SMG - External Rotary Screen
External Rotary Screens are high output, low running cost, small footprint, and non-Compaction separation units that can separate to a high level in a relatively simple way with a revolving horizontal cylindrical Sieve Screen. A unique method of separation because they perform well with sticky or greasy liquids/slurries that other methods can struggle with. Equally applicable for moderately small installations through to very large, high throughput projects. Apart from the Motor and Gearbox, these machines are a complete Stainless-Steel construction to combat corrosion, allowing them to be sited inside or out. The Screen is direct driven (no belt or chains etc.) through a gearbox by a fractional Hp motor, enabling the machine to run 24/7 at a very economic cost, requiring very little maintenance.
These machines are compact in size for the high output they produce. The separation process is done on the external surface of a slow revolving horizontal cylindrical Wedge Wire Sieve Screen.
The liquid/slurry to be separated is pumped, or gravity fed into the inlet chamber, which is the full width of the Sieve Screen and is sited one side, downstream of the discharge chute.
The Screen rotates up through this chamber taking any contained solids and any hung-up liquid with it as the liquid element simultaneously pass’s through and into the liquid channel or collection chamber.
The solids and any hung-up liquids that remain on the Screen surface are taken around 180° towards the outlet, further dewatering, to eventually being squeegeed off the Screen and onto the outlet chute by the exit blade.
Most applications do not need additional washing systems as the rotating screen constantly flushes the Sieve Screen, clearing any protentional blinding (blockages) with the liquid that has passed through the screen from the liquid/slurry.
The self-cleaning process allows significantly smaller gap size Sieve Screens to be used, enabling a high-level separation for a non-compaction machine.
In applications where the Screen cannot be cleared by the self-cleaning alone, there are options for additional automatic washing, as well as brushes, to ensure the screen is kept clean to maintain throughput and efficiency. SeeFiltration for products to enable the washing water to be recycled.
These machines are essentially a moving Rundown Screen, and with the self-cleaning, exposes a clean Screen to the entering liquid/Slurry to be separated, significantly speeding up the separation process, and providing high throughput.
External Rotary Screens are used in many applications & industries where high volumes of low DM slurries require to be separated or dewatered, as a standalone unit or integrated into a process line where the incoming slurry or outgoing solid/liquid elements are processed.
The small footprint lends itself to many applications where space is sometimes an issue, for example:
- Area of 0.6 m2 – with a throughput up to 100 m3/hr
- Area of 5.8 m2 – with a throughput up to 1,400 m3/hr
These machines rely on gravity and motion to separate and being non-compaction, there are limitations:
- Slurries with a low Dry Matter, simplistically are pumpable.
- The minimum solid particle size removed from the slurry and left in the liquid element is very good, as small as 50 microns in some applications, but the DM of the dry element is low, and non-stackable (needs containing).
- Certain slurries with hard or heavy solid particles are not recommended as they cannot adhere to the outer surface of the screen.
Slurry throughput is determined by a combination of three parameters:
- Slurry type and its viscosity:
- We can generally advise
- Machine size:
- Screen sizes by diameter:
- 600mm, 900mm and 1,200mm
- Solid particle size removal from the liquid:
- From 0.05mm – 10.0mm (larger gap sizes can be supplied)