CLEANROOM DRYERS
Sizing the Dryer
For a class 100 cleanroom laundry 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 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 84 cu ft drying capacity is required. For Class 1-10 operation the same calculations can be used be the load would be reduced be 20%. A 50 cu. ft. dryer would dry 100 x .80 = 80 lbs./load.
HEPA Filter
All cleanroom dryers use HEPA or ULPA filters to supply clean air. It is paramount the construction does not allow for any leakage in a cleanroom dryer. This is especially true if the air come in from an unclassified area in back of the dryer. An ISO 3-4 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 Lr “Load Ready” is displayed and the blower stops. The sudden stop of air flow 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 air flow is maintained and the Pulse is eliminated. This feature is a real plus for ISO 3 & 4 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 drop-out. 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 air flow can not 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 independent of the dryer controls. It is beneficial to monitor the exhaust temperature during the drying and cooling cycle. Most important the Digital Thermometer will sound an alarm if the temperature exceeds a preset temperature. With this it is possible to save a load of cleanroom garments if a steam valve were to stick open.
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. 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 if it is necessare to maintain a Class 1 operation. The hinged front panel makes it much easier and faster to open the large center front panel to expose the inner shell for cleaning. This feature makes it easy to access the inside of the dryer and wash any lint that has built-up. Also, I highly recommend cleanroom wipes are not dried in the same dryer as cleanroom gowns (suits). Wipes leave a residual inside the dryer. This requires the dryer to be cleaned more often and on a regular basis 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 a frame to place under the dryer so the dryer is at the same level as the floor.
