 In the last class, we had talked about the different techniques of maintenance available to us namely the preventive maintenance, predictive maintenance and breakdown maintenance. But we must be always wondering now, well in a large plant which maintenance is to be used where and to answer this question we need to look into this lecture on failure modes, effects and criticality analysis. Well, failure mode effects and criticality analysis as you will see has many applications particularly in engineering design in the process design. But we will see how this FMECA or known as FEMICA can be used to decide on which maintenance strategies to be used in which kind of machine in the plant. Well, to define FEMICA it is a methodology to identify and analyze all potential failure modes or the various parts of the systems. You know, the system could fail in many different ways. Failure can be in many different ways. So we will see how this FEMICA is going to help us decide on which is a critical failure, which is a failure which is not critical in the sense it is not going to affect the downstream operations that much compared to critical failure. So deciding on that we can kind of rank I will say within quotes the failure. So once we have ranked the failure, we can use different maintenance strategies. Well, we will see that how this failures have different effects on the system and how we can avoid the failures to mitigate the effects of the failure on this system. So in a nutshell, FEMICA is going to answer, give us answer to all these different questions. We have in terms of the severity of the failure, in terms of the frequency of occurrence of the failure, in terms of whether a failure can be detected at all or not. Well, as I was telling you, FEMICA is just not used for maintenance strategy but also to decide on whether my design has an alternate, whether my design is robust, the design has a higher reliability and whether all the effects of failure have been considered while designing the system, try to establish the different potential failure modes and their severity. Sometimes we can also decide on planning schedule for the test equipment and the planning test procedure to detect this earlier failures and of course we need to have documentation for future references in the sense, if the planned system needs to be improved in terms of its operation, in terms of its maintenance, the FEMICA worksheets or FEMICA numbers will help us do that and of course, you know, provide a basis for maintenance planning. As we know, we have discussed that there are three types of maintenance, preventive, predictive and the breakdown. Other words for preventive was periodic, CBM and reactive. In the last class, I had told you that through that economic analysis that sometimes CBM is much economic in the long run than preventive but because of the high capital investments involved in CBM, we always cannot put high capital investments for all machines in CBM. So we have to decide by FEMICA which kind of maintenance or which machines need, which kind of maintenance in the scheduling. So this will give us a quantitative estimate or a ranking as to which machine needs to be done with what kind of maintenance, excuse me. Well the FEMICA should be initiated early in the design process, we are able to have the greatest impact on the equipment reliability, I mean, if a certain amount of maintenance has already been initiated in a process or in a plant or in a machine, we need not change its maintenance schedule but had we done a FEMICA analysis on such a plant, we would have known from before that such are the critical machines and we need to be careful about their maintenance. For example, I will give you, I will illustrate this to you through an example. For example, let us talk of a cement plant. You know in a cement plant, there is a large rotary kiln and this diameter could be about 2 meter okay and this could be about 20 meters long kiln and this kiln rotates at a very low rpm of the order of 2 to 3 rpm okay and then we have a motor which rotates at about 1440 rpm. So to bring about a slower reduction of speed of the skill, this requires for a large gearbox and then there is a pinion gear which measures with a ring gear or a bull gear is a ring gear and there is a pinion gear, pinion on this gearbox and then what happens, there is a feeding mechanism of the raw material which goes here and then they get ground here and there are very hard grinding media here and then finally we will have the cement powder which can be packed and sold off. This is in a nut cell, a cement plant or the mill. If you see the most important elements are of course the motor, gear box and the mill okay because you know as you know standard motors run at 1440 rpm the mechanical speed and then we have to bring about a large speed reduction from about 1440 rpm to 2 rpm. So imagine in such a plant if you are dependent on the daily production of cement powder or cement from the raw material of limestone, gypsum etc. Then if this gear box fails for some reason, if there is a failure in the gear box no matter what because this is a critical component in the plant, if this gear box fail this mill is not going to rotate and then we will not have any cement. So this is going to critically affect the flow or the process or the output or the productivity of the plant. So I have to be very careful in the gear boxes maintenance. So we need to evaluate this gear box around the clock, CBM has to be done on this gear box to evaluate it around the clock. Now the question is for this plant if I was to list down the critical component one is the motor other is the gear box and the third is the cement mill. I cannot afford to have any failures in this because they will affect the process or the process by which I have my final product as the cement. Now I need to have obviously a robust design, I am sure the designers would have done a Femica study to find out a robust design of the individual components but for the maintenance question is where should I put CBM in this motor gear box or cement mill. Now the question I will pose to you is suppose only one critical machine is to be selected for CBM which one should be that. Well many of you will come up with an answer of motor, many of you will come up with an answer of gear box and many of you would be of cement mill. Well you can have your own reasoning for that but you will see through the study of Femica that I can easily come up with a number and which will rank these two or three items motor gear box and the cement mill in terms of their severity or in terms of their criticality and importance. So had I done Femica study on the entire cement plan right from the beginning I could have planned on which equipment needed to do, needed to have a CBM and that is what we are going to look into in CBM and for a simple cement plant case it was very important, very easy for us in fact when we had a motor gear box and cement mill. But imagine if this was to be carried out in a large steel plant there could be many critical processes. So Femica must have to be carried out in all these different processes. Well what are the different types of Femica? One is the design Femica it is used to carry out to eliminate failures during equipment design taking into account all type of failures during the whole lifespan of the equipment. Well we are not concerned with design Femica right now because you know the designers would have already taken care of this Femica while doing their design of the equipment. But the next is the process Femica for example it is focused on how the problems are stemming and how the equipment is manufactured, maintained and operated. So once the equipment has been designed and put in place we need to understand what is the problems for different equipment in terms of its manufacturing, in terms of its maintenance and that is what sometimes something we are going to focus in through another example. And of course in a large system where there are many assembly lines people needs to see the system Femica as to find out bottlenecks in the assembly process and the entire production line. So there are different types of Femica people use according to their needs and to summarize one is the design Femica that is the process Femica and the system Femica. So how do we do the Femica? So there are certain system prerequisites and then one needs to know the entire structure of the system and then provide the failure analysis and prepare the Femica worksheets and the team review followed by corrective actions. The question is how do we do as I was telling you we have to assess the risk, risk or criticality of a process or an equipment and basically come up with a number or otherwise a rank for a particular process or an equipment so that we can decide on you know which machine needs to be having which kind of maintenance. So in the Femica prerequisites we need to define the system to be analysis again if you go back to the case of the steel plant should I do Femica on the entire steel plant or should I do the criticality analysis on the different process of the steel plant. Again let us through take you through an example say of a steel plant okay. The many critical process one could be the raw material handling system in raw material handling systems you know I will not go to the details of the raw material handling system you know basically the raw material handling system for the iron ore for the limestone for the cooking coal etc okay and then the next would be the blast furnace of course blast furnace requires its cooling system its air handling system is again its material handling both the raw material and the molten metal then we will have the iron removal and handling system once the pig iron has been made we have the steel melting shop sms sms once you have the steel we will have the depending on the products we could have rolling mill or we could have forging processes and then we will have the finished product. So if I was to have the different critical areas of the steel plant I have just listed them that these are about 6 different processes they all could be equal important in a steel plant but in the individual processes if I was to find out a criticality of an individual process I need to do Femica on each one of them okay. So if I say that I will only focus my attention in the blast furnace well that is good and that is what I meant by defining the system to be analyzed if I decided that I need to do Femica on the blast furnace only in a steel plant well good but then we now need to study all the system parameters of the individual blast furnace that could be the again the blast furnace you know the blast furnace material itself the blast furnace control the blast furnace operation the blast furnace maintenance all these are the individual components of the blast furnace same as to for the rolling mill the rolling mill the process the motors the material handling system etc. So if I was to focus on any one critical operation or critical path I could decide on any one of them so once I am clear about the system which is to be analyzed I will now go into the individual system kind of find out its drawing specification schematics etc and then so that we know its functional description as well and another is it is best if you do maintenance on an equipment to know its past history in terms of the in terms of its information from the operator from the design personnel from the component suppliers etc. So once such information in a nutshell all I need to do is if I was going to implement Femica on an individual critical component I need to know its entire specifications its entire operation from the right from the start to the end and know whether the functional description of each of the components and the also the past history of its performance its maintenance its feedback from the operator from the management on the same system once such a prerequisite is available to the person or persons who are doing Femica on such a system they will be well equipped or well informed to make a judgment about the criticality of that equipment and that is very essential and when I talk about this person or persons I do not limit it to only the technical analyst or the technicians or the professional on that equipment but it could be anybody who has some say you know right from the bottom most tire on the plant right from the workers to even the executives in that plant or the critical on the further critical process. So all of them can rank this process as for what they feel in terms of few numbers and we will see how this numbers can be taken into account to evaluate the performance of such a plant or an operation. So we will divide this system into manageable functional elements just like you saw the example of the steel plant where even we divided the steel plant about 5 or 6 different functional elements and so on and sometimes to give a clear picture to the Femica team it is good to have a Femica functional block diagram and the system analysis should be done on a very high level as possible because this gives us a view to look from the top down and so that we do not leave out any component by an ominant inner inadvertent error and so on. So this team review and risk ranking is very very important for doing Femica and they develop a risk matrix or what is known as a risk priority number or P n and this is the most important number out of Femica is I have to find out a number which relates to the critical path or process well it may not be critical till you find out its r p n number so I will tell you the important processes for which you have to find out the r p n numbers and question is how do we do or what do we do to find out this r p n numbers for different components. So this is perhaps the most important slide in this lecture that this r p n number actually depends on three parameters one is the O which is the rank of occurrence of the failure mode that means how frequently this system is going to fail is that kind of a number O and another is the severity of the failure if there is a failure in this component how severe is it is it going to affect the other components in my process so that is how we give a number of severity and another is the detectability it is the rank that the likelihood that the failure will be detected before the system reaches the end user or customer. If I am not able to because you know we always if I multiply this three numbers r p n is equal to O times S times D so the lower the r p n number the better it is the lower is the risk so if a fault is not being able to get detected then I will give it a number that it is very high see if your fault can be detected in a because we are we will focus this for maintenance only in our understanding right now if a fault has occurred and I cannot detect it it is dangerous so the detectability if I can detect it I should give it a lower number if fault can be easily detected otherwise if fault cannot be detected and then if I give it a lower number it will have a consequence in the sense that a fault has occurred in the system and I cannot detect it and that should not be my maintenance strategy well the occurrence of a fault is I mean I would not like that a fault to occur but if a fault is occurring how frequently it is occurring if it is occurring at a very high rate I need to give it a higher number but then if I was doing a robust design of the component this occurrence could be brought down if somebody says you know in a component I have repeated failures well there could be many reasons for that one could be a bad design design is not robust another is that I have to make a better design so that the occurrence of failure is a minimum so that is the most important parameter or rather one of the most important parameters while doing Femica on a system if the system is designed in such a manner that there are too many frequent failures either the design is bad or we are not doing something we have the functionality is not proper or we are not operating it within the specs and so on so if our occurrence of failure is high it is the over number of the this number for RPN will be high and severity is another failure mode where we rank the severity suppose a failure has occurred is it important that the this severity or this failure is not going to affect my system if it is not going to affect my other processes or system I can give it a lower severity number okay and I have just explained to you about the detectability the if we give it a lower number if the fault can be easily detected so in a plant or a process if we can find out the critical parameters and specify their OSD numbers we can give them the RPN or calculate their RPN numbers and another thing which is to be done is all these numbers are given a rank 1 to 10 so the highest value of RPN could be 1 and sorry lowest value could be 1 in a highest RPN could be 1000 so any number which has an high RPN number is more critical and the maintenance efforts for that system or processes has to be the best and perhaps we can apply CBN for systems which have high RPN numbers so how do we calculate RPN numbers or risk priority numbers question is we can rank this O from 1 to 10 severity from 1 to 10 and detectability from 1 to 10 now there are many different processes and we have your FEMICA workforce which could consist of workers, engineers, designers, maintenance personnel and management so you can for a particular process you can pull out members from such different functionality group in your plant and ask them to evaluate the process a particular process where you have to establish a maintenance scheme ask them to give an individual RPN number or estimate an RPN number and you can come up with an overall RPN number and then rank them rank their processes. Now question is RPN has no units it is just a number RPN is just a number with no units so RPN has no clear meaning and how the ranks OS and D are defined depend on the application and the FEMICA standard that is used. For example the OSD in an RPN can have different meaning for different FEMICAs and it is since it has no basis of any it is very subjective it is a subjective evaluation reflected in numbers another definition another functionality subjective evaluation put in numbers okay. I will give you another example how people do FEMICA for example because this is a subjective evaluation it does not have units like 10 kg or 10 Newton so this RPN for a process for example I have two steel plants an RPN for one steel plant blast furnace is 780 the other steel plant blast furnace RPN is 500 I cannot say that the 500 RPN number means a better blast furnace I cannot say that because there is no clear meaning of this number from plant to plant because it is just to evaluate just to rank a process or a equipment in terms of its three parameters OS and D so there is no basis but in a plant or in a process where people have the familiarity with all the process and equipment they can decide on the ranking and then we can evaluate or put our efforts more efforts to the RPN where the RPN number is high and less maintenance efforts to the processes or equipment where the RPN number is low. I will give you another example just you will understand so let us take the case of a in fact this pen by which I am writing is a good example in fact if I take the case of this felt pen here felt pen if I had a manufacturer who is to manufacture felt pen he wants to do a FEMICA to evaluate the most critical component in his manufacturing processes do that let us assume the important components in a felt pen and this could be for example one could be the plastic cap with a short clip maybe number 2 is one is the felt with the writing nib writing tip the other is the body of the pen and of course there is a process of assembly of the pen. So in a manufacturing company where we have to produce a felt pen say for example if there are 4 different manufacturing operations one is the cap with the short clip other is the felt with the writing tip third is the body of the pen and fourth is an assembly line where we have to put all this different components together and make this pen the question is what which is the most critical component so that my maintenance efforts efforts could be put to the components which are the most critical. So I will list down this 4 components here in terms of OSD and calculate the RPN numbers so one is I will just list them briefly cap other is the felt tip and third is the body fourth is the assembly. Now let us try to give the ranks of OSD and RPN to this so cap if a cap you know how from a rank of 1 to 10 the failure of the cap you know caps are very robust at most the clip the clip may fail and it can occur out of the felt tip body and the assembly perhaps I will give it a rank of 2 felt tip it can become dry that would be an it can happen periodically for example you will have the pen for a lot of time and not use it the pell so this occurrence could be 3 or 4 body of the pen may not fail there could be an occasional crack and so I will give it a rank of 1 and then the assembly of the entire the pen once assembled make become loose and this occurrence is also very low and could be give it a rank 2. So the numbers I gave 2, 4, 1 and 2 this were very judgmental this were very subjective and I am sure if I ask each one of you to give your own rankings you may come up with a similar ranking as well. And next is severity of this failures now suppose this cap has failed how severe is it or how important is it to affect the failure of the pen as a writing media well this if the cap fails it will perhaps not influence or affect the performance of the pen that much so I will give a lower number felt tip yeah the felt tip fails it is very severe and it is going to affect the performance of the pen. So I should give it a very high number and the body fails in a felt pen the body fails it is not that severe because the ink is not going to leak out but suppose I had an you know the old days the fountain pen where we used to put ink inside the body and the body was used as a container of ink and if that failed it was severe in the sense that it would stain everybody but in the felt case of case of felt pen it is not that severe so I will give it a rank again of 2. Assembly of a felt tip is also very sorry the severity of the assembly yeah if the assembly was not proper the pen would not work so I will give it a high number now if you recall to my few slides earlier I told detectability is given a low number if fault can be easily detected obviously if there is a fault in the cap we all can see it from outside so I can give it a low number felt tip if there is a defect I cannot see it I cannot observe it unless I write it so I will give it a high number body if there is a crack I can see it while it can be easily detected so I will again give it a no number assembly if it has failed it can be easily detected so I will again give it a low number. Now let us calculate the RPN numbers of this so this is a 4 this is how much 49 36 times 7 7 3 21 plus 3 242 check my calculations and this is 4 and this is about 14. Now if you just do this calculations here you see the felt tip stands out among the cap the body and the assembly so in a pen manufacturing operation the according to the Femica analysis we just concluded the felt tip is most critical in its manufacturing so we can say that the machines which are used to manufacture in the felt tip have to have the best kind of all round maintenance and you see through this simple example we could very easily find out that how Femica is going to help us establish the maintenance schedule to be used on a different machine. So once we know the RPN numbers we can decide whether a CBM or condition based maintenance needs to be done to the most critical company so like in a steel plant now we can decide on the different processes and then try to establish RPNs and then find out in that in which process CBM has to be done in which process just a breakdown maintenance has to be done in which process a periodic maintenance is to be done. Now sometimes in the review of the Femica workshop once we have completed the Femica workshop whether we have to see whether what are the systems drawbacks whether it is acceptable not acceptable whether it is feasible to reduce the risk by reducing the likelihood of occurrence of the failure. So we have to work on the parameters which will reduce the occurrence of the failure so that will bring down the number O, reduce the effects of the failure that will bring out the number S and increase the likelihood that the failure is detected before the system reaches the end user because as a manufacturer if I am not careful that I cannot see or detect the fault easily then it is no good because you know if it goes to the hands of the person who is the end user and the faults cannot be detected but the faults keep on happening and that is not good design. So we have to ensure that the we have to make the D number the detectability low so that the low number is given in an RPN analysis the faults can be easily detected. Once such an analysis can be done we can then have established Femica as a tool to identify the different processes equipment so that more care or more efforts in maintenance can be taken in such equipment or plant. Well how do we reduce the risk? We can make design changes we can engineer certain safety features we can put safety devices warning devices and of course have the right procedure and training in place such that the RPN numbers criticalities can be reduced. But as a maintenance engineer we sometimes are called to maintain an equipment which has been already designed but like we did Femica for maintaining a plant or an equipment Femica could very well be done in the design stage as I was telling you right in the beginning by the designer itself to find out the different processes different factors by which the criticality of the equipment could be reduced so that there is enough robustness in the designs or the occurrence of failure is reduced. The process is laid out so that the severity of the failure is reduced and there are features in the system for example putting warning devices safety devices etcetera in the system so that the faults can be easily detected and that would constitute in a holistic manner a design which is very optimum a design which is maintenance friendly a design which is which brings down the number of failures and brings down eventually the loss of production. So to conclude in this design engineering the Femica worksheets are used to identify and correct potential design related problems in manufacturing the Femica worksheets may be used as an input to optimize production the processes the acceptance testing and so on but what we look today was in the maintenance planning in the maintenance planning the Femica worksheets are used as important input to maintenance planning for example as part of reliability centered maintenance maintenance related problems may be identified and corrected. So once we know that the maintenance is critical we will do CBM in such a maintenance once we know that it is less critical we may decide on whether to have a preventive sorry periodic maintenance or a breakdown maintenance. So we will talk about Femica in the future classes when we apply it to different systems and then we will see how Femica can be used how the RPN numbers can be estimated and how as a designer also we should have an insight how that RPN numbers could be reduced. Thank you.