October 24, 2000, Revised April 2003 ISSUE #M12
Questions about sand bedding as it relates to manure separators came up many times at this year's World Dairy Show. It is clear that sand bedding is very popular, and dairy farmers are well aware of the abrasion it causes.
Earlier this year a Vincent KP-10 was tested at the Everett Williams 400 head dairy in Pennington, Georgia. Good results were expected because of minimal wear experienced at McArthur Farms in Okeechobee, Florida. McArthur's has a great deal of coral sand in their manure, their press has held up very well over a period of years. (Although McArthur's is currently adding settling basins.)
The opposite occurred at Williams' farm. In only a few weeks the Georgia sand wore out a screw. The screw was replaced with one using improved technology: the screw flights were made of abrasion resistant plate, with two layers of MIG applied hardsurfacing followed by TIG applied Stellite or Colmonoy. This was a notable improvement and minimal wear ensued.
However in no time at all the screen was worn through. (The latest Vincent manure presses use sleeve insert screens that are inexpensive to replace.)
It was concluded that sand bedding and screw presses do not mix.
This same knowledge applies to other manure separators exhibited at the World Dairy Show. A drag flight conveyor separator is vulnerable because of chain and sprockets that must operate in the sand/manure environment. The same goes for the wringer/roller type machines.
Our advise to farmers who use sand bedding was to either have good separation of the sand and manure ahead of the separator, or to avoid manure separation. Sand can be separated by flowing the manure through a trench with velocity such that the sand settles out and the manure stays in the flow stream.
If this separation is not possible, then the farmer is better off draining the manureand sand into a pond, which will have to dredged periodically. If they buy a mechanical separator based on savings of avoided dredging costs, they are likely to face repair and parts expenses before the payback period is complete.