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The Pharmaceutical Industry Dehumidification Application
The choice for
desiccant dehumidification
®
® Reg. TM Bry-Air (Asia) Pvt. Ltd.
MOISTURE CONTROL
The moisture absorption properties
and characteristics of each
pharmaceutical material will
determine the optimum control level
for processing and packaging. In
general, a dry, cool environment
results in faster processing and
greater product quality. The majority
of tableting operations require
humidity levels between 20 and
35% RH. If there is a question as to
the ideal conditions for processing,
the engineer might want to contact
the manufacturer of the powder for
specific recommendations. If this is
not possible, it might be necessary
to work with an independent
laboratory that can perform a
moisture equilibrium analysis of
the material. This analysis can
determine the moisture absorption
rates of the powder at different
relative humidity levels.
MOISTURE LOADS
There are two types of moisture
loads within most tableting areas
- internal and external. In most
tableting operations the moisture
load generated inside the room
(internal load, i.e., moisture given
off by the product and moisture
generated by a process) is low.
Therefore, the designers main
focus should be on those moisture
loads generated from the areas
surrounding the tableting operations
(external load). In general, they are:
PERMEATION
The amount of moisture that can
permeate into the conditioned space
from the surrounding areas must be
considered. The method and type
of materials used for construction
and the materials and methods used
to seal and make the space vapor
proof are important factors that
determine the amount of moisture
that must be dealt with by the
dehumidifier.
Photo Courtesy of MCT Direct Photos
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Bry-Air environmental control
systems allow for consistent
control to efficiently prevent the
effects of humidity
Photo Courtesy of MCT Direct Photos VENTILATION AIR
In many cases ventilation air can
account for a large moisture load-
-as high as 50 -60% of the total
load. The amount of ventilation air
required depends on:
The amount of the air required
in order to maintain room
pressurization.
The amount of makeup air
needed for exhaust hoods, fans
and machinery.
The amount of outside air
required for occupants.
DOOR OPENINGS
It is important to be realistic about
the number of door openings that
will occur each hour. Each opening
will introduce a substantial load to
the conditioned space.
INFILTRATION AIR
In many pharmaceutical operations,
the conditioned space must be kept
under negative pressure in order
to eliminate the leakage of active
ingredients from that space into
other areas of the building. If this is
the case, it is important to remember
to include in the calculations the
additional moisture load from the
untreated air that will be pulled in as
a result of this negative pressure in
the controlled space. In addition,
it is important to control this air
volume through the use of balancing
dampers. Remember that even a
slight increase in leakage airflow
can result in a substantial increase
in the moisture load.
OTHER LOADS
Refer to the Bry-Air Application
Engineering Manual for additional
information regarding the calculation
of moisture loads. Although they
are often less than the moisture
loads listed above, product and/or
process moisture loads, personnel
respiration and/or perspiration, fixed or conveyor openings, etc. should
be included in all moisture load
calculations.
SYSTEM COMPONENTS
PRE-HEATING COILS
If the makeup air is a large part
of the total system air, it might be
necessary to use pre-heat during
the winter, especially in applications
where the makeup air is blended
with return air before entering the
dehumidifier and/or when chilled
water pre-cooling is used. If left
unheated, cold outside air could
cause the moisture in the return air
to condense or freeze which could
cause damage to the chilled water
pre-cooling coil. Of course, this is
not a problem in warmer climates.
PRE-COOLING COILS
As discussed above, makeup/
ventilation air adds a moisture load
that must be included in
ones calculations.
If the makeup
air is a large
part of the
total system
airflow, it
likely will need
to be pre-
cooled (using
either DX or
chilled water) before it enters the
desiccant rotor. This might result in
a substantial reduction in the size
of the dehumidifier required, thus
minimizing initial cost and operating
expenses.
AFTER-COOLING COILS
If the dehumidifier is to be added
to an existing air-handling system
and adds only a small sensible heat
load, it is probably not worthwhile
to add after-cooling coils. The
additional cooling can usually be
done downstream by the main air
conditioning system.
If such a coil is needed, the ideal
location of the after-cooling coil is
downstream of the dehumidifier
and bypass, but upstream of the
process/system fan. This allows for
the air from the bypass to blend with
the warmer dehumidified air before
it contacts the coil, thus ensuring
even temperature loading of the coil
surface.
FILTRATION
In all pharmaceutical manufacturing
applications, particulate
contamination is unacceptable.
Therefore, it is important to include
filters in the makeup air system in
addition to the filters located in the
main air handling system. Makeup
air not only is a great source of
moisture, but it is also a great
source of particulate contamination.
Bry-Air recommends that 30%
efficiency pre-filters and a minimum
of 55% efficiency final filters be
located at the intakes of the
makeup air and the system in
order to reduce the amount
of particulate that enters the
system. In addition, 30%,
55%, or 95% filtration should
be arranged in series at the
outlet of the system. This
will eliminate any residual
particulate or dust from any
upstream components. HEPA filters
can be placed at the end of the
system in order to capture smaller
particles located in the air stream
prior to that air stream entering the
conditioned space.
HUMIDIFIERS
Many areas experience cold winters,
during which time the air is very
dry. If design conditions require a
constant humidity level year-round,
it may be necessary to include a
humidifier in the system.
The humidifier should be located
in the blended air stream,
downstream of the dehumidifier, Bry-Air, Inc. - 10793 St. Rt. 37 W. Sunbury, Ohio 43074 - P: 740.965.2974 - F: 740.965.5470 - E: bryair1@bry-air.com
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www.bry-air.com
bypass, and cooling coils. Be sure
to allow enough space between the
humidifier and any after/final filters
so that all moisture is absorbed
into the air stream before the air
comes into contact with the filters.
OTHER CONSIDERATIONS
AIR DUCTS
At the points in the duct system
where the system is under
negative pressure, air leakage
can be substantial. Also, due to
the difference in vapor pressures
between the air in the ductwork
and the surrounding
air, moisture
can infiltrate
ductwork with
positive pressure.
In most cases
this infiltrating air is
untreated and has the potential to
both contaminate the air stream and
introduce unwanted humidity. The
designer/engineer should specify
high-pressure ductwork standards
for the humidity controlled spaces
and require a pressure test of the
room and ductwork system.
FLOOR, WALLS AND CEILING
It is important for the controlled
room to have a continuous vapor
barrier consisting of epoxy paint,
poly film, Alumiseal, aluminum
foil, etc. around the entire room,
including the ceiling and floor. When
the moisture barrier is consistent
and continuous, the moisture
permeation into the space is
reduced substantially, thus reducing
the initial size and cost of the
dehumidifier.
CONTROLLING COST
Minimizing the initial cost of the
dehumidification system is important
to most budget-minded companies.
The key to accomplishing this lies
in the ability to reduce the moisture
loads that are to be dehumidified.
Two important factors which will
assist in accomplishing this are (1)
the use of construction techniques
designed to minimize permeation
and (2) the ability to keep ventilation
air to a minimum. However, one
must realize that the system
should have adequate ventilation
to compensate for equipment,
occupants, fixed openings, etc. in
the controlled space.
There are several methods that can
be used to minimize operating costs.
For example, adding modulating
control to the units reactivation
energy source will reduce the
amount energy used
in proportion
to the changing
moisture load.
This can result in
considerable energy
savings. Additional savings can be
realized by adding a heat recovery
system to the reactivation exhaust/
supply.
Over the past 40 years, Bry-Air has
soldmany units for pharmaceutical
applications. Many companies
in Europe, Asia, Canada, Latin
America, Mexico, Africa and the
USA have come to trust Bry-Air
dehumidifiers for their critical
tableting operations.