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Confessions
22

Confessions

Confessions

(OP)
Many interesting links shared detailing other peoples screw ups. Anybody on here willing to admit to their own?

Not trying to entrap anybody, don't admit to anything you could still get prosecuted for. Just want to hear a few funny stories.

I'll start: My first job in a small engineering firm with very little senior experience, almost every day was a near miss:

- Prototype 24 ton dump trailer, my first folly with hydraulics, on placement from uni. I designed the small hydraulic rams that open and closed a gull wing style back door to operate on the same circuit as the very large rams that lift the 24 ton laden body, without any flow controls. On first operation the back door closed so hard and fast it damaged the solid steel door.

- Ordered a laser cut sheet steel kit for a first production batch of a new product. Didn't realise AutoCAD was set so that all files were scaled 10:1. Received a delivery of miniatures.

- Made a tolerance error on the pivot of a large arm that moved a prototype piece of machinery into operating position. It seized up so tight only the hydraulic ram on the arm could turn it, couldn't even get grease into it. Prototype was on a tight deadline for a demonstration in front of a large group of customers which we had to go ahead with. Started to move the arm and the screeching from the pivot was mortifying. needless to say we waited until everyone had left after the demo before folding it back in again.

RE: Confessions

9
I am twice divorced. Totally my fault because I asked each of them to marry me.

Brad Waybright

It's all okay as long as it's okay.

RE: Confessions

I dodged two possibly bad marriages through no device on my part; one rejected my proposal, the other canceled afterwards. Looking back with hindsight, it's easy to see that either would have been failures in the making.


TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Confessions

Watching units is always important especially when using software. Pipe weights may be off by a factor of 144 if you don't watch density units...

RE: Confessions

2-months ago, the hydrotest pressure on isometric dwg appeared incorrect. i did the calc & i got a higher value. oscar sierra . . . i got distracted and revisited 2-weeks ago. hydro test pressure was incorrect - too low. ouch.
meanwhile, about 60 pipe spools were prefabricated, hydrotested, and in the process of being shipped to site. double ouch.
engineer, not me, used 2014 code to determine test pressure and stress values were lowered in 2016 code, resulting in higher test pressures at higher design temps.
contract was signed before the 2016 edition became effective, so 2014 edition is code of construction. a goodie!
fortunately, 95% of the prefabricated spool pieces just barely met the test pressure by 2014 edition, but not 2016 edition. Whew!
the remaining 5% did not meet 2014 edition test pressure by 2-psig. final and bigger ouch, but a lesser eventual rework.
when suspecting or encountering an error, immediately followup and do not wait. trust your instincts. darn gremlins . . .

RE: Confessions

Everyone who works in a fab / assembly shop has stories of things gone wrong. It's human nature. It happens. You try not to let it happen ... but it does.

Back in my mechanical design days ...

I was design lead on a special-purpose CNC machine. In design review, the boss wanted additional workpiece clamping, so that assembly was designed after the main part of the machine was already drawn up. I completely forgot that the place where the boss wanted extra clamps already had another critical part of the machine occupying that space. This wasn't found out until the parts landed in the shop (this was LONG before the days of 3D CAD models). Question arose, "What do we do about it", my reply, "Don't install the clamp assembly, and see what happens." Fortunately, it worked fine without, and the only remaining sign of the oopsie was a pattern of holes in the base of the machine which was no longer used for anything, and a couple of blanking plates on the hydraulic manifold where the valves were supposed to be.

Sometimes the designers screwed up, sometimes the shop screwed up. Best one we had involved a hydraulic lift table with 4 cylinders tipping a plate from horizontal to vertical. Of course the project ran late, and the first time it was ever tested was when the customer was there for run-off. (Lesson: Don't do that. Don't let it happen. Delay the run-off if you have to.) That's when we found out that someone didn't crimp a fitting properly on one of the hydraulic hoses. It made it about halfway up before letting go ... and spraying the customer's representative with hydraulic oil.

I deal with robots nowadays. Anything you can touch ... you can smash into.

RE: Confessions

When I was first out of college, I was tasked with doing a quantity take-off of crane rail for a power house on the east coast that my employer was bidding on. I tallied up the total length in feet and used the value in the steel manual to determine the total weight. Of course everyone knows that rail is called out as so many pounds per yard. (Only item in the steel manual listed as such)



RE: Confessions

Way back, a few years after graduating, I designed a large mall... the fabricator wanted to change all the 'purlin' to girder connections to single angle connections... I spent half a day and decided this was a good revision. I should, however, have issued it as a Notice of Change... There was a huge savings that was never accounted for.

I'm of the opinion that contrition is not good for the soul.

Dik

RE: Confessions

One of my first jobs in process engineering a long time ago was to to set up a pump on a pressure controller. The system included a pressure tank. I was told that the system had to operate at a certain pressure, i don't remember the exact numbers now but lets say it was "400" . The gauge was in psi but what did i know and it was in a difficult spot to read and it was half dark.

Of course the 400 was kpa which is about 60psi but i was trying to get 400 on the gauge which it went to. The pump i was using had enough stages it may well have gone to 400psi. On the first attempt, a pipe blew. Second attempt the pressure tank started to emit pinging and cracking sounds passing about 200.

It finally clicked that the tank probably should not be making such sounds and i had better shut down and investigate.

Lesson learnt.

Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

RE: Confessions

We had an operator who failed to check whether all the gasses our diffusion furnace were turned off, and when she opened the end of the tube, she got a nasty little explosion that could have killed her. High purity oxygen and hydrogen running through a 900 C furnace and all that; luckily the flow rates were usually pretty low. For some whacked reason, she didn't get fired, but got essentially promoted to a QC position elsewhere in the facility.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Confessions

As a graduate, I once analysed a 12 storey RC frame building intended to be reinforced concrete construction, but I inadvertently used the Young's modulus & self weight of steel in place of using concrete material properties in my analysis model.

I picked up on it eventually and we all had a good laugh about how the simplest of things can be missed.

RE: Confessions

As an EIT I designed a wastewater lagoon for a single family house (allowed where the soils didn't "perc" on lots > 20 acres.

I had done the comps to size it then set about to drafting it in CAD, had the comps/plans reviewed, and out the door they went.

Fast forward a couple of months, I was designing another lagoon and pulled up my CAD file to reuse some of the elements. It was at that moment that I realized, "damn that thing looks kinda big..."

Turns out, while my comps were right, my drafting was not. I had computed the diameter needed for a truncated cone of a particular volume and depth. But AutoCAD queried me for a radius when I drew that first proposed contour. So I wound up with a lagoon twice as wide and 4X the target volume.

It has passed our QC review and was permitted. But fortunately had not yet been constructed when I brought it to everyone's attention. So aside from some wounded pride and quick rework, there was no real harm done.

RE: Confessions

Another engineer caught an error in my calcs, but after the fact on a very fast paced job. Turns out the steel connections for the hydrotest load were "overstressed" by a by something like 50%. And, the hydro test was scheduled for the same day we found the error.

I was calling up the contractor to warn them not to do the hydro test on this particular piece of equipment. It had already been done, would be the only time during the short life of this structure that it would be done. Nothing damaged, nothing failed..... Thank the lord for safety factors.

RE: Confessions

Telling my boss that I thought I was close to finishing something and being off by months. I hadn't done the job before but I honestly though it wouldn't be that much work. Now, if someone ask I always think about how much time I think it could take and then double it.

------------------------------------------------------------------------------------------
If you can't explain it to a six year old, you don't understand it yourself.

RE: Confessions

Timely thread. I was just thinking about something from my past work.

We were studying the load capacity of members existing within an old steel truss bridge which shall remain nameless. Bridge was built during the time of rivets and the only rolled steel sections you could get back then were angles, so in order to get larger box sections you had to build them up with angles in the corners, and either plates or steel x-lacing on the four faces (ie. built up sections). I developed shop drawings for a 3/4 scale model of one of the box beams, with plates on several faces and x-lacing on the others, and sent them to a professor, who shall also remain nameless, from the local university that was overseeing the testing program. The one thing I overlooked was to also scale down the spacing "between" the bolts stitching all of the pieces together.

Test took place in front of TV cameras, because this test was a big deal in the community. Immediately after failure the professor jumps in front of the cameras and goes on and on about classic plate buckling behavior. Problem was the main failure spot likely initiated BETWEEN two bolts along the corner of the section. I immediately saw it and knew my oversight. The professor didn't have a clue at the time, because I don't think he reviewed anything I ever sent him.

RE: Confessions

Quote (D Scullion)

- Ordered a laser cut sheet steel kit for a first production batch of a new product. Didn't realise AutoCAD was set so that all files were scaled 10:1. Received a delivery of miniatures.

I got a part made in inches when I designed it in mm. Got a part that was 25.4 times bigger than expected. Fortunately they were tiny parts so the duplicates weren't too ridiculous to deal with.

RE: Confessions

Metric VS Imperial;
In laws were visiting from Boston. We had a three hour drive to the airport when they flew home.
Highway driving and for mile after mile I had the speedometer pegged on 100.
My sister in law sat quietly in panic for quite awhile but finally said something about my speed.
She didn't realize that Canada is metric and that the speedometer was in KPH not MPH. The speed limit was 100 KPH, or 62.5 MPH.
She had a reputation as a fast driver and had she been driving with an MPH speedometer she would have been driving even faster.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

Okay, make confession part 2. You had that speedo sitting at 120, like everyone else does!

RE: Confessions

Since beginning engineers seem to make more mistakes than old guys, I did a drafting job the summer after first year as a CE student. There we had beginning surveying courses and did some map preparation. A furniture factory was upgrading their shop and placing new machines,etc. They put me to work mapping the shop. About half way through field measuring and drawing the plans, I found that the steel tape had more than 10 tenths per foot. Having learned to map in feet and tenths, what gives? Turns out the tape was feet and inches. Luckily they had a neat powered eraser. Guess we should have been taught that engineers and architects are different as to scales.

RE: Confessions

When I was younger, there was an engineer that often had his Z28 up at 150... and not kilos... He borrowed survey equipment from the University and chained out a measured quarter mile on the perimeter highway one morning... and used proper traffic paint, borrowed scrounged from the highways department, to mark the distance. There was an area of the perimeter used for racing on Saturday mornings.

Dik

RE: Confessions

About 10 years ago when I moved to Alberta I did drive a little faster than 100. But faced with the amount of driving and the distances to jobsites, I worried that if I didn't slow down I may start raking up speeding tickets and eventually loose my license. I find that there are quite a few drivers that feel like me and we cruise at about 105 to 107 KPH.
We let you and the rest of the 120 KPH guys go on past.
My confession #2 is about feet and inches.
I may have told this one before. I was working in a remote mining camp and the office trailer was moved.
I had to move the antenna for the VHF radio telephone.
I checked the length of a folded dipole for our frequency band and measured and cut a new antenna. As I was raising the new antenna one of the other workers walked by and dropped the comment;
"Did you use that tape measure? Did you know that there is about 17 feet missing from the middle?"
Good joke. I'd heard that one before. Three guys peeking around the corner as the victim of the joke looked for the "missing" inches on a tape measure.
Just the same, I did a check.
Sure enough, I found where the tape measure had been nicely taped back together with a big piece missing.
Down came the antenna to be remeasured and re-cut. (With new wire. Cutting the original antenna longer didn't work out. grin)

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

Quote (oldestguy)

Having learned to map in feet and tenths
Wow, I have never even SEEN a tape in feet & tenths. Where can I get one? I could create some serious havoc by leaving them around in the wrong places. He he. I would never do that.

My confession:
Customer wanted to install an instrument inside an aircraft wing. Access into the wing through the existing access holes did not allow the long cylindrical instrument into the wing so we needed a larger hole. Took measurements of wing and instrument and existing hole to figure out how big the new hole had to be to fit the instrument inside. Returned home (4-hour flight away) to office and started to draw, creating CAD model of the wing and its new access hole. Discovered I already had a CAD model of the instrument. Didn't confirm instrument measurements in the existing CAD model. Drawings done, customer cut the wing open, fit up the new access panel, and it was time to test-fit the instrument. Doesn't go in. After much to-and-fro on the phone, I eventually figured out the CAD model of the instrument was 2 inches too short.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

RE: Confessions

Quote (SparWeb)

Wow, I have never even SEEN a tape in feet & tenths. Where can I get one?



Get one here: Link

RE: Confessions

Had a 100' steel tape that was metric on one side and ft-1/10s on the other
The tenths of a foot (and tenths of those) are easy to mess up, 100 to a foot looks a lot like 1/8" marks (96 to the foot).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Confessions

All surveyors chains (tapes) are in feet and tenths. The surveyor rods are also in feet and tenths. I've used chains that are two hundred feet long. Hard to pull straight when two people are trying to get an accurate measurement.

It's a sin to break a chain.

RE: Confessions

Surveys in feet and tenths of feet.

Fence company or landscaping company workers do not understand what is a tenth of a foot.

They see 50.7' on a survey and think that means 50 feet, 7 inches.

A whopping 1.4 inch difference.

Or are those "survey feet" on the survey? Because those are different from "international" feet, which aren't used anywhere except the US.

RE: Confessions

Liberia and Myanmar also use Imperial measure

RE: Confessions

Since 1959, "American" feet and "international" feet have been the same. Curious note that I was a party chief in Liberia and was checking a French firms work on the elevation of a remote already constructed bridge. (1958) We used feet and tenths. It was to bad that the already constructed bridge was four feet too low.

RE: Confessions

I used to work with a guy who lived in an imperial world in a metric country (at the time we had been metric for something like 35 years). He was this old guy who never grasped metric.

For example I used to tell him to cut a piece of pipe 5678mm long, and I'd have to hold his finger on this mark on the retractable steel tape and he would coil up the steel tape in his hands and trot off to the location of the pipe and unravel the tape and attempt to measure and cut the peice of pipe without stuffing up his finger position marking the correct length. About 50% of the time after all that it was the wrong length, sometimes out by meters if he lost his spot. I quickly learned to only trust him with measurements under about 1500mm as he didn't have to coil up the tape.


This whole metric and imperial discussion reminds me of the NASA mission to Mars that plowed into the surface upon entering the martian atmosphere, afterwards it was revealed apparently that half the team was working in metric and the other imperial units of measure and neither knew it, but they had been happily trading numbers.



RE: Confessions

this aint an admission of error on my part, but since the discussion has turned to measurement units;
I once spent an afternoon trying to locate base plate positions for equipment skids on my first trip to Korea using a Chinese tape (1.3 US"=1 Cun") I think my assign engineer was having fun seeing the factory guy confussed

RE: Confessions

A mixup in metric fuel, we had the Gimli Glider... a Boeing 767 run out of fuel at about 40,000' and the pilot 'glided' it to land at an abandoned airfield north of Winnipeg... all 60 or so passengers survived.

Dik

RE: Confessions

2
I still can't get over feet in tenths.
Do you call these units "toes"?

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

RE: Confessions

A humorous twist to the Gimli Glider.
I read a report that a crew of mechanics were sent out to Gimli to assess the damage of the plane, and their van ran out of gas on the highway.
Of the two pilots, one had extensive glider experience and the other had flown out of Gimli when it was in use by the Air Force.
There was another report that Boeing set up the scenario in a simulator and there were a number of simulated crashes before one of their test pilots was able to simulate a safe landing.
Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

SparWeb:

You should understand that most civil engineering curriculums require a year of surveying - and all of the US measurements are in feet and tenths of a foot. The California civil engineering professional license test requires an additional a separate section on
surveying which would also require the use of feet and tenths of a foot. It's also easier to add tenths than it is eights. But a young surveyor almost immediately learns how to approximate the tenths of a foot into the nearest 1/8".

RE: Confessions

... and the pilot was found 'at fault'.

RE: Confessions

I made a PCB a few years back for a rush project (well, EVERY project was a rush project on that job). Our process was engineer #1 creates a part model, engineer #2 verifies it as correct, then everyone can use it. The part in question was an Ethernet jack, so it was hung off the end of the board an appropriate amount to fit through a faceplate, then the usual EMI-reducing components were stuffed in next to it. Board was sent out for manufacture.

The good news is the functionality tested great. The bad news is you had to insert the Ethernet cable into the jack from INSIDE the case. Yep, whomever made the model had rotated it 180 degrees. But to get even that to work, you had to desolder the jack and pitch it upwards about 15 degrees so the cable would clear the EMI components (but at least it was testable)

The really bad news? I was engineer #2 sadeyes $25k down the drain.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: Confessions

See my last entry in this thread: https://www.eng-tips.com/viewthread.cfm?qid=439755 (I'm confessing there for someone else smile)

==========
"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

RE: Confessions

It is super easy to discern the values on a grade rod graduated in tenths and hundredths of a foot. I can't imagine making multiple readings in fractions of an inch and then computing results quickly. Running clean level loops over a few thousand feet was pretty nerve wracking as it was.

RE: Confessions

I suppose another thing that I learned is that doing 6 things right is much better than trying to do 10 things but only doing 9 of those right. Slow and methodical is much better and faster than quick and loose. With quick and loose, you'll have to deal with the problems at the end of the project, waste time with redoing work, and people don't feel like they can trust you. Doing work or saying things that you are not 100% sure of is gambling and eventually it bites you.

------------------------------------------------------------------------------------------
If you can't explain it to a six year old, you don't understand it yourself.

RE: Confessions

When I worked back in the UK.. The company I worked for had a foundry with a pattern making department. A source of great amusement was to watch a victim enter that department to measure something without bringing his own rule. He would inevitably be handed an expansion rule. Needless to say the resulting part would always be slightly too big. requiring rework by the victim when he figured out what happened.
B.E.

You are judged not by what you know, but by what you can do.

RE: Confessions

My latest was a measuring error.
I recently acquired a newer truck to pull the rodeo trailer (3 horse trailer with living quarters).
I thought it would be a good idea to have a socket on-board to fit the wheel nuts. I pulled out the new, bargain caliper that I had bought a few months ago and not yet used.
30 mm wheel nuts.
The next time in town I bought a new 30 mm socket.
Didn't fit. That was a first. I had never in a long career seen a socket far enough off of the marked size to not fit.
But, you know, things are going to hell all over these days.
A few weeks later I was at a friends place and borrowed his sockets to check. Wait, his 33 mm socket fits?
When I got home I took a close look at my new caliper.
The scale was printed 3 mm offset from where it should have been. All measurements come out 3 mm short.
I guess that's why it was on sale cheap.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

G'day Berkshire,
This must be a "two nations separated by a common language" thing - I always called your "expansion rule" a "shrink rule(r)"!
John.

RE: Confessions

Had a boss from Europe who did the conversion from metric to english for his height for his driver's license and came out 9 feet tall.

Same boss had us fabricate a stainless steel backsplash for his kitchen that, per his hand sketch, was 2"x3" - we gave it to him in a picture frame with the caption under it "Check Your Units"

We had a bonafide rocket scientist working for us (it was a gig after he retired from his real job) and he wired a digital clock to battery switch power, so every time the vehicle was power cycled the clock would flash 12:00 and need to be reset. He went back to the schematic and sure enough that was how he designed it. "Huh, how about that" was his reply. When he did retire from the company I sent him a thank you email with an animated flashing 12:00 gif and cc'd the department

RE: Confessions

2
I mentioned this on the tower settlement site.

I may have caused the settlement of the Millennial Tower. In the late 60’s I was a concrete inspector for BART on the Lower Market Street Station, near the Tower. As you know, the station was constructed using soldier pile/slurry concrete walls. The slurry walls were used as both water cutoff walls and as the actual structure walls, a first at the time. While I watched the pours along that side of Market, just beyond where Millennial Towers is now located, I was also watching a gorgeous woman walking along Market Street. I think I watched her too much and missed some bad concrete that was placed here. And is now leaking and allowing the Tower to settle. I married the girl and we ran away to N.Y.

RE: Confessions

Well, you got the girl and had a hand in creating a future landmark. I think this is a win all round.

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If you can't explain it to a six year old, you don't understand it yourself.

RE: Confessions

I fail to see the failure in that.:)

RE: Confessions

You're just bragging now.

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

RE: Confessions

Aussiejohn2,
I guess that name would fit too. The patternmakers called it an expansion rule because it was bigger than the standard rule and was pre calculated to allow for the fact that the pattern had to be that much bigger to allow for shrinkage when the iron cooled . So your name of shrinkage rule is a bit after the fact.
B.E.

You are judged not by what you know, but by what you can do.

RE: Confessions

2
Confession:
I designed a power supply/relay board for refrigerated rail cars. It was part of a system to save Union Pacific $2M a year in fuel costs by forcing the Detroit 3-71 to an idle when the temperature setpoint was achieved.

It was a simple board that had a custom transformer, caps, rectifiers, and relays on it. We mounted it in the big electrical control panel associated with the generator and refrigeration controls. I built it on a nifty aluminum L. It weighed about 3 pounds. Unfortunately I had the board on the horizontal part of the L.

Everything worked just peachy in a month of testing in the rail yard and out in the fleet. Yay! We promptly cycled a hundred cars thru the Watsonville yard installing our fuel saving kits in the cars.

BTW: Never park with a rail switch lever unit directly behind your truck as you can't see them in any mirrors...

Anyway about 5 months after releasing all the cars out into the wild my boards started coming back... stinking with huge carborized gaping holes blown thru them. After getting about 5 back I figured out that there was a bunch of metal dust raining out of the contactors above my horizontal board. It took months for it to build up until it conducted, heating up things until the board literally toasted.

My boss said, "Fix it!"

I came up with a conformally coated board mounted vertically. This solved the problem except the cars were scattered to the for corners of our great country..

My boss said, "Go change them before they lose a railcar full of avocados or cured hams". (200,000lbs of them)

So I found myself in Seattle Washington, in the rain; Pocatello Idaho, in 2 feet of snow (midnite); Salt Lake City Utah; Jacksonville Florida, Dallas, El Paso, New Orleans Louisiana, and about 5 other places I'd never heard of, asking people, "Have you seen a refrigerated railcar around here?"

Keith Cress
kcress - http://www.flaminsystems.com

RE: Confessions

I designed a pedestrian bridge with 8 in. square tube columns at a 20 ft spacing along each edge. The roof was a translucent barrel vault arch system that had a thrust that pushed the tops of the columns apart. To counteract this, I added a small turnbuckle and rod system to hold the columns together. When they were installing the rods, the turnbuckles were sagging down a few inches. They tried to tighten them, but the rods pulled the tops of the columns closer together. I just eyeballed that the catenary-like force would be small, so didn't run any numbers. Boy was I wrong. We had to ditch the rods and turnbuckles scheme and change to a small steel tube that held the columns the correct distance apart.

On one project, I designed a composite spandrel beam that twisted so that the edge of the slab was an inch or two low. The overhang was 15 in. and the spacing to the first interior beam was very small, so the bulk of the load was on the outside. I think they also had a shear tab connection, which didn't help matters. We had to add a topping slab near the edge to result in a level surface.

I had other situations in which stuff wouldn't fit together, but these two actually failed to some extent.

RE: Confessions

That's a great story, itsmoked. Is that the origin of your name here?

RE: Confessions

Ha Rod. About, I'd guess, 2% of my handle.
I made a college senior project that was an intricately designed electronic apparatus that was carefully designed to self-disassemble over time in synchronization with my oral description of its function. It was carefully crafted and worked perfectly as capacitors exploded, MOVs smoked, and transformers fried.

As a high school student, with my crazy life-long friend, we did tons of destructive testing in his mad shop, lots of which let smoke out. Speakers hooked to the mains. Motors run under water. A display stand based salt water rheostat which we could modulate the voltage delivered to all the houses on our block with, etc., etc.

One especially memorable test was when we clamped a helicopter magneto in out bench vice and drove it with a large motor as fast as we could. Just as we peaked the speed/output the high voltage lead got loose and landed on the ancient workbench surface covered in grease and impregnated with metal filings and dust. The 3 dozen blue arcs that instantly appeared everywhere on its surface lit that sucker on fire instantly.

Finally I was kicked out of Eng-Tips 4 times (I have absolutely no idea why) and so was getting kinda cavalier about my usernames by the time I got to this one.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Confessions

Yeah, itsmoked, I had a few projects in my garage that turned out similarly. As my sound tech mentor kept telling me about electronic components, letting the smoke out is bad.

RE: Confessions

One of the other posts reminded me of the time as a graduate I had some steel diagonal angle bracing under a timber floor. I had long vertical gussets full height of the supporting girders for two beams framing out the braced floor bay that were running orthogonal to two larger steel floor girders at roughly mid span. I had detailed some short vertically orientated gussets for the diagonal brace with two bolts orientated vertically. These gussets were recessed right into the beam web/beam gusset intersection. All looked good on paper at least.

Turned up on site and the contractor had sliced a 20mm wide piece of plate out of the bottom flange all the way from the edge of the girder to the web, because there was absolutely no way that they could get the diagonal brace in past the full height gussets and the beam flange. Cutting the slot allowed him to lift the brace into position with no issues.

Once I discovered it, he proudly pointed out the fact that he had solved the issue without involving me. Much to my annoyance they had never asked, and never even pointed it out to me until I noted it myself on site.

Suffice to say I learned a few things that day around detailing/constructability and also fixing on site issues. Never done anything like that again. Always think about how someone is going to build what you draw.

RE: Confessions

How many of us have flipped up the welding helmet to discover something is on fire?

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

RE: Confessions

Agent; I was very surprised to see a bunch of ~6 inch I-Beams in a new wood house construction by my house about 2 weeks ago. Today I went by and was surprise to see they'd filled in all the contours of the I-Beam with wood, even the flanges!

Keith Cress
kcress - http://www.flaminsystems.com

RE: Confessions

I haven't had any spectacular failures, however there has been the occasional tolerance stack error mistakenly applying LMC or MMC when the other condition should've been used. I've never not had parts fit together, but I have sweated in front of techs a time or three. For me its always the little things, never the engineering that is flawed.

RE: Confessions

Spar web,
Been there got the tee shirt.
At one job I was doing, I discovered that the burning smell was coming from my beard.
About three very energetic seconds later it was out.
B.E.

You are judged not by what you know, but by what you can do.

RE: Confessions

We had an apprentice who set fire to his coveralls. He put the fire out and went back welding. There was some pain but he expected that and kept working. The pain got worse. Finally he stopped welding and discovered that he had not put the fire completely out and he was still on fire. He was burned badly enough that he was on light duties and on crutches for a time.
And if that wasn't bad enough, a few months later he managed to set fire to his prints. He wasn't welding. I was afraid to ask what he was doing. He may have been smoking in a restricted area and stuck his cigarette in the prints to hide it when he heard someone coming.
I'm guessing but it's an informed guess.


Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

Wow Bill.

Reminds me of a vivid episode in junior-high metal shop. The teacher, Mr. Streeter, had us all around while he pulled a yellow hot crucible of molten aluminum out of the furnace during our casting phase of the class. I don't recall what caused it but a dollop of aluminum slopped out of the crucible while he was holding it in long tongs and the dollop went right down the inside of his right boot.

To this day I am very appreciative of his spectacular grimace, loud involuntary gurgling sound he make, and the slow care with which he set the crucible down before screaming and ripping his boot off.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Confessions

That brings back a memory of a truck driver on his back in a snowbank with both feet in the air, trying to kick both boots off at once.
He had a piece of steel sticking out of the back of a dump truck and was trying to blow a hole in the 3/4" steel. When he hit the oxygen lever on his cutting torch a blast of molten steel and slag entered both of his boots.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

Wow guys, I've only welded once in my life, and even I know it's always pants over the boots...

RE: Confessions

(OP)
Talking of poor welding safety procedures, my biggest welding screw up was tacking up a prototype to speed things up for our fabricators to do the final weld. Spent the whole day doing hundreds of small tack welds while looking away or welding under an extended, gloved hand as I couldn't be bother lifting and lowering the visor every time. I won't make that mistake again, didn't get any sleep that night as it felt like a shovel full of sand under each eyelid

RE: Confessions

2
While we are talking about other peoples screw ups, my 9th grade science teacher was talking about safely using chemicals. He said that if you accidentally spilled a little acid on your hand, you should not go running down the hall screaming. Instead, you should go over to the sink and rinse the acid off. At this point he proceeded to demonstrate pouring sulfuric acid on his hand, calmly walking to the sink, opening the tap and nothing came out. He quickly ducked down under the sink to see if the valves were shut off down there. They were not. He then went running down the hall screaming "They shut the water off!".

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Confessions

I worked for a plumber/site civil contractor while I was in college. One day we were laying CMP at a new BP. That morning, I had put on a pair of old work jeans with a frayed bottom hem. My boss told me to go over and cut a length of 24" CMP. We used a demolition saw with an abrasive wheel to cut the pipe. About halfway through cutting the pipe, I got the feeling "damn it's hot," I pulled the saw out of the cut intending to roll the pipe and continue on when I looked down to see my pants on fire. I made the further mistake of trying to tamp out the flames with my hand. In retrospect, I was pretty much screwed with any course of action.

Robert Hale, PE

RE: Confessions

I once worked for a mechanical contractor for a summer. One day we were tasked with making a few connections with 6" PVC pipe with glued connections...in an access tunnel. That was a fun afternoon...or at least it seemed so. We even skipped our afternoon break, 'cause, heck, we didn't care! About half an hour after we got done unintentionally sniffing glue all afternoon, the massive headache counteracted all happy feelings.

RE: Confessions

I worked overseeing a foundry operation.
I usually wore cotton or wool trousers, but didn't really think too much of it.
On a hot summer day a wore a pair of lightweight synthetic ones.
Standing on the melt platform the radiant heat from the pour (Co based, 3200F) caused the synthetic to ignite.
Fortunately I had gloves on and I was able to just reach down and pat it out.
I just lost about 1/2 of the right leg up to mid-thigh.
I went home that eve and tossed all of my synthetic pants and shirts.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Confessions

Fires, burns, and melted clothing/objects are simply a part of hot work. In college I took the full welding series and became certified then spent a summer welding with union ironworkers erecting my alma mater's new student center. If you want to develop some real nerve then try welding (and the requisite catching yourself on fire) while balancing on a beam 50' up.

RE: Confessions

In a previous life, I worked at a place where they had mechanics for maintaining plant.

One day they were repairing a van, one guy was welding on it while the unknown to him another guy was drained the fuel lines.

Naturally the large bucket they were draining the fuel into caught fire under the vehicle. Not too bad they thought, and managed to quickly pushed the van out of the workshop with no issues. But now they had a large vat of burning petrol going hell for leather in the middle of the workshop, flames licking the roof. People started panicking, running around trying to find the fire extinguisher.

The next move one of the original guys took was to naturally try to kick/nudge it out the door, one slosh of the fuel later and the man is fully on fire running for the exit engulfed in flames. Those present managed to put him out after a bit of rolling around and being doused with a fire extinguisher which finally turned up.

Natural selection almost took hold that day. He was burnt a little on his legs and face, but no lasting damage, seemed to heal up ok. Never underestimate the stupidity of others under pressure.

RE: Confessions

Performing construction observations on an overnight welding crew at a large paper mill; hanging out while they torch out some damaged metal to replace it. Torch operator sees me reaching for a piece, says "watch out; that's still hot".
"Duh, I got gloves on", says I.
...I was wearing my finger-less mechanics gloves that night. flame

Ian Riley, PE, SE
Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries https://www.facebook.com/AmericanConcrete/

RE: Confessions

Years ago when I worked for a company that built truck based Explorational drill rigs we had a rig that was about 10 years old come back in to be placed on a new truck.
This rig had a 370 CFM rotary screw compressor that was powered by the trucks drive train via a split shaft gear box which is what wore out the old truck.
There was only 50,000 miles on the odometer but they ran the truck all day running the compressor, actually set the engine on fire about 7 times over the years.
So the big day came when the new truck was done and it was time to test the compressor drive.
The compressor was located just behind the cab up on the truck bed. The separator tank was on the drivers side.
Since the speed of the engine was controlled in the cab, I was standing outside the cab with the door open when the 3" hydraulic hose that was used as an air line coming from the separator bust pretty much right in my face.
Fortunately it hadn't been running that long and the 15 gallons of transmission fluid that blew out at me wasn't hot yet.
I think the temp gage on the tank went to 450 deg.
Any way I wasn't hurt, but when I looked in the cab there was tranny fluid dripping from everywhere in the cab even the ceiling above the passenger's seat. Some how the fluid made over a 180 deg turn.
That cab and everything around me was drenched, especially me.
It turns out that the shop had re-used all of the 10 year old hoses that were cracked and brittle from the high heat of the compressor discharge.
I had such an adrenaline rush the rest of the day I could fell my hair trying to stand up and few other side effects as well.

RE: Confessions

I set my brother on fire once. He was about 6, walked into my "lab" while I was doing something pointless and destructive with a gasoline torch of my own devising: a little gasoline in a test tube with a stopper and a 90 degree glass tube through the stopper. Heat it briefly over the Bunsen and pass the outlet by the flame to ignite it and while the liquid boils you have a nice flame thrower. I was wearing my welding apron but of course Joey wasn't. I jerked when he startled me causing a bolus of boiling gasoline to pass through the tube and then through the flame at high velocity, proceeding from there to his shirtfront. I embraced him muy pronto to extinguish the fire against my apron and thought we were cool but his lack of eyebrows gave the game away.

It not engineering, rather the opposite actually, but it was definitely a failure.

RE: Confessions

2
I don't have any good design error stories to tell but I've failed to recognize the flaws in systems for too long a few times. One plant we worked in had an "old" and "new" medium voltage network with a few big medium voltage motors and a lot of 480v, fifteen or so substations. The double-ended LV substations were fed from both MV systems and the MV lineup had a tie breaker in middle that was normally open.

The old system was solidly grounded, the new system was resistance grounded. And to start the mill motors with the mill full they had to close the tie, neither system was stiff enough alone. One day there was a ground fault on one of the resistance grounded feeders and a solid-ground substation on the other side of the plant blew up.

We had to tear the bus out of the back of the victim substation's MV section, it had arced to the enclosure all along its length. So I had a lot of time to think about how it could have happened. It wasn't until I started checking the specs on the (spent) lighting arresters that I finally twigged. Ground one leg of a resistance grounded 4160 and you get 4160V phase-to-ground. But the lighting arresters on the solidly grounded system expect a maximum nominal 2300V phase to ground.

There was another burndown in the same plant a while later. I had retrofitted digital relays on the MV breaker that burned just a few months earlier so I was keenly interested in the cause. There was water in the compartment, standing on the breaker frame, from a roof leak. But the digital relay had waveform data for the event and I could trace the progression of the arc half-wave to half-wave but I couldn't find any way to blame it on the water. It wasn't until we got the breaker back to the shop and one of the other guys discovered an important part was missing that the data made sense.

The "old" system in that plant had originally been a main-tie-main and was fed from two 5MVA transformers, with the tie replaced by a solid bridge. When I later went back to prepare the data for an arcflash study I realized just how scary that lineup really was. The high side of those transformers were from the dead end of a 115 kV transmission line and less than five miles from a 2 GW power plant. The only saving grace was the high-side fuses.

Different plant, not so many big motors and more modern overall but one of the substations had an oddball low side with no 480V main breaker. There was a 480V tie circuit from another substation that was normally de-energized ... except when doing high-side maintenance. I was looking at the highside bus with my boss, standing on the substation gravel bed with the doors open on the powerhouse compartments. We were just eyeballing it, planning future work, when I reached out to point at something. Made contact with a busbar and got a tingle, like a static shock more or less. It wasn't until some time later I realized I'd touched a 4160V bus backfed through the 480V tie. Dry gravel and the ungrounded source saved me. That was the beginning of the end for that job for me, I'm a developer, not an operator, and my mind isn't sufficiently checklist-oriented to work long term in that environment.

RE: Confessions

I was in Canada when I got a call from the owner of an ice plant in Central America.
One of his ice machines was tripping into harvest mode several times a minute.
About 5 local experts had been unable to find the problem. Some refrigeration men and a couple of electrical engineers had been all over the controls but couldn't find the cause.
The owner sent me a round trip ticket.
There was nothing wrong with the controls.
A liquid line filter was almost completely blocked off.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

We were commissioning a brand new air compressor / desiccant dryer system. Start up the system and the dryer is leaking at almost every filter; the cardboard gaskets were no good so they were replaced. Try again and the low pressure control valve on the dryer discharge isn't working right. I'm trying to help the vendor tech but he seems to be almost useless, so I grab our controls engineer who's at the site doing programming. The solenoid valve on the control valve was plumbed completely wrong. I'd love to know how it passed the factory tests that it was signed off for.

RE: Confessions

Bill, that reminds me of our service tech who took a 2.5 hour drive to a site. Once there, they took him out to the starter while telling him how it won't do anything when they give it a start command. He looks at the door, pulls out the e-stop button and tells them to "Try it now."

RE: Confessions

I was working near enough to see this drama unfold;
A fairly sophisticated loading ramp.
Bear in mind that this loading ramp could work with just one momentary push button, but this had a lot of added features.
There was a hook that engaged the trailer to prevent it from moving as it was being loaded or unloaded.
There was a traffic light to indicate to the driver when the hook was engaged or released, There were inflatable bags to seal around the trailer to keep the weather out of the building, and there was a button to start the loading ramp.
When the truck pulled away, the ramp would fall by gravity until it closed a switch that started a sequence to raise and park the ramp.
That switch was called the "below horizontal switch".
Because of the name of the switch, someone had it set up so instead of operating at the bottom of the ramp travel, it operated as soon as the ramp went below horizontal.
The system was controlled by an expensive PLC with communication back to the main computer.
It worked OK for most trailers, but when a low trailer came in, the ramp would operate the switch before the ramp came to rest on the trailer deck and the ramp would park itself.
Even worse was when a trailer was just a little bit too low. The ramp would deploy but as soon as the weight of a forklift truck caused the trailer to settle a little, the switch would activate and the ramp would try to park, with a forklift truck sitting on it.
One day, we saw an old hand teaching some of the new guys how to unload a low trailer.
He pushed to start button and then put his hand on the main power disconnect switch.
The hook grabbed the trailer.
The traffic light went red.
The ramp raised.
The lip extended.
The ramp started to descend.
The old hand said;
"NOW" and turned off the main power.
The ramp continued down under gravity until it rested on the trailer deck.
They unloaded the trailer and then turned the power back on and the ramp parked itself and the hook disengage and the traffic light went green.
"Ya, it's just like the ramps that they put in a couple of years ago on the other side of the plant."
End of the story?
No.
A couple of hours later, a couple of electricians would show up with a work order that had been generated automatically by the main computer looking for a reported power failure.
We just shook our heads.
Several thousands of dollars worth of sophisticated PLC that must be turned off to function properly.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

My all time classic problem similair to Lionels story.

I got a call from a Plant I once worked regularly, the plant had changed owners and I had been there in a decade or so, BUT my name was all over their outage reports.

So when this problem arose, I got a call. The reported problem was "we can't pick up load" for the steam turbine/generator. So back and forth with things to look for and return calls, it hit me the unit was tripped and thus not even spinning.

So now the same thing but this time why can't they reset. (there is a BIG diffenrence in expected problems between cant pick up load and not resetting)

It was getting a point in the confussion between what I wanted them to check and report and what they were doing. I am getting extremely aggrovated with my contact (a Shift Supervisor) and told him "lets just start at the beginning"

"Do you have your oil pumpS running?"
this pissed him off and replied OF COURSE we have A pump running!
but I pushed and explained that there were two oil pumps, one only provided bearing cool down and the other provided the hydrualics for the controls.

there was a silence....then he said he would get back with me and hung up!

Not hearing back, I called the purchasing agent number I had and the new guy said he was not aware of what was going on, but the unit was back on line.

RE: Confessions

Not mine- but I did find and fix it. At an un-named public safety dispatch center, we have a utility failure. The diesel generator starts, and the dispatcher says "I hope the power comes on before that generator quits...". I ask why he thinks it will quit and the reply is "It always does, it will run for a little while, then shut off". Ten minutes later I find that the day tank pump was not powered by the generator it was intended to serve - it only worked when the utility was on.

RE: Confessions

In a standby generator room, typically the discharge from the radiator is through gravity operated dampers that open under the pressure of the discharge air.
The fresh air intake dampers are held closed by a damper operator. Normally open, held closed by power.
The damper motor is on grid power so that when the power fails the damper starts to open.
I heard of a first time startup where the damper motor was configured, normally closed, power to open.
Part of the engineering team was in the generator room to witness the first start.
The generator started and everything loose, dust, paper, whatever started swirling through the air and out the discharge dampers.
The group tried to leave but the low air pressure was holding the door shut.
The generator came up to speed, stabilized and the transfer switch transferred and picked up the load. Then the fresh air damper motor was powered and started to open and let some air into the room.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Confessions

During my first year on a power plant an urgent call came through to our department's morning meeting where jobs for the day were assigned. A circuit breaker hadn't closed when commanded by the plant DCS, could we provide urgent assistance? The switch house in question was right over at the far side of site, a good fifteen minutes brisk walk away. Two of us went down there to investigate, only to find the problem VCB standing in the middle of the switch house floor. Micky's radio transmission back to the control room: "Hey marra, y'know this breaker that you can't close? Have any of you considered racking it into the f***ing switchboard before trying to close it...?" Embarrassed silence.



A few years later I responded to a callout that one of the steam turbine generators had run up, closed onto the grid and immediately over-sped. As anyone with a power generation background will know, this is simply impossible - one machine can't speed up the grid. What the hell have they done...?

A less-cheerful-than-normal Scotty arrives at site in the early hours of the morning and starts checking through the event history and trends for the generator. Everything looks normal - speed, voltage, governor positions - right up to the moment when the generator circuit breaker closes, at which point the governors open slightly to boost the machine from sync idle to minimum stable load... except there's no load indicated and the machine takes off like a scalded cat until it trips at 3300-odd rpm. What the hell have they done...???

The plant control system was pretty well integrated and the DCS did a lot of thinking on behalf of the plant operators, preventing silly errors. Among the things which weren't integrated at this time were the substation supervisory computers, because these belonged to the transmission system operator and not the power plant. Our generators each synchronised across a 275kV breaker in the transmission substation, and in addition to this circuit breaker were three additional HV switches - two busbar disconnectors and one line disconnector forming each switchgear 'bay'. The substation event history recorded that the auto-synchroniser had commanded the circuit breaker to close, and upon seeing the breaker closed status the generator controller had bumped the governors open, but the line disconnector was actually open because the shift guys had forgotten to close it. Based on the information it could see, the machine thought it was on the bars but it was actually running light.

There was a fairly colourful exchange of words with the individual who forgot to close the disconnector because he insisted that he had done so, and that the event recorder must have 'forgotten' to record this happening even though it had recorded the same disconnector opening a few days previously. I'd have had a lot more respect for him if he'd just admitted he made a mistake.

RE: Confessions

"…the moment when the generator circuit breaker closes, at which point the governors open slightly to boost the machine from sync idle to minimum stable load... except there's no load indicated and the machine takes off like a scalded cat until it trips at 3300-odd rpm. What the hell have they done...???

The plant control system was pretty well integrated and the DCS …"

This confirms my concerns I was having during my last days in the field. I never did a digital turbine control system, with my only acquaintance solving specific problems relate to their implementation on older system.

Trying to “learn” the DCS from conversation with their expert never gave me the feeling that speed control overrode all other functions. That was The Golden Rule

If the incident had been one of the analog controls I worked, the synch demand to load to say 10% would have only allowed an increase above speed of (0.1 demand X 0.05 regulation X 3000 rated =) 15 rpms

RE: Confessions

This was a Westinghouse machine with a DEH control system based on the WDPF II platform. Overall it was a very good system, but there were a few flaws. The generator CB 'closed' status was the signal which took the machine from speed control to load control. Once in load control the speed controller was effectively switched out other than the supervisory overspeed protection functions which were always active.

RE: Confessions

Speaking of smoke, two seminal events in freshman year solidified my EE subdiscipline. I built a Plastic Tiger stereo amp, which had a hand-wound damping resistor on the output. The first time I powered it up, the resistors ignited rather spectacularly.

The 2nd was the debugging of a color organ; I hooked up the ground on my oscilloscope, and a 741 op amp exploded from its plastic package, not unlike the creature from Alien, but that was to be for another 6 years.

So, I learned that anything over 5 V was clearly dangerous, and that designing logic ICs might be a pretty safe career choice.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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RE: Confessions

Another event which occurred in the transmission substation I mentioned above was my inauguration into the '900 Club', a far-from-elite bunch of people who had managed to trip an entire 940MW CCGT generating module off the system at one go. We were working on a teleprotection system which essentially multiplexed a pilot wire relay, a duplex 8-way inter-tripping scheme, and a number of voice-frequency signalling channels all down a single optical fibre pair. The voice frequency channels on this thing were the subject of much voodoo hoojoo when I joined, and it basically didn't work because no one really understood how to set it up and after years of tinkering very little of it worked as designed. I'd spent a lot of time replacing damaged components and then calibrating the boards and programming them, and things were going rather well.

One of the features of this system was that the duplex inter-tripping scheme was pretty quick by the standards of the day. It took in signals through optically-coupled inputs and provided a solid-state relay contact at the remote end. One of the factors which wasn't properly considered in the design was that in a large substation there's a fair bit of capacitance between circuit conductors, and between conductors and earth. Capacitors store electric charge, and under the steady-state conditions on a system powered by DC the charge is stored without anyone really being aware of it. If something happens to disturb the steady-state conditions - say an engineer inadvertently earths one pole of the substation tripping & control battery lookaround - then current flows into and out of those capacitances until some new equilibrium state is reached. That's fine in principle, unless some of that current happens to find its way through the high speed inter-tripping inputs...

As my test lead trailed across the cabinet floor there was a colossal 'bang' as five huge 275kV circuit breakers opened simultaneously in the tin shed substation. "What the f--- was that...? Are we alive...? We're gonna get bollocked for this..." By this point the roar of steam from the plant had become deafening as 300-odd MW worth of 100 Bar steam was released to atmosphere instead of going into the turbine. Four gas turbines were on their way down too.
And then the phone started ringing... wiggle

RE: Confessions

I’ll confess…I took credit for pure luck!

Former employer coerced me to visit a plant where their labor group had just finished a turbine outage. The unit was a make I had never even heard off. The problem was the unit would randomly have 1 MW excursions. During the initial conference call I impressed the customer my saying “who worries about 1MW” to which the reply the unit was 4MW rated.

Flew that night to the coldest part of the US I had ever been. On sight I found the drawings were in German and even more confusing was they used symbols I had never seen. The unit was a screamer, the size of an oil drum spinning at scary (to me) rpms. I spent the morning looking at the control cabinet and drawings with no idea what I was looking for.

I took a break and walked around the unit thinking how I was going to tell the owner and my company I was lost, afraid to continue and was going home.

I then heard a change in pitch and looking at the unit, I was in perfect alignment to notice a flash of daylight between a control valve stem and its actuator. The Operator paged me an event was occurring and I quickly went to the cabinet, spending time using a DVM pretending. I then reported that the electronics were responding properly and not the source of the problem. The reason was with the turbine itself, high probability something loose on the #3 CV actuator.

Shut the unit down, “found” the broken stem. I was a hero to the customer, but my employer was not so happy I identified a mistake they made. I left site while a labor crew was returning for repairs.

RE: Confessions

I almost forgot about the day we inadvertently converted a DC pump starter into a (very short-lived) 120kW incandescent lamp. lookaround

Each of our turbines was provided with three oil lube oil pumps: the main pump, driven from the turbine shaft; the AC-powered auxiliary pump, powered from the unit substation and used for start-up and shutdown when the shaft-driven pump wasn't at full speed; and the emergency pump, powered from the turbine auxiliary battery. The latter pump was last layer of protection for the rather expensive turbine-generator in the event of a Very Bad Day.

The emergency pump was driven by a fair-sized DC motor, and this motor had a starter of a type which dates back to the beginning of the 20th Century - old-fashioned resistors and contactors, no fancy electronics. The main purpose of the starter was to start the pump while preventing the motor from drawing a destructively high current which would both cause a severe sag in the voltage of the massive battery, and ruin the motor's commutator and brushgear. Ever since the plant was built until I arrived about seven years later, it had been 'just one of those things' that when the emergency pump was tested sometimes the generator tripped because of the disturbance to the control system which shared the battery with the pump. Figuring out what was wrong with these pumps and why they had such an aggressive starting behaviour was one of my first tasks. "Buy tools, buy test gear, buy whatever you need: just get this sorted out".

It became apparent that each pump behaved slightly differently, and also that they were not identically wired. "Eureka!", thinks I, "That's what's wrong with them!" So we set about blueprinting these starters, wire by wire against the schematic and fixing all the anomalies. "Once we sort out the wiring, order will be restored to the world."

Wrong. sadeyes

We were recommissioning the first of the pump starters and were fairly confident that we'd found the most significant defect: the two series resistances, of differing values, were transposed. We simulated a loss of oil pressure and the pump started. Well, it kind of started. Remember the end of "Raiders of the Lost Ark"? Exactly like that: white light, brighter than the sun, eyeballs melting.

We were transfixed, hypnotised: "F-u-r-r-r-r-r-r-r-r-r-k-k-k-k..... m-e-e-e-e-e-e....." shockedshockedshocked

"Switch it off! Switch it off! SWITCH IT OFF!!!" barked the the gaffer.
I heard the voice of common sense in my head too: "There's a nuclear reaction raging inches above that switch - run!!" and we dived for the safety of the switch house floor.

There was a report like a rifle shot, and the light went out. Silence. And smoke. Lots of smoke.

The underlying cause of the problem, when I eventually found it, was with the field connection of the motor. This motor was a compound design, with a shunt main field assisted by a field in series with the armature. The starting resistors were in connected in the armature circuit, while the shunt field was connected across the full supply voltage, or at least that's where it was supposed to be connected. The schematic actually showed the field connected to the armature side of the starter resistors, not to the supply. The result of this little draughting error was that the motor failed to accelerate properly because the field was only receiving about 15% of its rated voltage even though the motor was drawing about 600 or 700 amps from the supply, followed by a peak of several thousand amps for a fraction of a second as it started across-the-bars when the last resistor dropped out.

The volt-drop caused by the huge transient current was the cause of the machine trips which happened from time to time. It's a tribute to Fuji's motor works in Japan that the commutator wasn't totally ruined by the abuse it had suffered. We wired the field back to where it should have been connected, borrowed a resistor grid from another machine, and it worked beautifully from then on. The guy from Cressall Resistors was slightly bemused when I told him his 120kW lamps didn't last very long, and we needed to buy some more.

RE: Confessions

I still chuckle about this every time it crosses my mind ... a tire plant that has since been re-tired (ha!) had been built during a labor dispute. I don't know all the history but there were some dicey things in there. One Christmas I had to open every load box on all the miles of overhead LV distribution bus, hundreds and hundreds of them, to update the drawings for an arc flash study. Drove around the plant in a manlift for time and a half for a week. In one dark corner I popped a cover open and written inside in sharpie was the old paper matchbook slogan: Close Cover Before Striking. Had to take a break to avoid peeing my nomex.

In an even darker corner of the same plant I found a box that still had a lock on it belonging to a guy only the old-timers remembered. He hadn't worked there for a decade or more, but I was gone before the process of getting that lock removed had run its course. At least they took LOTO seriously.

RE: Confessions

Quote (dik)

A mixup in metric fuel, we had the Gimli Glider

Gimli Glider

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

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