Is Your Underwater Pelletizer Giving You Maximum Performance?
The performance of an underwater pelletizer is often taken for granted. Have you checked the performance of your underwater pelletizer lately? Chances are, you are not realizing maximum performance.
Most often, lack of performance is seen as poor pellet quality or reduced output. The underwater pelletizer die plate frequently causes this. The die plate was originally manufactured with a specific size and number of orifices.
Typically, it is assumed that all of the available orifices are open and flowing with product. But this is not always true. In fact, some orifices may be partially closed or completely frozen off when processing difficult products and when equipment diffiencies exist. The results are poor quality pellets and/or lower output.
How can you determine your pelletizer's performance? This Black Clawson Converting Machinery Tech Tip's "Pellet Count Procedure" allows you to calculate the theoretical number of pellets that should have been created versus the actual number that were created to check the actual performance.
Pellet Count Procedure
This procedure can be used to determine the percentage or the number of open and flowing orifices in an underwater pelletizer die plate.
- Count out at least 50 pellets from a sample of pellets that were taken at the same point in time that the pelletizer shaft speed and total production output were noted.
- Dividing the number of pellets counted by their total weight (in grams) equals the pellets per gram.
| Np | Where: | PPG = Pellets per gram Np = Number of pellets W = Weight of pellets in grams |
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| or | PPG = | W | |||
Determining the Percentage of Open and Flowing Orifices
1. Determine the theoretical number of pellets that should have been produced per unit of time.
| PPMt = Ns Nb No | Where: | PPMt = Pellets per minute (cuts per minute) theoretical Ns = Pelletizer shaft speed (revolutions per minute) Nb = Number of knife blades No = Number of die plate orifice holes |
2. Determine the actual number of pellets produced per unit of time.
| PPMa = 16.66 PPG Q | Where: | PPMa = Pellets per minute (cuts per minute) actual PPG = Pellets per gram Q = Output in kilograms per hour |
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3. Determine the percentage of open and flowing holes.
| PPMa | Where: | PPMa = Pellets per minute (cuts per minute) actual PPMt = Pellets per minute (cuts per minute) theoretical |
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| % = | PPMt | |||
Determine the Number of Open and Flowing Orifices:
| Nf = | 16.66 PPG Q Nb Ns |
Where: |  |
Nf = Number of open and flowing orifice holes PPG = Pellets per gram Q = Output in kilograms per hour Nb = Number of knife blades Ns = Pelletizer shaft speed in revolutions per minute |
NOTE: The accuracy of the measured values will greatly effect the results.
Upon determining your actual performance, changes to process conditions or equipment designs can be made to improve performance. After all, a correctly designed underwater pelletizer operating under the proper process set-up conditions can produce high quality pellets with great efficiency.
If you have a competitor's machine or an older Black Clawson Converting Machinery underwater pelletizer, take the challenge and compare the results to the performance of Black Clawson Converting Machinery's new pelletizer designs. You might be surprised what you will find.
For further information on how to improve your pelletizer performance or for a free Black Clawson Converting Machinery Pelletizer Performance Calculator, contact Charles H. Crumb, Business Group Manager of Extrusion Pelletizing Equipment, (315) 598-7121.
Questions? Call Black Clawson Converting Machinery at 315-598-7121 or e-mail us at bc@bc-egan.com
BC Publications is a technical newsletter designed to provide operational and maintenance information to improve the performance of your Black Clawson Converting Machinery equipment.