Depending on the application, paint booth operators may want to maintain positive, neutral or negative pressure inside their spray booth. A slightly positive booth pressure prevents dust and dirt from being pulled into the paint booth, while a slightly negative pressure may be recommended so vapors cannot escape the spray booth and contaminate other work areas.
The paint booth pressure is related to airflow. If air is pulled in faster than it leaves, you have positive booth pressure. If air is leaving more rapidly than it can be replaced, the spray booth pressure will be negative. Making manual airflow adjustments to the paint booth can be cumbersome, especially if you are painting items of varying sizes at different times, such as small parts, followed by a vehicle, followed by large parts.
When Global Finishing Solutions (GFS) calculates the desired airflow rate for a paint booth, it is based on an empty spray booth. If a large part or vehicle is added to the paint booth, a high velocity of air moves around that part or vehicle since the space is no longer vacant.
“In a situation like that, you may need to dial down the speed of the motors, so the air is not moving too quickly through the paint booth,” said Adam King, GFS industrial estimating manager. “If the airflow in your paint booth is too fast, the paint or powder will not have an opportunity to hit the part. It will be sucked right into the exhaust.”
What Is the Purpose of a VFD?
Regulating airflow speed and controlling the pressure in your paint booth, while also saving on energy costs, is attainable with a variable frequency drive (VFD). This electrical component allows a paint booth to adjust to a change in chamber pressure by increasing or decreasing the fan speed to compensate for the change in airflow through the spray booth. This variation requires minimal interaction, reducing a fan’s energy consumption for significant energy savings without the need for constant, manual monitoring.
VFDs come standard on all GFS pressurized paint booths. Having a VFD in a pressurized booth helps ensure overspray is collected properly and increases the exhaust filter life. A VFD on a non-pressurized paint booth is useful if you require varying air speeds. For instance, for an Open Face Paint Booth with conveyor openings, it can sometimes be difficult to control airflow.
How Do VFDs Work?
There is a costly spike in power draw when the motors on your paint booth are started. Motors on pressurized paint booths with VFDs are gradually ramped up, as the exhaust and Air Make-up Unit (AMU) fans begin to spin. Motor speed slowly increases until the proper amperage is attained, eliminating the spike in power. When used in tandem with a smart control panel, this saves at least 30 percent on electrical and fuel costs.
Thanks to technological advancements, today’s smart control panels give your paint booth a myriad of functions to improve your operation. The VFDs automatically maintain pressure inside the spray area, relying on a pressure sensor inside the paint booth and another sensor outside of the spray booth. This allows the airflow to be reduced with a flap or damper, keeping the system from having to run at full power. The system senses when paint booth filters are becoming loaded, then compensates by adding power to the exhaust fans.
What is Economy Mode?
Perhaps the biggest cost savings with a VFD comes from Economy Mode, in which the VFD forces the motor to produce a low airflow rate when the spray gun is not in use. The system runs at full power only when the painter is spraying. So, if the painter is working in a paint mix room or handling another task, the motors do not have to be running at maximum speed.
This alone can save thousands of dollars in energy costs over the course of a year. Running the paint booth on economy mode is much more cost-effective than shutting the paint booth down and starting it back up again. Plus, it is easier on the equipment.
What is Consta-Flow?
On top of paint booth pressure control, a variable-flow system, such as GFS’ Consta-Flow, provides automatic compensation for filter loading. GFS recommends Consta-Flow for all paint booths with conveyor openings or multiple filter stages that have high static pressure when loading.
Consta-Flow automatically adjusts the exhaust fan to the changing conditions of the exhaust filters. The system monitors static pressure, adjusting the exhaust fan’s RPMs to what is needed for the volume of exhaust air, based on how loaded (dirty) the filters are. The result is a paint booth with constant airflow even while the filters load with paint, increasing filter life.
As the need to operate as efficiently as possible becomes heightened due to the continual rise in energy costs, the payback period on a VFD can be as little as 12 months, depending on the size of the system. Whether purchasing new equipment or adding a VFD to an existing paint booth, a VFD can produce substantial savings, in addition to keeping the airflow speed in your spray booth regulated and the pressure controlled.
