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MANIFOLDING SPRAY BOOTH DUCTWORK AND IMPROPER AIRFLOW

Spray booth exhaust ductwork

In this photo, an installer has chosen to manifold three spray booth exhaust duct runs. (A manifold is a pipe or chamber branching into several openings.)

This layout probably looked great on paper and reduced the number of roof penetrations from three to just one.

Reality is such as nasty teacher.   The static pressure (resistance to the flow of air) was greater in the top portion of the ductwork than in the spray booths.  The ductwork downstream from the manifold point (above the joints) should be much larger than what is in the photo.   The air ventilated out of one booth actually flows into its neighbor.

Our booths are designed to meet specific airflow needs and we design them with ductwork. The spray booths in the photo were designed to have individual exhaust ductwork runs; they were not installed according to the design or instructions provided by Standard Tools.

Manifolding of exhaust ductwork is allowed by NFPA-33 only if devices exist in the ductwork that detect improper airflow.  The static pressure within the spray booth will change as the overspray builds up in the exhaust filters and as the obstruction within the booth changes (based on size and shape of parts in the spray booth).  This can be very technical and overly-complex.  The simple rule, and what Standard Tools recommends, is no manifolding of exhaust ductwork.  Keeping ductwork simple is the least expensive and best performing strategy in the long run. We suggest that you install your booth, and your ductwork, according to our recommendations to ensure proper airflow within your booth.

PAINT BOOTH AIR FLOW: HOW IT WORKS

During spray jobs in a paint booth, the exhaust system must draw substantial quantities of air out of the shop in order to operate. These volumes must be replenished with equal volumes of air coming into the booth.

STE_AMU Full CornerAIR MAKE-UP (AMU) is defined as…a mechanical means of replacing air that has been exhausted out of the booth.

It’s simple…. it’s all about paint booth air flow. How much air in being put into the booth and how much is being taken out. Airflow while spraying takes the over-spray away from the paint job and out of the booth.

Air in – Air out. Air in – Air out. Air in – Air out. Air in – Air out. That’s it. With the Sure-Cure Air Makeup Unit, you control the amount of air pushed into your booth. Why would you need to push air into your booth?

NEGATIVE AND POSITIVE BOOTH PRESSURE
When the exhaust fan of the booth is turned on, it creates a “negative” air pressure in the booth cabin (taking out more air than is being put in). When there is a negative air pressure, the booth will try to suck in as much air as possible, including dirt and debris from outside the booth. THINK VACUUM CLEANERS.   

To counter this “negative” pressure, an Air Makeup Unit (AMU) unit is used to supply air to replace the air being exhausted. If the AMU is designed to force more air into the booth than is exhausted…the booth is said to have “positive” air pressure. In this case, the booth has more air than outside the booth and when a door is opened, dirt and debris is pushed away from the booth. THINK STANDING IN FRONT OF A FAN. Continue reading PAINT BOOTH AIR FLOW: HOW IT WORKS

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