The question actually was, why am I losing production every time I install new tips or hammers on my grinder? So, the operator is not only taking care of routine maintenance, he is noticing that he is losing production at the end of the day. How can this happen?
• Every time you install new hammers, tips, screens, cutting edges or worse, more than one of these at a time, your production will drop. This is because the new parts are much closer together, reducing the distance between the tip and the screen for example, which increases drag, reduces rotor speed and loss of production occurs. The more new parts, the closer the gap, the more drag occurs and less production is the result.
But is there a benefit? Absolutely
• Because this distance is reduced, the product that is created is finer and more consistent.
• If this is a regrind application, or is being screened to size, the spec product needed, may actually increase in volume as being more consistent, more material may pass through a screen rather than being scalped off.
Can you use this gap between the screen and tips to your advantage? You can in many ways.
• If you are only reducing materials like logs, slabs or landclearing debris, and size is not an issue, a bigger gap will increase your production. Use old worn thin screens and shorter hammers or slightly worn tips. This will more eliminate the drag and the rotor or hammermill will rotate more freely and maintain rpm much better, increasing production.
• If you tried the same as above on a regrind application, production will suffer and the material will be much finer with a lot more sawdust type finish product.
• Keeping the gap tight by hard surfacing things like cutting edges and anvils, will produce a much more consistent product with less oversize pieces in finished product. If screening to size, you most likely will not need as large of a screening machine as these bigger pieces are reduced and the overall volume of material being removed is reduced so a shorter deck or drum can be utilized.
What to watch for?
• The increased gap will allow for material to get between the tip and the screen. Not a big deal on strictly wood but there are materials that will ruin your day. Palm trees and palm fronds, along with some stringy, pliable type of woods and brush will squeeze into this gap, wrap around the rotor and stall it and the engine in about 2 seconds. Not a fun day when that happens.
• On regrind, keep an eye on material daily. Pull a sample and pile side by side each day and you will be able to figure out how many hours of run time it takes before your product stops meeting spec. It’s easy to do and you just need to take the time to do it. Then change tips, hammers or hard surface screens or anvils and start the process over again.
Questions? Dave Whitelaw firstname.lastname@example.org