Paint Booth Filtration

Engineering paint spray booths so that theairflow provides a good environment isremarkably difficult.

Although the airflow design seems quite simple – blow air in from the top and remove it from the bottom – the airflow is often far from uniform. The sheer scale of the production line means that obtaining uniformity of airflow through the filters and avoiding a wind-tunnel effect from one booth to the next has often been more of an art than a science.

Paint savings

This flies in the face of attempting to optimise the paint spraying process and can add significantly to the operational costs and productivity of a production line in several ways. Imagine the paint savings that can be generated if the coating thickness can be reduced, made more uniform,and paint transfer levels increased, or the improved production efficiencies when the line requires fewer stoppages for equipment cleaning and maintenance.

In recent times an alternative approachhas been taken by Camfil to analyse the performance of booth designs in a more scientific manner with a view to optimising the airflow and thus address the performance/cost issues. The method adopted has been to use Computational Fluid Dynamics (or CFD for short) to carry out computerised airflow modelling of such scenarios. This work has been undertaken using a CFD program specially designed for modelling airflow ifn the production environment. It is the focus on the airflow in the paint shop environment and the ever advancing power of computers that led, first Ford, then others to adopt the CFD approach. The approach has gone on to be used for other production lines and for and other car companies.

Coat paint booth Paint Booth

A typical example is this base coat paint booth, figure 1. For clarity, the sidewalls and the silhouettes enclosing this booth are hidden.

Essentially air is supplied through roll out media filters on the top surface of the booth. The air is intended to flow down around the two overhead bells that spray the horizontal surfaces, the eight sidebells for the vertical surfaces, the vehicle bodies themselves and through the gridded floor to venture in the water table for exhaust.

The skid spacing is such that there is often more than one vehicle in the booth at any one time, so the space is quite cluttered.

In this case the two overhead bells are spraying different parts of the vehiclebody and so are at different levels, figure 2.

Although the air flows quite uniformly down around the right hand bell spraying the hood (bonnet), the airflow pattern is heavily disrupted around the overhead bell spraying the roof. Blue through green yellow and red represent increasing air speed.

This causes the air to be deflected side-ways around the bell resulting in recirculation and upward flow directly underneaththe bell. This airflow is potentially detrimental to the painting process.

Airflow

The upward airflow cannot be relied on for paint to be delivered to the surface of the vehicle. Further problems could also be caused by over spray being deposited on the spray automation or other pieces of equipment in the booth that in due course risks being transferred onto the surface of the newly painted car. Using CFD to simulate the design allows analysis without any unscheduled downtime.

This approach gives confidence in proposed modifications prior to implementing them

Contact

Getting in touch with us is easy

Contact details
KEEP UPDATED!

Subscribe to Camfil newsletter