ECN Forum Forums General Topics of the Trade General Discussion Area Hydaulic pumpmotor and overloading

wa2ise,
your understanding is fine,
perhaps at some point those two furnaces had their own pump, while sharing the same 3rd pump as backup.....I don't know....it would make more sense to power each furnace independently,
but that would only allow them to think they are one pump short, instead of utilizing the two spares that are doing nothing.....I did suggest an alternator ....but they didn't respond to that

their intransigence has allowed an already overloaded pump to overheat some more, trip out , and then someone has to run over there , reset OLs and sometimes change fuses , and put the same pump back in service, and occasionally pull a burned motor out.....( Iwas involved with that .how dam stupid is this???

but they are so pleased with the new setup..even with that motor running overloaded...that they are talking about simply replacing three 20hp pumps with two 30 or 40hp..

...and no one will take the time to determine what the cause of the overload truly is !

It isn't at all crazy to size the new motors based upon the current drawn by the old motors. The current on the old motors is a very rough measure of the torque loading the old motors. So if you make the presumption that the old motors were simply mechanically overloaded, then going to new motors of the same output shaft speed but higher torque capability is probably a good solution.

However the _evidence_ is that after the motors were increased in capacity, they were _still_ overloaded. Togol, I totally agree with you; this strongly suggests some serious other problem.

'Power factor' cannot directly be an issue here. The motors will consume current that is slightly out of phase with the applied voltage, but external factors cannot change the _internal_ power factor of the motor. As long as the voltages at the motor terminals are correct and _balanced_ the over-all power factor on the feeder to the motor is not relevant.

Can you confirm that the motors were replaced 'like for like', eg. a 4 pole 1800 RPM motors with larger 4 pole 1800 RPM motors? Are the motors of similar class with similar slip versus load characteristics.

Were any shaft speed measurements taken on the old and new motors? What I am wondering is if there is some strange interaction between the pressure regulation, the pumps, and the motors, such that the motors _never_ get up to speed. The motors could be happily running along in a high slip, low efficiency condition, burning themselves up. Note that if the problem is the motors not actually getting up to speed, then a larger motor might be able to push past the 'hump' and function correctly, but this is not the real fix to the problem.

-Jon

Togal, based on a couple of your posts the question that comes to my mind is why are you working there?

Find a new place to work, this one sounds like a total disaster.

BTW listen to 'winnie' he knows a thing or two about motors.

Bob

You said the voltage at the motor starter terminals was correct. What about at the motors themselves? How far is the run to the motors?

This sounds more like a hydraulic problem than a motor problem.

winnie....
the speeds on the dataplates are identical.. 1750
.but I did not compare other relevant info...I will tonite.!..( I just got home )


Bob..
this job was meant as a stopgap due to the slowdown of big new construction around here...it is NOT my intention to overstay my visit.one minute longer than necessary........nosirree

JBD....
the pump was in service when I checked voltages so I could not open the peckerhead, but the the whip is about 5' and amps were close 51...49.5....49.8


to everyone.......

I had tried to avoid this whole fiasco .....but as more of the history of these pumps was revealed, the more skeptical I became of the fix, and naturally more inquisitive....

my only remark was more from the gut, but their reponse to the PF question was more like..
..what the hell is power factor ?
even though there are five rather large induction furnaces right behind the pump wall..!!!

this place is a nightmare I know, but after sitting for almost 11months, I needed some sort of income,

I have (almost always ) endeavored during my career to find answers to problems,...... if I didn't understand the solution, there would always be someone who could get it to stick to something inside my skull

So, while I am there I will keep notes on this circus for my own knowledge.
besides, the last time I held a maint. job Carter was president


the one plus in this, is discovering that I have absolutely no grasp of PF fundamentals and need to head down to the Technical area..... oboyoboy

but please don't stop posting your thoughts on this thread...OK ,

its bedtime for me....g'night johnboy

I can just imagine all the money being blown in terms of blown motors, time spent trying to "fix" this, and all the downtime costs caused by the inability to use the affected furnaces.

When I used to work for Intel, they had a rule of sorts that said "Copy exactly" a successful production facility. We had semiconductor integrated circuit (chip) fabrication facilities and once we had a successful and reasonably efficient operation we wanted to duplicate exactly that facility and not try to improve it. Or you'd risk it not working and thus not being able to make and ship more of a popular product before the competition hits the market with something better yet. We wanted to be able to sell more stuff and make more money

Seems this iron foundry ought to just "copy exactly" the working "one pump one furnace" systems and forget about using bigger motors. But management there would have to realize that nobody really understands what the trouble is. Even if it costs more than yet another bigger motor, it should get them running reliabily.

[This message has been edited by wa2ise (edited 07-04-2006).]