Slotted screen: design and advantages

We offer Δ-shaped wire filter elements that are ones of the most up-to-date among the list of vessel screens we supply.

The slotted screen design (Johnson Screen) is constituted by a grid made of high-precision Δ-shaped wire (lengthwise elements) and transverse support bars (rods) welded to each other in every point of intercept. In such a way Δ-shaped wire forms smooth and rigid screen with lengthways slots of strictly defined dimensions (slot sizes start from 30 micrometers), and the support rods constitute the screen's load-bearing base.

In contrast to traditional screens made of mesh grids and cut panels, use of the slotted screens along with engineering solutions applied in construction renders possible the following:

• to prevent break-up of catalyst and emerging of catalyst fines; thus to decrease catalyst expenses;
• to prevent screen obstruction as catalyst granules contact with it only in two spots of Δ-shaped wire sharp edges which makes the screen perfectly transparent for gas or coke dust;
• to distribute feed flow uniformly in reaction zone;
• to exclude stagnant pocket formation on catalyst bed and to reduce reconditioning time;
• to lower differential pressure rise rate in reactor during interrepair period, i.e. to extend interrepair period and a reactor service life in general;
• to improve quality of production;
• to increase internals service life (up to 10 years and longer).

Slotted screens (Johnson Screens) can be pickled, passivated, annealed and finished by other methods during and after manufacture to increase their corrosion resistance as well as to increase their mechanical strength.