Sunday, January 11, 2015

The GrinderGuy takes on Pine Bark

                Over the past year or so, I have had several questions about screening, grinding or cleaning up pine bark. For the past half century or more, pine bark was debarked at lumber mills and run across stationary shaker screens splitting large nuggets, mini-nuggets and pine bark. As typical with shaker screens, if over fed with material, contamination of products occurs. But, this is just the way it has been forever.
                With the reduction of lumber production the past 7-8 years, pine bark has been in short supply.  To keep fulfilling landscape product orders, mills started trying to recover pine from old piles scattered about their sites. These piles had logs, stone and a mix of pine bark and fines pushed up into them.
                A year or so ago, I was asked to screen one of these piles.  I took a 3 product star screen to try and screen and recover some of the pine bark. Depending on the size of the unit, I used a Komptech L3 and Komptech XXL, production could be from 250-400 yards an hour. By being able to adjust speeds of the stars by the touch of a button, I was able to create:
·         Overs
·         3” or 4” large nuggets
·         1 ½” or 2’” mini nuggets
·         Pine mulch from 3/4” down
·         Pine fines of 3/8”- 1/4”
Because I only had a 3 product machine, scalping overs and making large nuggets was easy, but the mini-nuggets were mixed with pine much and pine fines. By running the 1 ½” product back through, we were able to split the pine mulch from the mini-nuggets and if the customer wanted the pine mulch in the mini-nuggets, with a touch of a button, it was done. On one demo, I used an additional screen, a Komptech Easy Star, and was able to create 4 products by splitting the pine mulch, ¾” minus, from the 1 ½” mini-nuggets at the same time.
One of the major problems with pine bark supply is typically suppliers sell twice as many mini-nuggets as large nuggets. A request was made to grind the large nuggets into mini-nuggets. In a typical horizontal, tub or stationary grinder, the speed of the grinder is way too fast and turns the soft pine bark to pine dust. We decided to try a low speed shredder, a Komptech Crambo, which has screens for product size and has adjustable shaft speed. By slowing the shaft speed 50-60% and using 7” screens, we were able to reduce the large nuggets and create mini-nuggets without creating too many fines.
                A call I received just last week, had a customer trying to recover an old pine bark pile. They were screening with a deck screen, but the 1 ½” mini-nuggets had rock in it from all the extra materials pushed into the pile over the years. A rock goes through a 1 ½” hole just like a piece of pine bark does. The good thing is, they do not weigh the same. We took a portable air knife, a Komptech Stonefex, and ran the conveyor from the deck screen right into it. By adjusting the airflow of the Stonefex, were able to use the air to push the lightweight pine bark to one conveyor, while the heavier rock fell onto another conveyor. We were about 95% effective in removing the rock from the pine bark. A totally acceptable result.
After the time we spent the past year on the pine bark, I said “Why can’t we use a star screen in place of the shaker decks of old?” It does way more production. It is much more adjustable for product sizes. It is inexpensive operate and the cost is insignificant if it produces results in profits. We are now installing our first star deck system for pine bark in a new lumber mill.
Now, you DO NOT have to use the same machines I used. You can try any machine. It doesn’t cost you much. Each of these machines work on mulch the same way they work on pine bark. You just have to try them! The ways of old are not always the best. The best productivity equals profitability.
Questions? Want to try something? Contact me, Dave Whitelaw

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