Manufacturing News

Cleaner workplace air

DONALDSON Australasia has compiled a study on specially developed technologies that replace commodity filter media to achieve better workplace air. This is an abridged version of its white paper.

Government regulations – employee health and safety – productivity. These are vital considerations when deciding what type of dust collection technology will help you get cleaner, in-plant air.

While there are many choices, significant differences exist in the performance of technologies currently available for dust collection.

Dust collection has evolved significantly over the past 30 years, and now it is essential to understand how certain technologies today are engineered to ensure that you maintain a cleaner, safer, work environment.

And while cleaner air is of major concern for businesses, advances in cartridge dust collection technology can also help extend filter life and lower costs for many manufacturers today.

The bottom line – proven and trustworthy information is your key to getting cleaner air. Often, the commodity filter media can be substituted with a dedicated technology that better fits the bill. After all, we are dealing here with employee safety and it should be paramount.

EPA sponsored research has shown that downward flow of the dirty air stream in the dust collector results in superior filtration performance.

In the USA, for instance, the American Conference of Governmental Industrial Hygienists also recommends the use of downward flow technology.

These endorsements have not being given to baghouse dust collectors that have an upward airflow path or cartridge technologies with a hybrid cross flow/upflow air path. Why?

Much like baghouse technology, cartridge collectors with a hybrid airflow path require its work against gravity and travel upward through vertically hung filters to disperse cleaned air back into the plant.

This causes uneven air velocity distribution and significant areas of high velocities in the collector, prompting greater potential for filter abrasion.

Sophisticated Fluent (Fluid Dynamics Finite Element Program) flow modeling software clearly indicates that cross flow pattern causes a significant hopper sweeping and an upflow air pattern, which can result in major dust entrainment and difficulty in pulse cleaning the filters.

In turn, this often results in higher pressure drop and shorter filter life. In addition, managing the airflow in a hybrid cartridge collector is problematic because, with high velocities through the collector, dust is suspended in the air and doesn’t drop into the hopper.

Like the baghouse, cartridge collectors with hybrid airflow technology enlist blow pipes across the filters for cartridge cleaning. This outdated method of cleaning doesn’t deliver and disperse enough energy to properly clean the filters.

On the other hand, cartridge collectors with a downward airflow have lower velocities as air travels with gravity down through the collector and filters, automatically depositing dust into the hopper.

With this more balanced and uniform air velocity distribution through the collector, operating pressure drop is stable, filters are more easily cleaned and potential for filter abrasion is minimised.

Donaldson’s own UltraWeb fibre filter is an example of a media that is a high-performance alternative to commodity type pleaded cellulose or cellulose/synthetic blended media that captures sub-micron dust particles on the surface of the media.

Cellulose and blended media are depth-loading media that allow particulates to penetrate deep into the filter and choke airflow.

By keeping dust on the surface of the filter, Donaldson’s ‘nanofibre’ allows dust to be more easily released through pulse cleaning and promotes self-cleaning in the collector, helping maintain a greater effective media area over a longer period of time.

Nanofibre is a cellulose/synthetic composite media that forms a web-like like net of very fine fibres, 0.2 to 0.3µ in diameter.

Cellulose and blend media have fibres at least 10µ in diameter and large pores between fibres (up to 60µ) that allows dust to penetrate deep into the media, quickly plugging and reducing filter life.

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