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Reliability Engineering for MaintenancePosts about Root Cause Analysis
ID FAN VIBRATION
Registered Member As others stated, mechanical looseness is present. The sidebands are most likely from the outer or inner race spinning. When the bearing spins in the housing/shaft, it is turning at a different speed which will create a frequency very close to running speed. Have seen worn gear couplings exhibit this same pattern. Down and dirty way of checking. Dial indicator on shaft of interest at top dead center, long bar and block/s of wood, gently pry up on shaft and record total indicator movement. [ more ]
Registered Member any other idea for this reading from experts [ more ]
Registered Member 5x?...how many blades the impeller? 1x, there is the unbalance, is clare. how many blades per impeller there is an imbalance, it is clear but, regarding the last photo, many nx armonics indicated like bearing/housing looseness... we see high 14x armonic, probably 14 impeller blades? but the sideband from 6x to 18x is look like a rotor bar problem about motor...? many things, but just my opinion [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Suction column oscillating problem in fire pumps@Offshore platform
Registered Member Sharath, Not sure of your pumping drive or piping configuration, IF this is a self priming application, then read on. You state pump is submerged 5 meters under the water? What is design point, pressure/flow rates, pump manufacturer, model number etc You do not address the fact that the suction lift for the pumps is not possible? 15 to 17 meters is 49 feet, ALL CENTRIFUGAL PUMPS follow the same laws of physics, the maximum amount of suction lift at sea level is 10.33 meters at sea level,... [ more ]
Registered Member Hey Dave thanks for your reply and ur time on this. The sea level is approximately 15 to 17 mts from the right-angle gearbox and the pump is submerged in water ~5mts. And all the pumps are placed on different platforms with different suctions and we also have 2 jockey pumps with same height and length but there is no any oscillation in column as fire pumps. All the pumps are installed recently may be 20 months. Suction lift and discharge pressure are getting as required but the only issue is... [ more ]
Registered Member Sharath, The suction lift you are trying to do is not fundamentally possible? Theoretically, all centrifugal pumps can lift water not more than 10.33 m at sea level. If the liquid is below the pump datum, the vertical distance between the pump impeller and the surface of the liquid on the suction side of the pump is referred to as the suction lift . Apr 13, 2017 Are these newly installed? Are there more than 4 fire pumps? Do the each have their own suction pipe? What is the altitude of the... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Vibration at 5X NDE AND DE V for Centrifugal Pump
Registered Member Is the pump running at BEP or away from it. [ more ]
Registered Member what was the cause of the 5X ? [ more ]
Registered Member 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... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
VERTICAL TURBINE PUMP -2 STAGE FREQUENT FAILURE OF SHAFT BUT DIFFERENT LOCATION
Registered Member Hello. We have similar column pipe bolt sheared. Shaft bent.Bottom neck ring to impeller stuck causing cold welding. But unable to find the cause. No overload motor trip. Few possibilities are 1) Column pipe bolt loose causing offset of bowl assembly. 2) Pump operating at closed shutoff. Recycle line PRV failure . 3) Low clearances of neck ring to impeller. Foreign particle stuck. Please provide your inputs. [ more ]
Registered Member Hi CBM, Dave Reynolds has attached some very good info on breakages and in Dave's literature there are images of misalignment breakages with ratchet marks, this breakage appears very similar with fine ratchet marks around the circumference of the shaft breakage, if you are still trying to solve this let us know and I’ll ask our metallurgist for an opinion and if it is of use we can post his comments here to assist, regards Rob S [ more ]
Registered Member The double paste can be edited by the OP, can it? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
remaining condensate water in drying cylinder
Registered Member david, thank zou very logical analysis, i will go through these points thx Pizo [ more ]
Registered Member Pizo, Your original post said that this has happened three times this year, I take that to mean that it does not happen every shutdown. This could be an error in the operator shutdown procedure or it could be an error in the operator running procedure. They may not be siphoning all of the condensate out during normal operations. You'll have to look for inconsistencies in how they run as well as how they shut down. Keep in mind that this only happens in one dryer section, what is different... [ more ]
Registered Member Hi, David, thank you... we opened all the cylinders check hole, the water was in several cylinder but little. it seems that this little water in many cylinders form an extra load on the motor. this happen only in a specific drying group, the other groups are working fine. they checked the siphons, they are ok. what a human error could be ? thx Pizo [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Fan Vibration spectrum analysis
Registered Member I think you are dealing with critical mechanical looseness, probably coming from the fan DE bearing (bearing housing / coupling / attachment as alternatives). Your spectra should have better resolution for detail analysis with some peak markers. Besides, imbalance could also be well increased, although it is hard to say in such bearing condition. I wouldn't operate much longer [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Reciprocating Compressor Liner Failure
Registered Member Greetings Pawan, Good case study. 1. One thing is sure after overhaul and fitted the piston ring failed with in 2 days. 2. Especially when lowering the piston into liner, the guide ring, if having any scratches or dents or when forcing the piston into the cylinder liner normally the bottom ring can stuck or break and continue to run the broken piece can damage the piston and liner. This failure occurs in Tandem compounding pistons. In Marine Industry we have faced this type of failures for... [ more ]
Registered Member dear sir have you n checked the suction and discharge valves ? if you sure about maintenance of all components and installation procedures ,you should looking for cause around operation after overhauling .for example be sure about condensate gas or liquid drainage during operation. best regards [ more ]
Registered Member Was the cylinder starved of processed gas? How about the end devices that was to shut down the unit for excessive vibration are they properly installed and working? from your explanation though not too clear- Rod reversal due to lubrication issues might be the root cause. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Screw Compressor Motor Overload Tripping
Registered Member Farhad, Apologies for the delay in replying. I have a couple of more questions and some things to possibly check for potential problems. 1. Is the Oil removal unit strictly for removing oil, or also a dryer? (I would recommend a dryer be installed if one isn't there) 2. Have you considered a receiver upstream of the oil removal unit (dryer)? 3. Does your receiver have a timed drain to remove any condensate buildup? I would check the receiver for possible condensate buildup. Verify that your... [ more ]
Registered Member Hi! Michael. First of all thank a lot for providing your input. I have attached schematics of system which I will be frequently referring in answering your queries below: First of all, please understand normal operation first. During normal operation, 3 out of 4 C-4202 ABCD compressors are put in operation to maintain receiver tank pressure near 7 bar. If one compressor out of these four is out of service for maintenance and we are struggling to maintain header pressure near 7 bar then... [ more ]
Registered Member All of the compressors should be seeing the same pressure at discharge if all valves are aligned correctly. I have a few questions to help troubleshoot. 1. Are all of the compressors set to the same discharge pressure set point? If so, do the pressure transducers or gauges all read the same? 2. Are these compressors variable speed or variable capacity? If so, are they staggered to have load picked up and shed in a sequential manner as system demand changes? 3. Do you have a system receiver... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
High Vibration on bearing #2 and #3 on gas Turbine frame 9E (100 MW)
Registered Member Hi We have same problem in GE frame 9 Load variation vib in BRG#2&3 vibration signature analysis is like misalignment 1X,2X,... also we have high vibration near 25 mm/s in BRG#1 at critical speed in running the unit and in BRG#3 in shutting down the unit. We suspect to misalignment of the bearing due to casing slippage Please help us that other reasons for this problem. Our thinking about source of vibration is right. thank you [ more ]
Registered Member First, I think you should give us some data (APHT trend, waterfall, SCL, orbit... if any)for review and also the arrangement of machine. I do not know where is bearing#2 or 3 and so on. You said that the casing have done bore alignment due to center of bearing housing 2 and 3 is not coincided. How about the alignment result and how about the rotor center position check (done at some hole on casing). how about labyrinth clearance at both side of bearing? how about the phase? [ more ]
Registered Member please to help me ??? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
High shaft vibration in GB
Registered Member the run out of coupling that you mean is on coupling hub ? if 0.25mm is on coupling hub (normally, it should be not over 0.05mm), it is too much run out and able to make unbalance at drive end? you should check at some points along with coupling hub to define it is eccentricity or shaft bow. You check unbalance in WS with or without coupling hub? what kind of coupling do you used? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Premature wear
Registered Member Jim, I hope that solves your problem. If you ever looking for an additional tool for predicting and analyzing system failure, please reach out to me. Our provides the tools for conducting proper diagnosis on your assets, avoiding uncertainty and downtime. My website is vantaviews.com thank you! [ more ]
Registered Member Hi Jake, Many thanks for the info. Much appreciated. Kind regards, Jim. [ more ]
Registered Member Above is a good graphic explaining how the stress is occurring. It could technically be both, however since it is premature wear, it’s hard to really tell. I’ll point you to this article for a great reference, knowledge and understanding. http://www.cscos.com/wp-conten...ng-Neville-Sachs.pdf [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
bearing unknown marks
Registered Member Looks like fretting wear at initial stage on raceway due to vibration [ more ]
Registered Member upper housing photo [ more ]
Registered Member Im not sure. I don't think so. Today we are going to measure housing. Also shaft and inner ring (see photo). Could be outer ring distortion because a possible possible housing worm? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing Failure
Registered Member Good catch with the feeler gage issue. The bearing being improperly set up with insufficient clearance creates the hoop stresses needed to crack the outer race in the way that you showed here. Rich Wurzbach MRG Labs [ more ]
Registered Member That's a really good point rich, to be honest I hadn't even thought about it, I should have really collected some of the old grease for that purpose. I'll remember that for next time. Yes so the grease line has been installed due to the access restrictions, it looks like it's achievable to just grease normally but it's actually about 7 feet off the platform, making it hard to reach. The grease line was checked after to make sure there wasn't any blockages. But I understand you're point , if... [ more ]
Registered Member There is another piece of information that can be added to help make the true root-cause determination more likely, and that is the analysis of the oil/grease and debris found in the failed bearing. While an outer race can crack due to significant weakening after a substantial amount of material has been removed, that is not the case here. It is more likely that a significant piece of the broken cage got trapped between the roller and outer race and caused deformation to induce the crack. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
type of bearing failure.
Registered Member https://www.timken.com/pdf/589...lysis%20Brochure.pdf Page 19-20 discuss false brinelling, text describes in detail what to look for, I would have anticipated the inner race to also display brinelling page 8 debris in lubricant Dave [ more ]
Registered Member looking into lubrication bearings are oil bath using ISO 150. endplay was set to .008 [ more ]
Registered Member It seems false brinelling due to vibration from an external source while stationary .low preload and poor lubrication also can be cause . [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Two Speed Induction Motors
Registered Member https://www.allaboutcircuits.c...or-induction-motors/ http://i-gard.com/site/assets/...und_rotor_motors.pdf https://easa.com/resources/res...und-rotor-windings-1 Now what you describe is a wound rotor motor design If you take the resistors/speed control out of the picture you can narrow down the problem. Put a short lead on the three slip rings and tie all three leads together. This essentially is causing the motor to operate at high speed with no resistors in the circuit. If the motor... [ more ]
Registered Member Thanks for taking the time to reply. I forgot to mention this is a 3 phase unit, low speed is 1440 and high speed is 2900RPM. The motor has 6 wires emanating from the frame with 3 field resistances at approximately 25 ohms and the other 3 at approximately 16 ohms. It uses a rotary switch with a number of bridges or links to energize the appropriate winding. Also, here's a good article on 2-speed motors. https://precisionautomation.ne...on-two-speed-motors/ [ more ]
Registered Member Assume 3 phase motor, what you describe is a single phase condition or shorted winding. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Sewage pumps premature failure
Registered Member Sorry it's been so long big factory to take care of. As I've stated before it's a pretty simple system when the waters down you can see the entire piping hose everything no leaks. As I also stated once part of the windings burnout that pump starts jumping around at the bottom of that pit like a cat on a hot roof and at that point the pump still pumps it doesn't have the force to evacuate the water at volume anymore. At this point we're just putting in a whole set of contactors timers and... [ more ]
Registered Member I do not believe either pump is VFD or soft start rated, this could be cause of winding failures. Yes under voltage can cause problems, but you state amps and volts were all good. Is pump controlled by contactor? Is there a coil that drops out when shut off? Could wiring be wrong? Single phasing cause loss of power and vibration. Verify contactor contacts are in good shape. Pipes typically do not break without excitation. Impeller out of balance, pump not fully submerged, hydraulics not... [ more ]
Registered Member Because I forgot to answer the question there are no loops traps or check valves for air to get trapped into , Just a straight shot up from the pump through the hose which is tucked into the 8 inch gravity feed line about 5 feet and runs downhill approximately 9 inches and 65 feet to atmosphericly vented cistern, part of the storm sewer system with open grated manhole cover that when everything is working correctly you can view the discharge. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Abnormal sound and high vibration from Motor in solo run
Registered Member Furthermore, in your first case there are harmonics of 80 Hz that are probably related to VFD (750 rpm / 990 rpm is almost 0,8). In your second case there can be seen frequency at 4xrpm, which could be related to number of poles. Although there are probably 8 poles. [ more ]
Registered Member All indicators are saying the problem has some electric background related with VFD or motor electric elements. What I find strange in your data is practically no rpm frequency, just harmonics. I have never seen anything like this at such big motors. I would also check your vibration collector settings, cables, accelerometers etc... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing current damage on NDE bearing due to bearing current
Registered Member First time on this blog and I see these postings are a few years old, but here goes it anyway: I reviewed the pictures and agree you are experiencing electrically induced bearing failure. Incidence rates of bearing failure on VFD motors is at least 60% by 2 years and only continues to climb from there. It is a well-accepted and pervasive problem that particularly plagues operations that run 24/7. The following information is based on long-term field and lab studies over 30 years. 1)... [ more ]
Registered Member Good point. We experienced fluting to varying degrees on 9 75hp Extruder motors. Installed a couple of ground rings and then had a rep from ring manufacturer test our motors and he showed we still had problem due to bad ground. Inspection found some ground lugs weren't tight but after fix we still had shaft voltages so all motors got rings. I check voltage levels every 3 months and shafts have to be cleaned regularly due to dirty environment. 1 motor has ring mounted internally but I worry... [ more ]
Registered Member I too would like to add some additional experience....Motor 450HP 900RPM 480Volt 3 phase with insulated shafts on both ends, intermittent duty, megged over 1000megs between bare shaft and insulating material on both ends, shaft grounding ring, both bearings have oil not grease and still have electrical fluting. The suspected root cause is the cables from the VFD to the motor not having proper shielding. Had over 300 volts from the rotating shaft to ground! Best to measure/test to better... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Is Bearing having fluting marks?
Registered Member First time on this blog and I see these postings are a couple years old, but here goes it anyway: I reviewed the pictures and agree you are experiencing electrically induced bearing failure. Incidence rates of bearing failure on VFD motors is at least 60% by 2 years and only continues to climb from there. It is a well-accepted and pervasive problem that particularly plagues operations that run 24/7. The following information is based on long-term field and lab studies over 30 years. 1)... [ more ]
Registered Member Yes, that's textbook fluting. There have been many good discussions here about it over the years: https://www.maintenance.org/top...63202347#77420702863 [ more ]
Registered Member innner race of NU230 Brg. in zoom view. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
GEAR FAILURE AT SCREW PUMP
Registered Member Thanks Dave for material. the lubrication is just follow the manufacturer and no any abnormal. The spec for oil is VG100, The oil was maintaining and changing as manufacturer then i have no doubt in oil issue. As see the defect mark, look like a very excessive load effect on gear and broken the teeth surface, the spectrum also shows high GMF relate to gear wear , also indicates very high load. then the next question is why the high load on the gear , i keep going my investigation on this... [ more ]
Registered Member https://www.machinerylubricati...ad/150/gear-failures https://www.rexnord.com/conten...ments/108-010_manual Here are a couple of links showing different failure modes Your images show the gear was loose on the shaft, lubrication is in question, gear material may not have been hardened to proper levels Dave [ more ]
Registered Member Dear DOMINICH.VO , increased noise floor with gear impact indication , are you maintaining and changing its lubrication as per the manufacturer recommendations and grade . Do you mean viscosity of pumping fluid , low viscosity might have some effect but i don't think so it is the main cause .For better understanding on this you can refer the manual and contact the support service . [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Complet root cause analysis on a wheel loader
Registered Member Apologies for the late response. Criticality factors depends on the type of machines and process. However, it is based on the risk of financial loss, safety consequence, loss of reputation etc. \ As a general rule, Risk= probability of failure X consequence of failure In terms of Plant machinery, During say one year time, Risk ($/yr) = Failure frequency (per year) X Cost consequence ($) Now consider the example below : Now say you have 5 mechanical failures and financial loss is around 100 $... [ more ]
Registered Member Let’s say that I perform a pareto and discovered that I have hydraulic failure, mechanical failure, Brakes failure, all representing nearly 80% of my downtimes. How do I rank them per their (criticality safety/production loss/etc) and what are the different factors of criticality? Then do I perform an FMEA on all those three failures to select the most critical, in order to add an RCA (ISHIKIWA) on that one critical problem to implement actions ? [ more ]
Registered Member Hi! thanks a lot for you reply. Regarding the point n°3, how do you rank the failure mode as per their criticality ? Regards [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
catastrophic failure
Registered Member You should use some pro tension meter like Trummeter, which has its own calculator for suitable belt tension in N or in Hz. Or measure the force directly at the installation. I think the measured belt force on the Trummeter means just force on one side of the belt so you should multiple it roughly by 2 (or consider angles for more precise value). For the new belt installation, the tension value should also be multiplied by 1,3. When you get this value, it should be reasonably lower than the... [ more ]
Registered Member hi i did not measure and compare, bu it is a good direction to search, but which load exactly should i compare ? Fap = maximum permissible axial load [kN] F r = radial load [kN] P = equivalent dynamic bearing load [kN] P 0 = equivalent static bearing load [kN] P m = equivalent minimum load [kN] ****i did not work with these calculations since 20 years ....out of my scope, but i will do my best go through... Regards Pizo [ more ]
Registered Member Did you measure belt tension in N? And compare it with the bearing load limit? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Reference for root cause analysis
Registered Member Thanks dear john for useful information [ more ]
Registered Member Conceptually, RCA is a wide field, but I assume you mean with respect to machinery. One starting point might be https://conference.reliablepla...root-cause-analysis/ . I would also suggest you look around that Conference operator for related info. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Gas Turbine Bearing Failure - Lube Oil Leakage Caught Fire
Registered Member During inspection, the brass oil seal was found damaged. So, there is a possibility the oil could leak from Brg#4 and got fire, but question is why Bearing#4 which is near to fire location is not melted and how the fire traveled from Brg#4 towards Brg#3 ? You know its Turbine Section , the pressure at Brg#3 is higher than the pressure at Brg#4 [ more ]
Registered Member It is possible that the shaft is been hot due to fire and make the babbit overheat like picture. You should take event sequence and see what happen near the event time. Focus to oil system and clearance, i think you will get your answer. [ more ]
Registered Member The Ventilation Fan was also tripped due to breakage of its belt which may increase the T of enclosure and which further melt the Babbitt white metal which leads to bearing failure ?? I am not sure, can u recognize from bearing pic, is it melted during running or stationary? or is it melted due to high LO temp??? I am not sure [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Mechanical seal failure
Registered Member Which fluid and which o-ring material. I think here is the answer. [ more ]
Registered Member Thanks Dave for some throwing some light [ more ]
Registered Member https://www.marcorubber.com/o-ring-failure.htm https://www.prepol.com/solutio...o-ring-failure-modes http://www.dichtomatik.mx/cata...alisis-de-fallas.pdf http://www.pspglobal.com/seal-failure.html http://www.madgetech.com/pdf_f...app_notes/orings.pdf Could be the type of barrier fluid you are using that is causing the oring to fail, could be the fluid you are pumping is attacking the oring, could be too hot for oring abilities. The above links have some good images and details of what to... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Firewater pumps p&id and network over pressure protection
Registered Member Not sure what you are looking at but my copy, NFPA 20 is titled Standard for the Installation of Stationary Pumps for Fire Protection . Further, chapter 4 has the following contents Chapter 4 General Requirements 4.1 Pumps. 4.2 Approval Required. 4.3 Pump Operation. 4.4 Fire Pump Unit Performance. 4.5 Certified Shop Test. 4.6 Liquid Supplies. 4.7 Pumps, Drivers, and Controllers. 4.8 Self-Regulating Variable Speed Fire Pump Units. 4.9 Multistage Multiport Pump. 4.10 Centrifugal Fire Pump... [ more ]
Registered Member Interesting, never noticed before because the title doesn't exactly scream "fire pumps". It also doesn't contain anything resembling a P&ID from a cursory scan, and simply references NFPA 70 (NEC) for electrical installation requirements. [ more ]
Registered Member What about NFPA 20? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Failure of synchronous motor to start up on no load
Registered Member Riyadh Salih, this thread dates from 2011. [ more ]
Registered Member Check the delay timer on PLC if it is tripping around 700 - 800 RPM or it reaches 1795 RPM and it trips? [ more ]
Registered Member Have you checked he slip guard relay, check diodes on the exciter / excitation panel / check the multilin motor control module what fault you are getting is it tripping because of vibration or power factor [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Gas Turbine Tilted Pad Journal Bearing Failure
Registered Member Dear Pawannlng, the possibles causes are: 1.- misalignment (external misalignment) 2.- bearing housing excentricity (internal misalignment) 3.- low lub oil pressure in bearing or any restriction in lub line. 4.- over radial load. 5.- Preload in bearing (internal or external) we can rule out the last possibles causes using technologies that Rotating Guy said (Shaft centerline, sequence of orbit and time signal, bode and polar possible, spectrum, etc). [ more ]
Registered Member Dear Pawan, Without referring the diagnostic plots i think its very difficult to pin point the root causes of the failure. For fluid film tilting pad bearings, we need to refer more plots and one plot may not give clear conclusion. My opinion, since i am practicing vibration analyst more into this type of bearings. For hydro machines this type bearings are commonly used. Sherub [ more ]
Registered Member Dear Sir Oil analysis was done six month back and report was normal. I am attaching only available vibration plot. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
3309 A/C3 Bearing Premature Failure
Registered Member Hey Thanks for reply. I think your doubt about cocked bearing is absolutely right. Because there was spacer between bearing&housing in axial direction, which was out of position in small portion.(we observed it in disassembly). At that time I thought it occurred due to disassembly. Thank you for clarifying my confusion. [ more ]
Registered Member The bearing is indicating excessive axial loading for some reason. It does not indicate the presence of excessive heat. Is it possible, the lubricant was not correct or incorrect amount? But that would indicate excessive heat. This was not a manufacturing defect anything related to the bearing. Could the bearing have possibly been cocked on the shaft? I have seen that once before, where the bearing was not seated correctly against the shoulder of the journal. Find the reason for axial... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Dry Gas Seal Failures
Registered Member How about materials of construction and pH of product, is the piping associated with the failing seal made of different material? Dave [ more ]
Registered Member Dear Ahmed contamination is from the gas process inside de compressor which brings with it particules of iron same problem for our case that happened last year , but with oil which came from another equipement and flood the compressor slowly . [ more ]
Registered Member Dear SAAD AHMED ! I don't know why iron can enter dry gas seal, because pressure of filtered gas always higher process gas at compressor. At our plant we have same problem with DGS, however root cause to failure DGS is liquid enter DGS to damage seal face. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Motor triping issue
Registered Member Thank you for the update. [ more ]
Registered Member Finally we found the problem for Motor Tripping issue ...... Rated AMPS = 88 Before tripping rely was 80 AMPS after that rely set 80 to 88 AMPS. Now equipment healthy condition and running smoothly . [ more ]
Registered Member Bijoy, Try to replace the thermal overload relay. regards, [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Primary air fan High vibration in Motor DE brg.
Registered Member do you have TWF data? if any please provide. regards, [ more ]
Registered Member why no one is replying? is this forum no more active? [ more ]
Registered Member my query is: 1. what is the stage of failure of bearing? 2. Should we change the bearing ? Motor is squirrel cage induction motor ,6.6 Kv Bearing on DE side: SKF NU230 [ more ]
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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 ]
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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 ]
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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 ]
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