The powder blast cabinet can be built up of plate elements. The plates can be of black sheet in plastic powder blest design or simply of plastic sheets. The elements are linked to each other with screwed bolt joints. In order to provide air tightness, sealing needs to be provided between the joint elements. The exhaust fan including the attenuator together with the air tank of the filter cleaner unit is placed on top of the cabinet. The fan exhausts the air from the air space of the working area of the cabinet through the powder separator filters to the so-called clean air compartment. The suction is provided by the fan placed on top of the cabinet. The fan exhausts the air from the above mentioned clean air compartment. The powder separator filters are fixed n the clean air compartment. The exhaust fan provides the continuous air flow to the cabinet on the entire cross-section of the spray opening. That air flow prevents the sprayed plastic paint from escaping from the work space to the air space of the room. The exhausted and cleaned air is returned to the room through the clean air compartment, fans, attenuator, and then the post-filter unit.
During the powder blasting operation, the powder paint can stick on the filters which spoils the efficiency of exhausting. In such cases, the filters need to be cleaned through. Cleaning of the filters is provided by the compressed air-operated shaker device inside the filters. The shaker unit receives the feeding of compressed air from the air tank on top of the powder blast cabinet. Upon the tart of shaking, by opening the magnetic valve, high pressure compressed air flows in the shaking device, be the effect of which it starts rotating around the vertical axis and the air being discharged from the bores placed tangentially, removes the powder paint stuck on the filters. The shaking unit is of automatic start. The automatic start is commenced with the help of an air flow sensor. If the air flow drops below the pre-set limit value, shaking commences automatically.
In the powder blast cabinet, there is a powder collecting tank, to which the shaken powder paint falls. That is where the powder paint dropped in the powder blast cabinet needs to be collected. In case of automatic cabinets, the supply of the blasting devices (that of the automatic and manual repair stations also) is provided from the powder collector tanks. In such case, also the fluidification of the powder is done in the powder collector. In case of automatic cabinets, the system needs to be linked with an automatic fire extinguisher according to the fire fighting requirements.
The mixture of powder/air exhausted from the powder blast cabinet is cleaned from the powder by the filter cartridges and the post-cleaner. After filtering, the powder content of the air will not exceed the allowed concentration; therefore it can be circulated back to the room.
In the blast cabinet, the lower explosion concentration limit (ARH) is 20 %, which is 10 gr/m3 of powder concentration which cannot be generated at efficiently operating exhausting of powder. The integrated differential pressure switch, in case of insufficient exhaust turns off heavy power as well as the air supply of the blasting unit, therefore preventing further powder paint to be blast.
The open blast cabinet means a different case which can be installed at mainly blasting large size work pieces. It is recommended with unique, individual cases only since the due to the large open surface, the suction is not that efficient than in a closed cabinet.
Upon request, the powder blast cabinets can be designed with detachable mechanical engineering devices as well. For the case of a quick change of colour, a new mechanical unit needs to be pushed in place of the detached one. If so, it is only the internal area of the cabinet that needs to be cleaned prior to any colour change.
A filter-powder blast cabinet may consist of the following man and auxiliary units:
- Powder blast (or plastic) plate structure
- Exhaust fan
- Attenuator
- Filter
- Filter cleaning device
- Air tank with valves
- Control unit as per DIN-standard with handling units
- Air-preparation unit
- Air-flow sensor
- Powder tank (manual or automatic)
- Automatic fire extinguishing system (with only automatic cabinets)
- Handling doors, side doors
