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Reliability Engineering for MaintenancePosts about Root Cause Analysis
backflow on a compressor train
Registered Member A great discussion and interaction with the several parties did bring out new insights.. The custumor gonna check every valve during planned maintenance. The proces has to be finetuned and monitored during shutdown. Those answers must lead to new actions. I'll keep you informed. to be continued.... [ more ]
Registered Member John, I did have contact with the writer of that document. Through this knowledge i strongly advised to place a 3300/52 reverse rotation monitor. Other advises were to ask the OEM's what could happened with the machine during this event. This is planned in september. I am looking forward to do this presentation because i want to set the safety and reliability to a higher/highest level. [ more ]
Registered Member monitor, I'm certainly not in any position to comment on the effects of reverse rotation relative to your specific installation. The Orbit article you site from 2007 does go into a particular situation with a compressor that reversed its direction and the effect on the ADRE data. If you need more insight with respect to how this was detected from the data let me know. The same article has some discussion of safety and reliability. But with respect to your specific machine I would think the... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Controversial paper on RCA
Registered Member I have reacted to the original article. A few years ago I have attended a RCFA seminar, which utilizied a cause-effect mapping method, presented by "Think Reliability". The instructor made a statement that once ALL causes were considered and mapped, the cause-effect flow diagram becomes a complete troubleshooting guide. I can't agree more with the above. In the author's example, one obviously wants first to eliminate a cause which is already known in general and is confirmed in his case -... [ more ]
Registered Member Which particular point are you reacting to? The original article or the responses? At our plant (as I believe many others), the level of effort expended to investigate the cause of a failure depends on the significance of the failure. If there was a big consequence or near miss for very big consequence, we spend a lot of time. If small consequence, not so much time. We have terms "root cause analysis" to describe the level of effort and rigor associated with the significant failures and... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Criteria of Preventive maintenance
Registered Member Vinay, Yes, that is the correct approach. Note that the MTBF you want is for the failure mode "Fail to start and take full load". Based on generic data sources and a 2% unavailability, we get to the 4-8 weeks interval I mentioned earlier. The formula is good enough but there is a somewhat more accurate one also available. [ more ]
Registered Member Gentlemen, Can we use the 'Failure Finding Interval' concept of RCM here. In this case the interval to diagnose the Standby Saltwater Pump should be equal = 2 X Unavailability of DUTY Pump X MTBF of DUTY Pump Its like if Unavail = 1 %, MTBF = 1 Year Then Interval should be = 2 X 1% of 1 Year = One month. So the pump needs to be inspected with the desginated checklist once a month. AM i right folks ? ? -Vinay [ more ]
Registered Member Shahid, from your description of the pump, I suspect that you do not change oil (so we can skip oil analysis ) What happened? Rotor came off the shaft? Guide bushings/bearings worn? Suction screen plugged? Corrosion? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing failure
Registered Member You may have something wrong with the bearing housing, like a bump or something taking clearance out of the bearing if it's doing it again. [ more ]
Registered Member Rennie, Just edit your message and delete. Strange thing. I posted a reply with a file attached and mine was the only posting I could see. Maybe something is wrong with this part of the board. Hmmm. The attachment posted this time. Strange. [ more ]
Registered Member Rennie Did you witness/quality control the replacement of the latest bearing that failed? cracked inner ring????? was the shaft greased to assist fitting because of heavy interference? was the bearing heated prior to fitting? if so what method was used? or was the inner ring bashed on with a hammer. Was the work carried out in a clean enviroment? Just some thoughts Jonesy. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
gearbox shaft broken
Registered Member David, i do not think so no ,only measure vib usually there is a flexible coupling to reduce misalignment.however,in"HS3"picture,i cannot see the elastomeric flexible coupling only the coulping locked on the input shaft of gearbox. may be the elastomeric flexible couping lock on the motor output shaft. in this case,i have to check the gearbox input shaft diameter,does it larger than motor shaft.if the motor shaft is larger.i should incrise the gearbox shaft diameter or intall a elastomeric... [ more ]
Registered Member Leisure, Are there ( such as in the the keyway, coupling ) any physical signs of torcional vibration? Can you measure motor current in order to detect variable torque. Also shaft misalignment will also contribute to shaft bending fatique in particular if coupling is locked. [ more ]
Registered Member sorry add again [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
viscosity lmit for lub oils
Registered Member If your not doing a baseline on your new (unused) oil you really don't know where your in service oil is. A general rule of thumb is +-10% of new oil viscosity to trigger an investigation. Baseline your new oil for ISO cleanliness, viscosity, acid number and additive concentration, and RPVOT. [ more ]
Registered Member cSt = 0.22 * SSU – 180/SSU 260-325 SSU corresponds to 56.5 - 70.9 cSt Note your specification for SSU should also indicate a temperature. If your SSU is specified at roughly 40C (or 100F = pretty close), then the conversion above is good. If your SSU specification is at 212F, then it won't work (let me know in that case and I will look up the other conversion) [ more ]
Registered Member thanks pete the test results available are KV(cSt) at 40 deg C:65.67 TAN(mgKOH/gm): 0.28 Forming Characteristics(Tendency/Stability): 30/NIL Demulsibility54degC/82degC(min.):40-40-0(30') what is the conversion between SSU and cSt? the manufatures recommends oil with KV b/w 260 and 325 SSU regards Radhakrishnan [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
What is the mechanism of these rods failures?
Registered Member The fracture surface appears to show fatigue across most of the surface. Typically, the heat-affected-zone adjacent to the weld nugget has the highest hardness, and correspondingly, the least toughness. That's why fracture occured just below the welding level. Post weld annealing and blending of the part surface after welding could help make the part more resistant to cracking. Shot peening of the surface would be an added plus. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
FREQUENT FAILURE OF THREADS IN CSTINGS
Registered Member Bill wrote: "Make sure that your torque wrench is calibrated" With all due respect, this is a common misconception which provides dangerous false sense-of-security and surprise when one's joint fails: If the intent is to attain proper bolt load (which it ultimately is, of course), calibration of torque tools is virtually useless. Having your tool calibrated doesn't mean that it will be able to accurately produce clamp load. "Clamp load" or "bolt stress" rather than torque is what we're... [ more ]
Registered Member Bill, I support your views on the helicoil design. Your suggested 'best practices' are also apt and useful. But I urge all the readers to step back a bit whenever an unusual problem appears. Get a good understanding of why the item failed before looking for a solution, however attractive and fast that may appear. Stronger or superior widgets are not necessarily the right way to go, because they sometimes cause other parts to fail, sort of just getting up the food chain. The RCA process... [ more ]
Registered Member I don't know what kind of magic the heli-coils use, but I can say from experience they do in fact work. Another thing I've learned from experience in racing... If you are having problems pulling threads out of a casting, try switching to a stud and nut combo (if possible) instead of a bolt. You get more even and consistant torque when using the stud and nut. Because the nut is turning on the stud while torqueing instead of the bolt threads trying to turn in the casting while torqueing. Plus,... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Failure of Water Chiller Compressor
Registered Member Seems overloading of the chiller , resulting in high thrust values which you presumed to be false. Is the chiller driven by VFD ?Failure of the bearing has occurred first resulting in failure of the compressor due to rubbing or impacting inside the casing.But Why the thrust bearing failed?Any maintenance done on thrust bearing in near past? What type of thrust bearing is there? Reagrsd Irshad [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing Journal (Pump Shaft)
Registered Member I agree with above posters that this is not fluting from electrical damage. Fluting occurs on active raceways only. I understand this is the ID mounting surface of a ball bearing. Knurling is frowned upon by bearing manufacturers. Rule of thumb is to maintain at least 80% intimate contact on mount surface. Any less contact can result in movement (fretting) at the mount surfaces. If knurled, this surface shows only about 50% contact. [ more ]
Registered Member Thanks for all the replies... All the input was greatly appreciated! [ more ]
Registered Member My comment is similar to those above. It looks like the journal was loose and was knurled to provide a tighter fit for the bearing. This is rarely (but sometimes) done at low volume manufacturers, but will often be done at some pump and motor repair shops. Definitely not electrical fluting. Sincerely, Howard [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
minimum suction line
Registered Member jawal, most pump manufacturers will recommend a maximum flow velocity at pump suction which is generally between 6ft/s and 10ft/s for liquid at vapour/liquid equilibrium. Exceeding these numbers will often lead to problems hammer, cavitation, etc.) during pump start up and shut down. The desire is to provide a smooth laminar flow into the impeller eye. In any given pump you should of course go through the calculations for NPSH which will take into account the critical variables. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Cummings Fire Pump Diesel Overheating
Registered Member Just a note and some closure- I have taken the thermostat out and it has been operating perfectly since. While the engine runs it has a good operating temperature and after shut down it is fine. I have no idea why or what actually caused the problem in the first place. Until I have a problem with it I am going to leave it the way it is. I thank everyone who posted and gave alot of great info -THANK YOU [ more ]
Registered Member Mike, Just curious, was this ever resolved. I just found this thread and think it's interesting. Couple questions: 1. Is the turbo water cooled? 2. What readings are you getting for your exhaust gas temperatures under load? 3. Is there a off-load cool down time protocol? [ more ]
Registered Member MIKE, In case of our engine NT-495 Cumins make the gear box supplier has installed a plug on the outside of the tube carrying oil to the top bearing. The plug is accessible anytime. Usually during engine running , we check the lub oil supply to the top bearing by loosening the plug. We can also install a gauge there for online visual indication. The gear box is Amarillo make right angled drive. Your suspect in this regard for choking of line seems reasonable. Also, cooling water line for... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
regarding lube oil duplex filtter.
Registered Member Domar, Even if your oil is bypassing the filter elements the outlet pressure should be slightly lower or about the same as the inlet pressure. I would investigate the guages first and then look at the indication points and tubing/piping. Perhaps the outlet is not in error but the inlet reading could be reading lower. Maybe there is a crimp (if tubing) or clog going to the inlet guage causing it to be restricted. If all this fails you could check to see if there might be some other source of... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Failure of Reciprocating compressor.
Registered Member I'd love to Dave but unfortuantely the readings were taken by an outside contractor, and we have since parted ways! [ more ]
Registered Member It would've been interesting to see an example of vibration signature which DID provide an advanced warning before failure occurred? May be some one has one? Although, likely the impending failure would progress too fast to be captured. Stephen, can you post your vibration data? Thanks, Dave [ more ]
Registered Member Rocky R. I can't compare the old pistons to the new ones unfortunately. Yes my first opinion was hydraulic lock also. Klaus K, I assume by hydraulicking you mean hydraulic lock? It's a chiller for a solvent recovery system. The problem with refrigerant getting into the suction line is that there is a superheater between the evaporator and the suction line. The chiller was up to temperature at the time of the failure, so you would assume that any liquid refrigerant would get boiled off before... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Long Time Waveform
Registered Member Bill, with thanks. [ more ]
Registered Member XYZ, Can you post very high resolution (12,800 lines), low Fmax (200 Hz) spectrums? Look for sidebands around 1x, 2x and 3 x which would be indicative of amplitude modulation, or most likely, 2 peaks near 1x which would be the beating frequencies. [ more ]
Registered Member Hi All, Thanks for sharing ideas, as requested by Marty, the file is attached. This pump B is sharing another pump A in one tank and they are nearby. Another pump C is line with other two but it has its own tank. First I suspected beating is being excited by some electrical problem, so I requested to replace the motor with a newly overhauled motor. Despite this, as Walt stated, this not an electrical fault but still worth a try. As two pump must be running and one is standby, I requested to... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Sundyne LMV 312 Oil Leak
Registered Member If possible replace existing lip seal with ISOMag seals. I suggested it to Sundyne about 7 years ago. I replaced it on all my LMV311 pumps. [ more ]
Registered Member A number of thoughts come to mind: The seal may be installed backwards. There is excessive pressure inside the unit. The machined surface that the seal rides on may have a texture (called the "lead") that pumps the oil out. Essentially this is a turned or ground surface where the marks spirals outward relative to the seal rotation. One way to check for lead is to loosely loop thread over the shaft in a single loop with a weight hanging on the bottom. Then check which direction this loop... [ more ]
Registered Member Mr VandenBroek, What type of driver you have been using for this sundyne Motor or Turbine driven? Is there any possibility of developing low pressure zone underneath or near by seal area of your driver to draw oil outfrom gear box? How do you check the seal is leaking from the seal after the driver assembly.Assume there is leak of port to detect(open to atmosphere), I have seen some operators used to plug that hole with solid plug which invites more trouble ? would like to know in your case [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
vibration due to unbalance
Registered Member I'd get a new rotor. Incase this one is weakened by the missing two. [ more ]
Registered Member What about your axial vibration in this case? [ more ]
Registered Member Vinay, I have done the same thing myself, but to a squirrel cage fan having many blades. In my situation, there were enough blades for the fan to keep moving air. But with your situation, on the surface is seems that while you may have balanced the rotor, you have reduced the efficiency by an assumed 25%. I agree with Danny - it's probably a decent emergency procedure, but not a "fix". [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Denver Airport accident
Registered Member Terry O, Since every RCA is evidence-based, it is clearly important to capture all the evidence, as that is a volatile item, and can 'disappear' or be made to 'disappear'. So one cannot but endorse fully what the NTSB Chief said. Such an investigation must be thorough and exhaustive, so it can take many months. There is always the danger though that reports that come out a very long time later may have less impact than one that comes out fairly soon. Vested interests get more of an... [ more ]
Registered Member Politics as usual. But things can look good on paper. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Pump shaft broken
Registered Member Beach marks can all but disappear if the amplitude of cyclic loading is even throughout the fracture process. But the fatigue striations will remain visible under SEM examination. I do see some evidence of striations at the lower right of the first picture (Shaft 1.jpg). Beach marks presented in text books usually show the appearance of fatigue with a single point initiation. This shaft has multiple origins around the circumference. Once the fracture planes join together, the fracture front... [ more ]
Registered Member Thanks all of comments. Kestas, I agree with your comment but why i am not find the beach mark? and why the final rupture not appear close to center of surface? I taked a photo after broken about 2 weeks. Best regards, Weerasak W. P.S. I am not fluent in english, sorry if I use no good. [ more ]
Registered Member The fracture surface shows evidence of rotational bending fatigue with multiple origins around the circumference. Fatigue covers roughly 60-80% of the cross section, indicating that there wasn't a whole lot of bending forces, but enough to fatigue crack the cross section. The picture isn't color-corrected, but it doesn't appear that corrosion played any significant role in this fracture. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Compressor failure
Registered Member Excessive big end bearing clearances may result in impacting but impact occurring in all stages , not very convincing. Regards Akhtar [ more ]
Registered Member Callins, This looks like an impact failure rather than a lack of lubrication failure to me. There is no visiable evedence of high heat in the bearing area. The bearings seem to have impact failure. I would investigate lack of preload on cap bolts, overload on the pistons or excessive bearing clearance. Good luck with your investigation. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing of Scrubber Fan High temperature.
Registered Member The most common cause of high temperatures is incorrect grease or overgreasing as Danny already mentioned. If your ambient temperature is high, then the bearings will run hotter as well and you will need to select a grease suitable for the higher temperatures. For a bearing that size and running speed, the Mobilux EP2 looks like an acceptable choice, but unless the load is high, a grease without EP additives can be used as well. It has a viscosity of 160 and at your higher temperature is... [ more ]
Registered Member No lube expert here, but EP2 seems pretty heavy to me. Have you checked to make sure that tis is the proper lubrication method? Are you certain that over-greasing is not occurring? [ more ]
Registered Member Dear mbensema For type of Bearing Now we used EARING 22215EK WITH ADAPTOR SLEEVE#H315 (SKF) and BEARING TIMKEN TYPE 39243 DEE/39415X (TIMKEN). But we find high tempertaure both brand. For lubrication is grease type MOBILUX EP2. Thank you very much. Ekk [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Taper roller bearing cage defect
Registered Member Mike, Your approach can work well too,but personally I have found I get more information out of the blokes if I show them that I'm there to make the job easier for them, I'm not there to point fingers and blame people. Lets find the root cause as quickly as possible and see what we can do to eliminate it. Hooch [ more ]
Registered Member In direct contradiction to what I said but I'd have to say some really good points Hooch. Thanks. Mike. [ more ]
Registered Member One thing to remember when thinking about this failure, WHAT DOES THE REST LOOK LIKE. I see it this way,the cone/cage is damaged (by a rotational style lock up)but the cup section of this bearing was not able to be recovered. Does this mean that there was excessive clearances as suggested? When looking at the rest of the bearing it does look to have excessive wear and a lack of lubrication (unless the rust marks occurred after the bearing was removed, which I very much doubt due to the... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Dissecting a pillow block bearing
Registered Member Another thought just came to me. If you have access to a good tool shop band saw, you can order a carbide-tipped blade, which essentially grinds its way through the cut. It's slow, but if someone doesn't want to lay out the capital for proper abrasive cutting equipment, this is one alternative. Or you could find a met lab, which could make the cuts for you. [ more ]
Registered Member for us Metabo (in europe) is the name of a German power tools manufacturer. www.metabo.com I know of 'grinding disks' and 'cutting disks' for the respective application [ more ]
Registered Member The surest way to know the difference is to use a grinding wheel to cut one side of a big bearing and then use a Metabo to cut the other. No further research will be necessary. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Root cause of a defective gear surface
Registered Member The damage is too advanced to tell for sure what the root cause is. The lube can easily be checked by a competent lube lab for water content. Anything over 1% is cause for concern. [ more ]
Registered Member The really thick brown sludge is most likely a mixture of oil, water and bronze. [ more ]
Registered Member Kevin, I'm no lubrication expert but the brown sludge alone is telling me there was a lot of water in the oil, as was pointed out above. I wish I could take macro photos like yours. They're very good. Best regards Joe Mc Cormack [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Simple RCA-Thermal and Vibration Usage
Registered Member Whenever I see a problem with bearing used in electrical motor applications, the first thing that pops up in my mind is electrical damage. All too often an electric motor design or installation results in stray currents across the bearing races. This comes from improper grounding or design and results in electrical microarcing from continuous current leakage. This microarcing builds up over time and weakens the raceway surfaces, making them brittle. The fluting you see in bearing damage... [ more ]
Registered Member Hello Jack, Thanks for sharing your success story with the forum. The combination of thermal and VA certainly seems to have helped make a difference on your plant. I know you said the story isn't finished yet and I wondered what your next steps are going to be. I would probably focus on some detailed RCA's and ask why my motors are getting hot, why are the bearings suffering from defects etc..... You may find some common causes associated to all the 40 problem areas you mentioned, that if... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Shaft worn out
Registered Member Correct responses above. The result is called "fretting", leaving a brown deposit on the mating surfaces. In this case it has gone beyond fretting and started to wear the shaft. After evaluating the interference fit between inner race bore and shaft, next time you mount a bearing in this application put a mark on the shaft and a corresponding mark on the inner race. This way, when the inner ring starts walking, you can catch this condition early before it ruins your shaft. [ more ]
Registered Member Kevin, Do you have vibration data associated with the presented cases which could be posted? Was this damage sdiagnosed based on vibration data? Thanks, David [ more ]
Registered Member Kevin, i also had similar experience, these type of occur when we have frequent replacements of brng over the same shaft. so i suggest that brng loctite should be used and while assembling it shd be with brng induction heater so that after getting cooled proper fits will be obtained considering the tolerance limits. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
calculating NPSHa
Registered Member To calculate the losses that Irshad speaks of, refer to the Cameron Hydraulic Data book. Basically, NPSHA is the amount of absolute pressure available on the suction side of the pump above that of the vapor pressure of the liquid in question. data example HTH's BT [ more ]
Registered Member Here is a pretty good site... http://www.mcnallyinstitute.com/11-html/11-12.html [ more ]
Registered Member NPSH AVAILABLE= H (ATMOSPERIC)+- SUCTION HEAD -FRICTIONAL LOSSES IN SUCTION LINE- H (VAP PR. AT PUMPING TEMPERATURE). WHERE H(ATMOSPHERIC)=ATMOSPHERIC PRESSURE=10.33 MTR OF WATER COLUMN AT STANDARD PRESSURE AND TEMP (CONVERT TO RELEVANT HEIGHT FOR THE RELEVANT FLUID). SUCTION HEAD =TO BE ADDED IF IT IS POSITIVE HEAD. IT IS TO BE DEDUCTED IF IT IS SUCTION LIFT. IT IS 79 mBar POSITIVE HEAD IN YOUR CASE. CONVERT IT TO PRESSURE HEAD. FRICTION LOSSES= LOSSES IN PIPELINES , BENDS, ELBOWS , VALVES... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Change management procedure for plant modifications
Registered Member Over here the OSHA requires all changes to be documented and approved. Additionally all parties involved have to be familar with the change if it'll affect them. [ more ]
Registered Member That is a tough one because it takes a culture change. The problem is that it is the hero cowboy mechanics that get all of the acclaim for doing the near-impossible with almost nothing while Production is tapping their toes and waiting. We are not there yet either. But it gets better every year. Our Maintenance Team Leaders and most of the Maintenance Management are very good about making work orders to make approved permanent repairs. If possible, assign the work order to the Mechanic who... [ more ]
Registered Member Trevor, Hmm........now you've mentioned a completely different scenario: emergencies. It is very difficult to write a 'general' procedure to cover all emergencies. Although the plant is down and people would be breathing on your neck, here comes into play the competence of the people involved. Don't let pressure rush you blindly into easy quick fixes solutions without having considerations of what might be the consequences of your actions (or the failure of your fixes)'cos this could be a... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Reliability
Registered Member May I give some comments about Reliability tasks for improvement. First go to bad actors that give impact to operation/production with higher opportunity loss Second set immediate action for correcting them as survival stretegy Third, as you said RCA might be useful to show us the root of problem and correct them as long term prevention but should start with the simply things without spending money too much Fouth, set up 3 year plan for reliability improvement with KPI ' s measurement. [ more ]
Registered Member That is a big scope of work you can do a structure approach starting with criticality analysis for the whole plant or can apply a fast track approach and go after the big problem areas measured in cost, downtime, RCA is not just for saving lives its a process to analyse problems and incidents including reliabiliy issues and failures RBI is for static equipment and vessels RCM is for building startegies based in desired function Hope that helps - buts its a big topic and without knowing plant... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Developement of a RCA Management Policy
Registered Member We have a best practice document and a RCA process/produre document that I will share with you if you send me your email. We are not consultants but practicioners. Bordelonk@zachry.com [ more ]
Registered Member Dave The new TapRooT® book has a whole chapter about making a sustainable program (Chapter 6) plus an appendix (Appendix A) about developing a policy. It also has an appendix (Appendix C) for current TapRooT® users that provides ideas for improving an already existing program. Also, most equipment reliability folks might be interested in Chapter 9, a whole cha[pter about the Equifactor® Troubleshooting methods that are derived from Heinz Bloch's work and licensed for use in TapRooT®. And of... [ more ]
Registered Member Hi Dave, Having developed an RCA process that was fairly successful until the next mill management change, I have a few comments. I concur with RR, a champion of the RCA process is essential. Since you specifically mention the management of an RCA process for sustainability, I am going to assume you already have a fairly solid RCA methodology in place with appropriate triggers for RCA investigations and a process to guide your RCA's from failure through to implementation of RCA action items. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
A Different Root Cause Analysis Experience
Registered Member Re: A Different Root Cause Analysis Experience [ more ]
Registered Member Vee, How can you read my mind so easily ? I agree with you totally. Please do keep in touch. My Warm Regards [ more ]
Registered Member Rolly et al, Amnesty? One should not even begin an RCA program if the intention is to name a person! That is the easy way out - if the purpose is to prevent recurrance, as it should be, then surely the punishment route is the wrong way... Instead of asking 'Why', which often leads to blaming somebody, ask 'How did this happen'? That is much more likely to find a systemic error. Sure, human errors are the biggest contributors (some say all of the contributors), but behind these lie a whole... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
An incident
Registered Member Hi Good RCA story. Yes, a litte thing can make big impact if you ignore. Thanks, Mugu [ more ]
Registered Member Thanks ,Rolly 12 , for rest of the story ! It is good to learn . . [ more ]
Registered Member Even when the PM was removed from CMMS, the user of the winch chain should do the pre-operational check as a safety measure first. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Tube bundle failure
Registered Member My observatio is 1.looks like that the temperature had gone high due(tube side). 2.Thinning of tube due to corrossion at elevated temperaure. 3. Something like Gas formation on shell side(may be nascent hydrogen release) the bucking is inside in all the cases as could be seen in the picture. 4. Has any alalysis been carried on steam quality,Where is the steam inlet in relation to the damage area shown in picture? [ more ]
Registered Member May be bi-metallic corrosion has caused the failure of the joint between tube and tube-sheet which resulted in buckling of the tube inwards due to weight of water flowing through it and its. velocity [ more ]
Registered Member Is it known for sure that the indentations did not exist when the tube bundle was new? I vote along with those who say it must have seen a large differential pressure (lower within the tubes). But I'm not a mechanical guy. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Bearing failure after 2 weeks operation of Horizontal Multistage Split Case Pump
Registered Member Bearings are oil lubricated. Are oil rings also there? Any data available about oil or bearing temperature during running. How the bearing have been installed? Face to face , tandem or back to back (depending upon thrust direction)? Is it a case of reverse loading? Anybody noticed how the bearings were installed at the time of dismantling? May be a talk with the concerned technician who dismantled the bearings after the damage help resolve the matter. also pl. attach a picture of damaged ... [ more ]
Registered Member PumpDoc, 1. Does the pump have a thrust balancing piston and balancing line? Any possibility of flow restrictions in the line? 2. What sort of damage pattern did you see on the bearing(s)? 3. Under loss of suction conditions, can there be sharp (impact type) movements of the shaft? [ more ]
Registered Member Have you got any pictures of the bearing that you can share? [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Lost production/RCA database
Registered Member Guys, I have been completely snowed under for weeks and have not been able to respond until now. By the sound of things, we have developed pretty much what Planty has asked for. Without going into a long email, our company, OMCS international specialises in reliability assurance which involves the integration of the CMMS with maintenance strategy development, data collection, investigation management. I have attached abrief overview. Our idea is to provide a reliability engineer with all the... [ more ]
Registered Member Good day, In the slides attached you can see some screen shoots of the system that was developed in SAP to track the Opportunity losses and Basic root Causes. Regards [ more ]
Registered Member We've been using a system like this for 8-9 years and have seen some merit to it. The current system has a basic product counter and OIT for the operator to input a 3-digit code pinpointing the downtime event. The terminal is loaded with a production schedule as many of our lines have different target rates for different products and to prevent logging DT on a weekend. When a DT evemt is sensed or the line is running @ a sub-standard rate, the operator of the machine deemed the "control... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Failing 600V breakers
Registered Member So did we. There is the template, and an accumulated record of failures, but not much in the way of the FMEA, or criticality analysis. Most of the major systems analyzed do have a better trail, but for some reason this system has limited documentation for future review. This is why I'm trying to build up this material to reanalyze and then move forward with the reviews in the future. [ more ]
Registered Member I thought the RCM process & results should be recorded for continous improvement, review, checking, traceability, auditability, etc. [ more ]
Registered Member Hello Josh, I wouldn't necessarily say we are confident. I have moved the maintenance back to 5 years to prevent these failures of operation. This lubrication causing the slow operation is not taken lightly, and it appears that up to 6 years there isn't a problem. The transfer schemes are checked every two years. (This involves an open and close operation of each breaker to confirm it is functioning.) Before the breaker is removed from service it is operated. This is unfortunately how we... [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Failure of incoming power supply fuse.
Registered Member Hello Josh, seems like you either had a faulty cable, acurrent draw overload or a loose connection. I would also second Jeremy's recommendation of initiating a Thermography program to monitor electrical and mechanical issues (part of your condition monitoring program) irrespective who the vendor is, However I would couple that with motor current analysis or simply with monitoring the amperage draw on startup if you have the capability to do so from your control pannel. Hope this information... [ more ]
Registered Member You should get a hold of Snell Infrared and talk to them about getting a infrared program started. Using thermography is a wonderful tool to find hot spots in you company's electrical systems. I don't know big your operation is but sounds like this would be the way to go. Here is there web site: www.snellinfrared.com We also have a company called Snell Inspections that can come in once a year or every quarter depending what your company needs are. There web is: www.snellinspections.com You... [ more ]
Registered Member Apparantly the nose test..... You get what you use. [ more ]
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Reliability Engineering for MaintenancePosts about Root Cause Analysis
Failure of Under ground CLosed drain Pipeline
Registered Member Akhtar, You are absolutely right. External corrosion is indeed a very common reason for pipeline failure. But it is not the ONLY cause of such failures. These include, e.g., internal corrosion, erosion, weld cracks, impressed current or stray current exits. My point is that we need to know what exactly caused this particular problem, and apply a solution that matches the specific failure mechanism that applies in this case. For example, if stray currents caused the failure, external wrapping... [ more ]
Registered Member Vee, what I said may be a probable reason and certainly not a conclusion. I think, you will not disagree that corrosion is one of the prominent reasons for undeground pipelines failure. One more aspect, I have seen at least 10 failures of buried piping in a period of 2 years. The problem was that the pipeline was not seamless and the lines had been laid out such that the seam welding was around 6 O' clock position resulting in deposition of sludge along the welding thereby further... [ more ]
Registered Member Akhtar, I am afraid I disagree with you. It is important to know why the problem has occurred before proposing a solution. We must gather supporting evidence first, prove our theory about the failure mechanism and only then can we think of solutions. [ more ]
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