Intelligent centrifugal blowers for laminar flow and other laboratory cabinets offer advantages including brushless motors, controllable airflow, and blocked filter alarm
Total Air Control (TAC) is the title given to a range of intelligent centrifugal blowers manufactured by Lemmens.
There are 11 blowers in the range; four double inlet type covering the range 2000 to 4400m3/h, three duplex types with airflows from 2200 to 5700m3/h, and four single inlet blowers offering 1000 to 2600m3/h.
Like all radial blowers the Lemmens products deliver a laminar air flow, however, the TAC system is said to offer many other benefits.
Firstly, the drive motors are brushless DC; the brushless technology, besides having spark-free commutation, is very efficient, long lived and easily controlled.
In the Lemmens system, conversion from mains AC voltage to the DC required by the motor is done within the motor housing; the user merely has to plug the motor into the mains.
Secondly, the airflow from any blower can be set to any one of 31 values within the range of the particular model, with 66% and 33% of the set speed being also available via simple switching.
When the blower is installed in a system such as a cabinet, the system can be interrogated and the normal system pressure monitored.
Three DIP switches then allow an overpressure alarm to be set to any of eight levels above the detected pressure.
In addition, an alarm is set if motor speed falls below 90rpm.
The alarms are in the form of local LEDs but a plug-in relay unit can also give no-volt, 1 amp capacity alarm indications.
In effect this is a blocked (becoming blocked) filter alarm.
It is possible to temporarily connect a computer to the blower; this allows the system to be set up to give constant air flow or constant air pressure without the need for a sensor. The chosen air flow or pressure will remain constant over a wide range of changing system characteristics.
With the use of a suitable sensor the blower can be made to vary its output with respect to an analogue signal from the sensor.
Alternatively, airflow can be made to vary such as to keep a certain output from a sensor constant, for example, to keep the level of CO2 constant.
A control panel has been specially developed for cabinet applications, it provides control and readouts of performance and alarm conditions and may be customised for specific applications.
