diffusion pumps into systems and ensure that
pressure relief motion is limited to safe
envelopes.
❑
Never permit the hazards in Table 3 to develop.
Table 3 Pressurization Hazards
Prohibited Action
Do not block inlet or
vent of liquid nitrogen
trap and lines
Do not close isolation
valves at inlet and
discharge of main
water cooling coils
when pump is heated
Do not pressurize
the pump body
(above 1 atm.)
Do not make a hole
through the vacuum
wall
❑
Pressure Relief Devices: Systems must be designed
with pressure relief devices to provide safe pressure
relief from internal explosions. Always recognize that
safety devices can fail or malfunction; provide redun-
dant protection by installing devices having different
failure modes, failure mechanisms, and failure
causes. Be certain that exhaust duct materials are
capable of withstanding the corrosivity, temperature,
and pressure of exhausted products.
High Throughput Diffusion Pumps
Result
LN
trap and/or
2
lines burst
Water turns to steam
and bursts coils
Body of pump bursts
Loss of structural
integrity of wall
Dangerous Substances
❑
Chemical Dangers of Acetone and Alcohol: Diffusion
pumps are typically cleaned with acetone or alcohol.
Acetone, alcohol, and most other solvents are irri-
tants, narcotics, and depressants, and/or carcino-
genic. Their inhalation and ingestion may produce
serious effects. Even absorption through the skin can
result in moderate toxicity. Always ensure that clean-
ing operations are performed in large, well-ventilated
rooms. Use of self-contained breathing apparatus
may be necessary depending upon the solvent type
and vapor concentration in surrounding air.
❑
Poisonous and Corrosive Compounds: When pump-
ing poisonous, reactive, and/or corrosive gas, vapors,
or chemicals, proper operation and regeneration do
not always ensure that all hazardous materials have
been totally removed. If hazardous gas, vapors,
chemicals, or combustible mixtures are pumped, suf-
ficient quantities may exist during operation or
remain after regeneration to cause severe injury or
death.
❑
Pump Fluids: Overheating the pump fluid, exposing it
to air or reactive materials, or overpressurizing it
above the normal operating range, approximately
3
1x10
Torr (1.3x10
and possibly makes it toxic. This is especially true of
backstreamed mechanical pump fluids which are
more volatile (unstable). Overheating of accidentally
introduced or backstreamed mechanical pump fluids
cannot be protected against by thermal switches
which are set for diffusion pump fluid.
❑
Process Gasses: Process gasses are frequently toxic,
flammable, corrosive, explosive, or otherwise reac-
tive. Agilent has no control over the types of gasses
passing through the user's diffusion pump as these are
entirely under the control of the process user and/or
the hardware systems integrator. Since these gasses
can cause serious injury or death, it is very important
to plumb the exhaust of the pump to the facility's
hazardous gas exhaust system which incorporates
appropriate filters, scrubbers and similar components
to ensure that the exhaust meets all air and water pol-
lution control regulations.
9
3
mbar) decomposes the fluid
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