For such machines where the BEP is relevant, like most pumps and fans, do you make a call when you find such a machine off the BEP? Do you actively fight to get them modified or the system modified so the machine runs at BEP as soon as possible? What arguments do you use to support this? Energy waste calculations? Workshop resource blocking and spares costs? Production loss due to repairs downtime? Anything else. Or is the analysts task only to detect when machines, running as they are, get a pending or developed damage on the way? Are there concrete walls between workshop, operation and bean counters where you work?

Most of the fights started after repeat failures made their way back into the shop for repair. Arguments usually consisted of documented damage evidence and the cause, followed by some sort of solution. Primarily, the concern was not with equipment destruction, but a fugitive emission resulting from mechanical seal failure. It seems mech seals are extremely sensitive to shaft deflection and cavitation!!! But, that's more in the chemical industry where the slightest leak can mean the worst for the enviroment and compliance. The paper industry (at least the one that I know) hasn't really put much thought into properly sized pumps and mechanical seal life. There's not a whole lot of time for us to spend spec'ing out systems, but control valves usually are a big indicator that potential BEP problems may exist. I will from time to time, report to an operator that the previous shift operated a particular piece of equipment at much less vibration, simply because of a valve setting difference. We have put "baby sitter" monitors on fans that let the operators know (by the use of colored warning lights) where the worst damper settings are. The issues can be dealt with, but usually it requires new construction while operating and tie-ins during outages. Proper training plays a big part in making improvements.

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There's not a whole lot of time for us to spend spec'ing out systems, but control valves usually are a big indicator that potential BEP problems may exist.

I agree with Sid.

I found this article a few years ago. I thought it covered a few good topics on pump performance.

Stop_Falling_Off_The_Curve.pdf (396 Kb, 53 downloads)

That's a pretty good article. The McNally Institute also has some good info thats written in very understandable terms. 'Pumps and Systems' magazine is great information source too.

In the following two articles it is suggested that operating off BEP is particularly harmful for pumps with long slender shaft and generally not as much a problem for shorted stouter shafts (although I'm sure the vibration is not good for the bearings and seals in either case)

http://www.pump-zone.com/articles/Shaft_Deflection_Part_One.pdf

http://www.pump-zone.com/articles/Shaft_Deflection_Pa_124440E.pdf

This message has been edited. Last edited by: electricpete,

Any pump or fan run off its BEP will show signs of distress eventually. We've had problems with running large vertical water pumps so far off whwere they should be that they would eat themselves on a regular basis. Being a Nuke we put a recommendation for an operating range in the Ops Procedure to try to keep them in the ball park. Operating in a better place on the curve and some better overhauls and we've gone from failures about every 2 years to greater than 5 years. Sometimes a little knowledge spread around to the right places can make a difference.

Thank you all for interesting comments. Just a word to rgf. Sometimes the pumps are just not right and the problem is constant, not shifting over the year. In such cases I have been very successful reducing the diamater of the impeller and recently, thanks to very reduced prices on high quality larger varible frequency drives been able to increase the speed a bit to adjust the curve point on similar pumps. Another surprisingly simple action was to adjust the inlet turbulence pattern with small guide vanes in the channel next before the pump, and the floor and box around the suction skirt. A few pictures taken when drying out the channel can show how growth is spread and give good ides how to correct. Life time to 10-14 years very much possible and will soon pay the efforts. Could be worth an investigation.