|
SECTION 6: Pressure and Vacuum
Systems
Working with hazardous chemicals at high or low pressures requires planning
and special precautions. Procedures should be implemented to protect against
explosion or implosion through appropriate equipment selection and the
use of safety shields. Care should be taken to select glass apparatus
that can safely withstand designated pressure extremes.
Pressure Vessels (top)
High-pressure operations should be performed only in pressure vessels
appropriately selected for the operation, properly labeled and installed,
and protected by pressure-relief and necessary control devices. Vessels
must be strong enough to withstand the stresses encountered at the intended
operating temperatures and pressures and must not corrode or otherwise
react when in contact with the materials it contains. Systems designed
for use at elevated temperatures should be equipped with a positive
temperature controller. Manual temperature control using a simple variable
autotransformer, such as a Variac, should be avoided. The use of a back-up
temperature controller capable of shutting the system down is strongly
recommended.
All pressure equipment should be inspected and tested at intervals
determined by the severity of the equipment's usage. Visual inspections
should be accomplished before each use. Hydrostatic testing should be
accomplished before equipment is placed in initial service. Hydrostatic
testing should be re-accomplished every ten years thereafter, after
significant repair or modification, or if the vessel experiences overpressure
or overtemperature. Contact the University Safety Engineer at 258-5294
for more information about hydrostatic testing.
Vacuum Apparatus (top)
Vacuum work can result in an implosion and the possible hazards of
flying glass, spattering chemicals, and fire. Personal protective equipment,
such as safety glasses or chemical goggles, face shields, and/or an
explosion shield should be used to protect against the hazards of vacuum
procedures, and the procedure should be carried out inside a hood.
Water, solvents, and corrosive gases should not be drawn into vacuum
systems. Pumps should be protected by cold traps and their exhaust should
be vented into an exhaust hood.
Glass Vessels (top)
Although glass vessels are frequently used in pressure and vacuum systems,
 they
can explode or implode violently, either spontaneously from the strain
or from an accidental blow. Therefore, pressure and vacuum operations
in glass vessels should be conducted behind adequate shielding. Glass
vessels should be designed for the operation intended, and should be
visually checked for star cracks, scratches, or etching marks before
each use.
Rotary Evaporators (top)
Glass components of the rotary evaporator should be made of Pyrex or
similar glass and completely enclosed in a shield to guard against flying
glass should the components implode. The rotation speed and application
of vacuum should be done gradually when using a rotary evaporator.
 Section
5 Section
7
|
