Dusting off your air quality woes

Solvents, lacquers, thinners and oily rags can also prove to be dangerous while simply sitting on the shelf.

Wood dust is a nearly invisible threat and the top hazard in facilities manufacturing furniture. When exposed to an ignition source, tiny, highly-combustible wood particles can serve as the eager fuel for fires and explosions.

Wood dust is particularly dangerous when it is allowed to build up the way it tends to – in cracks, crevices and corners. Wood dust fires and explosions are often started by open flames, uncontrolled smoking, sparks from grinding, welding or torching, or faulty or poorly maintained electrical equipment.

To protect woodworking or manufacturing facilities from wood-dust related fires, good housekeeping holds the key. Dust build-up thicker than a coin creates an exposure.

Factories and woodworking workshops should have dust control equipment in place, especially a system with its own safety shut-off and alarm facility. For example, dust control systems use a tube to suck the dust into the dust control system.

Inside a properly engineered system, a light will illuminate if it detects a spark caused by a piece of metal or nail entering the tube. When this bulb is triggered, the dust collection system will spray a mist.

When, the spark passes through, it will be soaked. It is basically a sprinkler system within a dust collection system!

Good practices

In addition to dust collection systems and proper housekeeping, managers and operators should service and maintain all equipment regularly. Ventilation systems and ducts should also be checked often to ensure no blockage is present.

In particular, housekeeping staff and operators must keep an eye on several areas within their facilities that tend to accumulate dust, including:

•         Vertical surfaces with adhered dust;

•         Horizontal surfaces, including beams, joists and tops of equipment;

•         Concealed spaces, such as that behind equipment;

•         Electrical panels and motor control boxes;

•         Motors, particularly in the area of the dust collection system;

•         Empty bins under enclosure-free dust collection systems.

But collection of dust at source is a poorly understood aspect. You must position the suction hood as close as possible to the source of emission – your lathe, grinder or other woodworking machinery. It’s crucial that dust be picked up, as it is generated, and then directed into the collector.

If you lose the dust to your workshop air, the task of collecting it becomes futile. You will be inhaling that dust and sweeping it from your machines and floor.

One can determine the efficiency of dust capture fairly accurately by a quick visual inspection of your machinery. Inadequate air volume/CFM allows dust from your grinder to escape onto the floor and into the air.

Ensuring your ducting is large enough in diameter and efficiently laid out are two ways you can minimise restrictions on airflow.

Most woodworking equipment requires about 250-1000 CFM. The amount of airflow or CFM required will vary depending on the size and number of woodworking tools running simultaneously.

Most average size table saws, planers and jointers with 2-5 inch diameter ports need approximately 300-600 CFM to clean well. A machine that loses a lot of chips or emitting a visible plume of fine dust needs more airflow.

Cyclone separator

Separating the bulk of the wood waste from the airstream before it reaches the filter keeps the filter from clogging. A collector that dumps all of the dust directly into a filter (using the filter itself as a dust bin) is a very poor design.

It will reduce system airflow/CFM and filter efficiency; not to mention that it won’t keep your workshop clean. When trying to maintain sufficient airflow at the woodworking machine to prevent dust loss, if the filter clogs too quickly, this becomes impossible.

A cyclone separator can exceed 99% dust separation efficiency, allowing only a very small amount of very fine dust to pass to the filter. The result is that filter cleaning is reduced by a factor of 50 and you maintain a constant, high level of airflow to the machine.

The final stage in dust collection is filtering the fine dust. It doesn’t make sense to go through all the trouble of collecting the dust if you still allow the finest particles to pass through the filter and out into the workshop air.

The smallest dust is the most unhealthy to breathe and when it becomes airborne, inhalation is inevitable.

Effective filtration requires a quality filter media of sufficient quantity or surface area. You want to filter near 100%, down to the smallest particle (10 microns or less in diameter). Ideally, one should install HEPA-rated filters, which are certified to be 99.97% efficient at 0.3 microns.

Other threats

Oil-soaked rags have a habit of piling up in residential home garages to commercial woodworking shops to major manufacturing factories. Though a simple tool – rags are handy for applying stains and finishes – those chemicals turn the rags into potent, highly flammable fuel for fires.

Spontaneous combustion and chemical reactions are a major cause of industrial fires globally. Spontaneous combustion occurs when an object increases in temperature without pulling in heat from its immediate area.

If an oily or chemical-laden rag is then thrown in a corner or into the trash, it could spontaneously catch fire. Those rags should be stored in a metal can that has a self-closing top on it – if they do combust inside, the fire can’t escape.

Solvents, lacquers and thinners are nearly as common as wood dust in woodworking shops. They can also prove to be dangerous while simply sitting on the shelf. These items should be stored in cabinets with fire-rated doors and grounded to a piece of metal, so that static electricity doesn’t build up inside and serve as an ignition source.

Solvent-based glue (‘red glue’) can also be very dangerous within a manufacturing facility. Red glues emit vapours that are highly flammable and could impair or sicken those who breathe them.

The vapours are heavier than air and sink to the floor, where they accumulate and can easily find an ignition source from an electrical outlet or furnace with an open flame, and cause an explosion.

The use of water-based glues (‘yellow glue’) is recommended, and that too in a booth protected by a fire suppression or automatic sprinkler system. An exhaust fan should also be used to pull the dangerous vapours from the room.

(Source: Oneida Air Systems, US).

Comments

 


Comment here