Tagged With "NDE"

Topic

Balancing of fan

vishal sharma ·
Dear all i am dealing with a RAW mill simple supported system fan 2500 kw motor with 990 r.p.m . The spectrum in DE bearing showing 1X with an amplitude 3.8mm/s overall vibration is 4mm/s in DE bearing in horizontal direction. vertical: 1.2 mm/s Axial: 1.4 mm/s but at NON DE side bearing we are having 5mm/s overall vibration in horizontal direction. the spectrum in NDE bearing showing 1X with an amplitude 3.9mm/s . vertical vibration is :1.8mm/s Axial: 2.4 mm/s by doing time wave form...
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Re: Balancing of fan

Ralph Stewart ·
questions: (1) Is it a centerhung or overhung fan? (2) Can you show us the impacting waveform? (3) Have you tried and failed with a single plane balance or are you planning on a single plane first or multi-plane balance first? (4)The 110 degree phase on the DE, what is the 110 referenced to, a refelection "tape" position on the shaft or reference to the NDE bearing? Thanks, Ralph
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Re: Balancing of fan

vipul@cmc ·
Waht is Displacment on DE & NDE brgs. @1x vibration rpm ? What is Phase diffrence on DE brg.between H & V Directions.? Have you properly cleaned the impller of Fan ?
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Re: Balancing of fan

Walt Strong ·
"So my question is can we perform Dynamic Balancing ??" Yes, if rotor is accessible to add/remove balance weights. "if yes will we get satisfactory results?" Yes, if rotor is clean and no cracks or looseness and bearings are tight and in good condition. You should also inspect bearing pedestals/housing for loose bolts and foundation (steel, concrete, grout) for significant cracks. Walt
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Re: Balancing of fan

vishal sharma ·
1 it is centrehung fan 2. i am planning for single plane balancing but i have some doubt in fan NDE bearing. 3 phase reference 110 on DE side is w.r.t to reflection tape position on shaft.
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Re: Balancing of fan

vishal sharma ·
phase differnce is 110 degree at fan DE side from H & V FAN IS PROPERLY CLEANED NO DUST IS THERE
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Re: Balancing of fan

vipul@cmc ·
You can do single plane balancing
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Re: Balancing of fan

vishal sharma ·
BUT i see some impacts in time wave form of NDE bearing. i am worry about that and on NDE bearing phase is not stable from H &V .
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Re: Balancing of fan

Ralph Stewart ·
Your waveform looks like there is a modulation (angelfish) pattern associated with 1x. Gs are fairly low, but concern-able. Also might have several (4 or 5) harmonics of 1x in the spectrum. There may be a problem with the inner race. Can you post a few spectrums of both bearings, horizontal and vertical? What is the phase relationship between the Horizontal DE and the Horizontal NDE (for balance reasons)? Is the fan actually centered between the bearings or is the rotor offset more toward...
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Re: Balancing of fan

Walt Strong ·
A center hung rotor with wheel between bearing can be symmetrical with double air inlets or asymmetrical with single air inlet. Single inlet fans can be balanced by single plane method with care. While it would be better to fix the bearing first, it may take less time to trim balance and extend the bearing life to a more convenient outage. Walt
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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...
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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...
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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,
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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...
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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.
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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
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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.
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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...
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Re: Stronger vertical than horizontal NDE side and the opposite DE side.

William_C._Foiles ·
One of the first things to suspect is resonance.
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Re: Stronger vertical than horizontal NDE side and the opposite DE side.

Kamilu ·
After some digging, I've found in the technical data for this fan/blower some interesting info: -for 9-stage rotor first critical speed is 4706 RPM. in our case it is 5-stage rotor and operating speed 4200 RPM, so it is only about 10% under critical speed of 9-stage rotor... Do You think it is could be too close to critical speed? I've already asked the manufacturer about critical speeds of 5-stage rotor and i hope he will answer. Thanks
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Re: Stronger vertical than horizontal NDE side and the opposite DE side.

William_C._Foiles ·
You should scrutinize the rotordynamics and verify by test. Rotors often have two modes closely spaced. Giving only one critical speed may not reflect the machines dynamics - check further. Are the critical speeds by analysis or test - test at site to verify? 10% is close, but depending upon what the basis for stating the critical speed, the actual margin may be more or LESS than stated. Try to get some data.
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Re: Stronger vertical than horizontal NDE side and the opposite DE side.

Kamilu ·
Thanks for your answers William. Fan manufacturer answered - according to their data, this rotor (5 stage) first critical speed is 8079 RPM, while maximum reccomended speed for ths fan is 4400 RPM. We run it at 4200 RPM. This data is taken from manufacturer - we havent made any tests yet. But there still can be structural resonance, am I correct? Before trying to balance rotor, i would like to perform bump test while running (can't stop machines for now). But we have very basic device...
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Re: Stronger vertical than horizontal NDE side and the opposite DE side.

William_C._Foiles ·
Did you get a rotordynamics report for this machine? Do the coastdown test - take data to verify. What is the machine configuration? Bearing type? 5 sages, length, mass, bearings, shaft diameter - all go into determining the natural frequencies. Support stiffness is important, too. How is the machine mounted? Regardless of the specifics, if you get the data you can determine whether there is a natural frequency or not.
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Re: Stronger vertical than horizontal NDE side and the opposite DE side.

Dave Reynolds ·
Take a set of normal readings or have past history to reference too, yes your setup should work fine for bump test, one bump per avg will work, you should be looking for a small mound/haystack/Hershey kiss to show up at the base of a peak or show up as a separate peak that which is not normally present Dave
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Re: Vertical Motor NDE high vibrations

Shurafa ·
Neat report. I would recommend to do impact tests to determine the natural frequencies. This information helps to see how much your efforts result in shifting the natural frequency. Also, to verify that the motor is not influenced by beating. I suggest to take a long waveform or a trend over enough time. If there are nearby machinery, try to stop them to confirm that the vibration is/is not transmitted. Regards- Ali M. Al-Shurafa
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Re: Vertical Motor NDE high vibrations

Kishore kumar ·
Dear Sir , Do blue match at Motor mounting flanges contact area . Add required shim at non contact / poor contact area ,tight all nut bolts .
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Re: Vertical Motor NDE high vibrations

Nagaraja ·
Blue matching done. Contact area is close to 80-85%. The only way is to provide additional rigidity or stiffness to shift the natural frequency above 1000 rpm. Which can be done through FEA route. If anyone carried out such analysis on a similar system Pls share. We are working on FEA to resolve this issue. I don't think there is any other method to sort out this problem. Can't give any isolation (material) between motor flange and stool as it will disturb the shaft length with coupling. ...
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Re: Vertical Motor NDE high vibrations

John from PA ·
New machine or an old machine with a new problem?
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Re: Vertical Motor NDE high vibrations

Nagaraja ·
This is a new machine. Motor is fine.. It's a case of mounting resonance issue so we are planning to take FEA route for a permanent solution Nagaraja
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Re: Vertical Motor NDE high vibrations

Vastocean ·
I agree with Mr. Ali M. Al-Shurafa’s recommendation, do a bump test of the machine can help support findings and suspected causes. A minimum separation margin of 10 percent shall exist between the natural frequency(ies). VastOcean
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Re: Balancing of fan

vishal sharma ·
the problem has solved. we did two plane balancing now the vibration reduced from 7mm/s to 2 mm/s. fan DE: 1.8mm/s fan NDE: 2.1 mm/s thanks for your suggestions.
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Re: Balancing of fan

Walt Strong ·
Vishal, Thank you for your feedback. Walt
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Re: Vibration analysis

Walt Strong ·
What does funny noise sound like? Did you measure sound to determine the dominant frequency? Do both the motor and pump have journal bearings (white metal), or perhaps the motor has ball/roller bearings? Walt
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Re: Vibration analysis

Rotating Guy ·
TSIETSI Hi, below comment is for clarification; 1. Does the funny noise occur during start-up? 2. Does your attached spectrum is taken during your so called funny noise? 3. Does the funny noise didn't disappear during operation? 4. Whats is the recorded enveloping acceleration for motor drive side and non-drive side? also the timewaveform? any significance changes in trend history? For me, when i encountered abnormal noise like a sound pressure noise at motor, i do phase analysis for motor...
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Re: Vibration analysis

Kishore kumar ·
Dear Tsietsi , Is that motor has a fan along with internal air circulation type ? , if so it might be due to air circulation or air turbulence issue with in the Fan casing . Did taken Fan reading while decoupled ? , is there any sound like this ? Please check these parameters and share your motor image . <form action="https://www.maintenance.org/record-share!execute" class="" data-ajax-form="" id="shareContentActionForm" method="post" name="shareContentActionForm"> </form>
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Re: Vibration analysis

Rohit02 ·
With reference to the attached spectrums 1. In one of the image RPM is showing as 985. What is this spectrum is there any speed reduction in machine train? 2. What type of a pump is it? no of vanes, no of diffuser, between bearings or cantilever? 3. As mentioned about the funny noise from motor, as I could read all the spectrums corresponds to pump side. Kindly clarify whether these spectrums are of pump or motor. If these are of pumps kindly attach some spectrum of motor to identify the...
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Re: Vibration analysis

Tsietsi ·
Hi Kishore the motor is water cooled. kindly receive the attached picture and the time wave form and velocity spectrum from both bearings. NDE and DE white metal bearings.
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Re: Vibration analysis

Tsietsi ·
it looked like a Rotating looseness, i stand to be corrected but after bearing inspection, DE bearing looked like it got damaged by misalignment and NDE bearing like overload. please receive the attached pictures
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Re: Vibration analysis

Walt Strong ·
What are the blue boxes on each bearing housing? Walt
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Re: Vibration analysis

vigneshpillai ·
send the details of velocity value both DE,NDE Acceleration value both DE,NDE
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Re: Electrical Motor NDE high vibration

Becar ·
About acceleration: It is very likely you have to deal with RBPS. To confirm RBPF you should have all the data to calculate it. Do you have any measurement history? It is not necessary the amplitudes are too high for this machine. Some high resolution spectra should help you to see the exact matching with the multiple of rotation frequency. It could also be the change in load between your two measurements. Velocity: The situation described shows high possibility of resonance present. You...
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Re: Electrical Motor NDE high vibration

Akhil Rathore ·
This to me looks more of a resonance issue rater RBPF. please give more details How old is this equipment setup? I mean the motor & pump. what is the trend of vibrations? are they high since commissioning or its a recent increase. If you are concerned about RBPF & do not have the number of rotor bars, you can still go for motor current signature analysis. Thanks Akhil
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Re: Electrical Motor NDE high vibration

Thimba ·
Thank you both for your comments. Here's a bit of background about the setup. Pump was commissioned back in 2008. The pump was overhauled back in 2013 due to pump failure due to bearing defect and again in 09/2018 (suspected from vibration analysis which turned out to be the case in 2018). This 1x vibration increase only occurred since the September bearing change. The condition monitoring program has only been going since August 2018 so not much data to go with. We do however have a twin...
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Re: Electrical Motor NDE high vibration

Becar ·
The reason to suspect resonance is high vibration level in just one direction and changing amplitude over time. This is from my experience with similar vertical pumps. I suspect the construction stiffness is lower in one direction and could be strengthened with additional welding supports at the bottom - at the base plate. However prior to this I would do field balancing to minimize the 1x and see the difference.
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Re: Electrical Motor NDE high vibration

Ralph Stewart ·
Re: Electrical Motor NDE high vibration
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Re: Electrical Motor NDE high vibration

Akhil Rathore ·
Hi Thimba Vertical orientation of machine - Any issues with pump also are reflected at Motor non drive end or cooling fan side or outboard side with possibly 1x running speed. but you recently changed pump bearings Pump is submerged - If pump vibration data can be taken it would be good to conclude, however l doubt the possibility for submerged case. The condition monitoring program has only been going since August 2018 - quite possible for the failures before the same indications were given...
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Re: Electrical Motor NDE high vibration

GKaiser ·
This sounds familiar to other Vertical Pump issues. I have experienced elevated 1x pump/motor speed vibration in the direction of the discharge of vertical pumps. Often the discharge flow from the pump will influence the Upper Motor bearing vibes due to the pipe not supported properly. The pipe flexing up/down pulls on the motor causing the increased 1x. I now will take phase/amplitude readings along the top of the pipe to at lease the 2nd or 3rd support away from the motor. This can be...
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Re: Electrical Motor NDE high vibration

Thimba ·
Re: Electrical Motor NDE high vibration
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Re: Electrical Motor NDE high vibration

Thimba ·
Many thanks for your contribution so far. Cheers! Thimba
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Re: Electrical Motor NDE high vibration

Thimba ·
I will hopefully by next week when I'm fit to clime the ladder! But phase readings are not possible as I only have one input and one accelerometer. Kind Regards =) Thimba
 
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