troubleshooting a vertical multi-stage pump

[cassandramyer]

thread407-263167

Hi I have recently installed a newly recondition drive motor of a Floway pump. the problem is during testing the pump is operating in low pressure. we only tested it for a little while because we could not see any immediate change in pressure gauge that would detect whether there is flow.

as I was reading on installation guide of possible cause of low pressure, it mentioned that there is a possible reason that the cause of low pressure is air.

I was thinking that since we did not test it longer maybe air is present on the pipe line that is why the pump is not delivering well, should we have tested it longer to eliminate this? or could anyone tell me how to commission an installed pump.

 

[Artisi]

What was happening before you installed the re-con motor, was the pump working?
Is the motor running in the correct direction? - (yes I know, of course it's running in the right direction) - go and check it yourself.
It is a vertical turbine pump- where do you think the air is?

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.)

 

[JJPellin]

Rotation is the most likely cause. Without more information, it will be difficult to be sure.

Johnny Pellin

 

[DubMac]

As long as you have the suction valve open, it is very doubtful air is the problem as long as you confirm fluid level is above your first impeller. Sounds like classic case of wired backwards.

 

[cassandramyer]

"What was happening before you installed the re-con motor, was the pump working?
Is the motor running in the correct direction? - (yes I know, of course it's running in the right direction) - go and check it yourself.
It is a vertical turbine pump- where do you think the air is?"

----The thing is they had this pump drive motor recondition because they said that they were experiencing noise and vibration during operation. what they are not certain is if the pump's pressure before re-con was okay because their pressure gauge which is used to determine flow was not functioning.

Is the motor running in the correct direction? - (yes I know, of course it's running in the right direction) - go and check it yourself.
It is a vertical turbine pump- where do you think the air is?

----well during testing there was water coming out of the discharge so that is my basis that it is running in the right direction.
or is it possible that it could still be running in wrong direction even if there is water discharge?

 

[Artisi]

Simple answer, yes. It may not be the problem, but ccertainly number one on the check list.

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.)

 

[DubMac]

Yes, water will still flow running backwards, but (depending on the impeller type) you will build no appreciable pressure.

Was the pump worked on at all??

Was the impeller clearance reset after reinstalling motor?? (if open impellers)

Are they keyed or colleted impellers ??

If running backwards is not the problem, answer these questions.

 

[cassandramyer]

We did not recondition the pump just the motor drive and we were not able to dismantle pump part, but we had to pull out the pump as well because we had a difficulty in re-installing the coupling in the pump shaft(pump is closed coupled).

Okay so air is not possible, I'm sure that the rotation is correct, Im drawing a conclusion here that we might have loosen one or more of its impeller due to handling. Now how do I check for that?

 

[JJPellin]

If an impeller dropped because of a failed collet or split-ring, you might be able to feel a drag and rub rolling the shaft around by hand. But, this depends on the size of the pump, the depth to the impellers, etc.

There are two types of wear surfaces on impellers of this type. Some use conventional radial wear rings. For these, the impeller lift is not as critical. It needs to be enough that the impellers don't rub. The second type uses a lateral wear surface that seals axially off the end of the impeller eye. For these, the lift is much less and much more critical. If it has a lateral wear ring and was set with excessive lift, it may not build proper pressure. Some pumps have both radial and lateral wear surfaces.

Our crystal balls are getting fuzzy. We can keep guessing for a bit longer. Then we are likely to get bored and drift away without more details.

Johnny Pellin

 

[JJPellin]

There are also pumps of this type that use open face impellers. These are also sensitive to lift setting. You must know exactly what sort of impeller you have and exactly what the proper lift setting is for that pump. If someone tells you that all pumps of this type can run well set at 1/8 inch lift, they are wrong. We probably have 100 pumps of this type in our plant. The lift settings vary between 0.75 inch and 0.020 inch.

Johnny Pellin

 

[DubMac]

A real guessing game with the limited info here....
I am ASSUMING this is a run of the mill, cast iron/bronze fitted, open lineshaft, colleted, open impellers, typical Floway VTP.

You won't be able to do much without pulling the pump again. If rotation is correct, my next guess would be the collets are no longer securing impellers causing them to slip on the pumpshaft.

If impeller blades are badly worn or deformed, and clearance was not set properly while fumbling with the coupling, this could cause low flow.

You say the unit was vibrating w/ noise prior; why was it assumed it was the motor?
What kind of difficulty did you have with the coupling?

Just swingin' in the dark here.

 

[QualityTime]

Just giving my thought....there could be air in the pump when the pump is at rest. Unless the pump is continulally primed, everytime you start up a vertical turbine pump there will be air between the discharge check valve, and the well top water level inside the casing of the pump. Typically with this type of pump one starts the pump up against a closed valve. An air relase valve on the pump discharge piping will pee out MOST of the air before the discharge valve is timed to start to open.


The problem with vertical turbine pumps, unlike dry pit pumps, is that becasue the pump is in the water you cannot hear if there is any problems. Cost trade off issue

 

[Artisi]

An application description might be of some assistance, is the pump in a pit, well or some other configuration. It could be an application problem rather than a pump problem (isn't it always the pump at fault?).
Was the pump operating ok prior to maintanace in terms of hydraulic performance?
Plus we are all assuming that there is actualy water present to be pumped.

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.)

 

[cassandramyer]

Thanks everyone, this is very informative and helpful also forgive me for not giving further information on the topic.

It is a non potable pump with a drive motor of 7.5hp 3540rpm
Model no. 5K213DTP5014. Brand floway
As I remember it is an 8 stages pump but im not really sure.
Out side casing of impellers are very similar to the characteristic of a carbon.

I will try to attach the photo as soon as I get to my laptop.

They assumed it was the motor because, the unit has not been reconditioned for 9 years so the assumed that it might be the motor bearing.

We had trouble installing back the coupling due to damaged thread of the shaft.

They are not sure if it was operating well prior recondition because their pressure gauge which is their basis if pressure of pump is okay was not working.

We will try to pull the unit this week to check. I shall keep you guys posted.

 

[Artisi]

After 9 years who would or could guess the state of the pump components. I would have thought that after this period of time and seeing as how the pump was "out" of its installation a look at the internals would have been one of the items on the top of the list, especially as there seemed to be a problem of some magnitude.
Guess we are all now waiting to see the outcome of the investigation.

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.)

 

[cassandramyer]

<a href="

http://s1251.beta.photobucket.com/user/cmlendrino/media/nonpotable/20130305_071525.jpg.html"

target="_blank"><img src="

http://i1251.photobucket.com/albums/hh544/cmlendrino/nonpotable/20130305_071525.jpg"

border="0" alt=" photo 20130305_071525.jpg"/></a>

above is the photo of the pump.

 

[QualityTime]

Are the impellers on every stage clear of debris? Are the impellors ok? Are the wearing rings clearances ok?

 

[cassandramyer]

Are the impellers on every stage clear of debris? Are the impellors ok? Are the wearing rings clearances ok?

- I will let you know once we get a chance to pull out the unit and dismantle.

 

[cassandramyer]

Would anyone know or give an instruction on how to properly dismantle this pump.

I'm really new to my work and I don't trust our technicians so much regarding this type.

 

[DubMac]

Before your "technicians" put chain tongs and cheater pipes on the pump, give Weir a call (or email). It looks like the pump Serial# you gave above; just send it along with basic questions, a request for a manual, or a Weir certified shop (most likely their Distributor) in your area.

They may be more expensive than the pump is worth and you may not want to use them, but at least asking that way will get you some info. Look for Walter Lee's name; he is a big shot with the vertical group in Fresno; but is a very good guy and will forward your info to the right person.