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Spray Booth Design Breakdown: Semi-Downdraft Booths

 

Read Time

3 minutes

TL;DR

  • Semi-downdraft spray booths are a popular choice for manufacturers who want to prioritize high quality results but also need to balance this goal with versatility and affordability.
  • The airflow of a semi-downdraft booth enters through the ceiling near the front of the booth, passes down and across the booth cross-section, then the exhaust passes through filters near the floor.
  • This booth’s air flow design is most commonly used for liquid spray booths, and can be equipped with supply temperature and airflow velocity controls.
  • Benefits of the semi-downdraft booths are reduced overspray and finish contamination, versatile design and lower installation costs than other downdraft spray booth designs.
  • This design sometimes creates an airflow “dead zone” near the front of the booth causing lazy overspray requiring attention of the painters.


Semi-downdraft spray booths are a popular choice for manufacturers who want to prioritize high quality results but also need to balance this goal with versatility and affordability. This type of booth is essentially a hybrid between the cross draft and downdraft designs so it shares several key characteristics with both types.

While the semi-downdraft design offers several significant advantages that make it an appealing choice, there are also some drawbacks and considerations that buyers should think about before making a final selection.

Semi-Downdraft Booth Design Basics

  • Air enters through ceiling near the front
  • Flow passes down and across the booth cross-section
  • Exhaust passes through filters near the floor

The primary purpose of the semi-downdraft design is to provide some of the benefits of the downdraft booth without the need for a concrete pit.

The semi-downdraft design achieves the benefits of a downdraft booth by pressurizing the air through a supply plenum that is typically located near the front of the booth. The pressurized fresh air is released from the top of the booth, then flows diagonally across and down towards the rear of the booth enclosure. A filtration system (exhaust chamber) is located at the rear of the spray booth and captures overspray before exhausting clean air back into the environment.

Available Features

  • This booth’s air flow design is most commonly used for liquid spray booths
  • Equipped with supply temperature control
  • Airflow velocity control

The customization options and available features of these hybrid spray booths are one of the main reasons they are the booth of choice for many manufacturers. They are easily capable of providing fresh or heated airflow using a heated air supply stream.

Semi downdraft booths can also be engineered to allow for accelerated air flow through the booth to enhance faster drying or further reduce overspray potential.

Key Benefits

 

  • Reduced overspray and finish contamination
  • Versatile design
  • Minimal installation costs

Compared to crossdraft booths, the semi-downdraft design is better at keeping the spray application clean and uniform. The downward angle of the airflow carries excess spray away from the object, as well as dust and other airborne contaminants.

The air supply intake's location at the top of the booth also helps lower the risk of introducing unwanted particles to the interior environment, which improves overall quality of the paint or finish.

One of the biggest advantages of choosing a semi-downdraft booth over a conventional downdraft unit is reduced installation costs. Conventional downdraft booths require a concrete pit below the unit to house the filtration and exhaust system. This can be expensive and create operational disruption depending on the current work environment.

The semi-downdraft design also offers flexible functionality and can be adjusted to fit the specific needs of the user.

Drawbacks and Considerations

  • This design sometimes creates an airflow “dead zone” near the front of the booth causing lazy overspray requiring the attention of the painters

Since the air enters the booth from the front and travels towards the back, the area at floor level directly below the supply plenum creates a lazy overspray condition. Operators must account for this “gap” when planning their spray or finish procedure. Compared to standard downdraft booths, workers in the booth may be exposed to more overspray so additional protective wear is necessary.

Choosing the Right Booth Design

Semi-downdraft booths can be a responsible solution to many types of manufacturing environments across a variety of industries, but they are not always the best choice. As a premier manufacturer of spray booths and high finish booths, we help guide clients during the decision process to help them find the best design for their needs. We are proud to maintain a tradition of excellence in our products and customer service, so please contact us to learn more about our complete spray and finish solutions.

posted on Thursday, March 22, 2018