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Minimum metal width between holes in a support plate

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guerky

Chemical
Feb 10, 2015
33
I'm changing a PTFE support plate in a packed distillation column for a SS316 plate.
This plate must have the maximum possible open area to minimize capacity limitations before flooding in the column, so i must drill the maximum possible number of holes (I know that there are special designed support plates to maximize the area, but im truth i need only a small improvement over the actual suport plate).

How can i calculate the minimum metal width between the holes of a plate with holes drilled in a triangular pattern (exactly like this one ?
1mm spacing between holes seems good enough for the plate not bending, given the small support beams spacing right bellow this plate. I've done some estimations based on cross-sectional sizing of wires supporting pontual loads, but i don't think it is the right aproach.

Data:
Column diameter: 300 mm
Plate diameter: 280 mm (16 mm calculated at max. thermal expansion)
Plate thicknes: 1,5 mm
Hole diameter: 15 mm
Temperatura range: 10-110°C
Total Load: 89 kg of packing (1,5 m of 1" ceramic random packing over a 70686 mm² area)
Support beamns width: 15 mm
Support beams spacing: 25 mm
316 tensile strenght: 485 Mpa

Thank you all in advance for your time.
 
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If the holes are punched or drilled, 1mm between holes in a 1,5mm sheet is pushing your luck.
At a minimum, the edges of the holes will be distorted by the mechanical stress associated with cutting the holes mechanically.

You can make thinner webs, and non-circular holes with more open area, by getting the plate fabricated by laser or waterjet cutting.



Mike Halloran
Pembroke Pines, FL, USA
 
MikeHalloran

You are right. Talked with maintenance team. It would be very hard to drill with less than 3 mm spacing without bending the plate, so it will be laser cutted.
2 mm spacing x 2 mm thickness was advised based on experience to be very safe values, and it's good enough for my intended performance increment. But i wish to understand how this kind of calculation could be done.

 
Tmoose,

Yes, there are fluids flowing thru the holes quickly.
But the holes are suposed to be well rounded. Thus, the thickness of the plate will be reduced from 3 mm (PTFE plate) to 1,5-2 mm (SS316 plate), wich helps reduce the head loss through the orifice (i'm not taking this "bonus" capacity due to thickness reduction in consideration, though).

 
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