Edgy perforated plates

"One of our customers uses our CONIDUR® plates in fluidized bed plants to fluidize a powdery product. CONIDUR® plates are often used for such operations because they have a special oblique perforation, similar to potato graters. This has the following effect: When air flows from the bottom to the plate, this air does not rise straight up – as would be the case with a round perforated plate – but obliquely out of the plate. This allows products to be dried, cooled and also conveyed."

Andreas Langen knows the special features of the CONIDUR® fine perforated plates inside out. He has been working in the CONIDUR® sales department since the mid-1990s and took over as sales director in 2018. He tells the story of a project where a customer needed individual adaptations of the CONIDUR® fine perforated plates used.

"One day, our customer approached us with a special specification request. He wanted to have unperforated edges on the sides of the plates. His expectation was that the plates in the plants could be fastened and sealed better in this way, because there'd be no more air flow through those areas."

The suggestion sounded relatively simple, but in fact posed a big challenge. The thing is that the manufacturing process of CONIDUR® fine perforated plates did not allow for any unperforated edges at the time.

"When we perforate our CONIDUR® plates, it does not work the same way as with conventional round or square perforated plates. In our perforation process, we punch a row of holes across the entire width. The next row after that is somewhat offset. This is how we punch row by row – and with each perforation process the plate is stretched. If we left an unperforated edge on the left and on the right, this would not be stretched. The metal plate would contract like a bathtub."

For purely technical reasons, it was not immediately possible to fulfil the customer's request. But he was quite adamant about it, so we at HEIN, LEHMANN gladly accepted the challenge. This is what we were faced with: The CONIDUR® plates were to have an unperforated edge, but the other properties of the plate were not supposed to be changed.

"It was important to our customer that just as much air should flow through the new CONIDUR® plates as before. In other words, we couldn't just punch fewer holes so as to make the plate stretch less."

So, that put paid to the easiest solution; but easy is what anyone can do.

"First, we took a look at the tools. As already mentioned, we would always perforate plates across the entire width. If we now wanted to have unperforated areas on the left and right, we first had to remove the respective teeth of the tools. And that's exactly what we did: We ground down the teeth."

That solved problem number one. But how to prevent the plates buckling? "We found a solution for the stretching by experimenting with different tools and hole sizes, which on the one hand maintained the pressure loss and, on the other hand, produced less stretching. At some point we succeeded in doing that. Our tests and trial perforations led us to a manufacturing technique that allowed for an edge of up to 50 mm without changing the other properties of the plate."

The new plates worked perfectly for the customer – and still do today.

"Initially, of course, the customer request was a difficult challenge. But our motto is that such challenges make us grow, and make us stronger. In the end, this specification request led us to a new product variant, and greatly expanded our wealth of experience. If we also manage to make a customer happy in the process, then the project is a complete success. That is what happened in this case."

Do you also have special requirements, and are you looking for an expert who can meet any challenge? Get in touch with us – we're up for it!