Broken plastic pellets

Posted in: , on 16. Jul. 2007 - 20:26

I am working to eliminated broken plastic pellets in a higher pressure dilute phase conveying system, to avoid angel air or streamers gamma bends and stepped pipelines were installed, piping installation was inspected some wrong construction details between pipes connections has been corrected, the broken pellets problem has not been eliminated.

What could be the cause of the broken pellets?

Any experiences or recommendation to eliminated this problem is welcome.


Re: Broken Plastic Pellets

Posted on 16. Jul. 2007 - 09:47

dear fgaona,

The aquired velocity of the pellets represent kinetic energy, which has to be absorbed by the pellets when they collide against the wall or amongst themselves.

This collission energy damages and possibly heats the pellets.

Therefore the velocity in the pipeline is a key parameter in case of particle detoriation.

As you already corrected the pipeline for stepped pipe lines, you must be aware of the occuring velocities.

Are the velocities high enough for conveying, but not too high in relation to damaging the pellets ?

(This question has to be answered for every pipe section)

good luck



Re: Broken Plastic Pellets

Posted on 17. Jul. 2007 - 03:57

You mention stepped pipes and Gamma bends but you didn't mention internal pipe surface treatment. Is there any?

What grade of Polymer are you running?

Is there an air cooler on the air supply discharge?

Do you have a layout of the pipe geometry?

We have performed many analyses to address the various issues with plastic pellets.

The solution is seldom just one element but more often correcting / modifying several areas.

Broken Plastic Pellets

Posted on 17. Jul. 2007 - 04:24

Dear Fgaona,

My experience is that broken plastic pellets are mainly caused by poor design, construction, and operation of the pelletizing system, not in pneumatic conveying lines. During pneumatic conveying plastic pellets can wear out but seldom break-up. It all depends upon the rheology and brittleness of the plastic that you are handling. Most of the plastics are not brittle.


Amrit Agarwal

Consulting Engineer

Pneumatic Conveying Consulting


Ph and Fax: 304 346 5125

Frans van der Zee
(not verified)

Re: Broken Plastic Pellets

Posted on 19. Jul. 2007 - 09:57

Dear Sir,

I suppose this is typical for a pneumatic system.

To avoid this kind of problems you could consider to use an EBS Conveyor (an enclkosed pouch belt conveyor).

Depending on the size EBS 800 or EBS1400 it is able to make horizontal curves with radiusses of 8 meter of 16 meter.

The system is economical for transport lenghts starting from abou 80 meters.

You can find more on:

Best regards

Frans van der Zee

Enclosed Bulk Systems bv