Buying a quality air compressor is important but it’s the whole air supply system that ensures you aren’t breathing in isocyanates or mixing contaminates into your paints.
Australian Standard AS/NZS 1716:1994 ‘Respiratory protective devices’ provides guidelines for the quality of air supplied to respirators and gives a minimum supply volume of 170 litres per minute for each person, measured at the respirator.
It’s important to have the right filters in the air supply system and to service them properly. The minimum is a two-stage filter with a water trap and an oil trap, but a three-stage unit is recommended. This adds an activated charcoal filter which removes oil vapour and other unwanted gases to deliver technically pure breathing air.
When air volume can’t keep up with demand, you’ll end up with mottle in basecoats, as well as hazing in clearcoats and a soft paint film.
It can also seriously reduce the effectiveness of tools. For example, high volume low pressure (HVLP) spray guns need more air volume but in return offer higher paint transfer rates which can reduce material usage and increase the life of spray booth filters.
Waterborne basecoat systems, such as PPG’s Envirobase High Performance, can also significantly boost paint shop efficiency but require higher air volumes to operate the air blowers that help minimise flash-off times.
Size matters
The bare minimum for the air ring main pipe should be 50mm (two inch) internal diameter. Drop-down points should be a minimum 25mm (one inch) internal diameter. Flexible air lines for spraying should be a minimum 10mm (3/8 inch) internal diameter no longer than 10 metres to avoid pressure drop.
Ensure ‘big bore’ couplings are fitted to all spray guns, breathing apparatus and regulator filters, and consider installing a split air system that separates the panel and paint shops.
Install a regulator in the booth and don’t skimp on quality. For example, a cheap model may hold as little as 30 CFM (an HVLP gun and an air hood typically require over 30 CFM) whereas a good quality regulator can hold triple that at around 90 CFM.
Consider having an appropriately sized air reservoir tank fitted near the booth to hold a reserve air supply just to the booth. Fit a dryer unit to the compressed air system to remove moisture and improve the quality of the air you breathe and spray with. And when replacing the compressor, buy a screw type unit for high demand applications.
Don’t take risks with PPE
Personal protective equipment (PPE) has progressed beyond the wildest dreams of its 19th century inventers. Once you’ve invested in making sure the air is clean, make sure your painters get the benefit of it by using the right respirator.
Don’t be fooled into believing that an old-fashioned cartridge-type half mask with an activated charcoal filter can offer the same level of protection in the spray booth as an air-fed hood.
Cartridge life
• This depends on many factors, such as:
• Cartridge filtering capacity
• Contaminants in the air
• Breathing rate of the user
• Environmental conditions such as temperatures and humidity.
Eyes and skin
Isocyanates and other hazardous materials are absorbed into the body through the eyes and skin so a full air-fed hood is essential. Safety glasses won’t stop fine airborne paint mist settling on the skin and eyes.
Storage
An activated charcoal filter cartridge absorbs vapours from the moment it’s removed from its packaging. Once that process starts store it in a sealed container when not in use. Leaving it hanging in the workshop or spray booth can dramatically reduce its life.
Fit
Facial features of different people vary so widely that it is difficult to achieve a proper fit right around the sealing area of a half mask. If it doesn’t fit, it’s not protecting the user.
Hood up
A closely fitting hood around the face and being fed from a remote compressed air source isolates the technician from contact with the surrounding air any absorption through the skin. Quality hoods, such as the SATA Vision 2000, also come with a belt unit that contains an activated charcoal filter, an air flow control, an air volume indicator and a safety device that sounds an alarm when the air supply drops too low.
You hear a lot of ex-spray painters saying ‘you don’t see many old spray painters’, to explain part of the reason why they are involved in other aspects of the business now. If business owners ensure the quality of the air and ensure the right protection is worn, then painters could, if they wished, continue mixing paints while leaning on their Zimmer frame.