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Bag filters for aluminium dust extraction

Odsávání při broušení explozních prachů

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In our catalog we have included filter units that are by design directly made for use in aluminum dust extraction applications. This dust is created by grinding aluminum or other non-metallic materials. Our catalog includes 18 basic baghouse units for dust created by grinding aluminum or other explosive material.  This dust forms an explosive atmosphere with air. The bag filter units are graded according to the required volumetric airflow.

Parameters of dust resulted from aluminium grinding

When grinding aluminum materials, dust particles are released into the work area, which can form an explosive atmosphere with the air. This dust is very important to extract efficiently, as even the dust sediments in the working environment are undesirable. Explosive dusts are specific by their values of Kst (bar.m/s) and Pmax (bar). The baghouse units included in the catalog are designed for the fine aluminum powder produced by grinding.

Dedusting when grinding aluminium

Extraction at the source

Extraction at the source of dusting is the most effective way of capture.The dust particles are sucked out using stationary hoods or suction tables. Exhaust hoods of abrasive aluminum dusts are best used at worktables where smaller pieces are abraded. The suction hood provides dust extraction so that the worker does not come into contact with the abrasive dust aspirating away from the dust source. Exhausting desks are advantageous by allowing extraction to the suction worktable itself and by the suction hood away from the worker.  For suction hoods, count with extraction flow rate up to 1500 – 2000 m3/h for 1 meter of hood lenght. For suction worktables count with extraction flow rate of at least 2000 – 2500 m3/h for 1 meter of the table lenght.

Dedusting of automated aluminium grinders

In terms of extraction and determination of extraction flow rate, it is always necessary to meet the requirements of the manufacturer of the grinding machine. Dedusting here with its proper function ensures suction of explosive dust that would otherwise settle in the interior of the machine and could result in an explosive atmosphere. The formation of an explosive atmosphere in the machine needs to be avoided. One of the options is to regularly clean the machine so that the sedimented dust does not create deposits in the corners and non-extracted areas of the machine. The grinding machines are almost always already equipped with suction hoods and covers, but it is very important to keep the manufacturer’s prescribed flow velocity in the connecting ducts, which is usually set at 30 meters per second.

Parameters of extracting explosive dust resulted from aluminium grinding

The design and implementation of extracting explosive dust must adhere to at least these basic rules. The suction line must be properly electrically connected between the components from the suction device to the baghouse unit. The whole system must be properly grounded. The baghouse must be equiped with proper explosion vents directed into a safe location. The filter housing must be pressure resistant, the bag medium must be antistatic. The exhaust duct must be fitted with a non-return backflap valve to prevent baghouse explosion spreading into the suction line, and the suction ducting flow rate must not fall below 20 meters per second.

Parameters of baghouse units for extracting Al dust

Baghouse units in the GIDLY catalog are fabric filter units equipped with automatic regeneration of bags by a reverse pulse jet technology. From our experience of individual extraction applications, the lifetime of the filter media lasts for more than 20,000 hours without the need of any manual refinement. The filter media are flat smooth fabric sleeves made of non-woven fabric with an antistatic coating and an area mass of 600 grams per square meter. The filter medium does not contain folds where the dust be sedimented and is very mechanically resistant to tearing or scraping. The amount of residual dust particles ranges from 0,25 mg/m3 to 1 mg/m3, which allows for cleaned air to be recirculated back into the plant for heating and save costs.  When returning the filtered air, it is necessary to place a residual dust sensor in the exhaust pipe so that the purity of the filtered air can be continuously monitored. If the set dust limit should be exceeded, the system must shut down immediately or switch the exhaust to the outdoor environment without delay. The filtering device must be positioned so that the explosion vents are directed into a safe space.

Recommended ducting solution for aluminium dust extraction

For aluminum dust extraction applications, we recommend to design the ducting with a combination of straight sections in spirally wound piping (a.k.a. SPIRO) with flanged joints and fittings (tapping, knees, flaps) in Group II welded flanged finish. We recommend this combination because of the extraction of the slightly abrasive dust, which usually abrades the places of  air direction change = branches and elbows. We do not recommend using riveted joints so that the inside of the pipeline remains smooth throughout its length. The part of the ducting between the baghouse unit and the backflap valve must be made of a pressure resistant pipe Group II or Group III.

Baghouse units for aluminium dust extraction in the GIDLY catalog

To find a specific assembly of the baghouse and fan, please go to the catalog and price list page. Select Baghouse units. From the list select „Manual aluminium grinding EX“. In the next step, select the required volumetric airflow of the bag filter unit. The result will be a set of items – baghouse unit+ explosion dust design parameters + fan +  silencer box, all of which form a dedusting system. You can then insert the items into the costing.

 

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