Sunday, January 11, 2015

Hey Grinderguy, should I use a Trommel or Star Screen?


Good Question.
The first question is what are you going to use it for? Topsoil, Compost, Mulch or something else?
The number one reason star screens became so popular was the ability to screen wet, damp materials. Because the stars are pliable, it is more difficult for material to build up on them and the speed of the rotating stars lessen the time material has a chance to build up on them.
Trying to screen wet compost or soil with a trommel screen is near impossible. Material builds up on screens and the framework of a trommel drum, choking off the screen openings and lessening the open screen area of the trommel drum. This makes screening ineffective. While the screen cleaning brushes on a trommel help with some damp products, the really moist materials are too much for them to work effectively.
This particular customer is a contractor that sells some topsoil and mulch also. Screening material on a job site to remove some larger stone or stump debris is not what a Star Screen is for. It works great screening sand and dirt out of landclearing grindings, but when you need to cleanup a jobsite, a trommel takes much more abuse and is much more versatile in these types of applications.
So, with common products, what screens are most effective?
Trommels:
Yard Waste Compost- Usually dry enough for a Trommel
Mulch- Can screen most any size
Topsoil- Works very well for this as long as it is dry
Aggregate- Can screen some aggregate
Star Screens:
Moist/Wet Materials- Sludge Compost for example
Mulch- Can screen fines or overs
Soil Blends- Soil Compost mixes, not so much straight topsoil
Compost- Very Productive compared to Trommels
No Aggregate

The downside of the Trommel is the need to inventory different screens or entire drums for different product sizes. With the Star Screen, motors drive the star shafts and just by changing speeds, different product sizes are created. While electric motors create a much greater range of product sizing than hydraulic models, there is a top and bottom size limit. Because of this range of size options, the product quality with a Star Screen is much better than the trommels. Hope this helps solve your dilemma.

Questions? Dave Whitelaw GrinderGuy  grinderguy@askthegrinderguy.com

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