Friday, March 23, 2012

Allowing for Proper Drainage

For effective galvanizing, cleaning solutions and molten zinc must flow without undue resistance into, over, through, and out of the fabricated article. Failure to provide for this free, unimpeded flow can result in complications for the galvanizer and the customer. Improper drainage design results in poor appearance, bare spots, and excessive build-up of zinc. All of these are unnecessary and costly, and another example of why communication throughout the project is key.
A few common fabrications where drainage is important are gusset plates, stiffeners, end-plates, and bracing. Following these best design practices will help ensure the highest quality coatings:
• Where gusset plates are used, generously cropped corners provide for free drainage. When cropping gusset plates is not possible, holes at least 112-inch (13 mm) in diameter must be placed in the plates as close to the corners as possible (Figure 1).

Figure 7: Cropped bracing

• To ensure unimpeded flow of solutions, all stiffeners, gussets, and bracing should be cropped a minimum of 3/4-inch (19 mm) (Figure 8). Provide holes at least 112-inch (13 mm) in diameter in end-plates on rolled steel shapes to allow molten zinc access during immersion in the galvanizing bath and drainage during withdrawal.
corners as possible (Figure 1).

Cropped Corners (preferred) ​​Holes close to corners (alternatively)

Figure 8: Cropped gusset plate corners

Alternatively, holes at least 112-inch (13 mm) in diameter can be placed in the web within 1I4-inch (6 mm) of the
end-plate. To facilitate drainage, end-plates should have holes placed as close to interior corners as
possible (Figure 9).