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Base plates and end plates welded to hollow sections require venting to allow pre-treatment fluids, zinc and air to escape during the galvanizing process. This will ensure that a high quality and uniform coating fully develops over the steel surface and eliminates the possibility of air pockets, zinc traps and bare spots.
Hollow sections connected to a plate can be vented through the plate. It is preferential to have a completely vented area equal to the hollow section. If it is not viable to remove the entire end of the hollow section for venting purposes, then smaller holes are acceptable so long as each is at least Ø10 mm. These holes should be located on the plate as close as possible to the corners of the hollow section.
In common base plate venting, a total of four holes, one in each corner is preferred. However, a lesser number is acceptable provided the total area of these holes is equivalent to the minimum drainage requirements. A single central hole in the end plate is never acceptable as it does not allow for fluid drainage and can cause internal bare spots or zinc traps.
Alternative venting is permitted and can be an excellent solution for some designs, provided the area vented and the location of the vent holes meets the requirements.
In all cases, the location of the vent holes must conform to the requirements of AS/NZS 5131 and AS 4100.