Positive And Negative Pressure Areas; Access To The Work Area; Design Details - Baker SterilGARD II SG400STD Operator's Manual

Positive and Negative Pressure
~<\reas
One of the n1any features that sets the
SterilGARD"':-n unit apart frorn
oL~er
cabinets is
the interaction of positive cu1cl negative pressure
areas. The srrtalJ posibve pressure pienwn is
cornpleteJy surrollnded by a negati'i/e pressure
area so that any partide passing through is
invariably drawn thrm1gh the blower and trapped
in a filter.
From the small positive pressure plenum, which
is shown .in Figure 1, about 30 percent of Ll-te total
cabinet airflow is expelled through the exhaust
filter. The remaining 70 percent is recirculated
through the supply filter and re-enters the work
area as particle-free air. Because the cabinet must
take in air to replace the air expelled through the
exhaust filter, the same volume of room air enters
the cabinet through the 8-inch front access
opening. This air, which never enters the work
area, cornp letes the air bar.rier at the front access
opening.
All air is combined under the work surface.
From here, the contaminated air is pulled, under
negative pressure, through a plenurn up the rear
of the cabinet into the motor-blower, which blows
it into a positive pressure plenum. Please note
again that the positive pressure plenum is
completely surrounded by negative pressure
areas. If
a leak should occur in a contaminated
negative pressure plenum, or in the side wall or
rear wall, the negative pressure will create suction
and pu !I air in, not allowing it to escape into the
operator's area. If there is a leak from the positive
pressure plenum, the surrounding negative
pressure area will recapture the contamicnated air
and recirculate it through a filter.
Access to the Work Area
For easy entry of apparatus into the work area,
SterilGARD"'ll has a vertical sliding viewscreen .
..
Its \4-inch safety plate glass allows excellent
visibility and may be opened to a height of 18 W'
to permit placement of items in the work area.
TI1e window should be set at a height of 8" while
work is being performed, and an alarm is
provided to remind the operator if the window is
not in the correct position for using th.e cabinet.
(Chapter 3 on "Proper Cabinet Use'' will explain
ho\v to use the ·v-ieTNscreen correctly vvlli]e the
cabinet is in use.)
As
with other Baker cabinets, the electricctl
outlets Lnside the
\Vork.
area have a circuit bre::tker
so that an electrical overload by ancillary
equipment will not affect air handling.
Overloading with electrical equipment should, of
course, be avoid.ed in
any
case. (See th.e
"A.ncillary Equipment" instructions in Chapter 3
on "Proper Cabinet Use", and in the "Appendix.")
Design Details
Performance assurance
Meticulous care in manufacturing is followed by
more than 14 separate performance tests prior to
shipment of your cabinet. In addition, a complete
factory test report on the performance of your
unit is included at the back of this manual.
Motor/ blower capacity
A motor/blower's capacity is measured by its
ability to provide a nearly constant volume of air
as resistance increases becau.se of filter loading.
Verification by a simulated filter loading test has
established that your SteriiCARD"Il cabinet is
capable of
auto~atically
handling an 80% (in both
4-foot and 6-foot 1mit) increase in pressure drop
across the filter without reducing total air delivery
more than
10~/o.
A convenient magnehelic gauge
(or bar graph display on the ULTRA models)
shows the current relative performance of the
blower. With the use of the manual speed control,
a 165');,/180% (4-foot/6-foot unit) increase in the
pressure drop across the filter can be handled.
The resulting long filter life means significant cost
savings.
One-piece interior wall construction
The interior side and rear walls of your
Steri!GARD®Il's work area are constructed from a
single piece of 16-gauge stainless steel. The easy-
to-clean 7 /16-inch radiused (rounded) comers
prevent buildup of contaminants and resist
corrosion.
Protective screen
Located under the work surface at the bottom
and sides of the rear return-air plenum, a