Dangerous novices programming plc's

[demmons]

I would really like to see controls programming/Design taught in Vocational High Schools. I took 3.5 years of machine shop 4 periods a day. The advantages are :

• No pressure to just get it done, learning is done at the students pace.
• Good supervision.
• Plenty of time to mess around and get the feel of what is going on.
• Plenty of time to learn both theory and practice.
• Usually a decent enough budget to get a lot of different equipment.
• Co-op opportunities for OJT.

 

[leitmotif]

I do not favor this type of instruction in High School for following reasons
1. the best instruction platform is with real world equipment 230 VAC and maybe 460 VAC.
2. High school kids are not mature enough to be around this stuff.
3. Many states will not allow under 18 in industry. There goes co op for OJT.
4. from what I saw granted years ago high school shop was just a glorified play room.

I do see the community colleges as a mucn better place for this type of program because
1. Older students
2. Not restricted to just high school age
3. Not as regulated as a school district is
4. More real world and no molley coddling - go ahead dont do homework - flunk - it is up to you.
5. Instructors are often as well educated as those in 4 year schools and are more dedicated - no research nor emphasis on publish or perish.
6. More able to have industry interaction than a high school.

Dan Bentler

 

[robertmee]

I do not favor this type of instruction in High School for following reasons
1. the best instruction platform is with real world equipment 230 VAC and maybe 460 VAC.
2. High school kids are not mature enough to be around this stuff.
3. Many states will not allow under 18 in industry. There goes co op for OJT.
4. from what I saw granted years ago high school shop was just a glorified play room.

I do see the community colleges as a mucn better place for this type of program because
1. Older students
2. Not restricted to just high school age
3. Not as regulated as a school district is
4. More real world and no molley coddling - go ahead dont do homework - flunk - it is up to you.
5. Instructors are often as well educated as those in 4 year schools and are more dedicated - no research nor emphasis on publish or perish.
6. More able to have industry interaction than a high school.

Dan Bentler

Also at community college you are paying to learn so you are usually more motivated to do so. At High School you're just trying to score chicks

 

[Clay B.]

I do not favor this type of instruction in High School for following reasons
1. the best instruction platform is with real world equipment 230 VAC and maybe 460 VAC.
2. High school kids are not mature enough to be around this stuff.
3. Many states will not allow under 18 in industry. There goes co op for OJT.
4. from what I saw granted years ago high school shop was just a glorified play room.

Not sure I agree here: I think High School is a real good place to introduce students to PLCs and automation controls.

1: Yes 480 VAC is most common for motors but most controls now are 24 vdc. Unless they are doing drive theory I do not see the need for high voltage
2: I am not sure what maturity has to do with it. If you do not do the work you do not pass the class
3: Agree here, a high school student would be useless for co-op reguardless of the regulations
4: That would depend on the teacher and the curriculum. We had drafting, wood working and automotive shop where I went to school and all were ran seriously.

I do see the community colleges as a mucn better place for this type of program because
1. Older students
2. Not restricted to just high school age
3. Not as regulated as a school district is
4. More real world and no molley coddling - go ahead dont do homework - flunk - it is up to you.
5. Instructors are often as well educated as those in 4 year schools and are more dedicated - no research nor emphasis on publish or perish.
6. More able to have industry interaction than a high school.

Dan Bentler

Biggest problem I see with Junior Colleges is how they are regulated. I have had several prospective employees come from a Junior College "PLC Program" that did not have a clue. Once again it goes back to the program. Alot of these colleges are using outdated equipment and even basic programming skills are being glossed over. Alot of these junior colleges are nothing more than paper mills where students buy their degrees.



In my opinion, it is up to the individual. He/she needs to make the call if they are qualified to do the job. Problem with this is the fact that you may not see what you are up against until your in it. Doing good research does help with the gotchyas but heck your going to go up against something that will stretch your abilities, it is just part of the trade.

The one thing my experience has taught me is how to ask better questions.

 

[demmons]

My vocational high school education must have been different from you folks experienced.

• We had to qualify to enter the county program.
• We worked with top quality lathes, bridgeports, surface grinders, both manual and CNC.
• We had a separate shop for electrical construction where high voltages were used, and these guys and girls were sent out to Co-op to work for electricians.
• I personally went to work in a machine shop instead of going to shop for the last six months of my high school career under our Cooperative Industrial Education program, and I didn't turn 18 until a week after I graduated.
• I was also taking extra classes in high school to prepare for college.

I guess what I am saying is...if vocational education is done right with motivated students and qualified instuctors, as it was done for me. It would be a good place to start.

 

[icky812]

I'm going to do something I rarely do and weigh in on this one.

All high schools are different, but in the case of the high school where my daughter goes it works like this for extra credit/advanced classes.

As a company AutomationDirect sponsors the local FIRST robotics team. It consists of middle and high school aged kids. They learn safety, electronics, programming, critical and logical thinking, and troubleshooting skills.

As you can see from the picture on the first page the kids have fun. The amazing part is, when it comes down to working they dig in and go. Some of the projects that they have done are quite amazing.

So far in the four years of the program I don't know of a single major accident. A few minor cuts and bruises, but no lost fingers, eyes or other major body parts.

By the way. All of it is done by the kids. All the mentors do is keep the kids safe, provide instruction, and provide guidance. The kids do it all. Even the webpage I linked up top is done by the kids.

Most of the programs at the local schools are similar. My daughter is n JROTC. It works the same way. The kids do it all. The instructors mentor and guide. I've never seen the instructor do any of the inventory or other general clerical work. His thinking? Quote; "The kids are going to have to do this stuff when they graduate. They might as well learn now. I know how to do it. They don't."

Don't do your homework? You're out. Commit a crime? You're out. Underage smoking or drinking? You're out. The kids want to be there and it shows. Depending on the circumstance, the kid may get a second chance, but there is no shortage of kids wanting in the programs.

They are great programs and great kids who are in them.

 

[TheStarr]

I have only been in the "industry" for a few years, my major experience came from the Air Force (Aircraft Mechanic).

Here is what I got out of all of this....

I started programming PLC because my company was in a bind, they needed things done NOW, and I figured it out. That was dangerous.

Luck played as much a part as thought, that I didn't hurt myself or anyone else.

It is sad to say, but most of my PLC knowledge comes from right here in this forum and from experimentation.

Should certification be required? Yes.

Should an apprenticeship be required? I think so. Just like a plumber or an electrician.

College courses, no matter how long or complete, can not prepare you for this industry. Only experience can make you safe.

And last... drum roll please......

Four sentences make a paragraph! Use the Enter key once in awhile!

I think I may be permenently cross-eyed after reading some of those novels!

 

[Tech7]

We make it look easy!

Right on Goody! I guess the expert programmers are somewhat to blame for this "how hard can it be?" menatality. Sometimes we make it look way too easy to the layman or CE's. Don't worry though, as we get older it gets much more difficult. Heck, it's tough just getting out of bed and going to work some mornings

 

[interd0g]

"The older I get, the better I was"

 

[henry5674]

the thing that concerns me the most is this statement:

"Machines controlled by plc’s can injure and kill people if something is not programmed right!"

to clarify for any newbies reading this thread. a plc should have NO control over the safety systems of a machine, accept if it is a certified safety PLC. The worst case could be very expensive damage but no-one should get hurt. though your boss may beat the **** out of you afterwards!
What worries me is not the inexperienced playing with PLCs but the "i'll just wire my e-stops to the plc inputs and i'm done, whats a saftey relay anyway?"
Learning PLCs is only a small part of the overall role of controls and if you ask me should be studied after the basics of machine control and design especially safety regulations and requirement. Even a tech that is required to make small modifications should be fully aware of these before playing with the "Fun" PLC bit

 

[CowDung]

the thing that concerns me the most is this statement:

"Machines controlled by plc’s can injure and kill people if something is not programmed right!"

to clarify for any newbies reading this thread. a plc should have NO control over the safety systems of a machine, accept if it is a certified safety PLC. The worst case could be very expensive damage but no-one should get hurt. though your boss may beat the **** out of you afterwards!
What worries me is not the inexperienced playing with PLCs but the "i'll just wire my e-stops to the plc inputs and i'm done, whats a saftey relay anyway?"
Learning PLCs is only a small part of the overall role of controls and if you ask me should be studied after the basics of machine control and design especially safety regulations and requirement. Even a tech that is required to make small modifications should be fully aware of these before playing with the "Fun" PLC bit

Perhaps in machine design, one relies on safety relays to keep people safe, but in process control, it's not necessarily that easy--improper programming can injure or kill people.

For example, a CIP (clean in place) system typically relies on prox switch inputs to verify that pipes/hoses are connected before allowing a specific circuit to be run. If the the incorrect address is used in the PLC for the prox inputs (or the programmer doesn't know enough to use them to inhibit the cycle), the pipe can be physically be open when the cycle is started and anyone in the area can be sprayed by hot caustic solution...

 

[henry5674]

For example, a CIP (clean in place) system typically relies on prox switch inputs to verify that pipes/hoses are connected before allowing a specific circuit to be run. If the the incorrect address is used in the PLC for the prox inputs (or the programmer doesn't know enough to use them to inhibit the cycle), the pipe can be physically be open when the cycle is started and anyone in the area can be sprayed by hot caustic solution...

But surely if there is risk of injury from this, shouldn't those prox switches be keyed safety switches controlled by a safety PLC or safety circuit enabling the circuits? I only deal with the machinery directive which is a european directive so not a clue on the requirements in the US or on process control, I guess there is a whole different set of standards in that area.Surely when it comes to risk of injury or death the same basic ideas apply?

 

[CowDung]

If that were really the case, why would they bother selling non-safety PLCs?

If the system is properly programmed and checked out thoroughly, those prox switches will do a fine job of keeping people safe without the added costs of safety PLCs and safety switches.

Pretty much any automated piece of equipment has the potential to hurt somebody. The idea is that the programmed system needs to be thoroughly tested and the inhibits/permissives verified before turning it over to the customer.

 

[bernie_carlton]

Safety deals with people. If people are in proximity to functioning parts of the machine then it is the responsibility of all to ensure that actions which can harm those people cannot take place.

If the chance of injury or the probable degree of injury is slight then ordinary devices and logic can be used.

But as the risk rises so does the need to ensure that fail-safe devices and methods are used. With non-safety PLCs this means that the inhibit to the actions must take place outside the control of the PLC. Redundant safety switches and self checking safety relays need to be used in these riskier situations.

Let's also not forget that operator safety training and rigorous enforcement of safety procedures must be used. The 'forget the safety procedures - get production going' attitude must not be tolerated from anyone.

In the CIP system noted with the possible severity of malfunction as described, then probably keyed magnetic switches should be used leading to a safety monitoring relay. Only if all was in place would power be switched to the devices which can be switched on initiate the flow.

 

[henry5674]

if there is a possiblilty of an inexperienced tech or newbie programmer causing injury from PLC changes then this should also be considered in assessing the safety requirements of the control system. there's always grey areas when it comes to safety control, even more reason for trainee students to be made aware that the safety control of a system should be studied and understood as well as PLC programming.

Scariest thing i every heard "don't worry about that power press , i'll change all those old yellow pilz relays for a neat little mitsubishi PLC"