posted 06-06-2001 09:14 PM               

quote:

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Originally posted by Cynbay:
What do you guys think of gear (melt) pumps?

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best thing since sliced bread if you can afford the entry fee, AND have long runs. great for stable output that results in close tolerance product - or down-gaging.

They are now used on everything from Flex and Rigid PVC to engineering grades of material such as Teflon

posted 06-08-2001 08:19 PM               

quote:

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Originally posted by Steve H:
When starting a line equiped with a M'pump, I presume that once line is up to run temps, you start the M'pump drive and then start extruder screw turning.
I know you can't run the M'pump dry (for long)
Any guidence on the operation of M'pumps gratefully received

Steve H

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To gain the benefits of a melt pump, you need pressure feedback controls on both the inlet and discharge end of the pump. These will control the pump depending on the pressure at the discharge end of the feed screw.

Once in operation, the pressure controls will vary the screw speed to maintain a constant pressure range on the input side of the pump.

Barring controls, I would start the extruder first, while monitoring the pressure, when I saw it bump up, I would then start the pump. Then ramp each up together until I reached the running speed selected.

But why run a melt pump without controls . . .?

Louis

posted 06-09-2001 05:26 PM               

The pump is a Maag unit, and as you point out
has presure controller (interconected to extruder drive), we have just been trying run
pump motor up ( with out pump connected) and
it will not run above 10 RPM. I presume that because the presure TD's are telling the drive there is no suction pressure and so it
is limiting RPM to prevent any damage to M'pump.

posted 06-11-2001 06:31 PM               

quote:

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Originally posted by Steve H:
Hi Louis

The pump is a Maag unit, and as you point out
has presure controller (interconected to extruder drive), we have just been trying run
pump motor up ( with out pump connected) and
it will not run above 10 RPM. I presume that because the presure TD's are telling the drive there is no suction pressure and so it
is limiting RPM to prevent any damage to M'pump.

regards
Steve

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Steve

That would be my guess - the controllers are limiting your dry run speed.

But why would you want to run it dry?

Louis

posted 06-12-2001 01:12 AM               

The line is a second hand one (Amut circa 1985)- the melt pump is a Maag and was added in 1990. The line was originally installed in Germany- and has been purchased by a New Zealand processor.

While we have all the manuals :-), they are either in German or Italian :-(. So we're translating, and guestimating, (quite a bit), to get it all back together, all controllers and motors correctly phased etc.

And then there'll be the challenge of running
it up for the first time- and I'd hate to get
it wrong.8-{

Steve