welding on plc

[goxx]

any of you guys ever seen and plc being "taken out" by welding being done on the machine that it is running? loss of program or fried plc?

 

[Ken Moore]

Never a PLC, but other electronics yes. Usually happens when the welder ground lead and the "stinger" are on opposite ends of the machine, the welding current then flows through the machine.


ken

 

[LadderLogic]

I've seen an older Micrologix 1000 losing its brains exactly because of that. It is never a good idea to arc-weld anything on the 'live' machine (lots of noise). If one has to do it, the grounding should be planned very thoroughly.

 

[Johnny T]

Yep, seen a PLC killed by welding... as has already been mentioned its usually because the welder hasn't been earthed properly. Always best to turn power off to the panel before doing any welding.

 

[ArikBY]

I saw it few times.I hate to see welding on the machine after the PLC installed.

 

[jstolaruk]

Shop labor here does it too often (against my recommendations). It raise the hair on the back of my neck. Management won't wake up until they have to replace a ControlLogix processor and/or a drive at a couple of grand a pop.

 

[LadderLogic]

Well, it's their money, after all. For them to waste...

 

[leitmotif]

ALWAYS
place work clamp as close as possible to where you are welding.
IF you don't then you can weld thru bearings or hoist cables (they can start smoking). Makes the bearings "lumpy" and weakens hoist cables.

ALSO watch out for TIG.
I don't know about "modern" units
BUT I KNOW
with my 1976 era Hi Freq unit I disrupted my neighbors TV reception,
and one time at school I screwed up any and all computer within 100 feet -- BOY did I hear about that one.

Dan Bentler

 

[CaseyK]

I have never seen any one weld with a plc hooked up.

I have always recommended disconnecting them before welding, and never weld when they are running.

I have seen many that fried.

regards.....casey

 

[jstolaruk]

Many of the machines I've designed have had TIG welders as part of the machine so maybe thats why we've been lucky.

Naaaw, that couldn't be it. I just think it hasn't caught up to these guys yet.

 

[CaseyK]

I have never seen any one weld with a plc hooked up.

That is not true.

My first two projects each had four mig welders with PLC-2's, and no problems.

Plus, what about all the robot welders out there.

GROUNDING must be the the important factor, so I will conclude, it depends on proper installation.

regards.....casey

 

[Tim Ledwith]

I've lost too many PLC's because of this (including some very expensive 5/40E's). I always "overground" my PLC Chassis (biggest wire I can get to fit) but it still happens. I think the problem is that they put the welding earth on the work table the enclosure is sat on while they do the welding instead of close to where they are actually welding. What I do now is after the Factory testing, I remove the PLC, any communications adaptors and any computers, box them up and send them seperately. This has saved me any fried PLC problems. Now I get lost and missing PLC problems . . . .

Tim.

 

[leitmotif]

Huh ?????????

I've lost too many PLC's because of this (including some very expensive 5/40E's). I always "overground" my PLC Chassis (biggest wire I can get to fit) but it still happens. I think the problem is that they put the welding earth on the work table the enclosure is sat on while they do the welding instead of close to where they are actually welding. What I do now is after the Factory testing, I remove the PLC, any communications adaptors and any computers, box them up and send them seperately. This has saved me any fried PLC problems. Now I get lost and missing PLC problems . . . .

Tim.

Wait a minute Are you guys telling me that weldors weld on the cabinet the PLC is in? They fry the PLC from heat alone? They don't look inside to see what they can burn up or what just MIGHT need a welding blanket or plastic to keep the burning paint off?

Forgetting to move the work clamp is one thing and I guess I can sort of forgive that, but too lazy to protect or remove cabinets guts is ,,,,,,,,
If they worked for me that would not last long. On other hand as an electrician I guess I have to be grateful for added job security.

Dan Bentler

 

[rsdoran]

Wait a minute Are you guys telling me that weldors weld on the cabinet the PLC is in?

I kind of left this alone because I am sure many have seen the results from welding on machines that have electronic devices, not just plcs.

What happens is many cases is maintenance etc has a portable or buzz box welder that has one short lead and one long lead. The "ground" clamp lead is usually placed anywhere close to the welding machine but the welder with the electrode lead may be 100 feet up/down/away.

Simple electric theory will show that you "ground" will now carry current, if an electronic device is in the path that ground is using it can "backfeed" into its circuitry causing damage.

I have not only seen it...I have done it and fried devices...actually more than once. I have also drilled a hole in a cabinet door for a PB and the shavings fell into a DL20 and it died. I have also....thats enough for now.

In the past you would not learn things like this except by making the mistakes, its good to see this kind of question posted and the general answer showing what the results can be.

 

[Doug_Adam]

Luckyly, no.

I have seen:
Cables that we pulled out were burned through due to welding from years ago, somhow it kept operating.
Stuck barings due to welding.
People drilling through the tops of cabinets and letting the swarf fall on everything inside. Lost a couple of drives this way, but it could have been worse.