First question (newbie)

Hi, Let me get these newbie questions out of the way, I know they are painfully naive but you gotta start somewhere!

Just exactly what is it that the maint techs do in a typical plant? I am confused. Are they "electricians" are they "techs"? I thought electricians ran wires and installed electrical stuff. Have they gone all high tech these days?

I went to an interview at a pipe factory and my resume didnt have anything about PLCs or working in plants. They seemed to be impressed with my experience but when I got there the 20 minute tour (with two shutdowns) centered on PLCs, and I admitted I was unfamiliar with them but could quickly learn. No job offer.

What was strange to me(Im an experienced electronics tech(no PLCs)) was there was no electronics bench or any test equipment except for a handheld fluke! WTF! There was all this high tech microprocessor controlled equipment like welders, giant chop saw (Italian made) and inspection equipment, and they maintained it all with a friggen fluke?

They used the fluke to take periodic current measurements inside the PLC cabinet because they were having some sort of issue with the saw. Well, thats better than nothing, but you cant stand there all day and wait for an abnormal reading. A periodic measurement might tell you something, but havent these guys heard of multiple channel digital storage scopes or all the data aquisition equipment that could monitor that and a lot more 24/7 and store it you? Cant you also use PLCs for that within limitations of sampling rates? Dont they think 2 unscheduled shutdowns in 20 minutes is well, bad?

Thats right, my ego took a little bruise. Waaaaaah!! Thought I had that job in the bag, and they probably thought I was ignorant of PLCs (I was) and thus of no use.(I disagree!)

There is no way I could accurately diagnose anything but the most obvious problems with just a fluke,on a PLC or whatever. especially the kind of intermittent failures that might trigger a shut down.

What I think was going on and might be commonplace for all I know (I dont work in plants) is that plant electricians learn PLCs to a basic level and are considered qualified to maintain the line. Maybe they have an engineer at the plant as a technical resource and farm out all the actual fried boards and such. The maint dept apparently just springs into action during the frequent shutdowns, does some quick band-aid and thats considered a repair?

Im not knocking electricians, but dang, I could accurately diagnose all the electronics in the plant and find the root cause of the shutdowns so long as I had all the manuals and schematics and the proper test equipment, once I get up to speed on all the PLC programming and applications. Is it a union thing? No techs allowed? Do all plants subcontract out all the electronic repairs? Would I just be a board swapper?

What about "instrument repair" techs, do they just swap out faulty devices and install and calibrate new ones? Dang, they sure make good money at any rate.

Dont get me wrong, Im just trying to find out things to help my training and job search, and I am currently dumb as a post with PLCs anyway, so I wouldnt even know which board to swap! If all I have to do is swap boards for 30 bucks an hour, then I know that just a crash course like on this site will suffice. (and pay for itself before lunchtime if I get a job!)

I dont know PLCs, but Ive repaired hundreds of I/O boards, DAC and ADC boards and Ive dealt with sensors, encoders, servos, and so on various equipment but not on PLCS. Now how can I parlay that into a job in a plant that dosent have to know that a few weeks ago I didnt know what PLC even stood for! Ive gotta talk the talk at any rate! Just be honest? As soon as "I have never ever touched a PLC" comes from your lips, your future high paying plant job is in great danger! LA is not silicon valley, and plants dominate the job market.

Thoughts? TIA

carwashblues said:

Hi, Let me get these newbie questions out of the way, I know they are painfully naive but you gotta start somewhere!

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Welcome to the forum. You have come to the right place.

carwashblues said:

Just exactly what is it that the maint techs do in a typical plant? I am confused. Are they "electricians" are they "techs"? I thought electricians ran wires and installed electrical stuff. Have they gone all high tech these days?

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Some places have their maintenance techs divided into groups like mechanical and electrical. Some places have "multi-craft" techs who do electrical repairs as well as mechanical jobs including all trades. Automation is taking over most industries, but there are still some low-tech plants out there, I am sure.

carwashblues said:

I went to an interview at a pipe factory and my resume didnt have anything about PLCs or working in plants. They seemed to be impressed with my experience but when I got there the 20 minute tour (with two shutdowns) centered on PLCs, and I admitted I was unfamiliar with them but could quickly learn. No job offer.

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Better to be honest than to get into a job where you'd have to wing it and might cause all sorts of havoc during your on-the-job "training". No doubt you can learn a lot, and, with your background, probably very quickly, but I would continue to be honest at future interviews.

carwashblues said:

What was strange to me(Im an experienced electronics tech(no PLCs)) was there was no electronics bench or any test equipment except for a handheld fluke! WTF! There was all this high tech microprocessor controlled equipment like welders, giant chop saw (Italian made) and inspection equipment, and they maintained it all with a friggen fluke?

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Yep. We don't fix board in the plant these days, we are good at finding the faulty device or module and quickly replacing it. Many of the boards can't economically be repaired anyway with multiple layers and surface mounted components.

carwashblues said:

They used the fluke to take periodic current measurements inside the PLC cabinet because they were having some sort of issue with the saw. Well, thats better than nothing, but you cant stand there all day and wait for an abnormal reading. A periodic measurement might tell you something, but havent these guys heard of multiple channel digital storage scopes or all the data aquisition equipment that could monitor that and a lot more 24/7 and store it you? Cant you also use PLCs for that within limitations of sampling rates? Dont they think 2 unscheduled shutdowns in 20 minutes is well, bad?

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Sounds like you already have the right attitude ... thinking of things that can make the job easier/better ... and increase productivity. Those traits should help you land a job.

carwashblues said:

Thats right, my ego took a little bruise. Waaaaaah!! Thought I had that job in the bag, and they probably thought I was ignorant of PLCs (I was) and thus of no use.(I disagree!)

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You are probably right, but they're probably thinking they can get a guy with PLC experience and shorten the learning curve and their training costs.

carwashblues said:

There is no way I could accurately diagnose anything but the most obvious problems with just a fluke, on a PLC or whatever. especially the kind of intermittent failures that might trigger a shut down.

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You will find (if you end up in factory maintenance) that most problems boil down to a failed field or control device and are therefore logic problems. "Who cares which resistor or diode is bad? we only care that the machine is running again because you replaced a card, and that you find the cause of the damage so it doesn't bite us again." You can use your skills with high tech test equipment on rare occasions, but 95% of the electrical problems in a factory can be remedied with a Fluke Multimeter and two or three screwdrivers.

carwashblues said:

What I think was going on and might be commonplace for all I know (I dont work in plants) is that plant electricians learn PLCs to a basic level and are considered qualified to maintain the line. Maybe they have an engineer at the plant as a technical resource and farm out all the actual fried boards and such. The maint dept apparently just springs into action during the frequent shutdowns, does some quick band-aid and thats considered a repair?

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That would be a very astute observation in my opinion. That is exactly what goes on in the places I have worked. The quick repair may be a band aid if the source of the trouble is not found, but the speed of the repair is very important when downtime can cost thou$and$ per minute.

carwashblues said:

Im not knocking electricians, but dang, I could accurately diagnose all the electronics in the plant and find the root cause of the shutdowns so long as I had all the manuals and schematics and the proper test equipment, once I get up to speed on all the PLC programming and applications. Is it a union thing? No techs allowed? Do all plants subcontract out all the electronic repairs? Would I just be a board swapper?

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You may become a supertech who can keep the machines running AND take the fried parts into the shop and repair them, saving the company lots of money. Guys like you are very handy to have around, especially when the parts that fried are out of stock, or obsolete. Every plant has at least some amount of obsolete stuff in service, and I have never seen a plant that had a spare for everything on the shelf.

carwashblues said:

Dont get me wrong, Im just trying to find out things to help my training and job search, and I am currently dumb as a post with PLCs anyway, so I wouldnt even know which board to swap! If all I have to do is swap boards for 30 bucks an hour, then I know that just a crash course like on this site will suffice. (and pay for itself before lunchtime if I get a job!)

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Don't underestimate the importance of hands on learning. Although you may come into the field with great aptitude and supporting experience, you will still need to put your hands on real equipment before you'll be proficient.

carwashblues said:

I dont know PLCs, but Ive repaired hundreds of I/O boards, DAC and ADC boards and Ive dealt with sensors, encoders, servos, and so on various equipment but not on PLCS. Now how can I parlay that into a job in a plant that dosent have to know that a few weeks ago I didnt know what PLC even stood for! Ive gotta talk the talk at any rate! Just be honest? As soon as "I have never ever touched a PLC" comes from your lips, your future high paying plant job is in great danger! LA is not silicon valley, and plants dominate the job market.

Thoughts? TIA

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Get your hands on a PLC. Learn how the software and communications work. Find out what brands are most common in your area and focus on those. Then go to your next interview and tell them you have some PLC experience...

Paul

I've heard about them fancy flukes, but are they really any better than my lamp and buzzer ?

L D[AR2 said:

I've heard about them fancy flukes, but are they really any better than my lamp and buzzer ?

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I used to work on some old relay logic machines where the only way to find the intermittent flaw was to have a test light screwdriver in each hand on two (or more) different test points, and listen to the chatter pattern while watching the order of flashes...I only resorted to the test lights when absolutely necessary though, but they do have their place.

As you have managed to start a new thread and not append your question to a set of 10 year old unrelated posts you have already made it onto the first rung of the ladder (pun intended).

Thanks guys, That clears things up a lot. LD, "rung of ladder"....hmmmmmm a "ladder logic" joke? lol

Ive worked in a factory (GD) but not on plcs, so I know that management loves the quick fix and couldnt understand the underlying root cause unless you made a cartoon featuring "Bad Ground George" and "Flaky Connector Carl" as the villians! They couldnt care less either. No way they can afford a 2k scope, but they dont bat an eye when 5k in parts get thrown at something so long as line gets moving.

Also I will never get this: A whole bunch of 5 minute shutdowns and bandaids are seen as highly skilled repairs by top notch techs, no problem, Let the line go down for an hour and its a travesty. Does no one ever calculate that a dozen annoying shutdowns and a single longer shutdown are awfully similar in terms of production? I noticed this at GD. I know plants might have a batch go bad and thats different.

Multilayerd boards can be fixed sometimes but I hate them. My thinking is there is some production capacity to be gained in many plants by ferreting out all the "routine" shutdowns root causes which could be anything but is lived with. Also not every problem in my experience is a hard failure with a component on a board. In fact, swap boards long enough over the years and you get flaky connections with the female connector getting wore out. Its no fun replacing a 120 pin connector. I bet they just junk the thing.

I know my skills could be exploited in some capacity, but of course in the real world I have to peddle my skills the best I can.

Thanks again guys, Its nice to chat with actual folks out there doing it. Im no saint myself, Ive worked jobs where jury rigs were the rule and proper repairs seen as pretentious wastes of time! I am no stranger to the quick-fix. I like to do things right, but the real world just dosent work out like the textbooks. To be honest probably maybe 20 percent of all my repairs were textbook. A lot of adaptations have to be made!

I'm sorry but I had to ask, is the original poster's real name Rip Van Winkle?

Lol, Peter it seems I havent kept up with the times, and they were sure a changin!

I was just considering that a while ago. My component level skills could be going the way of the dinosaur. Kinda like consumer electronics, everything is made to be disposable. Anything that can be put on one chip has been and the rest they have crammed into a triple layer board and potted it in some **** you cant get off.

Im not quite ready to go to the old folks home just yet. There are still boards out there that get repaired. You cant dissipate much power in a chip, so discreet components are still around.

I figure at some point the failures just might need my old school diagnostic approach where you have to know how each circuit works to get to the root cause of an issue. Maybe not often but needed real bad when needed.

From my experience, there comes a time when the band aid that always works dosent and replacing everything that fixed it before dosent pan out either. Then what?

At that point Ive seen companies just scrap the whole supposed equipment that is causing the trouble, they put in a shiny new 10k gizmo because at least that will fix it for sure, they reason and be a great investment. Only that dosent work either. Even more problems, turns out the old gear had dozens of little workarounds and jury-rigs custom made over the years that allowed it to work with the rest of the gear, which in turn had even more undocumented band-aids. Only a functioning gizmo A with bandaids and jumpers and such would work with gizmo B assuming gizmo Bs "field mods" were left intact!

Sooner or later someone had to break out the dusty old prints that were full of typos to start with and never updated with the "improvised" stuff. They had to roll up their sleeves break out a lot more than a fluke and figure out how to make everything work right as well as the original issue that eluded the usual efforts.

When a fluke does find an open this or that,unless its a worn out switch or obvious fault, I tend to think "what exactly caused the failure, is there some underlying deeper problem?" Lol I know, "current surge" "stray inductance" and the all time favorite, "a glitch" but what if that current surges again 2 hours later and smokes the new board? With board swapping, what happens when 3 boards are fried in a couple days and no more spares? What if the issue isnt an easily swapped out subassembly? Are they just going to uproot a 5 ton machine and replace it?

I think a lot of my work has gone away due to circuit board miniaturization and making things disposable, sure, and board swapping is certainly going to do a lot of quick fixes, but sometimes someone has to do things the hard way. Heck Ive had to hook up 4 channel storage scopes to catch intermittent faults in old cars. The fault is only there for miliseconds sometimes. Tracing out with a test light wont cut it.

Today's plc are much more advanced than even 5 years back. They come with all kind of diagnostics built in. They can quickly pinpoint a problem, display a message to an HMI and point the maintainence guy to the problem. A lot of new devices are going ethernet, that even adds another level of diagnostics.
We rarely will send a part out to be repaired. The repair costs can be as much as 75% of a new component. They are exceptions of course with some of the more expensive items. Its cheaper just to throw the old component away then having to deal with all the shipping and paperwork.
Some components may be looked at but if its anything more than a blown fuse or a loose wire, the part will probably be scrapped. If a component contains mutible parts, some parts may be salvaged for future use however.
I am sure that some of these decisions involve economics and the bean counters being able to write off bad parts.

Thanks for the insight Mark. I had a feeling the plants would just scrap the boards. A thousand bucks to a plant isnt like a thousand to you or me.

Believe me, I know board swapping is quick and the majority of problems arent like the nightmare scenario I pointed out.

I have to respectfully disagree with computerized diagnostics being so powerful, even with my ignorance of PLCs. Ive worked on a lot of fairly modern systems with self diagnostics and Im not sold on the quickly pinpointing failures part. I have found them to be a tool for futher investigation. The algorithms typically assume something to be either 100 percent good or bad, and cause and effect is often not distinguished.

Also why would the pipe making facility I visited have two shutdowns in 20 minutes, given PLCs reliability and diagnostic capabilities? They just take a roll of steel and form it into a tube, and cut off pieces and inspect the new pipes. They should have it down to a science and all the bugs worked out years ago, no?

My guess and its only a guess, is that all the board swapping and throwing parts at the line for decades along with the status quo of frequent but short shutdowns being acceptable, along with band aids and workarounds when all that pinpoint automatic diagnostics didnt reveal subtle issues have left them with an unreliable line.

The remaining problems arent likely to be solved with a board or part replacement, Probably every easily replaced part has been replaced several times allready.

The mindset of black and white good or bad and letting the computer do the diagnostics dismisses a lot of potential faults,imo and dosent bode well for long term reliability. I suppose it would all boil down to how many shutdowns will management live with. Since most plants do things the same way, the industry standard might not be too hard to beat.


Take a switch, for example, everyone knows how it works. They dont go from flawless operation to 100 percent bad all the time. A mechanical limit switch that is about worn out might only cross a failure threshold just enough every few hundred cycles and shut down a line. No problem right? The 2009 PLC monitors all that stuff, so it has detected a bad switch on its very first bad cycle after 10 years thats awesome so just replace it. Not so fast, that little extra intermittent resistance could be the switch or it could be a subtle fault any where from the switch to the computers and it might be neither a bad switch or wiring, but it all looks the same to that diagnostic program. The test light and Fluke might find it, depending, might not. Then what? Now we know from this example that the switch really is going bad, but the point is that the diagnostic program didnt really prove it. And thats just a simple switch.

Of course once I get a job in a plant, all that will probably not matter. If I cant rally the maint dept to get management to rethink the approach, then really, why complain? They are giving you a blank check for parts and a 10 guage double barrel shotgun diagnostic authority. I wonder if you can just say "Well Ive replaced everything else so that 10 ton machine must be bad, order a new one"? lol.

Now all that said, I dont really care personally if a plant wants to pay me 25 an hour to start replacing parts one by one wherever the computer thinks the trouble is at. Im just glad the bean counters havent caught on. Ive got to get in the door so Im going to emphasize that I have abilities beyond the typical board swapping, parts changing electrician, and try to convince them that I know enough about PLCs to keep my resume out of the trash can.

I get your drift, though, thanks again. This forum is helping me quite a bit. I went to that first interview woefully unprepared and probably seemed retarded. Hopefully my next one I can come across a lot better.

Im hoping that once I master the ladder logic basics, I can sell the company on my background making me valuable in spite of no plant experience. Heck from what I see here, PLCs are hardly standardized anyway. A guy could work with band x for 10 years and still have to find his way around all the programming quirks and protocols of brand y. Besides in a new plant he would still have to learn which I/O boards are hooked up to what and encounter unfamiliar equipment just like me.

Again, thanks for the info. I mean no offense. There is a lot I have to learn yet, easy or not its still a lot and vital. Im just rattling a few cages for a very specific purpose, to try to understand things from the perspective of real plant maint folks so I can get my foot in the door of the industry.

I don't quite understand, so you are a electronic tech, right? Seems to me that you have a real narrow focus. A plant tech/plc jockie/sparky need to have a larger view of thing. You were wondering why the shutdown when they have PLC. to me, that's ocmpletely off a tangent because most likely it has nothing to do with PLC, could be a process issue, mechnical, equipment fatigue, a million other things. I have rarely see a PLC fault as the root problem.

You get the idea; to troubleshoot, you have to know the process. PLC are nothing more than smart relays in a pipe plant.

I'm with Harry...

It seems you have very narrow focus. All problems are not electronic in nature.

On the subject of the pipe plant, I would be willing to bet good money that they have not been operating with exactly the same process for 10 years. The standard today is constant change. Having all the bugs worked out is pretty much impossible. The process keeps changing and causing new bugs. Operating machinery without schedlued downtime for maintenance means repairs get made when it breaks. That's pretty common too. Finding the fault quickly and getting it back running is what is required. It's usually not rocket science to determine what went bad. A burnt bearing, broken gearbox, fried motor, limit switch smashed to bits are pretty obvious.

The assumption you have made is that there is some common hidden fault that is going undiagnosed that is causing the shutdowns. While we do run into the occasional difficult problem that requires high speed data logging or high speed cameras to figure out, it is pretty rare. They are usually very simple failures. Identifying which of literally hundreds of possible failures have occured and taking the proper action is the name of the game. I think you will find root cause analysis is used quite a bit in manufacturing. However, if the root cause is "we're running the equipment 24/7 and it's bound to break eventually" don't be surprised if that is ok with management.

mellis said:

I'm with Harry...

It seems you have very narrow focus. All problems are not electronic in nature.

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I would even dare to say that most problems are not electrical in most plants.

Thanks for the feedback

Whoaa..Hi speed cameras!!Coooolll !! I tend get "all NASA" already!!! I wish I hadnt heard of that approach! Now Im ruined for sure. Wow I should have thought of that. A frame by frame playback of an event undetectable by the eye!Who could doubt that kind of test? Better yet each frame synchronized with a bunch of supporting data giving both an electrical and visual play by play. Awesome!

Seriously though guys, I appreciate your thoughts. You have me pegged right, I have been accused of not accepting routine failures and over doing things before. Naturally Im going to focus on electronics too, thats what I did for 9 years.

I think I might be scaring off some potential employers with my cover letters, maybe their thinking I would take to long with a bunch of uneccessary tests. My thinking was it might make up for the lack of PLC experience, but I probably come on too strong in one area.

I think I will tone it down a bit and maybe point out my hydraulic and mechanical experience a little more.

Oh yes I agree PLCs should be dead reliable, they are made to be isolated from harms way and really from my experience digital circuitry is very reliable. Kinda like a PCM in a car. Nothing much ever bothers them unless someone manages to short something out.

With the pipe plant I was just looking for some opinion. Decades of troubleshooting have taught me never to assume anything, and starting your testing with the most likely and easy to check areas makes sense. There was a lot more to that line than PLCs of course, so long before I would start looking at probably the most reliable things in the plant, I would eliminate any easy to check more likely cause just like anyone else.

I dont like explanations like "it got in a bind" and would like to know why, but in a plant going 24/7 and equipment run till failure with no unscheduled shutdowns allowed, my conscience is clear, a later catastrophic failure that takes out some high dollar gear, well too bad, just dont blame me! Thats management rolling the dice not me.

Thanks guys, I was under some misconceptions due to not working in a production environment like a plant, so this feedback might help me from saying something retarded thinking it will help my prospects during future interviews.

You should probably have a read up on the communications protocols popular today. If a plc can't talk it can't think.