Safety First

These enclosures are made from steel framing and fire-resistant PVC to contain all particulates and gases. Photo courtesy of Duroair Technologies.

Shops that finish parts with a painting or coating process have been aware of the airborne dangers for many years. And, although lead-based paints are a thing of the past, other dangers still exist.

Nearly every manufacturing business that requires a coating to be applied to it‘s products—whether its paint, powder coating, or any other application that involves spraying— has two major problems. First, the work area needs to be contained so that it does not get contaminated with dust or other particulates. Second, the spraying process contaminates the air, which needs to be filtered or exhausted, or both, from the building.

Typical solutions to these two problems involve fixed, single-purpose rooms requiring that high volumes of air be exhausted. These enclosures require floor space that permanently reduces the square footage available for other processes, and limits the size and shape of objects that can be moved into the booths.

Exhausting air also means that replacement air must be brought inside. If outside air is significantly above or below the indoor air temperature, it must also be pretreated through makeup air processes. These pretreatment units have high initial capital costs with significant ongoing operating costs.

Cleaning the Air

Determining the type of airflow, filtration, and exhaust setup can be a daunting task, so shops should consult experts who understand both the technology and the jurisdictional compliance.

There is a difference between dust particles resulting from a grinding process and what is created during a spraying process.

“If a manufacturer is laying down a coating, for example, we need to trap the isocyanates,” explained Ryan Watt, general manager for Duroair Technologies, Burlington, Ont., a manufacturer of indoor filtration units. “These are chemical particulates that become airborne during the coating process and should not be breathed in by workers.”

According to the Centers for Disease Control (CDC), isocyanates are highly reactive, low-molecularweight chemicals that are widely used in the manufacture of coatings such as paints, varnishes, elastomers, and spray-on polyurethane products.

Workers exposed to these chemicals can experience persistent or recurring eye irritation, nasal congestion, sore throat and cough, shortness of breath, and chest tightness.

“The other major group that we need to capture are volatile organic compounds [VOCs]. These are gases that can be poisonous, but also can be flammable and explosive,” said Watt. “A system needs to capture VOCs, eradicate them, and ultimately keep the levels under what is acceptable to OSHA and the Ministry of Labour.”

A shop air analysis needs to be performed to determine what types of contaminants are present, the type of filter to use, and the best way to configure the system to meet the needs of the shop. Also, it must be determined how often the filters need to be changed. Photo courtesy of Duroair Technologies.

VOC exposure limits are important to keep track of in a shop environment. If there are 50 parts per million (PPM) in the air, workers have an 8-hour exposure limit. However, if there are 100 PPM, this time drops to 15 minutes of exposure.

Depending on the location of the shop, local authorities also are starting to limit the volume of VOCs that can be exhausted into the outside air.

“Manufacturers are now looking for low-toxicity coatings, which is forcing the coating developers to change their offerings, but we’re not quite there yet,” said Watt.

New water-based coatings have limitations in terms of how long they last. They simply are not designed to last 20 years, according to Watt.

“The bottom line for most shops is that if the VOC levels are low enough, they can likely recirculate their air,” he said. “Most air recirculation systems use some type of carbon filter that essentially grabs on to the VOC molecules and contains them in the filter.”

Filtration and Exhaust

A shop air analysis needs to be performed to determine what types of contaminants are present, the type of filter to use, and the best way to configure the system to meet the needs of the shop. Also, it must be determined how often the filters need to be changed.

“We know that the filters will capture what they need to, so it simply becomes a question of how long it takes them to become loaded,” said Watt. “If the system recirculates the air, we need to ensure that the air is safe to breathe. Our systems, for example, have monitors to ensure that the filters are catching what they need to catch, that they are not becoming loaded, and that no bad air is getting through.”

Sometimes the air cannot be recirculated because the compounds are just too toxic, so it needs to be exhausted out of the building. However, if only low toxicity is present in the air, it can be filtered and recirculated.

“This saves a company money because an exhaust system doesn’t need to be installed to remove the dangerous air from the building,” said Watt.

Flexible Air Cleaning

Duroair’s air-cleaning units comprise two pieces: the enclosure and the filter/ exhaust system. What’s unique about them is that the enclosure is retractable and modular in design. “When you look at the main reasons that companies outsource their painting work, it’s often because they don’t want to make the capital investment in a paint room or they don’t have the space,” said Watt. “If you don’t need this type of room on an everyday basis, it can be difficult to get an acceptable ROI. The flexibility of our enclosure gives companies the opportunity to be able to keep that work in-house.”

Retractable environments enable manufacturers to use floor space for other tasks when they are not painting. Photo courtesy of Duroair Technologies.

Reducing outsourced work has multiple benefits, including better control of costs, timing, and quality. “The main benefit we’ve found is that it helps the bottom line, because the faster you can ship finished parts to the customer, the faster you get paid,” said Watt.

The company’s DuroRoom™ enclosure systems do not permanently take up any indoor real estate, and because they are retractable, existing overhead cranes can be used to move large or heavy objects, which can be enclosed after they are put in place.

“We look at this type of work in a totally different way,” said Watt. “By using modular, retractable environments, companies that don’t need a paint booth all the time still can use that floor space when they are not painting. We are able to use similar designs and essentially do any height, length, and width, and pair the size with the correct airflow and filtration.”

The enclosure is made from a hinged steel framing system and fireresistant PVC. The PVC, produced as a single sheet to contain all particulates and gases, is supported by the steel framework.

For smaller enclosures, Duroair uses a combination of 1-in. and 2-in. square steel tubing. For larger constructs (more than about 16 ft. in height or width), the entire framework is made from 2-in. square tubing. For spans more than 20 ft., a triangular and box truss system is used. A welded hinge assembly allows the enclosure to extend and retract. Galvanized and powder-coated steel also can be selected, depending on the system’s needs.

“The filtration and exhaust system really is the heart of the entire setup,” said Watt. “The enclosure moves in and out and grabs a lot of attention, but the exhaust system, airflow, and filtration that we provide is the real benefit, because of the health and safety aspect.”

The enclosures can be created to contain either positive or negative air pressure.

Negative air is suitable for controlling dust and also works with paint and coating applications. Positive air is used to create a clean-room environment.

“The cleanest room we have produced so far is a Class 1000 room, which means there can be no more than 1,000 particles per cubic foot,” said Watt. “We’ve also done Class 10000 and Class 100000, which is what most industrial processes require.”

Keeping the air clean is a problem in many industrial situations where a large workspace is required either to keep dirty air away from a critical process, or where air is made dirty by a process and other employees need to be protected from the contaminated air.

www.duroair.com