Sign up Calendar Latest Topics Donate
 
 
 


Reply
  Author   Comment  
OLi

Sr. Member
Registered:
Posts: 1,913
Reply with quote  #1 
If you are out on the pump curve to the left there are some names for that. Regarding waste pumps in municipal systems you do a thing that may be called slurp or surge or whatnot maybe, you drain the chamber and suck the goodies from the bottom so you have flow but no pressure sort of so you get out far to the right. Do you know any special name for such points on the pump curve? What would it be called eventually in serious circumstances or are there no names on that side as it is rarely used?  
__________________
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
Curran919

Avatar / Picture

Sr. Member / Supporter
Registered:
Posts: 599
Reply with quote  #2 
Hi Oli,

At overload, the phenomena are similar to slight partload. You get flow separation on the impeller vanes, but recirculation is in the "opposite direction". Your fluid velocity also increases over the impeller, which decreases local pressure and increases risk of cavitation. As far as I know, there is no relative flow limit where the flow significantly changes and you develop some surge-like state. Flow separation will just get worse until your head shrinks to near zero and efficiency takes a nosedive. Even at partload, as long as you have a stable Q-H curve, nothing extreme/discontinuous should happen like stall or surge.

I would not be surprised to hear I am wrong though.
OLi

Sr. Member
Registered:
Posts: 1,913
Reply with quote  #3 

Well it seems to be a "little" increased vibration is normal. [smile]

Question was, do you know of a name for this operating condition that is frequently used?

My wastewater contact that is the one asking suggest something that in translation would be like "Unrestricted point".
Any better suggestions?


__________________
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
Curran919

Avatar / Picture

Sr. Member / Supporter
Registered:
Posts: 599
Reply with quote  #4 
Quote:
Originally Posted by OLi

Well it seems to be a "little" increased vibration is normal. [smile]

Question was, do you know of a name for this operating condition that is frequently used?



Unrestricted Point sounds like it is related to the Prefered Operating Region (POR) or Allowable Operating Region (AOR)?

Depending on the pump/standard, POR is often at 80-115% BEP and AOR maybe at 70-130% BEP. Many standards define these regions not as fixed numbers,  but the regions of the curve where the vibration is below a certain limit. For example, API 610 sets the POR where vibration is less than 3 mm/s and AOR where vibration is less than 3.9 mm/s. In a funny way, this makes it impossible for vibration to be to high on a pump unless it is too high at BEP. There can just be an unacceptably narrow POR.

Other than that, there is little other vocabulary that I've heard besides overflow/overload. Naturally, I hang out with engineers, so they tend to describe these phenomenon in numbers (q* > 1.25) or even above-POR rather than colloquialisms, so I'm sure that something must exist, but its not going to be as well-known as stall or surge.

EDIT: colleague also offers 'run out' as a possibility, but this is only the opposite of shutoff, i.e. at maximum flow (no head).

OLi

Sr. Member
Registered:
Posts: 1,913
Reply with quote  #5 
Yes, run out would be a suggestion, not so easy to translate but could be used as is. Thank you.
__________________
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
Curran919

Avatar / Picture

Sr. Member / Supporter
Registered:
Posts: 599
Reply with quote  #6 
Quote:
Originally Posted by OLi
Yes, run out would be a suggestion, not so easy to translate but could be used as is. Thank you.


It translates pretty directly to German, as I'd also use "Auslauf" in this scenario. What's wrong with Swedish? [crazy] I just learned the Swedish Egenfrekvens on Monday. Very Elegant. I'm happy with that being the only Swedish word in my vocabulary.
OLi

Sr. Member
Registered:
Posts: 1,913
Reply with quote  #7 
We normally don't run pumps that way [smile]. Run out is more used with eddy probes and then translated to "egenkast" and that would not work. Otherwise we are happy for the word "lagom" that presumably are used when the beer is enough to make everybody around the table happy and "ombudsman" that we are proud to have given to the rest of the world and also the Swedish Chef in Muppet Show.....


__________________
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
http://www.vtab.se
Curran919

Avatar / Picture

Sr. Member / Supporter
Registered:
Posts: 599
Reply with quote  #8 
Egenkast ¡s a massively better name for it than run-out.


We use run-out for so many things that ¡t is heavily context dependent what exactly someone means.
German usually gets it right with Eigenfrequenz being so much better than the English Natural Frequency
or French/Italian  Frequencia Propria (Proper Frequency?). However, they fail in this case with run-out
translating to Wellenschlag. Expectedly ambiguous, but Welle is a personal hatred of mine given
the dozens of unrelated definitions. Together though, you would expect something specific, but still no.
When you google image search Wellenschlag, it is just waves crashing on a beach.



Where are my shaft balancing pictures google!!!!!
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.