Flat Welded Screens are structures where the surface profiles are welded at each intersection at 90° angles onto support profiles.

Welded screens are directly produced as flat screen. This avoids the chance of stress corrosion and the weakening of the welds, which does occur with opening and flattening slottubes (this is normal way to manufacture flat screens).

For special applications welded screens can be made out of slottube. The welded screens are available in very light constructions (11S/Q25) as well as more robust forms (50S/50x3) and can be provided with the necessary frame and/or reinforcements.

In contrast to flat screens (produced by opening and flattening a slot tube), Trislot® Flat welded screens are manufactured on dedicated welding machines. This results in the following advantages:

• flatness to within tight tolerances
• no weakening of the welds, because of flattening (and no stress corrosion problems as a result)
• accurate distance between support profiles
• possibility of different support wires in one screen
• possibility of variable spacing between support wires in one screen

Trislot offers standard Flat Welded Screens in a large variety of surface and support wire combinations, that can be applied for simple screen plates to heavily reinforced reactor internals. The Trislot design team can also design screens tailored to your specific requirement.

Special constructions

• A combination of different support profiles and pitches within one flat screen is possible
• Variable spacing between support wires in one screen
• Curved screens; curve direction and filtration direction are to be determined by the customer
• Frames and reinforcements can be designed and calculated on request, provided that we know the temperature, supports and differential pressure (ΔP).

Finishing

• Standard finish:
  • cutting of width and length of Flat Welded Screen
• Optional finish:
  • deburring
  • degreasing and pickling
  • post-machining for tighter tolerances

Cylinders, conical baskets and reverse rolled slot tube

Cylinders and conical baskets (conical shape) are manufactured out one or more flat screens that are rolled and welded. Also slottubes can be used for this purpose after opening and flattening the elements.

The standard construction is as follows: slot direction is axial and the filtration direction is from the inside towards the outside (smooth surface is at the inside and support profiles are at the outside). Slot direction can be configured radial if requested. This is called a reverse rolled slot tube.

Technical information

· Minimum cylinder diameter = 25 mm depending on the profile combination and construction

· Maximum diameter = unlimited

· Slotopening: see flat screens, slottubes

Applications

Trislot welded screens can be used as flat filters or processed to make cylinders

Flat screens

• Static sieves for dewatering or classification: the screen is set up at certain angle or is curved so that the surface profiles are perpendicular to the filtration direction. Through gravitation the slurry flow over the screen.
• Vibrating screens, dryers and coolers: screens used as support for the product that has to be treated.
• Band filters: screen as support for paper or textile, for example for the separation of cutting oil
• Support screens: in this application, the screens are assembled inside vessels to support catalyst, active carbon, resin, molecular sieve…

Cylinders and baskets

• Drum screen with or without internal transport screw
• Screw presses
• Centrifuge baskets and cylinders for the food and paper & pulp industry