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Old 08-14-2017, 01:31 PM   #1
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Welding issues on steel boat

Hi,
Yesterday I hired a guy to do some electric welding on my steel boat while I was somewhere else..
Shortly after arriving to the marina he called me to say he would not start welding if he had no access to the engine room to disconnect all the batteries.
I told him that all the switches were in "off" ... and he said that the only way of preventing "things" to happen was by physically disconnecting all terminals from the battery poles.
As I did not get what he meant, and did not want to argue about stuff I have never heard about, I told him to come back some other day.
Was the guy right? is there a reason to be concerned about?.
Mi primitive knowledge of electricity understands that the current involved in the process will only circulate between the electrode holder and the welding machine´s ground. Am I right?
What is your experience ?
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Old 08-14-2017, 02:11 PM   #2
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I've been around construction equipment for 35 years. I've always been told (and I've read in operators manuals) to disconnect one or both battery leads before welding on a piece of equipment.

That being said, I've welded on dozens of pieces of equipment and heavy trucks without disconnecting the batteries, and I've never seen an electrical failure directly attributable to the welding.

But, I can't blame your welder for being cautious. In my case, I own the equipment that I work on, so I'm not always as careful as I would be with other folks' equipment.
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Old 08-14-2017, 02:51 PM   #3
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I also would not want to trust an owner's knowledge of electric details with my life.
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Old 08-14-2017, 02:55 PM   #4
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It's not a safety issue as much as protection for electrical and electronic components on the vessel.
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Old 08-14-2017, 03:07 PM   #5
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Welder probably got blamed for some electronics failure and decided to take no further chances. Can't blame him. And the failures may have had nothing to do with his work.
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Old 08-14-2017, 03:11 PM   #6
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Quote:
Originally Posted by neurodoc View Post
Hi,
Yesterday I hired a guy to do some electric welding on my steel boat while I was somewhere else..
Shortly after arriving to the marina he called me to say he would not start welding if he had no access to the engine room to disconnect all the batteries.
I told him that all the switches were in "off" ... and he said that the only way of preventing "things" to happen was by physically disconnecting all terminals from the battery poles.
As I did not get what he meant, and did not want to argue about stuff I have never heard about, I told him to come back some other day.
Was the guy right? is there a reason to be concerned about?.
Mi primitive knowledge of electricity understands that the current involved in the process will only circulate between the electrode holder and the welding machine´s ground. Am I right?
What is your experience ?

Your welder was right and playing it safe. When welding a steel vessel you have to remember, in most cases it is sitting in water!


The whole vessel is one big ground and there could be a large arc anywhere throughout the vessel. That arc could damage things if they are grounded to the vessel.


Hence batteries are connected to the starter and the starter is connected to the motor and the motor in connected to the vessel.


The welder did not what to take a chance in frying something is all.

I hope that helps.

Cheers and best of luck.


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Old 08-14-2017, 04:14 PM   #7
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Your welder was correct in not doing any work until the batteries were disconnected. John Deere specifies the cables be removed on their electronic-controlled engines or the warranty will be voided.
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Old 08-14-2017, 05:25 PM   #8
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I have been welding on our steel yacht for over 20 years. On the mooring, in salt water. Some quite large jobs, both MIG and stick.
Never have disconnected anything, and have never had the slightest problem.
Only electronics on board are radios and GPS.
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Old 08-14-2017, 07:43 PM   #9
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From a marine engineer.....

"As you recall, I posted some photos of a largish Deutz engine being removed from a 40m yacht aft through the saloon. That engine and its running mate both had to be rebuilt because of careless welding of piping in the engine room. Poor grounding permitted current to flow between the crankshaft(s) and bearings creating arc craters that destroyed the bearings and cranks. The cost was many hundreds of thousands of dollars.

It is a good practice to disconnect the batteries, especially on a small boat that might have DC connections before a battery switch. Few owners worry about isolating the ground. It might be belt and suspenders in the OP's case but considering the potential costs of a stray current experience it is a wise choice.

The ground should always be as close as possible to the welding arc and nearby equipment should be carefully checked for solid grounding to preclude any chance of becoming part of the welding circuit. Just because electricity follows the path of least resistance doesn't mean it won't take the one "less traveled."
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Old 08-14-2017, 08:33 PM   #10
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A steel boat is basically a giant ground, ie. conductor. Even if the ground clamp is close to the area being welded, it is possible to generate induction currents (I think that's what they are called) from the cables laying on the surface of the vessel. I've seen some rather large and cool looking magnetic field lines left on my garage floor in the grinding dust when working on my vehicles along the welding cables.

It's POSSIBLE to generate a current in a hull along the weld cables next to wiring that might damage sensitive electronics. Disconnecting the batteries should eliminate this since it breaks the circuit.

My 2 incomplete cents. I don't understand it completely, but enough to know it is wise to disconnect the battery
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Old 08-14-2017, 08:48 PM   #11
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Quote:
Originally Posted by psneeld View Post
Just because electricity follows the path of least resistance doesn't mean it won't take the one "less traveled."
If the ground selected for your weld can't handle the full current needed, it WILL find its way around other paths to complete the circuit via the least resistance possible. Yes, that path can be down and around a shaft and back up through a bearing shell

Again, I don't know everything there is to know about welding...but I know enough to be cautious
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Old 08-14-2017, 08:49 PM   #12
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Why argue it takes 30 seconds to disconnect a battery and 30 minutes reading about the rights and wrongs
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Old 08-15-2017, 06:50 AM   #13
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Hi, thanks to all for the input!
Although a lot of welding has been done on my boat without disconnecting the batteries before I got recently warned (so far nothing happened, or at least I did not notice it). I will take your advice and do it from now on.
Is it enough to disconnect the switches, or do they have to be actually disconnected?
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Old 08-15-2017, 06:18 PM   #14
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In building wiring, the hot and neutral conductors must share the same raceway. When AC welding, the cables are not usually run close/parallel. This makes an opportunity to cause induction heating and/or current coupling in ferrous metals and possibly into lone dc power wires. (If one welding cable looped around a dc feeder). Eliminating any chance for this ac current through the battery is a good idea. Either lift the neg or switch pos to open.
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Old 08-15-2017, 06:27 PM   #15
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I know on my motorhome if they do any welding on the chassis, they unhook the batteries.
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