Dangerous novices programming plc's

A major problem of inexperienced and many expert programmers is that they usually do not know what they need to know. This is why specific industry experience is important when designing a process.

I believe we need to be teaching risk analysis, as in "how to figure out what bad things will happen if things don't work right". For example, if you have a crane using an electro-magnet to transport steel, should an E-stop really disconnect all of the power sources?
 
With regards to safety. A machine should NEVER be designed to rely sole on software for safety.

A machine should be designed to be mechanically safe AND electrically safe AND programmed safe.

Unfortunately, it doesn't matter how well (safe) you design a system. If the proper procedures are not followed during normal operation or maintenance, people can still be injured.
 
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A major problem of inexperienced and many expert programmers is that they usually do not know what they need to know. This is why specific industry experience is important when designing a process.

I believe we need to be teaching risk analysis, as in "how to figure out what bad things will happen if things don't work right". For example, if you have a crane using an electro-magnet to transport steel, should an E-stop really disconnect all of the power sources?

Excellant example
1. One person cannot think of all contingencies permutations.
2. I worded in a steel mill magnets were used.
3. The last thing you would want E stop to do is turn off the magnet.

Not even sure I would want a PLC operating a crane in a steel mill after all. Lot to be said for that human in the cab or on ground with remote control.

Dan Bentler
 
Peter / Tom

I am not convinced that either of you actually dissagree with me.

My point is simple, we need something more than what we have.

None of the examples you give use less certification than PLC programming.

"I think I'll be an architect............"...oh wait that's not enough.

I am not sure what the solution is, but I have thought about it many times.

Why are car mechanics trained and certified so much?

I can rebuild car engines..........I can build a house........by myself even. I can weld. I can do lots of things, but not professionaly. Why is that? Is it because someone thinks these things need to be done carefully with some degree of training and accountability?

That's all I am saying. We got nothin.

Say you can............ and then do something that appears to work and TADA! your in.

As for the how or what or which.................well I am pretty good with general machine issues, but that does not qualify me to make standards for industry.

All you need is to be smart enough to figure it out as you go and have the balls to jump in and do it. And the nerve to stay in till payday.

If there were any real accountability in industry things would work out eventualy , but there is no accountability.

I used to be a calibration/ electronics specialist. I was traceable to NIST and audited and certified as trained and held accountable for errors.

BUt now, all I have to do is make it work and then help explain how the software doesn't change itself.

If I were less ethical or safety minded, I could be dangerous. Like many I have worked with.

I don't see how any of this is something to dissagree with.

What exactly do you dissagree with?

Do you argue that there is no need for any oversight or certification? Or just exactly which way it should be framed.

Or are we happy with the wild west?

I am doin ok with the way things are. I don't think any change would benefit me on a personal level.

I have met a bunch of graduates who are complete idiots. Some have been average some have been interesting to work with. No system will solve all the problems.

I have even had to explain simple mechanical issues to MEs.

My point is , nothing will be fool proof and make everything perfect. But I find it interesting that certain jobs have so many requirements and others seem to have none.

I just don't get it. Look what you have to go through just to sell houses, and nobody can die from a bad house deal.
 
safety is no where near the top

A major problem of inexperienced and many expert programmers is that they usually do not know what they need to know. This is why specific industry experience is important when designing a process.

I believe we need to be teaching risk analysis, as in "how to figure out what bad things will happen if things don't work right". For example, if you have a crane using an electro-magnet to transport steel, should an E-stop really disconnect all of the power sources?

I just worked at a foundry that had 2 overhead cranes that carry over 10,000 lbs of steel over workers routinely.

While I was working on one of the cranes rebuilding the rectifier, I asked about the machine to determine exactly how it worked. I did not understand how it could be expected to hold steel when the rectifier failed.

I had never worked on an overhead crane and I suggested we call a crane specialist and have the crane certified OK by a reputible crane service company. Such companies are certified and licensed by the state.

No dice,

Then I discovered that niether crane had a UPS to hold the magnet in case of a rectifier failure. I brought this up and was told the cranes were not required to have a UPS because of their age!

All new cranes are required to have a UPS.

And I suspect if you call the crane service for repair they would require a retrofit to add a UPS to give the crane pass on safety.

The metal cabinet and guard rails looked like play doh after the bar fell off the magnet when the rectifier failed.

I have run into this at every job I have ever worked.
 
I just worked at a foundry that had 2 overhead cranes that carry over 10,000 lbs of steel over workers routinely.

While I was working on one of the cranes rebuilding the rectifier, I asked about the machine to determine exactly how it worked. I did not understand how it could be expected to hold steel when the rectifier failed.

I had never worked on an overhead crane and I suggested we call a crane specialist and have the crane certified OK by a reputible crane service company. Such companies are certified and licensed by the state.

No dice,

Then I discovered that niether crane had a UPS to hold the magnet in case of a rectifier failure. I brought this up and was told the cranes were not required to have a UPS because of their age!

All new cranes are required to have a UPS.

And I suspect if you call the crane service for repair they would require a retrofit to add a UPS to give the crane pass on safety.

The metal cabinet and guard rails looked like play doh after the bar fell off the magnet when the rectifier failed.

I have run into this at every job I have ever worked.

I think this is why the concept of the service guy PLC guy electrician being trained certified is a bunch of BS.

MANAGEMENT should be inspected and certified for being rectal cranial inversion free.

NO battery backup for a crane magnet running loads over people? What kind of - ahh hell I already know
- the codes dont call for it
- costs too much
- Production God will be ****ed
- we have never had a problem.

Who cares if there is no code ? ACTUALLY there is - ie General Duty Clause which says "shall be free of recognized hazards" non compliance is more common than compliance.

I am so glad I am out of the steel business because of things like this and the same goes for the last job I worked at.
 
2 points:
1.We were all dangerous novices once.
2. If you are relying on software and a PLC to make your system safe you are doing it wrong. All safety systems need hard-wiring. ( specific safety PLCs such as Piltz etc excepted)
3.What about us experienced programmers? I've done some howlers. Thats how you become more experianced.
4. two points wasnt enough.
 
Although I agree with formal training I'm against some kind of licencing.
Point 1. I have been doing this job for 25+ years, have formal qualifications etc. & at my time of life with my experience would not like to have to pay extortionate costs to pass a test I don't need.
Point 2. passing a test does not make you good at your job it is just a licence to say you have passed the test.
Take the Part P system in the UK, what a load of cobblers.
They came up with a test for electricians with a number of parts, but suddenly realised that kitchen & bathroom fitters also needed to install sockets, switches etc (this part of the test is more comprehensive).
So they came out with a simple test for them which means they can work in bathrooms & kitchens where a qualified 16/17th ed. electrician cannot without the more intensive course.
Again the costs of passing this is expensive unless you can get your employer to pay for it.
Incedently they changed the wiring colour code at the same time so any mods after the cutoff date would use the new colour codes(convienient).
It's not getting any easier in other trades, my brother is an HGV driver & after 20 years driving lorries he has now had to take city & guilds!. Madness.
As we have no manufacturing in this country now I suppose it's the governments way of creating jobs welcome to service industry brittain, unfortunately we will be a nation of trainers with no students to train becouse we have no manufacturing, perhaps we can all emigrate to other countries that will have a need for trainers.
Well... that made me feel better Iv'e had my go.
 
I lost an arguement with a engineer about the MCR and Estop issue.

He used the Estop as an input to the PLC and then used the PLC to stop the machine.

I argued that the Estop should control the stop condition directly and ALSO be an input to the PLC so the control knows why thing have stopped and can do a reset.

I lost this arguement.

They contacted OSHA and got the OK to do it their way. Or thats what I was told.

Thats not good.
I don't believe they contacted OSHA.
Surely you can just quote the regulations to them.
In Europe we have the EN written standards to work to.
 
We need a spot for tangental non specific communication

Thats not good.
I don't believe they contacted OSHA.
Surely you can just quote the regulations to them.
In Europe we have the EN written standards to work to.

Quoting regs will you get you to the front of the next "lay off". You become the new "smart@ss know it all". Once I shut down a whole plant for a safety issue. And 2 weeks later they didn't need me anymore.

In regards to the Estop/PLC issue.......I re-wired it to stop the outputs and inform the PLC of the stoppage.

Same as theirs but mine actually stopped the outputs, which on the machine in question would render it safe.

They never noticed the difference, because if all went well there would be no noticeable difference.............IF all went well..............

I try to imagine whats the worst that can happen ...............if the PLC out gets "stuck" on, or the isolation relay fails closed, or the Estop sticks. I have even had to fight the companies I worked for to add a redundant Estop circuit!

What do you think the second set of contacts are for on an Estop???

They were just jumping them together at the switch!!!!!!!!!!!

Oddly the safest machines I worked with were huge hydraulic presses that were capable of 1200 tons and 30 strokes a minute! Talk about scarry.

Textiles and chemical plants are the most unsafe places I have worked. Small margin low profit no protection and then "free trade". No oversight no regulation or no enforcement of regulation............OSHA is a joke in the south east US.
 
osha and estops

Does OSHA really allow the PLC to shut down the outputs on an estop? I thought they required estops to be hardwired and to remove power from outputs as needed (ie, on furnaces, we only shut down things in motion (belts, fans, etc)). Thanks

matt
 
Does OSHA really allow the PLC to shut down the outputs on an estop? I thought they required estops to be hardwired and to remove power from outputs as needed (ie, on furnaces, we only shut down things in motion (belts, fans, etc)). Thanks

matt
No, they do not allow the PLC to handle estop functions -- unless it's a specifically rated/designated "safety PLC". An EStop needs to put the machine into a "neutral energy" state.
 

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