Industries are dealing with high pressure system, vacuum system and
their operation. When a system operating below atmospheric (14.7 psig) pressure,
then it’s a vacuum system. When working with vacuum system, during backfilling
(the process in which vacuum system is returning to atmospheric pressure after
Normally these type of vacuum system must be designed, fabricate,
operated in accordance with standard, codes, proper principles, guidelines.
When dealing with high pressure systems it may be high hazard system or
low hazard pressure system. Following type system are consider in high hazard
pressure system. The system which contain poisonous, dangerous, radioactive,
unsafe, harmful fluids operated above 15psig pressure. When system consist of
oxygen, flammable material and operated above 15psig pressure. When vessel or
system contain gas operated above 150psig pressure. When system contain 100kJ energy
of total energy.
Following type of system consider under low hazard pressure system, when
there is air and inert gas system operated below 150psig pressure and inert
liquid at 1500psig pressure, system with total energy is below 100kJ, utility
system operated at 300psig pressure.
Working with Vacuum systems
Vacuum systems include those activities involving mechanical vacuum
pumps, building vacuum systems, water aspirators, or steam
aspirators. Work with vacuum systems poses a substantial danger of injury
to the operator from flying glass shrapnel released during an implosion. Other
hazards may include: 4
The toxicity of the chemicals in the vacuum
Fire following breakage of a flask containing
Toxicity from the mercury in manometers and
Over- or under-pressurization arising with thermal
Electric shock with hot cathode ionization
Vacuum Apparatus 4
Vessels used in vacuum operations shall be
protected with suitable relief valves (vacuum breaker).
A protective shield shall be placed around
“Fish net” or electrical tape shall be wrapped
around all glassware under reduced pressure.
PPE for laboratorians shall include safety glasses
or goggles and face shields when working with evacuated systems or setting up
The vacuum system shall be been arranged to allow
the equipment to be moved without transmitting strain to the neck of the flask;
flasks are to be supported from below as well as by their necks.
The vacuum apparatus must be well out of the way of
traffic to avoid being struck inadvertently.
Belt-driven mechanical pumps shall be equipped with
protective guards to enclose the moving belts (machine guarding).
of Contaminants 4
Each vacuum system used for solvent distillation
operations shall be protected by a suitable trapping device (cold trap, filter,
liquid trap) with a backflow check valve.
Water, solvents, and corrosive gases shall be
trapped and not allowed to be drawn into the building vacuum (house)
When mechanical vacuum pumps are used with volatile
substances, the input line to the pump shall be fitted with a cold trap to
minimize the amount of volatile materials entering the pump and dissolving in
Use pump oil that is appropriate for the
contaminant such as Fomblin® when working with corrosives or other materials
that are not compatible with hydrocarbon based oils.
If particulates could contaminate a vacuum line
(e.g., from an inert atmosphere dry box or glove box), a HEPA filter shall be
If pump oil becomes contaminated, it shall be
drained and changed to prevent the exhaust of chemicals into room air.
Used pump oil shall be labelled Used Oil
and disposed of through GT EHS.
Records of pump use shall be maintained for
general-purpose lab pumps in order to forestall cross-contamination or reactive
chemical incompatibility problems.
The exhaust from evacuation of volatile, toxic, or
corrosive materials shall be vented to an air exhaust system such as a chemical
fume hood or local exhaust duct.
Glass vessels used in conjunction with the vacuum
system should be checked with polarized light for cracks, scratches, or etching
each time the vessel is used. At minimum, a visual inspection will be
Dewar flasks shall be wrapped with tape or enclosed
in wooden or metal containers.
Reduced pressure must never applied to
flat-bottomed flasks unless they have been designed for this purpose.
Vacuum desiccators shall be made of
borosilicate/Pyrex glass or plastic.
Evacuated desiccators must never be carried or
Desiccators shall not be opened until atmospheric
pressure has been restored.
If rotary evaporators are used, increases in
rotation speed and application of vacuum to the flask are gradual.
with high pressure systems
High-pressure reactions are those experiments that are carried out at
pressures above one atmosphere. This includes most hydrogenation reactions
since explosive oxygen-hydrogen mixtures can be formed as a result of these
Pressure vessels should be labelled to indicate the
maximum allowable working pressure and temperature.
Service lines shall not be not connected to any
closed apparatus incapable of withstanding the maximum pressure of the service
line (air, water, etc.).
All pressure systems shall be protected with
appropriate pressure-relief devices.
The pressure-relief device shall be installed
so that the discharge is directed away from the area where a person could be
affected (preferably toward the back of a hood)
Pressure-relief devices shall be inspected
periodically by lab staff. Orifices on both sides of the pressure-relief device
should be checked for obstruction.
Pressure gauges with pressure ranges about twice
the working pressure of the system shall be used.
Containers, fittings, and other equipment to be
used when working with pressure vessels shall be chosen to able to withstand the
stresses imposed by the given pressures and temperatures.
Pressure vessels containing liquids shall not be
filled above capacity (no more than half full is preferred).
The pressure levels of high-pressure devices shall
be monitored periodically as heating proceeds.
More details and instruction
for the pressure systems is provided in the Pressure Systems Safety
Regulations 2000 Approved Code of Practice and guidance.