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Author Topic: Welding reminder  (Read 4217 times)
John316
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« on: November 05, 2008, 06:05:01 PM »

I'm sure that you all know this already, but this is just a reminder. Make sure that when you weld you disconnect your batteries, engine ECM, and Tranny ECM, which is what MCI tech support said to disconnect (ant-lock brake computer if you have one, we didn't). It would be a big deal to "fry" a ECM or batteries.

Another thing that I think everybody should know (a lot probably do) is that, when welding keep your ground as close as you can to what you are welding. We found out about this when a friend said that one time (many years ago) he had several things to weld on his dad's bulldozer. He didn't bother moving his ground around when he was welding, and he ended up welding a lot of things together. He welded a lot of the pins and bushings together, the differential, wiring, and a lot of other stuff (expensive "stuff" too!!!). Moral of the story, make sure that your ground is as close as you can to what you are welding.

FWIW

God bless,

John
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MCI 1995 DL3. DD S60 with a Allison B500.
quantum500
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« Reply #1 on: November 05, 2008, 09:24:25 PM »

The only thing honest you mentioned is keeping the ground close to what you are welding.  If it is mechanical or computer controlled make absolute sure your not conducting current through something you shouldn't this includes any type of wiring that spans the void between engine/transmission and body, any bearing or pivot point.  Most mechanical damage that occurs will not present its self quickly, you cannot weld pivot points together on a dozer without doing so purposely .  The worst thing that happens is making arc marks on a bearing or bushing.  Detrimental, but not permanent.  Disconnecting batteries and ecm's are a complete waste of time if you do the above. FYI  I have never ever disconnected any electrical process from the countless vehicles and heavy equipment I have personally welded on and never ever have I had a failure. 
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Dreamscape
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« Reply #2 on: November 06, 2008, 02:58:09 AM »

Quantum500,

You just got lucky!  Wink Any welding done around electronics should be done with caution. Always do as John suggested, unplug it and you are good to go, no worries. I have seen boards fried because the procedure was not followed.

I have seen sensitive electronic stuff do weird things if the procedure is not followed. It's just not good to pass the current through something you don't need or want too. It will mess up your day! Wink

Best thing to do is follow the manufactures recommendations. Better safe than sorry. Wink

Keep the ground as close to the work as John said, that's what I was taught by the way many years ago. Smiley

Paul
« Last Edit: November 06, 2008, 03:09:13 AM by Dreamscape » Logged
ArtGill
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« Reply #3 on: November 06, 2008, 03:16:19 AM »

Disconnect!!  I've got the DDEC to prove it.!
Art
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Art & Cheryll Gill
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John316
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« Reply #4 on: November 06, 2008, 05:37:49 AM »

Quantum500,

I'm glad that you haven't had any major trouble. First off with "not being able to weld parts on a bulldozer together unless on purpose" idea that you said. The friend that did this to his dad's bulldozer, cost him thousands of dollars to repair the damage. I'm not saying that this happens every time, but it can, and it is better to be safe than lazy sorry. LOL. About disconnecting the ECMs and batteries. One MIGHT not fry them every time but again, better to be safe than lazy sorry.

From my viewpoint, we don't have the extra money sitting around (even just for the batteries, those things are expensive!!!) for things to get fried. So I go to the extra hassle (it is a hassle disconnecting everything) and make sure we are absolutely safe.

That's my .000002

God bless,

John
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Hartley
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« Reply #5 on: November 06, 2008, 09:07:04 AM »

All things electronic with circuits can become the subject of what is called cascade failure.

I have seen it so many times in the computer business and other areas that it scares me to think that a $2,000 ecm system could also be subject to such
a failure.

A Cascade failre is where something seemingly harmless that doesn't cause a failure to immediately appear may have later problems. It used to be as an example that a line surge might damage a modem in a computer. Otheriwse the computer may be fine after the modem is replaced. Only a few weeks or months later you encounter strange problems and then failure of components that were not initially affected.

I have seen pickup trucks that were taken to a welding shop to have heavy duty hitches installed and within weeks of some of the work they suffered computer problems which could not be explained. Brake controllers dying or locking up after a trailer was welded on while hooked up to the truck. Engine and Antilock systems faltering and a few other things like accessories not working and stuff like that. A change of the Computer module always seemed to fix them.

Once the shop started disconnecting cables they had no more complaints.

I had a Buick once that I broke a bracket on the alternator. I carefully grounded the bracket and repaired it with a small weld. 3 weeks later the A/C compressor would not come on and the check engine light started flashing at random times.
I took it to be diagnosed and found that the ECM was damaged and slowly some of the control circuits were starting to fail ( for no apparent reason! )... Eventually the engine started cutting off. The computer was fried..
Changed the ECM and everything started working again. $800 gone just that fast!

Later I found out by actually reading the manual that IF you were going to weld on the vehicle you MUST remove the battery cables, Negative First and then the positive. Jump them together and it was then safe to weld if you were careful.

On a Bus with miles of wire acting like a large ( loop) antenna it is a wise man who diconnects electronics before welding. It is a lucky man who gets away with welding. Just one time doing it wrong can cost you an ECM, Transmission ECU and or an ABS computer which is usally more costly than the whole bus was when you bought it. You never know when a failure will happen, It could be immediately or even years down the road in the middle of some lonesome highway.

Don't take chances. Do things the right way ONCE !

This is also why I like the Manual Engine. ( MUI ) and simple transmissions...
They don't exhibit sensitivity like computer controlled stuff.

Dave....
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quantum500
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« Reply #6 on: November 06, 2008, 09:26:23 AM »

The friend that did this to his dad's bulldozer, cost him thousands of dollars to repair the damage.

Did you personally see this?  What did the welds look like that held the bearings, pivots, u-joints together?  Have you ever tried to weld 2 large pieces of iron together with current and no shield?  I'm not trying to start a pissing match but come on this sounds like a story of a story that got told at the bar the last time with lots added to it for the shock factor.  I will admit its easy to fry wiring and computers and I probably am lucky but what ever I'm doing I must be pretty good at it.  Odds are I should of had to deal with electrical failure if I wasn't doing it right.  I have literally welded on hundreds of vehicles and equipment with no effect and its my stuff or my families so if it had a failure later I would have known.
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Hartley
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« Reply #7 on: November 06, 2008, 09:55:08 AM »

Now see... Now that you know it can happen you can avoid it.

I have seen bearings get spots on them from current flow. I messed my lathe up just that way. Made the main shaft bearings noisy and now has a clunk noise as the balls roll across the charred section. Of course that was after I broke it loose again. It was an accident when my ground slipped off the work and onto the spindle.

Major failures in heavy equipment does happen due to welding mistakes and weld splatter. It would not surprise me of a dozer having such an issue..

Good Luck...
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John316
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« Reply #8 on: November 06, 2008, 10:03:50 AM »

Thanks Dave, I wasn't going to get into this much more. I know this guy, that told me the story. He is a good Christian gentleman, who has been welding for years, he welded his dad's dozer together years ago. I certainly don't question his honesty. He is a great guy, well know in our town for his honesty and integrity, and I don't think that he would tell a story about that!!! His elderly dad, on a different occasion, told me the same story, all on his own.

Quantum500 to answer your question, the man is not a drinker, and he is not a liar. That story is true. I didn't want this to be a argument, just an informative thread, for those who didn't know (like me before this guy told me). Again, better to be safe than lazy sorry. I hope that you aren't offended. Keep your advice coming.

God bless,

John
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quantum500
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« Reply #9 on: November 06, 2008, 01:50:34 PM »

Nope not offended in the least.
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rv_safetyman
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« Reply #10 on: November 06, 2008, 02:07:44 PM »

For a few years after retiring, I taught a class to maintenance folks on the subject of bearings, gears, belts and chain.  The bearing part of the class had a very specific part that covered bearing failure analysis and one of the reasonably common causes of failure was roller/race damage due to current flow through the bearing.  The problem is that the grease resists the flow of the current until the voltage builds up enough to spark across the separated surfaces.  That causes minute pitting damage that then becomes worse with time.

Here are a couple of references that touch on the subject (I can't find the specific source we used to cite in the class):

http://www.vibanalysis.co.uk/technical/electric/electric.html
http://evolution.skf.com/zino.aspx?articleID=79&lan=en-gb

Bottom line, it just make sense to take every precaution possible to prevent damage.  It only takes a few minutes to isolate the various circuits and keep the ground very close to where you are working (making sure that nothing that could be damaged is between the ground and the welding source)

One thing that has not been mentioned is the inverter.  That has a ton of electronics. 

Dave, I had not heard of the process of removing the battery cables and then tying them together.  It sounds logical.  Does that then mean that we do not have to remove the connectors to the engine/transmission/inverters?  Not doubting Dave, but has anyone else heard of the same process?  If it is acceptable procedure, It would sure make the protection process easier.

Jim
« Last Edit: November 06, 2008, 02:12:43 PM by rv_safetyman » Logged

Jim Shepherd
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John316
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« Reply #11 on: November 06, 2008, 04:52:54 PM »

Jim, good point about the inverters!!! We have two four thousand watt, Trace inverters, and I would sure hate to burn them up!!!

God bless,

John
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« Reply #12 on: November 09, 2008, 08:26:09 AM »

I thought I would bring this to the top again to see if anyone else had heard of/used Dave's process of pulling the battery cables and tying them together.  My understanding is that this would allow welding without removing the ECM connections.

Jim

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Jim Shepherd
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Kristinsgrandpa
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« Reply #13 on: November 09, 2008, 11:53:51 AM »

BEFORE WELDING..........since it's that time of the year.....

The one thing I never see, is the reminder to get out the leaf blower and clean out under the coach.

A pressureized garden hose, close by, might be handy also.

Ed
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JackConrad
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« Reply #14 on: November 11, 2008, 06:33:41 AM »

   A piece of advice I received years ago was to plan your work so that when you finish welding, you stay around doing somerhing else for a hour or so.  This is to prevent a fire starting from a small smoldering spot that was not noticible when you finished welding.  It would be a shame to leave immediately and come back the next day to find a burned out mass of metal.  Jack
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