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Nip Impressions® is Paperitalo Publications' flagship publication.  Published every Thursday afternoon (US Eastern Time), Nip Impressions® is eagerly read by pulp and paper professionals around the world.

29 Jan 14: Computerization 1--Not reliable


I'll have to be a bit circumspect about this situation to avoid revealing the mill's identity, but I think I can get the point across, even with this limit.


This particular situation arose when a set of valves controlling oil pressure to some vital cylinders on a paper machine inexplicably opened.  This allowed an over pressure condition to exist for one second. Yes, one second.  The monitoring data shows it very clearly.

The result was five (5) days of downtime plus equipment damage. 

Why did this happen?  It appears a USD 500 mechanical pressure relief valve could have prevented the entire episode.

I was talking to a mature friend (old man) about this.  He asked why the designers had not specified the pressure relief valve. I calmly pointed out that the designers, even if they were in their forties, have never worked on the old mechanical equipment we grew up operating.  They have always done it by computer.

So, despite your standby generators, back up algorithms and so forth, sometimes you need protection that just works.  A lesson well worth remembering.
Any comments?  Let us know by sending an email to jthompson@taii.com with "LGMI Frontiers" in the subject line.


LGMI Design Practices
As always, your comments will be appreciated.
Think light!


Brian Brogdon, Ph.D.
Executive Director




Jim Thompson

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or Jim Thompson!

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