Life Expectancy for Electrical Components

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charlie b

charlie b

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Is there a "standard" that states how long electrical components should last before exceeding a reasonable life expectancy? I am talking about "major" components (e.g., switchboards, panelboards, transformers, motors, conductors and such), not the "small stuff" (e.g., switches, relays, luminaires, and such). I have generally thought 40 years was reasonable, though we have all seen things far older.

I am working on a project that will upgrade the main service and some downstream panels for three old buildings. We are saying these items have exceeded their useful lives. But the accounting folks are challenging us to produce a standard that backs up our claim that replacements are needed.

Any ideas?
 
I don't see age alone as a criteria for replacement. Parts don't become worn just from sitting there.
 
I found this:
1652461906568.png
I think if I were a production facility I would perform PMs on all of the equipment and expect 20-25 years.
 
Wow, if most everything has a service life of 20 years or less, I guess we have exceeded that by twice here and more, and still getting along fine. I guess they should replace everything, including me.
 
This is a tough question with a lot of variables. For example, you want to add feeders, etc to existing and the SCCR and AIC rating of the existing may be unknown. or unrated.
 
Those expected lives will typically be based on 100% of the rated load at the standard ambient temperature. Reducing the load or ambient temperature will increase the expected life. I think I remember hearing that every 10 degrees below the rated temperature rise a transformer operates at will double the expected life.
 
infinity said:
20 years is far too short for things like circuit breakers.
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My parents' house was built in 1961. As wretched as FPE breakers are, the ones in their panel have functioned when needed, so, just over 60 years now.
 
mayanees said:
I found this:
View attachment 2560598
I think if I were a production facility I would perform PMs on all of the equipment and expect 20-25 years.
Click to expand...


The IEEE working groups establishing these guidelines have significant participation by equipment manufacturers, so that might have some influence on the numbers. ;)

That said, I agree with mayanees that for production or other critical applications these guidelines would be useful.
 
texie said:
This is a tough question with a lot of variables. For example, you want to add feeders, etc to existing and the SCCR and AIC rating of the existing may be unknown. or unrated.
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Yeah that's a big one. I have done several projects replacing 50-year-old square D switchboards and QO load centers. Although overall the stuff was mostly totally fine,. Often all it can take is one bad obsolete main breaker (had this twice with 1200A PAL frames), under dutied or no series ratings, and it's going to often be cheaper to just replace it than bring it up to snuff (if it can even be done), especially if you got to pass like a plan review or inspection.
 
Another aspect of this is changing technologies. My field was mainly variable speed drives. An example was Leonard Speed Drives. In my early days these were being phased out in favour electronic systems. The Leonard Drive systems were were not an issue of life expectancy - they had more major parts and their efficiency was poor compared to solid state drives. That evolution continues apace.
 
If the switchboards are all fused, the accountants could be right that the lifetime is not limited by time. I would be looking for heating and discoloration of the copper but it could still have (not limited) useful lifetime. QO branch circuit breakers, old ones, I would have full confidence in.

Old feeder breakers in the switchboards, there would be no assurance they will trip well when they have to, especially compared to modern electronic trip units. They would be (advised) to have the old breakers tested, then the testing could get too expensive, and they would be (advised) saving money on the entire round trip, value over the long term, by going new, compared to testing the old breakers and living with the other unknowns.
 
charlie b said:
Is there a "standard" that states how long electrical components should last before exceeding a reasonable life expectancy? I am talking about "major" components (e.g., switchboards, panelboards, transformers, motors, conductors and such), not the "small stuff" (e.g., switches, relays, luminaires, and such). I have generally thought 40 years was reasonable, though we have all seen things far older.

I am working on a project that will upgrade the main service and some downstream panels for three old buildings. We are saying these items have exceeded their useful lives. But the accounting folks are challenging us to produce a standard that backs up our claim that replacements are needed.

Any ideas?
Click to expand...
I think you are going to have a hard time finding a standard somewhere that says a specific electrical component only lasts for X number of years.

As often as not, people just leave the stuff alone until forced to replace it when it fails or they need to upgrade due to increased loads and the old stuff is not available anymore or is no longer suitable.

I would want to take a close look at what is there and have someone competent come in and test it all to make sure it is still functioning in accordance with modern safety standards.
 
The US military has a “standard” of sorts for electronics. But what stands out is the section that says that 60% of the life expectancy is determined by environmental factors alone! That one single statement all but invalidates they entire standard in my opinion. Think about it…life expectancy has very little to do with product design or manufacturing.

Also there are extensive guides put together by a consortium of nuclear plants on life expectancy. They have hundreds of pages of pooled data on switchgear breakers. It is some amazing work. Each one has some very typical failures that I also happen to see in the field. You cannot make wide sweeping generic statements about anything. Things are wildly different between the various GE lines, Amptectors, Square D lines, and ABB.

Even with something as “simple” as a power distribution transformer conventional wisdom says that oil filled transformers last much longer than dry but that hasn’t been my experience. IF you do the annual oil testing and follow recommendations and keep it away from corrosion and don’t overload it excessively you can get 40-50 years out if an oil filled transformer. But fail any of this and 20-25 years is not unusual. With dry transformers there are several on board dragline excavators built in the 1970s that are still running fine despite exposure to mining environments in less than ideal service.

Consider for instance induction disk protection relays. Everything about these screams low reliability. Don’t get me wrong calibration drift is awful. Yet many have been in service for 50 years. In the 1990s we saw the rise of analog solid state protection relays. Everything about the design would seem to suggest it was a step up. However within 10 years the failures started to appear and the reliability was far worse than the old induction disk relays. Then microprocessor relays which one would think would be even worse came out yet have much lower failure rates. The only conclusion we can reach here is you can’t necessarily predict reliability based on design like the military design manuals.

The “predictive” crowd would have you believe you can reliably predict failures ahead of time. I would say this is partly true. My company makes good money on both predictive maintenance and remanufacturing. But the concept here is that you can predict and make repairs reliably. That is simply not true in practice. Plenty of things slip through “the net”. And as we all know you reach a point where you are just throwing money away on something that is well beyond useful life. This flies in the face of theoretical infinite life according to the predictive maintenance crowd.

Another major concern is technological life. When equipment goes obsolete, parts availability is a huge problem. For instance you can continue to repair old GE AK breakers, Powerbreaks, and Limitamo starters but the repair parts are also 30 years old, just as old as the equipment. Reliability of “new” is just as bad as the parts in service. In other words it’s a lost cause.

Nowhere is this more apparent than VFDs. The power components have a 10 year product life cycle (availability). The drive manufacturers in turn adjust the expected component life to 100,000 hours (10 years) and obsolete everything in…ten years. It can be shorter. I have a customer with a terrible hydrogen sulfide issue that only gets 36 months and others with nearly perfect HVAC pushing 20+ years. Durham county, NC had a couple early 1990s Westinghouse VFDs that finally failed almost 30 years later. That’s impressive!

So some of those recommendations are based on planned obsolescence. Can you exceed them or fail to meet them? Yes. So it’s a nice long term planning/budgeting target so you can estimate capital expenditures over time but individual failure rates are not nearly as predictable. As I tell customers that manage to maintain equipment well past ifs expected life, it doesn’t “owe you anything”. By that time the accountants should have easily amortized the value to zero. So when you start to see failures, even crazy ones like all the plastic falling apart or alignment issues and goofy corrosion issues, it’s time to do deep diving as far as repairs or just replace. But I would not suggest replacement based on age alone. I’ve seen far too many cases of old equipment that continues to perform at close to double it’s expected life.

Might want to look at Nolan and Heap. So these two guys started studying failure rates and curves. At the time the belief was everything follows the “bathtub curve”. At first you get a lot of infant mortality issues from things like installation errors and factory defects. After that equipment performs at low failure rates until it is worn out. If everything followed that you could just do an “overhaul” or “replace” based on age or say number of cycles of a starter. Nolan and Heap found in practice a half dozen different failure patterns. Worse still most electronics follows a true random failure pattern. This means “overhauls” don’t work. There is no “clock” to reset. Testing and repairs to detect hidden failures becomes your best option, I agree with their conclusions but aging is a definite factor too.
 
charlie b said:
Is there a "standard" that states how long electrical components should last before exceeding a reasonable life expectancy? I am talking about "major" components (e.g., switchboards, panelboards, transformers, motors, conductors and such), not the "small stuff" (e.g., switches, relays, luminaires, and such). I have generally thought 40 years was reasonable, though we have all seen things far older.

I am working on a project that will upgrade the main service and some downstream panels for three old buildings. We are saying these items have exceeded their useful lives. But the accounting folks are challenging us to produce a standard that backs up our claim that replacements are needed.

Any ideas?
Click to expand...
If MV breakers are serviced every year should get 50 years out of them. At the large company that I retired from they had over 500 VFD'S and was lucky to get 20% reach the 20 year mark for two reasons. Can no longer get replacement boards after 8 to 10 years and read that capacitors have a 70,000 hour life span. On small drives of 3 to 10 HP now considered throw aways when they stop working.
 
garbo said:
If MV breakers are serviced every year should get 50 years out of them. At the large company that I retired from they had over 500 VFD'S and was lucky to get 20% reach the 20 year mark for two reasons. Can no longer get replacement boards after 8 to 10 years and read that capacitors have a 70,000 hour life span. On small drives of 3 to 10 HP now considered throw aways when they stop working.
Click to expand...

Don’t care how often you service MV breakers. The FR3 parts start to break down at 25-30 years. Puffer tubes fail at 10 years. Vacuum interrupters are claimed 20 years. Any caps such as snubber circuits common on early VCBs fail at 8-10 years if electrolytic. Some are approaching 30 years and quality has improved but there are no guarantees. Plus use has a role to play. Even GIS mostly claims 40 years. Service it at 10 and 30 years, replace the mechanical parts once at 20 years, discard at 40 years.

VFDs are designed for something like 70-90% to last 100,000 hours (11 years). Capacitors are 8-10 years if electrolytic. Metal film caps have almost indefinite life but are 300% more expensive and 300% larger size. But even if you get past this, silver solder hits a brick wall on joint failure at 12-15 years in power electronics.

BUT in high end high dollar systems there are alternatives. Semikron makes IGBT modules used extensively in transportation systems and utilities which are sintered (welded) with much larger IGBTs (run cooler, increase the MBTF) and metal film caps. This pushes expected life out to 20+ years. Does it work in the real world? I’ll let you know in 10 years but so far it’s looking good. The big disadvantage other than cost and size is that the infant mortality on these things is horrendous. It’s around 3-5%. But six months out all the failures stop and changing a module takes 10 minutes.
 
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