Product buildup in Surge Hopper
Product buildup in Surge Hopper
(OP)
Hi,
Plastic pellets in my company sometimes build up in surge hoppers even though the rotary valves below the surge hoppers are running near maximum speed. (The rotary valves are not under-designed for this application.)
One possible root cause is that the clearance between the rotary valve housing and the rotary wheel has increased. That can be solved easily through replacement of the rotary valve.
The other possible root cause is that the pellets have static on them, which can be observed on a rotary-type classifier screen.
1) Is there any possible root causes to the product buildup in the hopper, other than those 2 mentioned above?
1) Is there any way to remove static on product pellets?
2) What process can cause static on plastic pellets?
Many Thanks
Plastic pellets in my company sometimes build up in surge hoppers even though the rotary valves below the surge hoppers are running near maximum speed. (The rotary valves are not under-designed for this application.)
One possible root cause is that the clearance between the rotary valve housing and the rotary wheel has increased. That can be solved easily through replacement of the rotary valve.
The other possible root cause is that the pellets have static on them, which can be observed on a rotary-type classifier screen.
1) Is there any possible root causes to the product buildup in the hopper, other than those 2 mentioned above?
1) Is there any way to remove static on product pellets?
2) What process can cause static on plastic pellets?
Many Thanks





RE: Product buildup in Surge Hopper
Thanks
RE: Product buildup in Surge Hopper
Check-up whether "bridge" formation is taking place at the conical bottom preventing the plastics flow to the bottom and to the RV itself.
KRECian
RE: Product buildup in Surge Hopper
yes, that has been checked, no signs of bridging.
As an additional step to prevent product buildup, we have been operating the hopper at empty level, i.e. what comes in goes out immediately.
The product buildup is more frequent for non-surface-lubricated products than for surface-lubricated products.
Thanks
RE: Product buildup in Surge Hopper
RE: Product buildup in Surge Hopper
RE: Product buildup in Surge Hopper
Thanks. But the funny thing is that we have another line with exactly the same line-up but it does not show such problems at all. Strike any note? Let me know pls. Thanks.
Dear spettitt,
There is a air-leak pipe leading from the side of the RV housing to the top of the hopper. I have observed pellets being carried over before through this pipe. Could be one of the contributing factors.
Have tried varying RV speed and airflow but no significant improvement. Have even tried knocking on the conical bottom to ease product pellet but to no avail.
Many thanks to all, please keep your ideas flowing despite my product not doing so as much as I wish.
RE: Product buildup in Surge Hopper
RE: Product buildup in Surge Hopper
You may want to consider an eductor if all else fails.
RE: Product buildup in Surge Hopper
saxon
RE: Product buildup in Surge Hopper
RV clearance is 0.23mm ~ 0.3mm versus 0.15mm (manufacturer's spec). Conveying line pressure is higher but due to this product buildup problem, airflow has been increased so the conveying line pressure has now dropped to a value which I deem pretty low. Rotary valve is dropping pellets into a pipe.
*** saxon, very good suggestions. I will keep them in my pocket after establishing the exact root cause. Thanks.
RE: Product buildup in Surge Hopper
You probably have a combination of static accumulation leading to bridgeforming because of RV blowby , having read all the above mentionned comments.
I had similar problems in the past with similar products. I solved it by putting a rotating pin system inbetween the RV and the vessel , The rotating pin system being powered by the RV thru a chain connection. This kept the product constantly moving , just above the RV inlet , and we didn't have to worry anymore about air pressures leak or new different product also being transported in the line.
That component was subsequently installed every time we feared some problems with airleaks or static issues.
See on www.spiromatic.com for a picture of this system.