CLEANROOM DRYERS
Sizing
the Dryer
For class 100 cleanroom laundries you can dry up
to two times the cubic foot volume of the cylinder. For example you can dry 2
lbs./cu. ft. x 50 cu. ft. = 100 lbs./load in our Model 170. It takes 30 to 50
minutes to dry a load depending upon the extract speed of the washer-extractor
and the amount of cool-down time. The drying time will increase when the
outside air is cold and humid. The cool-down time is normally extended on
cleanroom dryers, as this is when most of the particles are removed from the
gowns. The dryer removes up to 80%
of the particles so an extended cool-down and adequate cylinder size is
critical. As the dryer removes 70 to 80%
of the particles and the washer removes 20 to 30% of the particles, a
quality cleanroom dryer is a must to having a successful operation. For 1000
gowns per week a minimum of 84 cu ft drying capacity is required. For Class
1-10 operation the same calculations can be used, but the load would be reduced
by 20%. A 50 cu. ft. dryer would
dry 100 x .80 = 80 lbs./load.
HEPA
Filters
All cleanroom dryers use HEPA filters to supply
clean air. It is paramount that the
construction does not allow for any leakage in a cleanroom dryer. This is
especially true if the air comes in from an unclassified area in back of the
dryer. In our class 1-10 all moving
parts are upstream of the dryer. A
class 1-10 cleanroom dryer will cost approximately 25% more than a Class 100
dryer.
OPTIONS
to consider when
purchasing a Cleanroom Dryer:
Particle
Counter:
The Particle counter is activated during the cool
down cycle. The sampling port is located near the discharge of the cylinder
into the Turbo Box. The air sample is then run to the outside of the cleanroom
dryer where the air is cooled prior the entering the particle counter. The particle counter is located inside
the cleanroom and has an adjustable pump to ensure the sampling rate is 1 cu. ft./
min. We use the Met One brand particle counter. We buy it with a special
modification for manual/remote control.
This is a new option we recently introduced.
Two-Stage
Blower:
When the dryer reaches the end of the cool down
cycle “Load Ready” is displayed and the blower stops. The sudden
stop of airflow causes a pulsation in the dryer and some of the particles in
the bottom of the dryer are carried into the basket and deposited on the gowns
that were dried. We have solved this problem with a Two-Stage blower. Instead
of a sudden stop, the blower is ramped down to a low speed. The direction of
the airflow is maintained and the Pulse is eliminated. This feature is a real
plus on class 1 and 10 cleanroom laundries.
Turbo
Box:
The Turbo Box is a stainless steel transition
that mounts to the discharge of the inner shell and connects to the inlet of
the blower. The velocity of air is maintained to eliminate particle dropout.
This eliminates the need to clean the lint compartment from the cleanroom side
on a daily basis, as it would contaminate the cleanroom.
Ionization:
Required if the product builds up static
electricity. Static electricity
attracts and holds particles to the fabric so the airflow cannot carry the
particles away. The ionizer emits positive and negative ions. If the cleanroom gown builds up static
electricity and has a positive charge, the negative ions will be
attracted. When the negative ions
make contact with the positive ions they are neutralized. Eliminating static
electricity allows the particles to be released and lowers the particle count
of the cleanroom garment. This option is used on over 70% of our ISO 3-4 (Class
1-10) dryers.
Digital
Thermometer:
This temperature gauge operates independently of the
dryer controls. It is beneficial to monitor the exhaust temperature during the
drying and cooling cycle.
Humidity
Instrumentation/Control:
Knowing the dryness level of the cleanroom gowns
can prevent over drying and under drying. Over drying reduces the life of the
garment. Under drying will result
in moisture appearing on the surface of the plastic bag the garments are
packaged in. When the Humidity Control is used it interrupts the power to the
solenoid valve when the garments are dry.
Digital
Thermometer with High Temperature Control:
If a steam valve were to stick open the
temperature in the dryer would continue to rise and possibly harm the cleanroom
gowns being dried. This instrument will sound an alarm at a preset temperature
(70°C) and alert the operator to call for assistance. With this it is possible to save a load
of cleanroom garments if a steam valve were to stick open.
It is also handy to have the temperature
displayed during the drying cycle.
Pressure
Gauge across the Filter Assembly:
As the combination heating assembly and VLSI
filter system is mounted above the dryer (Usually above the cleanroom with the
air handling units) it is very convenient to be able to read the pressure drop
across the Filters from an area below.
This reading is usually done on a monthly basis as part of their quality
control.
Hinged
Center Front Panel:
It is necessary to keep the inside of the dryer
very clean to maintain a Class 1 operation. The hinged front makes it much
easier and faster to open the large center panel to expose the inner shell for
cleaning. This feature makes it easy to access the inside of the dryer and wash
out any lint that has built-up.
Also, we highly recommend that cleanroom wipes not be dried in the same
dryer as cleanroom gowns (suits). Wipes leave a residue inside the dryer. This
requires the dryer to be cleaned more frequently, especially for class 1-100
operations
12"
High x 48" x 53" Angle Iron Frame:
Only required if you have a built-up cleanroom
floor and want to raise the dryer to the same level as the floor.
Washer\CR_LaundryArticle