The "CLEANAIR" filter is a fabric dedusting unit made with "media" suitable for the type of dust to collect and with 99.92% efficiency according to B.I.A. tests (Berufgenossenschaftliches Institut für Arbeitssicherheit - Inter-professional Institute for Workplace Safety) which the "media" are periodically subjected to.
PRINCIPLES OF OPERATION
The filter works with low pressure suction, which means that the dusty air is sucked in by the centrifugal fan downstream. The fan creates the necessary low pressure to overcome the load loss of the circuit and losses caused by filter resistance, once the system is working steadily. It is common knowledge that every filter requires a few days to reach a steady state to perform with maximum efficiency after a cake of dust, which operates as a prefilter, has formed on the filtering fabric.
Therefore, it is not a good idea to measure residual dust in the chimney right after starting the filter system.
The dusty air is sucked in by the fan, enters the decanting chamber and gravity causes the infeed speed to slow down and the first separation of larger particles from finer particles takes place.
Bag filters are arranged vertically in the baghouse. Air goes through them from the exterior towards the interior. The air loses its dust content, which deposits on the external surfaces of the bags. As the air flows, it reaches the "clean room" through the hole where the venturi ejector is located. From here, the filtered air comes out of the filter body, and is expelled through the fan, usually, into the atmosphere through the chimney. In some cases, it is possible to recirculate the filtered air in the internal environment, with considerable financial advantages due to a lower heat dispersion.
The cleaning system is the classic "reverse pulse jet" system, in counter current of jets of compressed air blown inside the filter bags, row after row, in cycles, according to the program set on the electronic sequencer provided.
Compressed air is blown inside the venturi ejector, which is fitted on each filter bag. The pressure wave produced by the short but intense compressed air jet mechanically deforms the bag's surface. The shock wave causes the dust cake that has formed on the exterior of the cartridge to detach. Since cleaning takes place during the normal operation of the suction system, it has been verified that part of the dust that detached due to the "venturi effect" is sucked into the fabric filter again by the fan. It is necessary to go on to the "post cleaning" phase and allow the "reverse pulse jet" system to continue working for a short time, even after the centrifugal fan stops. The absence of suction facilitates the cleaning of the fabric bags, and almost all of the dust detaching during this phase falls into hopper. The time necessary for the "post cleaning" phases depends © Bruno Balducci srl – Italy – Cleanair UK Rev.1/2015 on the nature of the dust, their granulometry and concentration. Sophisticated electronic sequencers monitor the cleaning operations, during after the suction system function, checking: the "Δp" value, the planned cleaning and "post cleaning" operations and the dust leak detector. Lastly, any dust leaks are highlighted and the filter with the crack in it is identified.
Dust that is filtered and separated from the air is collected in specific metal containers and moved towards the exterior with mechanical systems such as rotary valves, screws, etc.
Filters are designed according to the Client's specifications, in compliance with DPR 152/06 for the external environment and Leg.
Decree 81/08 for the improvement of employee health in the workplace. Each filter is accompanied by a sheet with the design characteristics and the User and Maintenance Manual.
All filters have one or more preseparation and decantation chambers. They are fitted with electronic differential pressure gauges and nonsilenceable hour counter, as required by the current laws.