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geliberman (Mechanical) (OP)
2 Jul 11 11:16
can anybody advise me how can I solve the pump overheating.
I have a flowserve DMX pump, the pump bearings has failure due to overheating. Overheating is due to low flow, can I use an ARC valve to increase the flow and modify the pump working piont?
Artisi (Mechanical)
2 Jul 11 11:48
If the overheating is due to low flow - have you considered changing the pump for one suitable for the application.

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.)  

geliberman (Mechanical) (OP)
2 Jul 11 11:52
Thank you Artisi,
But I can't change the pump.
Artisi (Mechanical)
2 Jul 11 11:59
A lot more detail might help in identifying the problem - ie, pump model, speed, BEP flow / head, actual flow / head, product, temp etc.   

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.)  

geliberman (Mechanical) (OP)
3 Jul 11 10:37
pump model: flowserve 6x11 7stages
speed:2965 rpm
Capacity: 288 m3/h
Head: 875m
actual head:1025m  
Pumpsonly (Mechanical)
3 Jul 11 13:58
288m3/hr is the pump BEP flow or actual flow?
You have also not inform product and operating temp.

Is it the pump casing over heat or bearing over heating?

Bearing failure due to over heating could be caused by bearing cooling failure or inadequate cooling. Is it water or air cooled?

If you are sure it is due to low flow  the quickest solution is to add a ARC valve or a minimum flow by pass line with a RO.
GPRnD (Mechanical)
6 Jul 11 23:52
You need to post more details as the others requested.

Typically minimum flow on these pumps should be at least 30% of BEP.  For reliability I would always recommend higher than that.

What we need is the following:

Pump BEP
Pump rated flow
Pump minimum flow
Bearing temperatures at rated flow
Bearing temperatures at minimum flow
Type/size of bearings
Cooling method for bearings

It is possible that at low flows the thrust balance is not great.  This can happen due to changes in the recirculation patterns.  Typically we design BB3 pumps with 500 to 1000 lbs of thrust, but in reality the thrust calculation is not always correct.  The only way to know for sure is to measure it on test with thrust studs.
geliberman (Mechanical) (OP)
22 Jul 11 15:41
The system characteristics are as follow:
Service=water
SPEED=2965 RPM
SUCTION=8"
DISCHARGE=6"
BEP (Q=358M3/H, H=795M)
RATED(Q=288 M3/H, H=875M)
temperature= 16 C

____________

MOTOR NAME PLATE SPECIFICATIONS: V=660V 3 PHASE 50 HZ, I=98 A, COS(PHI)=.92, IP=56, TH. CL.=F, 5.300t, 2987 RPM
_____________

OPERATING CONDITION:
PUMP INLET PRESSURE=4.66 BARG
PUMP OUTLET PRESSURE=95 BARG
Q=221.4 M3/H
I=86.75 A
Q=221.4 M3/H

The motor front bearing is cooled by oil ring, this bearing is overheated(80 c).
The temperature of pump casing and bearings are OK.

Thank you.

 
rmw (Mechanical)
22 Jul 11 19:14
Sorry, but I just boxed my old Byron Jackson pump manuals for an office move.  I think this is one of theirs (or United's) before Flowserve swallowed them up.  I can't remember which company designed that pump, but I have used this series pump and they are generally reliable if operated correctly.

But I believe you have given enough information.  I can from the above see that the rated point is already to the left of the BEP and your operating point is even more to the left of rated and fastly approaching 50% of BEP.  I'd need to see the curve to see the implications of that.

Other than the fact that my old manuals are in English units and I'd have to convert all the above to those units I think it is safe to say that you have to increase the flow and run the operating point out on the curve somewhere nearer rated point or better, all the way out to BEP or at least between those two points if you can.

What are you doing with the excess head now?  Can you live with the head reduction if you bypass and get that far out on the curve?

Do you have the capablilty to recirculate some of the pumpage back to where it came from to increase the pump flow if the answer to your question about the ARC valve is yes?

rmw
Artisi (Mechanical)
22 Jul 11 22:16
Seems some what confused, initially you said the pump bearings were overheating, your last post said the motor bearings are running at 80c which you believe is overheated and the pump bearings are ok ?????????????????.  

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.)  

geliberman (Mechanical) (OP)
22 Jul 11 22:59
Dear Artisi,
You are correct, initially the pump user told me that pump bearings overheated, but after site visit, I found that the motor front bearing is the main problem,
I have enclosed the pump curve.
I have another question, when the flow is low, the power is also shall be decreased, but in this case the motor power is increased.
Why the motor power consumption is so high!(the electric current is very high I=86.8A  3B&utmu=
GPRnD (Mechanical)
22 Jul 11 23:17
Ok so you got me off track with the whole pump bearings are hot but now it is the motor bearings thing.

When I see an issue of an overheating motor bearing, my immediate questions are:

1) What type/model of coupling are you using, specifically does it transmit significant axial thrust?

2) Is the overheating motor bearing, the thrust bearing (rolling element type) or does the motor have sleeve type bearings ?


I'll think about your motor power question over the weekend.
PumpSmart (Mechanical)
24 Jul 11 3:38
DMX IS A HORIZONTAL MULTISTAGE PUMP, OLD DESIGN OF INGERSOL DRESSER PUMP, NOW FLOWSERVE PUMP, BB3 CONFIGURATION.
SINCE IT LOOKS LIKE YOUR OPERATION IS A LOW FLOW POINT THAT IS LESS THAN MINIMUN CONTINOUS FLOW OR MINIMUM THERMAL FLOW OF YOUR PUMP.
MINIMUN CONTINOUS FLOW IS A DESING POINT CAPACITY PUBLISHED BY MANUFACTURER.
AT THOSE LOW FLOWS, RADIAL LOADS INCREASE AND CAUSE SHAFT DEFLECTION WITH CONSEQUENCES IN MECHANICAL SEALS AND BEARING FAILURES.
YOU CAN USE PREDICTIVE TECHNIQUES TO KNOW THE HEALTH OT THE BEARINGS, SPIKE ENERGY AND VIBRARION ACELERATION WILL HELP, THEN DOUBLE CHECK TYPE OF OIL, MISALIGMENT, ETC TO BE SURE THE PROBLEM IS LOW FLOW.
IF YOU CAN MEASURE FLOW IN THIS PUMP, AND CONFIRM THAT THE PROBLEM IS LOW PROBLEM, IN OTHER HAND WITH 1025 M OF ACTUAL HELP IT LOOKS LIKE IT IS A LOW FLOW PROBLEM.
YOU SAID THAT PUMP CONSUME MORE AMPERAGE , IT PROBABLY BE BEACUSE
INCRECREASING WEAR RING CLEAERENCE.
DID YOU MEASURE CAPACITY?
DID YOU CHECK MISALIGMENT?
WHAT KIND OF BEARING DOES THE MOTOR HAVE?
DO YOU USE CONTROL VALVE IN DISCHARGE POSITION?
WHAT FLUID IS PUMPED?
WHAT TEMPERATURE IS THE FLUID?
geliberman (Mechanical) (OP)
24 Jul 11 4:41
The fluid is water.
Water temperature is 16 C, the water temperature is low.
We use a control valve in discharge position.
There are not any vibration or misalignment in system.
Thank you
 
PumpSmart (Mechanical)
24 Jul 11 5:28
SHOULD BE LOW FLOW OPERATION.
YOU WILL ANALIZE WHY DESIGN SAYS 875MTERS BUT YOU HAVE 1025M.
IT IS 150METERS MORE.
WHAT COMPONENT OVERPRESSURE THE SYSTEM?.
ANY LOW PIPING DIAMETER, HIGH PIPING LENGTH, HIGH STATIC HEIGHT, FILTER, CONTROL VALVE,  ETC.

SECOND, YOU SHOULD ANALYZE VALVE CONTROL OPERATION, LOGIC CONTROL AND VALVE SPECIFICATION, IF VALVE CONTROL IS NEAR TO BE IN CLOSE POSITION SO PUMP TENDS TO RUN IN HIGH PRESSURE/LOW FLOW POINT.
IF YOUR VALVE IS ALWAYS IN OPEN POSITION, YOU SHOULD KNOW HOW MUCH LOSS OF PRESSURE IT PRODUCE.
SO YOU WILL HAVE SOME OPTIONS, CHANGE LOGIC CONTROL ON CONTROL VALVE OR USE/INSTALL RECIRCULE LINE ON DISCHARGE PIPE.
SOME LOGIC CONTROL LIKE CONSTANT LEVEL ON SUCTION TANK  ALWAYS MADE THIS KIND OF PROBLEM.

PLEASE INDICATE TYPE OF MOTOR BEARING, IT IS VERY IMPORTANT.
I THINK YOUR MOTOR IS NEAR TO 1500 HP, SO MOTOR MANUFACTURER WILL USE FRICTON SLEEVE BEARINGS. IN THIS CASE YOU SHOULD CHECK IF MAGNETIC CENTER IS CORRECTED POSITION BY COUPLING, IS THAT IS THE PROBLEM YOU HAVE TO MOVE THE MOTOR. BUT IF MOTOR BEARING IS NON-CONTACT BEARING AND IS HOT YOU SHOULD CHANGE TYPE OF OIL, SOME MOTOR MFG SUGGEST TO GO TO ISOVG68 WHEN YOUR OPERATION IS UNDER 82C AND GO WITH ISOVG100 WHEN IS ON THIS VALUE.

IT HELPS, PLEASE DOUBLE CHECK MY SUGGESTIONS.
rmw (Mechanical)
24 Jul 11 21:18
PumpSmart,

Your responses have good information in them but could you use lower case for typing.  Upper case is hard to read and it is equivalent to yelling or screaming in print media.

Thanks,

rmw
geliberman (Mechanical) (OP)
24 Jul 11 23:47
Dear Pumpsmart,
The pressure difference between suction and discharge is 95-4.66=90.34 BAR, so we have 920.9m, please let me know how you say 1025m for Head.
There is a control valve in the dischage area to set the flow (FCV) I must check this control valve.
Can anybody suggest a P&ID to set the outlet pressure and modify the working point of the pump.
Thank you in advance.

 
Pumpsonly (Mechanical)
25 Jul 11 0:26
geliberman,
Your started off with pump bearing over heating problem but actually is the motor bearing problem.

You still have not provide those info on the motor bearings.

Quote:

I have another question, when the flow is low, the power is also shall be decreased, but in this case the motor power is increased.
Why the motor power consumption is so high!(the electric current is very high I=86.8A  3B&utmu=

At 221 m3/hr operating flow you have I=86.8. Motor FLA=98.

How did you conclude that the power increased with reduced flow?
What is the motor kW rating?

For a pump of this size, I would expect you already has a minimum flow spill back or by-pass line loop in place.
You operating flow (221) is >60% 0f the BEP flow(358), so is not a problem with the pump operating point as you confirmed there is no vibration.


 
Artisi (Mechanical)
25 Jul 11 0:33
Seems a waste or time, misinformation, lack of meaningful information as well as a shotgun approach to the problem/s, it has gone from overheated pump bearings to P&ID requirements without any problems solved or acknowledged so far.   

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.)  

geliberman (Mechanical) (OP)
25 Jul 11 1:28
The Motor is 1000KW, 50HZ, 6600V, 98A, Cos(PHI)=0.92 with one sleeve bearing and one antifriction bearing.the rear bearing (near the fan) temperature is OK, but the front bearing which is cooling by oil ring (has a small oil compartment)is very hot.
There is a missunderstanding, I say that if we have a low flow (lower than BEP) then we shall have lower power consumption, I=86.8, V=6600, Cos(PHI)=0.92, then P=1.732x86.8x6600x0.92=912850 W, if you see the pump curve 912KW is not correspnding to a low flow.
Please apologize, if I waste your time.
Pumpsonly (Mechanical)
25 Jul 11 2:32
You left out the motor effcy in your motor output calculation.

Base on the name plate details the effcy of the motor at full load is 95%.

From the pump curve the BkW at 221 m3/hr is about 750kW which is 75% of motor full load. The PF and effcy at 75% load is expected to drop 1~2 percentage point.The actual value can only be known from the motor test data.

From motor running current of 86.6 provided, the out put is about
840 kW which is higher the pump curve. But than again we are not sure how accurate are the operating data provided.

Btw, oil ring is not a cooling method, it i just to help splash oil on to the bearing and shaft.


 
PumpSmart (Mechanical)
25 Jul 11 17:59
geliberman,
I based on yout previous post:
"pump model: flowserve 6x11 7stages
speed:2965 rpm
Capacity: 288 m3/h
Head: 875mactual head:1025m"   
But based on your last post (221m3/hr@920m)you are around 61% BEP, it is like 80% as reability capacity factor so it sounds aceptable but, yes, it probably will improve but it seems like is not cause related to hot motor bearing. In other hand P&ID depends of your process and variables and varies site to site.
But if low flow was an issue, pump bearings/mech seals was a problem with some vibration but as your previous post it did not happen.
Increment of power, from expected 750 KW to 840 KW (estimated by Pumpsonly) could be motor symptom since 221m3/hr@920mm (I asumme as field data) is very close to performance curve (lab curve you sent previously, so pump is not out of performance).
So mainly you have a hot bearing motor problem plus high motor power consumption.
I review some GE Motor literature, and it could be a several things like oil level, oil type, oil ring position, oil quality, sleeve bearing radial clearance, and says 41% of motor problemas are related to bearings. GE says that normal temp for noncontact bearing is around 95C for Custom 8000 series:
http://www.geindustrial.com.br/download/manuais/motores/espanhol/geep145e.pdf  Page 18.
(it is in spanish, i look in english in GE web site, but is not available)
Maintenance people could help you with some data like complete last motor diagnosis and tell you how old is this motor?, temperature bearing trend (so it is always near to 80C? trend is very important), if stand by motor has the same problem, if a thermogram is available, when did last non-contatc bearing repair, etc.  
I hope respectfully, it helps






  

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