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Author
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Topic: Extending L/D
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TRENT
Member Posts: 2
From:
Registered: Jun 2001
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posted June 15, 2001 12:29 PM
  
Great stuff guys! I love the contributors input and advise. It is great finding people who know what they are talking about.
What is the feasibilty of extending a 4 1/2"
24:1 extruder to 32:1? Working with 250HP motor, compounding HDPE. IP: Logged |
Tom C
Moderator Posts: 137
From:Wharton, NJ, USA
Registered: Jun 2001
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posted June 15, 2001 07:32 PM
You have enough HP, but this is a big job. I would recommend sending out the line as a rebuild project to a reputable organization, possibly the original manufacturer. Cost should be much less than new.Tom @ CCS IP: Logged |
Peter P
Senior Member Posts: 55
From:Nottingham, Notts., U.K.
Registered: Jun 2001
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posted June 15, 2001 07:56 PM
quote:
Originally posted by TRENT:
Great stuff guys! I love the contributors input and advise. It is great finding people who know what they are talking about.
What is the feasibilty of extending a 4 1/2"
24:1 extruder to 32:1? Working with 250HP motor, compounding HDPE.
I ask myself - why would you want to extend the barrel? Is it because you are not getting a satisfactory melt after 24 turns? In which case it would be much cheaper to modify the screw rather than the barrel.Regards, Peter P.
pepe@polytech.co.uk
www.polytechconsultants.com [This message has been edited by Peter P (edited 06-15-2001).] IP: Logged |
TRENT
Member Posts: 2
From:
Registered: Jun 2001
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posted June 18, 2001 01:09 PM
True, but I'm also lead to believe that one can obtain more output as well? IP: Logged |
Peter P
Senior Member Posts: 55
From:Nottingham, Notts., U.K.
Registered: Jun 2001
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posted June 18, 2001 02:39 PM
quote:
Originally posted by TRENT:
True, but I'm also lead to believe that one can obtain more output as well?
Not true - the output of a single screw (in the absence of a grooved feed pocket) depends on the geometry of the screw in the metering section. See for example our website at Drag Flow Regards, Peter P.
pepe@polytech.co.uk
www.polytechconsultants.com
[This message has been edited by Peter P (edited 06-18-2001).] IP: Logged |
Tom C
Moderator Posts: 137
From:Wharton, NJ, USA
Registered: Jun 2001
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posted June 18, 2001 08:09 PM
To my knowledge you can achieve greater output on a longer extruder when consideration is given for melting ability and pressure stability. After a certain point, diminished returns sets in quickly.Tom @ CCS IP: Logged |
2beeps
Moderator Posts: 46
From:Silver City, NM, USA
Registered: Jun 2001
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posted July 01, 2001 11:25 PM
Hi Trent, Tom, Peter,In my (humble but always correct  ) opinion, a longer L/D single screw extruder allows more residence time to acheive a stable melt- and under a less severe temperature profile, so that higher RPM's and output can be acheived with less chance of frictional heat buildup in the metering zone. At least this was the case for powder RPVC compounds.  Regards, Skip IP: Logged |
malikengg
Member Posts: 4
From:Mumbai, Maharashtra, India
Registered: Jul 2001
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posted July 05, 2001 02:42 PM
The same screw and barrel can be easily extended to 32:1 L/D as required by you. We go to know the existing dimensions of the screw and barrel before we give our techno-commercial offer. We are Indian manufacturers of single and twin screw extruders.Thanks
R V Malik
Malik Engineers (info@malikengg.com) quote:
Originally posted by TRENT:
Great stuff guys! I love the contributors input and advise. It is great finding people who know what they are talking about.
What is the feasibilty of extending a 4 1/2"
24:1 extruder to 32:1? Working with 250HP motor, compounding HDPE.
IP: Logged |
louis33
Senior Member Posts: 56
From:Allentown, PA - USA
Registered: Jun 2001
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posted July 07, 2001 11:32 AM
TrentHow much of that 250 HP do you think you are using? Output is dependant not only on the screw and feed throat design, but the available HP. I didn't look it up to verify it, but a 4 1/2" 32 - 1 may need a bit more than that. As Skip said, you should be able to get a more consistent melt with the longer L/D - and it might be less aggressive on the HDPE. You can turn that stuff into LDPE with a twin screw that's set-up for really aggressive mixing. So my theory on plastics is to be "gentile" with them. Back in the dark ages when I started, we ran 15/1 machines. You took a solid and turned it to a melt and pushed it out the end in a very short period of time. As to the retrofit itself, it should not be a problem. If you do any maintenance in-house and have changed out barrels before, then go for it. You can order the new barrel and screw from someone like Xaloy, order the heaters, thermocouples and a new instrument (assumes you will ad more zones to the barrel than the three or four you have?)and keep the machine running ($$$$$$) while they are being made. Come delivery time, you will need to work out the finer details such as barrel covers, fans or other cooling for the barrel. (Do all compounders really leave the extruder barrel covers on? - I've seen some pretty nasty pics ;-) Having said all that - I would search out a good screw manufacturer that was familiar with the compounds you run and get a screw optimized for you application. You would be surprized with how much you can increase output with the proper screw. Louis IP: Logged |
Jay_B
Member Posts: 1
From:Compton, CA. 90221
Registered: May 2003
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posted May 14, 2003 04:13 PM
we have done over a dozen of these projects in the last 10 years. The name of the game is to get more output. As long as your downstream can keep up it has worked well for
everyone. We have bought new barrels for some and extended barrels for others. Either option is viable. The ones that have add a welded piece to extend the length have use 4140 or nitrolly 135 and nitrided the end. We have some that have gone as long as six years before replacing the barrel with a new one. One other note. Make sure if you do this to support the end. It's a lot of weight sticking out and that could cause premature wear on the screw and barrel.Happy Trails,
Jay IP: Logged |
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