Re: Pipe Build Up Transferring Pvc Powder
Can you clarify where in the process the build up is occuring? From what you say it sounds like the issue is build-up being released from within the pipeline. Have you broken down your system to inspect where the worst build-up occurs? Are you certain that you are not handling material from a bulk silo operating at low inventory?
If you could give some information regarding, pipe bore, air flow rates, routing, numebr of bends, bend radii, temperature, length, etc, this would help.
Regards
Richard Farnish
The Wolfson Centre for Bulk Solis Handling Technology,
Univ.Greenwich, London
r.j.farnish@gre.ac.uk
www.bulksolids.com ■
Re: Pipe Build Up Transferring Pvc Powder
This build-up is due to melting of PVC powder on the pipe wall due to frictional heat. Filler and TiO2 get embedded in this molten layer, freeze, and become hard.
To solve this problem use a low velocity dense phase conveying system and make sure that all of the powders are well-blended before the mixture is conveyed. Try reducing the conveying velocity first before making this expensive change. Lower velocities will reduce the frictional heat and improve the present situation.
Regards,
Amrit T. Agarwal
Pneumatic Conveying Consultants
polypcc@aol.com
www.powderandbulk.com/pcc ■
Re: Pipe Build Up Transferring Pvc Powder
Vacuum conveying of "rigid" PVC compound is typically not a problem, depending upon the amount of TiO2 present. I agree that more details need to be shared regarding the pipe diameter, horizontal and vertical conveying distance, number of bends, and ICFM of the vacuum blower.
The only time I can recall having a problem of this nature was when the temperature of the blend was too high when it entered the conveying system. I am assuming that you are using a high intensity mixer to create the dry blend. Are you utilizing a cooler? If so, what is the material discharge temperature? It may be that you need more residence time in the cooler, and/or you may have to chill the air entering the conveying system.
Another option is to simply screen the dry blend before delivering it to your customer. Of course, this does not solve the root problem. ■
Re: Pipe Build Up Transferring Pvc Powder
the air speed is 15m/s. vacuum pressure is 290milbar.
76mm bore stainless steel pipe.
High speed mixer to cooler dropping from the ccoler at 40C, however, the build does occur on vacuum line when material at room temperature as well.
flexible pipe of 2m length, slight bend to vertical, vertical pipe 7m high to a 90 degree bend then 3 m straight back to the vacuum pump
(see attached basic model)
Any more infor that is required then just let me know.
Many thanks already
John
Attachments
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Pipe build up transferring pvc powder
i am experiencing a very hard build up in the pipework. The PVC dry blend is transferring at a rate of 3T/hr in a vacuum transfer system. This hard material is made up of mostly fill and titanium dioxide and comes of in very small particles (350 - 500 micron) and then canno be broken down in the customer processing. They then show up as imperfections on the window profile.
Can anyone shed any light on this for me?
Thanks ■