Tagged With "NDE"

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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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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.
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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 ·
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

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

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 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

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: 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: High horizontal vibration in fan

Kishore kumar ·
Dear Vishal, If the fan is not responding to the Balance ,it might have other issues like structure looseness , resonance etc... with or without unbalance condition. We should check phase and TW data , Could you please share spectrum if possible.
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Re: High horizontal vibration in fan

Becar ·
- did you check bolts? - increased clearance in bearing/housing/shaft - cracked rotor or construction issues
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Re: High horizontal vibration in fan

Rohit02 ·
Dear Vishal, Kindly share spectrum or waveform data for better analysis. Regards Rohit
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High horizontal vibration in fan

vishal sharma ·
Dear experts After solving my preheater fan and raw mill system fan problem with your precious recommendation now I want share my new problem that’s I am facing now a days i have two bag filter fan both are 18kw motor. both have overhung impeller.During continues monitoring fan A has high horizontal vibration 12 mm/s at fan NDE side with 1x domination in FFT spectrum. So first I check alignment of fan and I found it’s okay so I start single plane balancing and after balancing vibration...
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Re: High horizontal vibration in fan

Ralph Stewart ·
Re: High horizontal vibration in fan
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Vibration analysis

Tsietsi ·
below are the data for the industrial motor coupled to a centrifugal pump motor speed 1487RPM bearing are white metal bearings both NDE and DE power is 970 kW please assist me with the analysis attached there is a funny noise from the motor when running
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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

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

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

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: High vibrations on Alternator NDE

Becar ·
I have looked at you photo from the previous case. Is the NDE bearing housing attached to a cover only? Or has it some hidden support inside the cover?
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High vibrations on Alternator NDE

Chetan Patil ·
Hello Team, Once again I am coming here with similar kind of machine and vibration problem. EMD engine with an Alternator (with single bearing at NDE) RPM : 900 RPM Alternator: 600V, 2525KVA, 1400kw, 60 HZ Engine vibrations are within range (around 8-9 mm/s) Alternator NDE is vibrating with High vertical (24 mm/s , purely 1X) & Axial (16 mm/s with 1X = 8.6, max peak 12 mm/s @7182 cpm and minor 2X,3X, 4X) vibrations. (due connectivity issue at offshore I counldn't upload the spectrum...
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Re: High vibrations on Alternator NDE

Becar ·
From the information given so far I am quite sure the issue is some crutial part resonating at the rotation frequency. Most likely the holding cover/cap. It could be some sort of original construction issue. Will wait for other experts to say their opinion.
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Re: High vibrations on Alternator NDE

Chetan Patil ·
NDE bearing is rested in hub or housing which is attched with end cover. & it is supported by four limb look likes bullock cart wheel.
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Re: High vibrations on Alternator NDE

Chetan Patil ·
Sorry walt. But this vibration problem persist with some steady phase readings than previous one.
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Re: High vibrations on Alternator NDE

Walt Strong ·
Why are you posting twice for the same problem? Walt
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Re: High vibrations on Alternator NDE

Ngo Dinh ·
Steady phase with changing amplitude, i do not think that it is dynamic unbalance but i agree with Becar that it could be due to resonance issue. Besides, could you take a look with load. Is it changing with?
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Re: High vibrations on Alternator NDE

Chetan Patil ·
Thanks for reply becar. I gone through previous shop-balancing reports of machine. Alternator's were balanced by 2-plane method at 350RPM, whereas we are operating machine at 900 RPM. I also observed today that vibrations were normal at ideal speed up to 450 RPm and then drastically increased as we increase in speed to a rated 900 RPM. once an alternator reaches to 900 RPM, the vibrations were fluctuating in cycle of like 9.5 ,11 , 13.4 , 15 , 17, 19.2 , 21 within a period of 8 to 9 sec but...
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Re: High vibrations on Alternator NDE

Chetan Patil ·
I was tried 1-plane balancing here. as we don't have direct access to weld balance weight at alternator NDE rotor (because it comes under vicinity of stator and welding nearby stator was not allowed by customer) so, 2-plane balancing is not possible to carry out on field site. With 1-plane balancing trial I experinced, there was reduction in vibration amplitude from 20 mm/s to 12 mm/ s but still its fluctuating in cycle. (12, 13,14 , 16,17) When we synchronized an alternator with load the...
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Re: High vibrations on Alternator NDE

Becar ·
As this is your second similar machine with similar symptoms I think it could be some sort of structural characteristics of those bearing supports. I would say the NDE bearing attachment lacks of stiffness. It could lead to resonance. Every small eccentricity or other issue could result in higher vibration levels than expected.
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Re: High vibrations on Alternator NDE

Walt Strong ·
The 4 axial values are in-phase. The 2 horizontal values and 2 vertical values are in-phase with each other after correcting for the sensor orientation (180-degrees). I still believe you need to conduct tests for natural frequency near 1xSS. These are the 4 typical tests: Variable speed with engine overspeed, as possible Operating Deflection Shape (ODS) with engine at normal speed Impact test during operation Impact test during shutdown Walt
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Electrical Motor NDE high vibration

Thimba ·
Dear all, I'm monitoring the vibration of a 1.2MW vertical submerged pump(RPM: 595/ 9.917 Hz ). The motor 1x radial vibration appears to be high in one direction (pump discharge side). Radial vibration at 90 deg seems relatively low. I have checked the alignment at the coupling and any structural looseness and all seems ok. The Motor acceleration spectrum shows harmonics of 734 Hz with a 2xline frequency side-bands. I'm assuming this is rotor bar or a winding slot pass frequency. I'm not...
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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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