When designing the perfect spray paint booth, the direction of airflow is not the only primary consideration. Among other things, manufacturers must account for adequate exhaust filtration systems when designing a booth for their operation. These serve the necessary purpose of capturing paint overspray and other contaminants before they are vented to the atmosphere through the exhaust system. In order to minimize downtime, maximize efficiency and maintain compliance, these filtration systems need to be customized for the specific production process they’re being integrated into.
There are two main types of spray booth filtration systems found in modern booths—water wash and dry filtration. While these two paint booth filter types are both designed to capture and contain hazardous compounds, there are numerous differences that have significant advantages and disadvantages depending on their intended use.
What is Water Wash Filtration?
Water wash spray paint booths use water as a filtration medium instead of dry filters. Paint overspray is collected and trapped in the water curtain or scrubber section of the washer and then is dropped down into a collection tank. The collection tank eventually becomes filled with paint sludge and then needs to be cleaned. A centrifuge or sludge removal system can help reduce downtime for cleanings: they can be designed into the booth system to remove the paint sludge on a continuous basis. Water wash filtration systems require a high initial investment but are ideal for operations using very high paint volumes that need a uniform and consistent airflow.
Water wash filters are composed of a series of metal baffles and reservoirs that force air to pass through multiple curtains of water before reaching the exhaust stack. These units are fabricated with galvanized steel components that resist corrosion from constant exposure to moving and standing water.
Manufacturers must be aware of stringent regulations on the draining and treatment processes for water with sludge. The water, which is chemically treated to bond with spray particles, separates the compounds through an ionization process that causes them to float on the surface or sink to the bottom as a sludge. Without a centrifuge system, floating compounds must be periodically skimmed from the surface to ensure consistent and smooth operations of the washer, and to remove the sludge to hazardous waste. The particles that sink to the bottom of the tank are shoveled out and disposed of as hazardous waste.
Advantages of Water Wash Filtration
Due to their durable and efficient design, water filtration systems are ideal for manufacturing processes with an extremely high rate of production: they can handle significantly more overspray volume compared to dry filters. Water wash is preferred by many occupational health and building safety codes and is appropriate for spray and finishing compounds of various viscosity and drying speed. Other advantages include:
Flexible for various applications
Clean and efficient collection
Accommodate high production rates
Water wash booths can maintain constant uniform airflow in the booth due to constant static pressure through the washer as compared to dry filters that load with paint
Eliminates recurring expense for dry filters
Reduces downtime needed to replace dry filters
Centrifuge available to eliminate sludge cleaning downtime
The apparent advantages of water filtration make it seem like an obvious choice for almost any application, however, there are some disadvantages.
The water must be consistently treated with chemicals, which can add further operating costs
Higher initial booth equipment and installation cost
Requires a sludge removal system (manual or automatic)
How Do Dry Filter Systems Work?
Dry filter booths use layered filters to separate the paint particulate from the constant airstream passing through the exhaust filter. There are many types of materials and designs available for dry filter media, dry exhaust filters and even reclaim systems available, each of which is ideal for certain volumes and applications. Buyers should discuss dry filter options with their booth manufacturer to ensure they choose one that will operate efficiently and up to code.
Dry filtration systems require dry filter replacements. Clogged filters redirect air to a different path of least resistance, which will effect uniform airflow in the booth. Dry filters have a relatively short life-span and must be replaced regularly to ensure efficient operations. Despite the periodic maintenance needed, dry filtration is the ideal choice for low- to medium-level production volume operations.
The vast majority of spray booths in the industrial manufacturing industry utilize dry filtration systems. Water wash booths can only be justified with very high production rates, so dry filters are ideal for most other operations.
Advantages of Dry Filters
Dry filtration is a popular choice in most industrial manufacturing sectors since it can easily accommodate fluctuating demand and changing part sizes. Advantages of dry filtration systems include:
Lower operating and maintenance costs than water filtration systems
Lower initial booth capital equipment costs and installation as compared to a water wash booth
Ease of operation as compared to a water wash booth
Reclaim systems are available to recycle powder coating finish, for example
All can result in a significant impact on the profitability of the production environment.