# Tagged With "5X"

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#### 1.5X,2X, 3X ,4X multiples causes

y@sh ·
Hello Every one, Recently i am facinga issue in so many motor and pumps in my site. 1.5X harmonics 1.5, 3, 4.5, 6, ........1.5 is dominant 2x harmonics 2x,4x,6x,8x, even harmonics .......2x is dominant 3X harmonics 3x,7x,9x,11X odd harmonics. 3X harmonics 3x,6x,9x,12x harmonics 4x harmonics 4x, 8x, 12x,16x guys anyone please give some valuable suggestion for above mentioned problem.

#### Re: 1.5X,2X, 3X ,4X multiples causes

Dave Reynolds ·
Loose hold down/anchor bolts on motor/pump/base, loose bearing to shaft/housing, worn bearings, worn/loose coupling and/or its element, rotor stack loose on motor shaft, electrical noise, inner race fault, imbalance, misalignment to name a few Dave

#### Re: 1.5X,2X, 3X ,4X multiples causes

ivibr8 ·
I agree.....when you see harmonics (as you've described) = LOOSENESS It may or may not be the root cause however. post edit - as I re-read this, I'm concerned that you may not be talking about a specific machine but in general. So I would ask you clarify what you mean by "having issues with so many motor and pumps in my site". You dont go into any detail at all and It would seem odd to me that there is a generic problem with harmonics in so many (sic) machines. Harmonics (generally) are a...

#### Re: High Vibration at 1.5X in electrical motor

Walt Strong ·
What is belt ratio or driven machine speed? What is driven machine (blower?)? Walt
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#### High Vibration at 1.5X in electrical motor

Andre Alburqueque ·
Hello everyone, I measured the vibration in the vertical direction of the electrical motor (1800 rpm) shown in the picture below. And the spectrum showed a high peak at exactly 1.5X. Someone could tell me what problem it should be? Thank you

#### Re: High Vibration at 1.5X in electrical motor

Andre Alburqueque ·
The driven machine is a Homogenizer Rannie APV (3 pistons) with ABB motor. The driven speed is 600 rpm.

#### Re: High Vibration at 1.5X in electrical motor

fburgos ·
Please provide more info, number of lobes, sync gears, model looks like an aerzen? i think its harmonic of a 0.5x.

#### Re: High Vibration at 1.5X in electrical motor

fburgos ·
Walt, totally agree, investigation steps would include searching for structural resonance, on the other hand reviewing my math homogenizer running speed is 600/1800=1/3=0.333x piston discharge frequency is 600*3/2=900 rpm or 900/1800=0.5x therefore i think it could be normal operation for the Homogenizer to show this frequencies. the third harmonic of piston discharge frequency (900*3=2700) is 1.5x motor speed a very odd combination why i was thinking harmonics of 300rpm must be all around,...

#### Re: High Vibration at 1.5X in electrical motor

Andre Alburqueque ·
Dear Walt, FBurgos, We are gonna make routine monitoring, because I also think that it is a low level vibration. The parameters of instalation are good as recommended by manufacturer. what makes me surprise were both peaks higher than 1x. Any way, we are gonna look how does it change over time. Thanks both of you.

#### Re: High Vibration at 1.5X in electrical motor

fburgos ·
Is hard to understand the problem if we leave all to the imagination, but 3 pistons, and imagin two strokes, I think 300rpm (0.1667x) harmonics would be normal but 0.5x harmonics its loseness

#### Re: High Vibration at 1.5X in electrical motor

Walt Strong ·
I have not worked on a Homogenizer, but I did some online searching. There is a good possibility that the Homogenizer has an internal gearbox (like some blowers) that further reduces speed of piston crankshaft. According to this excerpt from a pulsation damper supplier, the pulsation frequency is at 3x crankshaft speed (not necessarily at input sheave speed). "the most frequently used homogenizer type with 3 pistons delivering 12000 liters per hour has been used as a reference in the below...

#### Re: High Vibration at 1.5X in electrical motor

Walt Strong ·
300 rpm for Homogenizer is 0.3333 x motor speed (300/1800) Vibration at 1.5 x motor shaft speed is a symptom of looseness from motor rotation speed. Possible locations for looseness include: shaft bearings, cabinet base at floor/foundation, motor base, homogenizer base, pipes connected to homogenizer and cabinet. Since homogenizer runs at or near 0.333 x motor speed, the vibration at 1.5 x motor speed would be nearly equal to 4.5 x homogenizer speed. Cannot rule out either mechanical...

#### Re: High Vibration at 1.5X in electrical motor

Inspect the all holding bolt any looseness and Belt tension .
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#### Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
Vibration was observed in a recently overhauled centrifugal pump in 5X at pump NDE and DE V.FFT is attached There is no chance of vane pass effect since the pump was overhauled recently and no damages where observed.

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
The pump was overhauled as a part of routine maintenance ,there was no indication of vibration prior to overhauling. LPT was carried out on impeller during overhauling and no damages where observed also when we calibrated the rotor for balancing we found that it was already under tolerance. This are the main reasons I ruled out vane pass. This horizontally mounted centrifugal pump acts as a overhung rotor,having a bellow in the suction side and connected to motor using a flexible...

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

Rotating Guy ·
WSS spectrum wasn't sufficient enough for analysing, if you could provide enveloping and TWF will help to know what is fault. try to run motor alone and gathered the data and check if this frequency arise. regards,

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

Dave Reynolds ·
WSS Many styles of centrifugal pumps, can you add more detail Most of the time, pumps have 2-3 bearings/shaft/impeller/coupling. So if you truly have a 5x peak synchronous to machine running speed and you have 5 vanes on the impeller, then it is vane pass. Bearings will be non-synchronous data I also see what appears to be harmonics of vane pass, did you change impeller size recently, is there a check valve or valve in general that is stuck or not working properly? Just by "overhauling" a...

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

Dave Reynolds ·
The pump was overhauled as a part of routine maintenance ,there was no indication of vibration prior to overhauling. ok, then it should not be vibrating now right....then something changed...is the pump running backwards, just because the valve handle moved does not mean the internals moved, did something fall/collapse and block pump inlet, are flows and pressure normal, did you change impeller size I assume "calibrated" means balanced the impeller This are the main reasons I ruled out vane...

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
Thank you guys for your reply.The pump is at site and we are service contractors.So is it safe to conclude that occurrence of vibration is not due to any wrong procedure in overhauling (ie. balancing,Replaced bearings and gasket,mech seal test)? Please note we had changed the bearings too.

#### Re: High Vibration at 1.5X in electrical motor

chary tatta ·
Greetings Good case study. Team members covered well in all aspects. Please take vibrations on Homogenizer and motor NDE and DE side. When )0.5x, 1,5x and even 2.5x indicating, though the values are on lower end, the looseness is creating in the driving system. Please look into pulley tightness and when was last tightening performed. Rest all others covered by Mr. Walt Strong effectively. Request you to share once the problem identified about the looseness or else any other for this forum to...

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

wss ·
Dear Mr.Chary, Its 4.8mm/s now.We are planing to take it down once it peaks over 5.5mm/s and give a check of the valves and other flow condition.The check valve on discharge line is normally on full open or full closed condition.

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

chary tatta ·
Greetings team Very Interesting case. only 5X dominating. No problems noticed in spectrum. All unique components are in good condition. 3.84 mm/s at 5X is still in normal condition. However, the cause of 5X dominant can appear due to flow conditions like impeller stall. Check the pump suction and delivery valves, system flow conditions (full flow or throttled flow) Load on motor etc., Pleased to see such isolated case. regards Chary

#### Re: Vibration at 5X NDE AND DE V for Centrifugal Pump

chary tatta ·
GREETINGS WELL NOTED. THANKS FOR YOUR FEEDBACK. PLEASE FOLLOW THIS METHOD AND TRY HOW YOUR VIBRATIONS ARE INDICATING. 1. CLOSE DISCHARGE VALVE AND START THE PUMP AFTER FEW SECONDS AT FULL SPEED AT MAXIMUM PRESSURE MEASURE THE VIBRATION SLOWLY OPEN DISCHARGE VALVE AND MEASURE THE VIBRATION. IF FLOW INCREASING TIME VIBRATION RISING IT IS RELATED TO FLOW SURGES CAUSING THE VIBRATION. IF STEADY AT EVERY DISCHARGE VALVE POSITION THEN THE VIBRATION IS NOT FLOW RELATED. ALSO TAKE RUN UP AND COAST...

#### Re: Orbit

William_C._Foiles ·
A rub is a good possibility. I would plot (track) 1X amp and phase over time, also. Depends upon the steam turbine if this is a worry or not. Is there anything running at 1/2 X? Cross-compound turbines will show this on the HP - and it could be normal. Some TGs have excitors with a 1 to 2 speed ratio; those two can have this and be normal. I did see a cross-compound turbine with a cracked pedestal show this on the HP, but this was not your usual case. In that case the 1/2 X was probably...
Topic

#### Orbit

white walker ·
Can anyone help me about the below plot orbit.i am expecting orbit looks like some rub.vib is 40mic.it is steam turbine and 10000rpm.please share ur views.spectreum has 1x and 0.5x.there is no reverse procession at that time in waterfall and orbit.if it is a run what kind of rub it is either it occured in bearing or some other?? Thanks in advance.

#### Re: Orbit

Shurafa ·
The difficulty of such cases (possible rub) is that identifying the exact location of the rubbing is difficult while the machine is running. Is it in the bearing, seals of the bearings, shaft end seals, inter-stage seals etc? Also, you would be lucky if you can fix the problem without shutting down the turbine. Please keep us posted on the findings. Regards- Ali M. Al-Shurafa

#### Re: Orbit

John from PA ·
You might also do a long term polar plot and see if you get a characteristic spiral pattern. See http://downloads.hindawi.com/j...ijrm/1995/102137.pdf , specifically Figure 10 on page 10.

#### Re: Orbit

Rotating Guy ·
What brings the high 1x? unbalance? misalignment? also why is there 0.5x? Rub? what knid of rub? partial rub? dynamic fluid force? thermal unbalance? there is a lot of speculation will foreseen in the given limited data. Anyhow. i will stick to fluid instabilities. As far my experience concern and with my case studies and analysis., fluid instabilities will relate to 0.5x to 0.8x. Cheer up! RG

#### Re: Orbit

Vib282 ·
Fluid induced instability doesn't occur with high 1x. Also oil whirl or whip will not lock at exact sub integer like .5x For the limited amount of data in this case we can suspect rub or looseness or brg over clearance. The provided data is not enough judge. Also like what ali al shurfa said if it is rub then where it is happening. Another question will be what is causing it bcz rub is secondary defect.

#### Re: Orbit

Rotating Guy ·
It is looks like your buying a car and you doesn't know the details of what you are buying. Anyhow, this is my perception in your limited data. Based on your orbit plot, its like a fluid problem ( likely fluid instabilities). But, if this orbit is from the steam Turbine side DE or NDE it is unlike an fluid issue due to tilting pad type bearing. But if it is in Generator its likely a cause. (i am not rooting that its most likely the cause with your given limited data). Please check the...

#### Re: Orbit

John from PA ·
Everything you wanted to know about rubs can be found in a presentation by John Yu, PhD of GE/BN. See Rub, Morton Effect, Parametric Excitation, and Shaft Crack in Rotating Machinery - Real Cases . John's a former co-worker of mine from days prior to my retirement. Another good article on the Morton Effect, a phenomenon that has characteristics to a rub can be found at Morton Effect .

#### Re: Orbit

white walker ·
here are the few plots for further discussion. hint n 25-07-19 morning 6:52AM there was a sudden drop in RPM from 10500 to 10000RPM with in a min span RPM reached to 10500RPM during same time orbit seperated.upto 3days occassionally observed seperated orbit same time 0.5X peak observed thanks

#### Re: Orbit

maximize ·
Hi All, Can anyone help me what's wrong with our Generator by the orbit plot & spectrum details attached? Generator is driven by Steam Turbine running at 3600 RPM. This is a newly installed equipment and on commissioning stage. My initial observation, there is a misalignment on the shaft of the Generator. Please see the attached data. Thank you very much.

#### Re: Orbit

maximize ·
Thank you Shurafa. I think you're right.

#### Re: Orbit

Shurafa ·
Maximize, Your case might have a better attention if it is posted as a new thread. The details of the two cases here could be mixed up. Regards- Ali M. Al-Shurafa

#### Re: Orbit

Vib282 ·
do you mean that when speed reduced the 0.5x vanished ??

#### Re: Orbit

Rotating Guy ·
Hi, can you share more detail please, also if you share the filtered orbit also please share the unfiltered, i cannot seen your purpose on sharing 1x filtered orbit alone. Why there is a sudden drop of RPM? have you gone in any testing? or your running steady state operation then the RPM sudden change? any problem in line frequency? How many bearing do you have? 4 bearing? if 4, can you share to use the data of Bearing 2,3,4 = Turbine DE, Gen DE an NDE. Also whats the point in sharing polar...