Discussion created on 07/13/2018

Roll shell configuration and feed ingredients

Srs. Any technical docs about roll shell configuration (e.i, dimpled, corrugated, helical etc.)? What's the best configuration? Does it differ or affect in the kind of feed ingredient used? Appreciate all your ideas and answers, Thank you.

Mark Allan Chacon
Mechanical Engineer
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Enrique Diaz Enrique Diaz
Agro Engineer Zootechnist. Product Line Manager Vegetable Oil & Animal Feed Divisions
July 17, 2018

Mark;
This is a wide open point of discussion.
Are you focusing your question on performing a particle size reduction in the feed ingredients by using a cracking mill?

Both, rolls profile and corrugation amount per lineal inch are related with the material being ground and the species being fed with those ingredients. Straight corrugated verse spiral corrugations also depend on the material.

Please be a little bit more specific so I can try to better elaborate about this.
Regards,
ED.

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Mark Allan Chacon Mark Allan Chacon
Mechanical Engineer
July 19, 2018

Sir Enrique Diaz

I am referring to pellet mill rollers. Also, would like to add on how to avoid pellet mill skidding? What big factor contributes on pellet mill skidding?

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October 14, 2021
Mark Allan Chaconwhich raw materials causes more slippage.. Maize, soybeans, poultry meals etc..
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Urs Wuest Urs Wuest
Mechanical Engineer
July 18, 2018

I assume you are talking about roll shells for pellet mills.
There are different configurations possible with roll shells.
In general;
Dimpled rolls have a better pressure distribution in the die but the gripping action is moderate.
In general, the wear is more even in the die due to the fact that the product cannot escape to the side of the roll.
Used for regular feed products with limited slippage in the die and for smaller die holes.
Corrugated or grooved rolls have a poor pressure distribution but a better gripping action.
The wear of the die can be uneven due to the product distribution and the flow to the side of the roll. (corrugated rolls with closed groove ends can solve this issue partly)
Used for products which tend to create slippage due to moisture, formulation, liquids added but also the fat content and the bulk density of the mash have an influence. The conditioning of the mash is very important and sufficient steam quality should be provided. Are also used in special applications like high fibre formulas or wood pellets.
If the question was indeed in regard to pelleting; there is plenty of information available on this subject from various suppliers.
Another possibility is the Swiss Institute of Feed Technology (SFT); they have regular courses on pelleting and feed manufacturing.
Regards,
Urs.

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Mark Allan Chacon Mark Allan Chacon
Mechanical Engineer
July 19, 2018

Sir Urs Wuest,

Thank you for your answer. Is it better to combine roller configuration per pellet mill? (e.i left side is corrugated while right side is dimpled).

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Mark Allan Chacon Mark Allan Chacon
Mechanical Engineer
July 19, 2018

Sir Urs Wuest,

I would like to add on how to prevent frequent skidding on pellet mill? What are the big factors that contribute to this event?

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July 20, 2018
Urs Wuest Excellent response!!!
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Mark Allan Chacon Mark Allan Chacon
Mechanical Engineer
July 20, 2018
Amin Nthanga Indeed!
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Urs Wuest Urs Wuest
Mechanical Engineer
July 20, 2018

Dear Mark,
There are many different designs and configurations of roller shells. You should check with the pellet mill supplier what designs and combinations are available and the experience they have in regard to gripping, even wear or smooth operation without vibrations as well as what products are best pelletized.

If you mean roll slippage by skidding; there are multiple reasons for this. Formula has a high fat content, low bulk density or ingredients that are critical in pelleting.
Roll gap not set properly or working with a gap (intentionally) for a formula that is sensitive, rolls and dies have very different wear, water content in the mesh to high, steam installation and steam quality not ok, sudden increase of moisture due to condense from the steam line, capacity to high in regard to maximum intake angle (nip angle) of the roll and die especially for lighter feed with high fibre content and pellet mills with 3 rolls.
Modern pellet mills today can measure the differential speed of the die and the rolls and therefore prevent slippage or roll gap adjustment can help in order to improve the pelleting process and quality.
An issue with roll slippage should be investigated in more details regarding product and running parameters and then the proper countermeasures taken.

Regards,

Urs.

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Mark Allan Chacon Mark Allan Chacon
Mechanical Engineer
July 20, 2018

Sir Urs Wuest,

Thank you for sharing your ideas. That would be enough answers to investigate our process with the roll slipping issue. If i'm not mistaken we are using your pellet mill die products (Buhler) and other machines as well.

Best Regards,

Mark.

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July 20, 2018

What is the method of controlling the speed of the roller and the pellet die differently, and also how to calculate the corrugate per inch of the pellet die hole size?
Please, Infomation above asking sentence.

Thanks,

Choi.

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July 21, 2018

Let me explain exactly the point of the question: the roller diameter of the 8 inch X circumference is 8 inches X 3.14 and the diameter is 25.12 inches. At this time, if the pitch of the arithmetic is 1/8 inch, the total GROOVE number is 100 GROOVE. My question is that when using pellet die HOLE SIZE 3.2, 4.5, 6 MM, it is better to use several grooves per die hole size Autumn is to ask a question.
example : pellet die hole size 3.2 mm : total grooves 140 ea. ?
pellet die hole size 4.5 mm : total grooves 110 ea ?.
pellet die hole size 6.0 mm : total grooves 90 ea ?

Thanks, Choi.

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Urs Wuest Urs Wuest
Mechanical Engineer
July 23, 2018

Dear Mr. Choi,
Roller slippage detection: There are various systems of different suppliers on the market in the meantime. Bühler has started with the ABS system years ago.
The point is to check the rotation speed of the die and the roller. If the control system detects a difference in speed; means the roller starts to slip slowly and is losing traction due to the condition in the pellet mill like moisture etc. In this case, the control system will react and initiate an action (feeder, roll gap, conditioning, etc.) to prevent blocking of the pellet mill.
These systems allow pelleting with a narrow operation margin and improved efficiency in regard to capacity and uptime.
Regarding roller shell design; this could be discussed for ages but the most important point is having the right solution for the actual pelleting issue at hand. Therefore, the selection of shells and dies should be optimized for the individual product and the die (corrugated, dimple, fishbone, curved etc.) Changing corrugations according to die holes does not really make sense to me and is not very practical.

Why don't you ask your pellet mill supplier?

Regards,

Urs.

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Jale Jale
Scholar
July 23, 2018

Dear Mr. Choi,

For the same diameter of roller, more total grooves mean less duration. As we know, chutes are processed as gear, so more total grooves mean less depth for the chute, which could be easier to wear.
Theoretically, total grooves depend on the mobility of the material, and mobility mostly depends on how fine our material is. Coincidentally, we choose screener of Hammer Mill according to Pellet Die hole diameter more or less. I think that is how your total groove numbers for different pellet die hole size came out. It is really hard to measure this principle, and practically not have much influence on.

It is nice to see your question and discuss it. It is quite late now and I hope I can discuss slippage with you next time.

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July 27, 2018
Thanks for the good information.
THANKS, CHOI
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