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Bag filters for foundry dust extraction

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In our catalog we have included filter units that are by design directly made for use in foundry dust extraction applications. This specific dust is emerging when working with coal. Our catalog includes 18 basic baghouse units for foundry dust that forms an explosive atmosphere with air. The bag filter units are graded according to the required volumetric airflow.

Foundry dust characteristics

Among the foundry dust in this filtering group are specks of dust that are created when handling the foundry sands, when regenerating the sands and when shot blasting the castings. The most common applications of dedusting are related to knockout machines, sand coolers, conveyor drifts, elevators, pneuconveying vents, sand cleaner, shot blasting machines and others. The Foundry dust is very abrasive, rough and heavy.

Foundry dust extraction

Dedusting of knockout machines

The knockout machine is one of the major sources of dust in foundries. For the extraction of foundry dust, this task is very specific, because it is necessary to provide dust extraction from a relatively large space of the knockout machine where the castings are loaded by a crane. Knockout machines are thus often enclosed in cabins to ensure efficient dust extraction. The castings are mostly hot and the released dust tends to quickly climb upwards to the top of the box. The extraction is designed so that the extraction occurs at the top of the box and at the sides near the crane rope grooves.  The required extraction flow rate is determined by the size of the knockout machine and ranges around Q = 20000 – 30000 m3 / h for smaller knockout machines and 50000 – 80,000 m3 / h for larger ones.

Foundry sand cleaner machines dedusting

The foundry sand cleaner machines have an important task to keep the required sand quality for its another use. They are always included in the technological system of sand regeneration.  This is a specific task for the extraction system because the cleaner machines are very sensitive to an extraction flow rate difference which directly influences the proper function of the cleaner. We recommend that the extraction flow rate is controlled with a vacuum sensor in the ducting, placed directly behind the cleaner. The fan thus increases/decreases its RPM so that the airflow conditions are as constant and invariable as possible on factors such as fluctuating pressure drop of the bag medium, the amount of dust extracted, and others. The extraction flow rate for each type of cleaner is usually determined by the manufacturer of the technology and ranges from about 5,000 to 10,000 m3 / h, and maybe even higher.

Conveyor and elevator drift dedusting

Usually, belt conveyors and elevators are used to handle foundry sand. Sands are transported over relatively long distances, and these transport paths form a link between knockout machines and sand regeneration technology. The biggest dust sources in belt conveyors are their drifts. In the drift, whether it is a transfer between belt conveyors or an inlet/outlet to the elevator, there is a significant leakage of dust into the surrounding area. The dust extraction is then carried out by connecting the extraction pipe to the cover, which is built around each draft. For larger conveyors and drifts that reach through each floor, it is necessary to provide extraction both in the top and bottom of the cover. The extraction flow rate is designed according to the width and speed of the individual conveyor belts and ranges from 1500 to 5000 m3 / h per drift

Shot blaster dedusting

Blast machines are used for basic cleaning of the cast iron casting from foundry sand residues. In the blasting process, both the abrasive particles from the blasting machine and some of the sand and cast iron dust get into the extraction dedusting system. Separators are therefore included in the extraction ducting to ensure that only the dust particles of the cast iron are filtered by baghouse and the abrasive recirculates in the blaster only. The blasting machine is usually pre-equipped with dust separators from the manufacturer, and the manufacturer also sets requirements for the extraction system. The extraction flow rate for cast iron blast machines should be around Q= 3000 – 10 000 m3/h per machine.

Shot blasting chambers dedusting

Shot blasting chambers are used for surface treatment of large cast iron castings. Blasting is performed manually by a worker using a pressure nozzle with compressed air and the abrasives. Blasting chambers are very demanding for consumption of extraction flow rate.  Air and dust extraction is done by suction grills located at the bottom of the blasting chamber, drawn through the ducting into the baghouse, and the cleaned air is then returned to the top of the blast chamber. Determination of the extraction flow rate is based on the volume of the blasting cabin – the air should be replaced 100 to 150 times per hour. The extraction flow rate, therefore, ranges from 10,000 to 100,000 m3 / h, according to the size of the blasting box.

Specification of the filtration medium

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 foundry dust 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 is sedimented and is very mechanically resistant to tearing or scraping. The amount of residual dust particles ranges from 1 mg/m3 to 5 mg/m3, which allows for cleaner air to be recirculated back into the plant for heating and to save on heating costs. The solids are collected into a big bag or a steel container with the help of a rotary valve.

Recommended ducting solution

We recommend using Group III Ducting for foundry dust extraction – a thick-walled, welded ducting. Pipeline components such as elbows, flaps, and branches are subject to abrasion from the dust particles and material fragments. Despite the thick walls of these components, it can not be ruled out that after a certain period of time they will be damaged by abrasion.

Baghouse units for foundry 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 „Foundry dust extraction“. In the next step, select the required volumetric airflow of the bag filter unit. The result will be a set of items – baghouse unit+ fan +  silencer box, all of which form a dedusting system. You can then insert the items into the costing.

 

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