Explosion - Agilent Technologies HS-16 Instruction Manual

Explosion

❑
Operation of the diffusion pump without continuous
evacuation below 0.5 Torr (0.67 mbar), or without
coolant and introducing a strong oxidizer (such as
air) or explosive vapors or powders or materials
which may react with pumping fluids in a hot pump
(above 300 °F or 150 °C) can cause an explosion.
Such an explosion can violently expel valves and
other hardware, slam open doors that are not
designed for appropriate pressure relief, or burst other
components of the vacuum system. Serious injury or
death may result from expelled parts, doors, shrapnel,
and shock waves.
❑
Three elements are required for explosion: fuel, oxi-
dizer, and an ignition. A combination of temperature
and pressure can be a source of ignition. Most diffu-
sion pump fluids are fuels. Hydrocarbon fluids are
more prone to oxidize and explode than synthetic
silicone-based fluid. The oxidizer can be air, which
can be introduced by a leak, deliberately brought in
via a process, or inadvertently admitted by operator
error.
Oxygen and other strong oxidizers are even more
dangerous than air. Certain conditions of temperature
and pressure can cause a combustible mixture to
explode. The larger the diffusion pump, the greater
the risk of explosion and the greater the risk of dam-
age and injury. Never operate large diffusion pumps
utilizing hydrocarbon oils without a complete safety
analysis for the entire system and for the application.
❑
Explosion and Fire from Acetone and Alcohol: Diffu-
sion pumps are typically cleaned with acetone and
alcohol. When combined with air, oxygen, and other
oxides, alcohol and most other solvents are very
flammable and explosive. Never permit any trace of
these cleaners to remain in or on the pump. Always
remove all traces of alcohol and acetone and other
cleaners with clean, dry, oil-free compressed air.
Never operate a large diffusion pump under the condi-
tions listed in Table 2. Any of these situations increases
the probability of an explosion.
High Throughput Diffusion Pumps
8
Table 2 Explosive Conditions
Prohibited Action
Do not run pump without
cooling water
Do not run pump with
low level of pump fluid
Do not run pump without
proper backing or holding
pump
Do not run pump when not
evacuated below 0.5 Torr
(0.67 mbar)
Do not admit air to, or
rough through, a pump
with hot boiler
Do not open drain or
fill plug while pump is
under vacuum, especially
when it is hot
Do not contaminate pump
with explosive vapors
Do not remove, defeat,
or override safety
counter-measures such
as pressure and thermal
switches and valve
sequencer interlocks
Do not machine or weld
any part of the pump
without removing all fluid
or solvent residue in pump
Do not use unsuitable
pumping fluid
Explosion-Causing
Condition
Overtemperature
Overtemperature
Overpressure
Overpressure
Overpressure plus
strong oxidizer
Overpressure plus
strong oxidizer
Lower explosive
threshold of gas mixtures
Overtemperature,
overpressure, more
combustible mixtures
Source of ignition
Lower explosive
threshold of gas mixture