Skip to main content

MaintenanceForums

Sorted by last update

Reliability Engineering for MaintenancePosts about Root Cause Analysis
Fan Vibration
Registered Member Most probably the reason resonant, balancing is not solve problem and we try very much [ more ]
Registered Member 6/. Measure vibration in 3 directions at all 4 Bearings. Shut fan off, lock out, Mark coupling with paint marker, unbolt coupling and rotate 90 degrees. (We usually start with keyways 180 degree apart, or locate original match marks if they exist) Get the vibration as low as you can using the coupling and than balance the fan wheel as low as you can time permitting. 7/ Record final set of readings and begin New Trend. Let us know the outcome Thank You [ more ]
Registered Member 4/ Based on your Spectrums, I would replace the Fan Bearings again. Continue to "Trend" the Fan Bearings until you reach an optimum time to schedule replacement. Be certain to pay particular attention to the Outside diameter of the bearing and the inside diameter of the Bearing Housing. If the Bearing is loose in the housing, the movement can produce similar Spectrums. (3X appears more often 2X, but I've seen similar Spectrums on Monoblocks (fan bearing housing) 5/ Check fan bearing Housing... [ more ]
See all 18 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Has anyone come across AC current as source for piping vibration?
Registered Member Hi Dave Thx for reply. You are not alone in not having seen it before. Internet is virtually empty on the subject. It appears to be intermittent bursts of current ~1 kHz. Finding the culrpit may take some work. Those in the know say it, e.g. might be a transformer that shuts on/off as the phases always are out of symmetry when turning on. In the same gist, it may be something major that shuts off where I expect the reverse. I imagine a fix would be simple - just add a grounding cable between... [ more ]
Registered Member I myself have not seen what you describe. My two cents, if something is breaking it is moving, if it is moving it is happening at a given frequency or it is a sudden burst of energy. Once you identify the frequency on the pipe support then you can work backwards to find what machine can cause the vibration? Recommend you place a large coil spring in between the anchor source and pipe support, the spring will then absorb the energy Dave [ more ]
See all 2 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Cyclic vibration pattern analysis
Registered Member I would suggest checking more operating parameters in order to have a better chance to understand the possible problem. Sometimes, compressor upstream or downstream equipment are unstable and affect the compressor. Sometimes, compressor auxiliaries such as lube oil temperature control system is not tuned perfectly and can result in compressor instability. Spectrum comparison could help a little if you can post data for high and low times. I tend to agree with the comment given about the low... [ more ]
Registered Member Actually, In my experience, i have not met the morton effect yet. So, my thinking is just my sense. The speed could be not exactly in the case but i think that your case is not morton effect. Your phase change is not cyclic and i sure that your compressor is between bearing type which motorn effect is rarely occurred. My thinking could be total wrong! NVD [ more ]
Registered Member Dear NGO DINH Why do you think that my case is not morton effect due to speed of 3000rpm? Could you explain more detail with speed? [ more ]
See all 8 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
High Vibration in tilting pad bearing in integrally geared single stage centrifugal compressor
Registered Member I think that: Q1. What is the clear effect of water to the comp performance?and how can be observed thru vibration monitoring? The water in air/gas will effect to comp performance (changing density of gas/air) and it depends on how many water in. In my experience, one of effect you can see when you inspect impeller is erosion/corrosion on surface of impeller. I have no experience with much water in gas so I do not know how it is. However, I think that if the water in gas too much, it will... [ more ]
See 1 reply...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Root cause for increase in vibration
Registered Member Have you check the soft foot well? [ more ]
Registered Member Vidya, if you have the technology, use your vibration analyzer to perform an ODS ( operational deflection shape) test on the motor and gearbox to look for any possible flexing. If you do not have this capability, find a contractor that does, it may be instructive. This sounds very similar to a fan problem I troubleshot at a glass plant where the fan/motor kept coming out of alignment and showing high vibration at 1X. The key indicator was when the foundation finally fatigued to the point of... [ more ]
Registered Member Hi Becar, Alignment done between motor to gearbox . [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
SKF Spherical Roller Bearing Installation / Adapter Sleeve Thread Damage
Registered Member Well, That is about the next, to the best, excuse anyone could have. [ more ]
Registered Member I left that company 3 months ago, thats why i haven't replied. Checked with my friends today and they haven't faced with that problem since i've left. So looks like i am the problem... I ordered SKF TMFN wrenches before i left and they are using those tools. These are impact wrenches to tighten the nut. I think proper tools fixed the problem. By the way, we used to put lock washer with the bearing. Those days the problem was damaging lock washer tips while tightening the nut. Thats why we... [ more ]
Registered Member Serdar , Been 4 months since your post. Just wondering if you have found a possible solution for the problem. Thanks and Hae a Great Day, Ralph [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing seizure and cage crack with out any high vibration
Registered Member Quote..."we inspect this bearing every fourth nightly but the vibration is in with in limits 2.1mm/sec and 0.5g before failure ." I see this was posted 6 months ago but I was wondering, since you said "we inspect this bearing every fourth nightly", can you post a few spectrums from this "inspect" ? My first impression is lack of lubrication, but seems like the data should have shown something, even lack of lubrication, during this inspection period. I am not sure what is meant by " every... [ more ]
Registered Member What's your said vibraiton point and direciton? How about axial vibraiton? it seems your bearing once bear high temperature from your photos [ more ]
Registered Member Actually here floating bearing is NDE , fixed bearing fan DE. if it is axial load damage it has to damage on inboard race way but inner ring two race ways are damaged [ more ]
See all 5 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
axial vibration of bearing
Registered Member Hi Trinh & Tony. As per my experience in cement industry for the overhung centrifugal fan, high 1X axial vibration compare to hor/ver is likely relate to shaft bend influence or bearing cocked/skewed. Is there any Enveloping/PeakVue value did you measured? 9mm/s at axial direction for me is high since axial not always contribute a vibration problem. Try measure shaft roundness w dial gauge. If ok, the answer is change the bearing to get a peace of mind. Because the peak frequency is... [ more ]
Registered Member Rotate the bearing outer race 180 degrees with respect to the bearing housing [ more ]
Registered Member A 187 hz impact will be spaced (1/187) = 0.005 seconds. It is hard to see that in your 2 second long time waveform. Can you show a FFT and TWF for a 2,000 hz or 4000 hz range? Based simply on amplitude levels, it would appear that the outer race defect (the initial evidence suggests its there) would be in the NDE bearing location. [ more ]
See all 7 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Cracks in impeller of three stage integrally geared centrifugal Air compressor
Registered Member I highly recommend the use of HEPA Filtration system, to avoid impeller erosion and incustration. Freudenberg EMaxx E10 or equivalent could be a good option [ more ]
Registered Member Dear Mr. Kanzariya, We too clean the impellers on a regular basis because we observe coke dust deposition on the impellers and it causes some unbalance in the rotors and cleaning does improve the vibration. We observed some erosion (not corrosion) on the impeller vanes. This could be due to moisture or coke dust on these high speed machines. And in one case pitting at the impeller backside where it sits on the tie rod. Don't just eliminate FOD. I have seen many cases where the foreign object... [ more ]
Registered Member Dear Yasaswy Thanks for sharing information. Bent...I think the bent one vane due to previous broken piece got chocked between diffuser and impeller that could damage the consecutive vanes....If it could be FOD that there might be any hitting marks in impeller eye but there is nothing in eye...Another way my point to share is that when there is long time deposits and fouling on impeller vanes that creats pitting on impellers ...same has been experienced in same make other compressor of same... [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Fluting
Registered Member Depends on if bearing frequency is the source of the g's or is it electrical noise from the vfd, how far are you from the bearing when you collect data, does demod/peakvue/enveloping data also show high g values Dave [ more ]
See 1 reply...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Submersible pumps burn out every week
Registered Member Thanks Dave, very helpfull. I will now gather data based on your suggestions, then analyze afterwards. [ more ]
Registered Member As others stated, need more details. Burn out, you mean the motor windings fail? Is there any temperature alarms for winding, moisture alarm for seal? Who is the OEM, the model, all will help in the diagnosis of your problem. IF the system has ran fine for years and you are now having issues. KISS principle, keep it simple stupid is a good practice, pardon the analogy, have you checked the discharge check valve for proper operation? Just because you see movement on the outside of the check... [ more ]
Registered Member Yes, it has enough power. It is the original design. [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
O ring failure in Pilot Operated Safety Valves
Registered Member https://www.slideshare.net/Tom...resentation-2015-new slide number 38, very good information, it would appear from your images that the oring melted or creeped due to excessive temperature Dave http://www.marcorubber.com/o-ring-troubleshooting.htm http://dupontelastomers.com/Pr...tails.asp?show=div04 http://www.dupont.com/products...tant-elastomers.html http://www.kalrez.nl/Products/...gGuide/extrusion.asp http://www.kalrez.nl/Products/...ngGuide/cracking.asp ... [ more ]
See 1 reply...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Power Limitation and High Exhaust Temperature of Single stage Impulse (Curtis) Steam Turbine
Registered Member Sounds like the steam is slipping by the turbine blades and going directly to exhaust. As the turbine heats up, internal clearances will expand, I would focus my attention on how the steam can short circuit from the nozzle to the exhaust. If this were happening I would expect a loss of HP/KW, loss of speed, increased exhaust temp. If the turbine is not meeting performance expectations, then there is something wrong. The distance from nozzle to the turbine blades, the condition of the... [ more ]
See 1 reply...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Cement mill VRM MOTOR 5500KW DE bearing inner ring crack with out any vibrtaion severity.
Registered Member As suspected....the axial face of the bearing also shows it was "moving" on the shaft. If this just started to happen with this motor, fixing the loose fit on the motor shaft should fix your problem. Do not overlook the bearing housing fit also...... Dave [ more ]
Registered Member Since there is less contact between the bearing and the shaft, vibration values are to be low only. But the increase in the temperature is a very clear warning. That is the reason newly installed bearing temperature monitoring is mandatory. Luckily there is no damage to the shaft. [ more ]
Registered Member Re: Cement mill VRM MOTOR 5500KW DE bearing inner ring crack with out any vibrtaion severity. [ more ]
See all 11 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Problems in Gear Couplings, and their Remedies
Registered Member Well again, if you have some specific problems, post some pictures. I would suggest you visit http://www.rexnord.com/Content...ll-Types-Failure-Ana or http://www.tribology.co.uk/wp-...o-Gear-Couplings.pdf and download the content. One of the likely key issues with a gear type coupling at 13000 RPM will be sludge collecting in the teeth which can in time partially or totally lock up the coupling; see the attached diagram showing lubricant path through the teeth. This causes forces to be... [ more ]
Registered Member RPM: ~13k; Oil Lubrication [ more ]
Registered Member Share some photos of the failed coupling to start with. [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Generator Shaft wear where the bearing sits.
Registered Member Thank you very much for the help gentlemen (Mark and Dinh) i will check my grounding [ more ]
Registered Member Please check your ground system especially shaft ground and casing ground. In normally, for motor, we usually see insulation bearing at NDE side. But your case, it is not. I think Mark have the same case. YOu should learn from him for solution. [ more ]
Registered Member Hi mark thank you, the wear you had on the shaft of your motor is very alike as the one I have in my generator, so I guess you are correct this electrical erosion is caused by shaft currents, no issues in the motor driven by the generator, but yes the generator is on VFD. [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Screw compressor, rotor rubbing failure
Registered Member hi dear all; i need compressor clearances for aerzen vm 45.please help me thanks [ more ]
Registered Member OK, now there is much more info available. In most similar cases the cause is inappropriate lubrication (wrong oil selection, old oil, metal pieces in oil, pump damage, unclean filter, congested oil pipes). Is the lubrication system external? The other possibility is that journal bearing ring is too tight regarding the shaft. I suspect that in the beginning there was a lubrication issue. It caused the surface's (shaft and ring) thermical and mechanical damage. At that time the overhaul guy... [ more ]
Registered Member Yes, male rotor shaft of drive side was worn out severely. And this shaft color also was changed by thermal effect and was bend. But I'm not sure which one is first. Because if journal bearing was not good, shaft and packing could be rubbed each other. and if rotor rubbing was occurred, it effect to bearing and shaft packing. Oh, I'm sorry there is one i missed to explain at first. Before this trouble, i mean after overhaul, this machine was start up and stop 8 times for 3 months. It makes... [ more ]
See all 8 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Vacuum Pump grid coupling failure
Registered Member I wouldn't make any assumptions about alignment not being a problem without having checked it first. Overload is also a possible factor in a machine train like this where all shafts are the same size and in general designed for driving one machine. The middle machine coupling has to carry it's own load and the load of the machine after it. The first coupling (at the motor) carries the greatest load, I'd inspect it as well. [ more ]
Registered Member Alvin, 2 cents, the coupling hub teeth appear to be severely worn, the wear allows the grid to put pressure at the corners of the teeth instead of even pressure distribution across the tooth face. The teeth to the left of the three that are missing appear to have a very wide gap between the teeth? The teeth that are missing, the break appears to be old, suspect they have been cracked for awhile Do you have pics of the grid? It too holds valuable visual evidence Dave [ more ]
See all 2 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Abnormal Behavior of Centrifugal Compressor
Registered Member ❤️
Registered Member Faisal, from a physical properties standpoint the only way to get lower temp and increased pressure is for an inter-stage leak to be occurring. Otherwise, ideal gas laws apply and the result of lower temp would be lower pressure. You are seeing a volume of cooled gas entering the discharge path which gives you the indications you are seeing. Short of a verified instrument error, you must believe your indications. For future (post repair) troubleshooting help, is there any way you could... [ more ]
Registered Member Dear SAB; No vibrations increase at any bearing. Vibrations trend is stable before and after the issue. Compressor impellers are In-line and not back to back. i have attached Cross sectional dwg for your further review and suggestions. Dear MICHAEL; Compressor is Barrel type which have an internal horizontally split casing and outer single casing like barrel of Pistol. So thermography will not help as all happenings are inside internal casing. Unfortunately there is no similar machine from... [ more ]
See all 4 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Gearbox Bearing Failure
Registered Member While the design certainly isn't optimum, I hope you have trained your mechanics to be aware of potential excess interference issues in bearing seats resulting in high stress concentrations. The design issues could have been compensated for in the installation process, ensuring that the bearing seat/pin was as close to flush as possible, minimizing the stress point. Craftsmanship is important in maintenance and reliability, and training is key to good craftsmanship. Turning RCA into lessons... [ more ]
Registered Member Update: Root cause of failure was found to be a combination of poor bearing seating and hoop stress causing the inner ring to crack. This poor design had a pin hole where the bearing goes on the shaft which created a localized high load/stress spot if the pin wasn't flush with the shaft. Any high/low pin position would induce stress point. Some high spots around the hole were also noticed which created "hoop stress" on the ring causing the ring to crack after cyclic loads. The true root... [ more ]
Registered Member Gearbox was in service for 6yrs, and is believed to be rebuild before by plant maintenance. Gearbox is wall mounted to the rotary valve housing itself and motor is flange mounted to the gearbox. Intermediate and output shaft have tapered bearing, the input shaft had two ball bearing and the inner bearing is the one failed. The bearing company is FBJ, made in Taiwan. [ more ]
See all 4 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Motor Current of Dilution Air Blower is very high
Registered Member I would definitely do a holistic look at the entire system. I would suggest one of the points to check would be an infrared scan of the power wiring to the motor including contactor, and the connections at the terminal box. A high-resistance connection will give you high current with a constant horsepower load on the line and will cause excess heating as well. Best Regards, Michael Meehan, CMRP, CRL [ more ]
Registered Member Is the motor current the same (high) on all 3 phases? Is the motor on an across the line starter? Has any part of the system changed compared to when it was working properly? Are there any louvers on the ductwork system that have been neglected or changed? Louver adjustments are commonly an overlooked cause of problems. People tend to take the louver system for granted. The louvers controlling air flow in a fan and ductwork system is analogous to a throttle plate and choke plate in a... [ more ]
Registered Member How about the fan performance? Blockage on the suction side will starve the fan of air and reduce motor amps, air flow and static pressure Fixing the belts would also cause the fan to increase in speed, this in turn will cause amps to increase, more air flow and more static pressure http://www.solutionsforair.com...t/pdfs/fancurves.pdf The fan will have an operating curve, changing wheel size diameter or width, fan wheel style, fan rpm, ductwork length/diameter or air temperature, humidity,... [ more ]
See all 3 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
7.5 MW Turbine Rotor Seizure
Registered Member Reading the events as presented, I did a little exercise in RCA and noted some things that should probably be corrected even exclusive of identifying the root cause of failure and correcting it. 1. You stated that operations personnel did NOT use steam coil heaters to maintain lube oil temperatures during shutdown, so the machine was started with cold oil. I would insist that the steam coil heaters be used as designed and never allow the machine to be started with cold oil. 2. You stated... [ more ]
Registered Member I have an SME willing to advise on this and we need some more info to make a valid determination. Was varnish testing done? Are there UOA lab reports and do they show trends? Which lubricant is in question and how long has it been in service with what rate of replenishing? [ more ]
Registered Member ❤️
See all 4 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
WHPU LP Pump failures
Registered Member Hello RGF12, Thank you for the reply! Unfortunately we do not have any vibration data, there is no vibration routes for these pumps since the stand-by is started whenever the duty pump fails and it does not trip the plant/result in a production loss (not a priority for proactive maintenance). In addition, the pumps do not run 24/7, the pumps provide pressure to accumulators in the hydraulic system, hence, only operate when the accumulators are low, therefore, it is difficult to retrieve data... [ more ]
Registered Member Great presentation. Do you have any oil analysis data? These type of pumps are sensitive to oil condition and routine oil analysis with an emphasis on particle counts and wear metals may give you some early warning of pending failure. Do you have any vibration data? [ more ]
See all 2 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Cooling Tower Gearbox Failures
Registered Member Sir, i want to know that how bearings or gears generates high frequency vib. esp more than 40Khz. is there any examples of high frequency vibration with calculations? [ more ]
Registered Member Originally Posted by rgf12: Attached is a report on a recent GB failure on one of our plants cooling tower fan drive gearboxes. It looks to me that the concentration of the failure area on the shaft side of the gear would indicate either a misalignment under load or a general overloaded condition. I'm thinking that the wear would be more uniform if it was lubrication related. Any thoughts? This is not a lubrication issue. Have seen this kind of failure before and this seems to be due to... [ more ]
Registered Member Originally Posted by Rbt: I believe part of the problems the gearboxes face is how they are started. Our plant below us, same size(14 gearboxes)when they push start it is straight to 1800 rpm. Whereas ours has low speed when started and then to high speed. They have changed out roughly 9 gearboxes during the same time period. On the gearbox we pulled out,it had an intermediate bottom bearing issue. Through the inspection plate you could see the shavings and the damaged inner race. The gears... [ more ]
See all 15 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Repeated Static Unbalance problem in a 2.4 MW ID Fan
Registered Member Yes, i acknowledge ur query about the balancing details....there are 4 fans (2 fans per unit) are having the same problem with same symptoms(Getting unbalanced statically at different times), 2 other fans are running without any unbalance problem since commissioning time and running with Max 1 mm/s at any RPM.. In the fan which was balanced recently, the phase after welding remained Same... Ofcourse yes, I agree with u that there is some shift happening, but what could be a possible reason... [ more ]
Registered Member How many fans of the 6 are having an issue? 2 fans per "unit" are there 3 units? Are the 2 fans with issues on the same unit? Are there more than the 2 fans with issues and are the symptoms the same? So if I read your post correctly...two previous balance jobs you had the same 120 degree when completed, vibes down to 1 mm/s. You added 5 kgs/11 lbs on one of your balance jobs, then another 15 kgs/33 lbs at the same location as previous balance job? With fan balanced to 1 mm/s the final phase... [ more ]
Registered Member Mr. Dave, Thank you for expressing your earnest interest in responding me. The fan blades are fixed backward curved solid airfoil cross section,with two planes separated by a distance of 1.5 m. Regarding the impeller ash deposition, a small loose layer of ash dust observed and that too on the inner side which gets removed by itself when the fan is started in no-load. The Rotor is 16 Tonnes heavy and handles fly-ash and flue gas at 120-135 degree C.The amount of ash handled is quite high... [ more ]
See all 4 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Shaft Failure of Turbo Type Air Compressor [PAP]
Registered Member Do the key and its groove have sharp angles or radius? [ more ]
Registered Member Hi Seo, Based from our failure analysis, we have ruled out the possibilities to two causes: 1) unbalance and 2) SCC; with unbalance as the more likely of the two. Similar to your case, we are now considering the upgrade of the impeller attachment to shrink fit (stud attachment is completely eliminated in this method). May I ask specifically what you mean by disturbance due to dust influx? In our case, we found dust/coal accumulation in the impeller shroud and blades which may have caused... [ more ]
Registered Member Dear Jeff We're still experiencing shaft failure repeatedly, so now I'm about to improve rotor design including fit type. Cuase our team conclude current design is too weak against disturbance like dust influx. Your case SCC seems really interesting to me. Could you let me know where SCC is found or initiated? If you don't mind me asking, can I see your upgarde method which you mentioned above? Regards. Seo [ more ]
See all 14 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
High turbo expander load bearing temperature
Registered Member Dung, Yours is different from mine. Mine is the turbo-expander which is unique in Vietnam. Sorry that I have no idea about your issue. Kind regards. Tu Thanh Pham [ more ]
Registered Member Hi Tu ! i have the same problem with our Bearing @ 3000 rpm detail spherical double ring bearing . I follow the specs from supplier with radial clearance . but when motor start to full load , the temp rise up and after 30mins the temp steady at 63 degC ( alarm at 75 deg and stop at 80deg) . it look unusual . I do not know the reason why and check with vibration tool they have acceleration (gE ) it is exceptable . What i think is the seal , you crosscheck it again ? [ more ]
Registered Member Dear Turb1, Thank you for your response. This issue still exists now. The load bearing temperature is still high, reaching the alarm limit when the speed is over 25600 RPM. I also think the bearing clearance is the root cause, but because of the plant process, I have to wait until September 01st for shutdown the machine and re-inspect it. Thank you and kind regards. Tu Thanh Pham [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Vertical pump vibration when suction pressure fast reduces
Registered Member Thank you very much for you guys reply. Your information is very helpful to me. Last time I checked trend from another server, where data is copied by 1m frequency. Today when I check again in DCS, vibration increases when water level (suction pressure) decrease. Best regards - Ha Dung [ more ]
Registered Member It is not clear in your question . What is the first out indication? A vibration level trip or suction pressure or flow trip ? [ more ]
Registered Member Pete gave an excellent input. I would emphasize on having a close look at the data. What do you mean by "in this case no vibration increase except pump shut down spike"? Do you mean the vibration was stable and continue to be stable except for the high vibration samples that caused the trip? Or, during the shutdown (after motor switched off), the vibration increased? Sometimes the difference is very small between the actual events: existence of high vibration, initiation trip command, motor... [ more ]
See all 4 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
VERTICAL PUMP
Registered Member It can be a challenge to distinguish whether the "cause" lies in pump or motor. One thing that sometimes work is to arrange to uncouple the motor from pump and run motor uncoupled. If the vib goes down dramatically, that suggests the cause was pump or maybe alignment. If the vib remains substantially unchanged in magnitude and pattern, that suggests the cause was the motor. But also beware some potential complicating factors: 1 - by uncoupling, you are changing the system. You may have... [ more ]
Registered Member I guess some readers of the original post may wonder if the pump is really "submersible" or it is "vertical" whose motor is above the ground. In neither cases the pump itself is accessible. In the case of submersible pump, even the motor is not accessible. I guess TCVib referred in his/her post to vertical pumps. Regards- Ali M. Al-Shurafa [ more ]
Registered Member If you have high radial vibration on the top of the motor it is most likely from your pump. Have seen this a lot in vertical pumps, mainly in long shaft submersibles. Sleeves may be worn/bad. Have seen 1X improved by balancing from top of motor. This was a large vertical pump with a ratchet(anti reversing device) in the top. [ more ]
See all 3 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Helical Gearbox failure and sub-synchronous axial vibrations
Registered Member NOT the expert on this subject, what I see in data provided is axial thrusting on the double helical gear teeth. This can be caused by unlevel gearbox and worn gear tooth profile to name a couple. The gear tooth broke toward the outer edge of the gear which too can indicate axial thrusting. Sub synchronous, do you mean vibration is below motor or compressor shaft speeds? Are the failed gear teeth next to each other or just a couple of teeth apart? Can you share more data, gearbox... [ more ]
Registered Member John in PA would be your best resource on this board in this matter. [ more ]
See all 2 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Transient Load or Temperature
Registered Member Thanks that makes sense, thanks again for the response [ more ]
Registered Member Yes. [ more ]
Registered Member The Wikipaedia definition of transient load is: In electrical engineering and mechanical engineering , a transient load or natural load is the response of a system to a change from equilibrium. The transient load is not necessarily tied to "on/off" events but to any event that affects the equilibrium of the system. The impulse response and step response are transient responses to a specific input (an impulse and a step, respectively). For load you can substitute temperature. Transient... [ more ]
See all 7 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Challenger accident report
Registered Member Feynman passed away shortly after that. His testimony in front of the challenger commision cut through the BS to demonstrate a pretty simple principle of O-ring set at low temperature which he summarized in understated tones "I believe that has some significance for our problem". https://www.youtube.com/watch?v=MWZs8l2AMps Morton Thiokol engineers knew well of the risk and tried in vain to persuade M.T. and NASA management to postpone the launch. For some reason management at NASA was... [ more ]
See 1 reply...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Low pressure Steam Turbine blades Failure
Registered Member the turbine was given by Shanghai turbine works/company in year 2000. it operated almost 15 years. during the operation no signs and symptoms shows that the blades were damaged. the plant was shutdown for the maintenance purpose and after the non destructive testing (NDT) we found that the 23 of the blades in stage 6 were damage in both of LPs the inlet steam pressure at Low pressure (LP) turbine is 0.721 MPa with temperature of 253.4 degree Celsius . four (04) steam extractions are taken... [ more ]
Registered Member Take metallurgical samples to determine the failure mechanism. Stress Corrosion Cracking is very likely. For GE machines there have been a number of TILs issued in covering L-1 bucket (blade) failures. What is the make and year of this machine? If you have not done so yet consider making an insurance claim. Most property (and machinery) policies should pay for such failures. Talk to your risk management department. [ more ]
Registered Member Aftab, What is the inlet steam pressure? Are the steam lines equipped with enough traps? A separator would be nice for a saturated steam turbine along with traps in the turbine belly. the last couple of stages would probably be in a vacuum and running cool. The reason I mentioned the balance piston leak off earlier is this leak off would be reintroduced to the turbine at maybe the 6th stage? this steam would still be hot in comparison to the blades at low loads due to the reduced flow rate,... [ more ]
See all 6 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
BALL BEARING FAILURE ON 1,3 MW / 6KV SCHORCH MOTOR IN REFINERY
Registered Member Here is an example of severe false brinelling, separable inner race roller bearing with a side load belt tension. The rollers that did not have belt load against them slowly rotated while at rest and made .020" grooves at the roller spacing. Then at sometime the machine was ran then shut back down, this time the rollers were in a different location. Then it again sat for a long period of time and created a new set of roller marks at the new "sitting still" location Dave [ more ]
Registered Member Hello Dimaz , thanks for your reply. Actually now no chance to measure , because the motor has rebuilt and put back to the site . Have been in the bearing business for more than 30 years , this is first time i see such wear pattern . The motor will be monitored from now on . If i get more news i will post Many thanks to all . [ more ]
Registered Member Hello George , I am agree with the caused of the problem is due to false brinelling . The possibility of a combination of false brinelling and Fluting . What have you done the measurement of shaft voltage and grounding ? To verify this problem [ more ]
See all 5 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing temperature swings
Registered Member I have heard presentations by UE Systems. Check their website. Ken On Jan 18, 2016 7:38 PM, AMP - Asset Management Professionals < forum@maintenance.org > wrote: > > == To reply by email, write above this line. == > Hello, lubeguy: > We're sending you this notification because you are either following the forum, the content, or the author listed below. > New Reply To Topic > Subject: Bearing temperature swings > Reply By: Missisquoi > In: Reliability Engineering... [ more ]
Registered Member I like SDT's line of products. They have different models to fit any program. Simple meter with a digital readout and a magnetically held transducer is all you need. Procedures are very simple...less than 30 minutes of training until you are making a positive impact on your program. Same meter can also be used for air leaks and steam traps! Great little piece of equipment. [ more ]
Registered Member I have read about ultrasonic devices for guiding greasing. Any recommendations on which ultrasonic device to use or the best place to get one? Thanks! [ more ]
See all 11 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Cooling tower fan motor current variation
Registered Member Is a 10 amp swing really a problem with this unit? [ more ]
Registered Member Sometime problem rotor cage can be seen and measured only with load , increasing temperature and growth cracks and poor joint between rotor cage and conductor . Motor offload running with nearly synchronous speed it may not be sufficient to confirm a problem with the rotor in some cases . Good luck [ more ]
Registered Member There is no abnormal sound so far yet. As far as the fan stallation is concerned how could that be analyzed? Our electrical section is neglecting the rotor problem they are saying if problem is due to motor then it must be reflected on motor offload condition which we tested and found normal. [ more ]
See all 5 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Generator overcurrent trip
Registered Member If no doubt about the generator, you should check the electrical transformers on the line just after. You should also check that the AVR is working without any problem (observing the trending photos, even before the problem electrical parameters are not stable) . To get more precise and significant data, an oscilloperturbograph report is better for instant recording of generator outlet electrical current, voltage and frequency, and excitation voltage and current measurements. Good luck. [ more ]
Registered Member After 4 hours of running, does this mean this is the first time the unit has generated power since rewinding? Was there a problem before and that is why the generator was rewound? Have you performed and infrared scan of ALL electrical components while in operation? Even though rewinding has been done, I would not think the problem would jump from phase to phase. If you are feeding parallel to a grid, is the grid also seeing this same amp swing or it is just your system? [ more ]
Registered Member Dear colleagues, Sorry for my late response, I have just collected some information. The generator is feeding a network as parallel to grid. Current increasing occurs on individual phases An AVR is used to manage excitation and stator voltage The generator is driven by a MAN engine. The customer checked all related issues about engine side and additionally generator (rotor, stator, excitation windings,diodes,..) No abnormal findings. Meanwhile both rotor and stator have been rewound by a... [ more ]
See all 5 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Conveyor Tail Pulley Bearing Damage
Registered Member Originally Posted by MarkSl: My customer recently removed an NTN 22220KC3 bearing from the tail pulley of a conveyor due to increasing floor noise in the FFT spectrum and impacting in the waveform. We have taken a grease sample from within the rolling elements, cleaned and dismantled the bearing. Wear is evident in the raceways and the rollers which is consistent with grease contamination from iron ore dust (site is a iron ore loading facility). Grease analysis showed 7669ppm of iron and it... [ more ]
Registered Member Egg shaped bearing housing/shaft and misalignment of the bearing can cause 180 degree roller issues [ more ]
Registered Member I would dig more in the installation and the way it was mounted, and how long has it been stationary while loaded. Why don't you use a shielded bearing to avoid any failure in case the seal failed? [ more ]
See all 12 replies...
Reliability Engineering for MaintenancePosts about Root Cause Analysis
Dry gas seal leak
Registered Member You should check your buffer gas(nitrogen) supply.I gues that I would be because of high pessure or high flow of buffer gas.Just lower the pressure of buffer gas [ more ]
Registered Member Which standard is it? [ more ]
Registered Member Yes,we checked with the dry gas seal standard. But this case has the commercial reason. We want some explanation or comment for dicuss with OEM. [ more ]
See all 4 replies...

Join Us!

The Association for Asset Management Professionals (AMP) is dedicated to making the world work for everyone, with no one left behind.

The mission is to provide a path to a safe, sustainable, successful workplace and world through reliability and asset management.

AMP is a Florida based 501 (C3) not-for-profit organization that delivers

  • Professional Certification (CRL and CMM)
  • Online Community of Knowledge
  • Competency Based Learning (CBL)
  • virtual Special Interest Groups (vSIG)


 This web site is FREE to use for registered members and has been called the LinkedIn or Facebook for Reliability Leaders and Asset Managers.  The Community of Knowledge is simply fantastic.

The Association of Asset Management Professionals (AMP) is licensed to develop competency based frameworks using Uptime Elements Reliability Framework and Asset Management System and its related Frameworks.

Uptime Elements Reliability Framework and Asset Management System
Uptime Elements Reliability Framework and Asset Management System

Uptime Elements Digitalization Framework
IoT Knowledge Domain

Vibration Elements
Vibration Analysis and Diagnostic Framework
Lubrication Elements
Asset Lubrication Framework

 You are also invited to join the Association of Asset Management Professionals

LinkedIn Discussion Group with 53.000+ members

https://www.linkedin.com/groups/1636387

LinkedIn Company Page as well
https://www.linkedin.com/company/association-of-asset-management-professionals

Join Now

Already a member? Sign In

Upcoming Events

VIRTUAL CMM EXAM
VIRTUAL CMM EXAM
VIRTUAL CRL EXAM
VIRTUAL CMM EXAM
VIRTUAL CRL EXAM
VIRTUAL CMM EXAM
VIRTUAL CRL EXAM
VIRTUAL CMM EXAM
VIRTUAL CRL EXAM

Complete Calendar

Online Now

×
×
×
×
Link copied to your clipboard.
×