pump models

[cfboiler]

Could anyone please explain if pump manufacturers design and manufacture pump models to run on both 50/60Hz or do they have specific pumps models that run on 50Hz and a separate set for 60Hz. what are the implications if say we use a pump designed to run on 50Hz and use it for 60Hz application? thanks in advance.

 

[DubMac]

Of course. The only difference you're talking about is pump speed; no other mystical changes take place between 50 and 60 Hz. Just run it at 50 Hz or 40 Hz or 30Hz and use the affinity laws to adjust to desired running speed.

 

[Artisi]

If testing a 60Hz duty at 50Hz you need to convert the 60Hz performance to 50Hz.
You also need to ensure hydraulic and mechanical capability for the higher speed.

Up until now all discussion is theory, how about posting the 50Hz curve, pump manufacturer / model etc. and the final 60Hz duty - for something meaningful.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[TenPenny]

Most test facilities have VFD capability, so the concept of testing a pump at 60Hz in a 50Hz world or vice-versa is a question that was dealt with years ago.

 

[DubMac]

Yes, Artisi, I should have said that there are mechanical limits to speeding up a pump (properly applied ankle-bite).

I recall working as an Application Engineer ( a couple of centuries ago) having to select 20-30 pumps at a time for a refinery or chem plant. We would always try to fit each service into 2-pole speed first (smallest, cheapest) and then work down to 4, then maybe even 6 pole motor. Very common to only have one curve for a pump model at say 3600 rpm, and if the service required 1800rpm, we would just whiteout the flow and head values on the axes and handwrite in the corresponding 1800rpm numbers. It was a real luxury to have curves for separate synchronous speeds. We would do the same thing to convert to 50 cycle speeds, same curve for all speeds; the original cut&paste I guess.

I remember the old guys commenting on how lucky we were: "back in the day, we used to hand draw every curve on tracing paper, for every pump, with French curves and slide rules"......We just said: " go away old man, I don't have time to listen to your babbling, I have pumps to select".

The point is,

While I would have loved to have had the current computer selection programs back then, I often wonder what, if anything, has been lost by not having to "think" you're way through speed changes and so forth. Maybe some people would not be so puzzled by 50 to 60 Hz changes??

 

[Artisi]

DubMac
Been there and done that.
I think having to draw / redraw, extrapolate your own curves and make informed decisions gives a much better feel of what is what - especially when selecting a bunch of pumps for a major project and trying to rationalise the number of pumps within the overall selection. Plus if you are experienced in the application and know your pump range/s well - it's probably quicker to select manually than cranking up a computer programme with the myriad of blanks you have to fill in to derive a selection - miss a box of useless info. and what do you get - an error message.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[stanier]

Come on guys. The wet end of the pump is designed for 50 or 60hz. A four pole motor would run at 1500 rpm at 50 Hz or 1800 rpm at 60 Hz. same pump end could be fitted to a two pole motor and run at 3000 or 3600 rpm respectively. Then of course it could be coupled to a gas or diesel engine or a an oversdped variable frequency drive and run upwards of 110% of these speeds.

Of course the Sundyne LPG pumps run at 18,000rpm.

There maybe some mechanical issues with lubrication, critical speeds etc at higher speeds.

There is an argument to use lower speed four pole motors as the pump lasts longer. This is common in the water industry. The counter argument is that two pole motors operate more efficiently. Spares are cheaper as they are smaller and the pump room can be smaller.

The economics of forty years ago have changed and so should engineers thinking.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[Artisi]

There is no guarantee that a 50Hz design is hydraulically or mechanical capable of running at 60HZ. My post 2# gives some thoughts on this as well as comments from others.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)