You are right about Age and condition being directly dependent on each other. This is the reason why the condemnation is done only on Age-cum-condition basis. The locos' calculated lifetime is not a particular number, rather it is spread over a range and the actual point of failure only depends on maintenance, kind of operations that locomotive is handling etc. And if you look through the document you have shared, you'll notice that each and every component of the locomotive,right from the control stand to the traction motors also have a codal life. By the time a loco is condemned, except the shell and the bogies, almost all of the other components inside would have been completely replaced at least once. That is why the codal life in the document is mentioned as 'Average lifetime in years'. It is not that beyond a particular age, a loco will fail compulsorily. The...
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rated lifetime might be 30-40 years. And even after 40 years, a locomotive might still be in excellent condition based on the build quality, usage conditions and maintenance status ( Any engineer will attest to this).
In the specific case of the WAM4 ( I keep harping on this because several people seem to think that since it is an 'old' locomotive it must be 'very inferior' to the new ones) it is a very capable locomotive. Very good tractive effort (higher than P4, almost on par with P7), can easily handle 24 coach loads ( it is a mixed class loco designed to haul freight as well so the puny passenger rakes are not a problem for this) and most important of all, it's ruggedness. Throughout the WAM4's lifetime in IR, it has been mentioned countless times by IR engineers, general literature on locomotives and several RF's about the extreme ruggedness of this class and how well it is suited for Indian track conditions. Even after 35 years of service, they have a similar failure rate as the latest batch of locos (both 3 phase and conventional ). There are no safety concerns, in general,on running trains with these locos ( if there lapses in maintenance, even the most advanced locos will have safety concerns).
You have mentioned correctly in another blog post that " Just because these can do the job, we cannot be stuck with them till eternity". At the same time, they are not restricting progress on IR in anyway. CLW is improving it's 3 phaser count every year and more and more trains are being run with 3 phasers these days. WAM4's can comfortably haul trains with reasonably aggressive schedules. Let them continue with their job until the replacements are ready. There is no need to scrap 170+ locos in a short time (especially when they are performing well). If all of them are scrapped immediately, where will IR get the extra locos to replace them from? Current WAP series production is at best 60-80 locos a year. Better to scrap these locos as and when new locos are available or if their reliability degrades.