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| Author | Topic: Feed throat Problem |
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Vic Senior Member Posts: 12 |
posted February 09, 2003 08:33 PM
  
We are currently experiencing problems of bridging and loss of material thru our vacuum system. We have an SSE with a combined vacuum and feed throat system. We have noticed an increase in agitation of the dryblend in the feed throat(we are flood feeding) therefore we are also noticing an increase in material pickup in the vacuum chamber. The agitation seems to be caused by an air leak of some sort down in the screw/barrel area. I have had our fitters look at it but they have not found any leak. Would anyone have any other ideas? Any info would be appreciated. IP: Logged |
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Tom C Moderator Posts: 737 |
posted February 10, 2003 09:50 AM
Have you checked the screw seal in the back of the throat? The only way to check it thoroughly may be to take the screw out. Tom C [This message has been edited by Tom C (edited February 10, 2003).] IP: Logged |
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Bob Cunningham Senior Member Posts: 115 |
posted February 10, 2003 10:33 AM
I don't quite understand - are you applying a vacuum to the feedthroat of the extruder? Or do you meant that your vacuum loading system is mounted on the feedthroat? What process is this for - blown film, etc.? Is there any regrind, or is this all virgin material? What material is it? -Bob Cunningham IP: Logged |
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Vic Senior Member Posts: 12 |
posted February 10, 2003 05:56 PM
Bob, We are applying a vacuum to the feedthroat of the extruder which then empties into a separate chamber. We make foamed PE sheet using both dryblend and where acceptable regrind. Vic IP: Logged |
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BrianAndLiz Senior Member Posts: 42 |
posted February 11, 2003 02:31 PM
quote: Then I would wager that you have a gouge in the seal area. Piece 'o resin worked its way between the seal and the frame and wore the seal out. Stop the line, take the back end apart and rebuild the seal. I helped do this once on a PS foam extruder (secondary extruder.) We didn't find anything wrong, the act of rebuilding seems to have taken care of the problem. Good luck and let us know how it works out for you. [This message has been edited by BrianAndLiz (edited February 11, 2003).] IP: Logged |
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Vic Senior Member Posts: 12 |
posted February 16, 2003 06:49 PM
Thanks for the replies. We did replace the screw seal but unfortunately at startup this morning the problem still persists. A question I would like to ask is that the fitter told me that the seal they use is an oil seal. Is this the appropriate seal to use? Should we be using say a silicon seal or something different? regards IP: Logged |
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Tom C Moderator Posts: 737 |
posted February 17, 2003 08:22 AM
Was the condition of the screw shank seal surface checked during the change? What does an oil seal look like? Tom C IP: Logged |
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Steve H Moderator Posts: 386 |
posted February 17, 2003 02:28 PM
Hi Vic You'll need to obtain a high temp seal (Vitron) for your screw shank- standard oil seals have insufficient resistance to both temperature and abrasion to last in this application. I coat the lips of mine with silicon grease, which seems to give them a little more life. Steve H IP: Logged |
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Vic Senior Member Posts: 12 |
posted February 17, 2003 05:14 PM
Tom, The oil seal we used is essentially a steel ring casing with a black polymer insert within. No we did not check the screw shank seal surface. I assume this is the surface in contact with the seal. I am new to this area (I am a materials science graduate) so apologizes for my ignorance. Vic IP: Logged |
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