Welding a steel craft whilst afloat - electrolysis?

[LittleVlet]

Hello

Can you arc weld steel afloat or will electrolosys dissolve the boat?

I've searched for this topic, but couldnt find anything but apologies if this a repost,

I own a 9M (29.5ft) x 3M (9ft) Dutch Steel Cruiser, built Texel 1978. The boat is currently in the water and I am working on the roof - removing rust, the old hatch and repainting. I also need to replace 16 brackets around 2" long each which have rusted away from the roof. These brackets are n shape in profile, made from 8mm steel and are used to bolt the hand rails onto the roof.

My question is, being a complete novice to welding - Will any kind of electical welding on the roof of the boat burn away my anodes due to leaking currents etc? I understand that you have to earth the hull whilst welding to it, so I guess thats a lot of ampage going into the water. Is there a way around it? Can I earth the boat to mains shorepower?

Many thanks for reading. (if you are wondering why I haven't just taken her out of the water - £430 lift out and block fee. )

Chris

PS not sure what kind of welding technology is best to use either. I've got to weld around 64" of 8mm steel. Will a £50 ($80) welder from B&Q be up to the job? 130 amp arc fan cooled?

[CDK]

Put the welder on a sheet of rubber or plastic so it is isolated and keep the area dry. Treat the outside shell of the welder as hostile, it may sting if the shore ground connection fails. Avoid contact between the hull and shore ground: the hull is in the water so it is already grounded.

An $80 welder will make this an endless job because it has a low duty factor. Once the thermal relay has cut in, you can use only a few electrodes and have to wait again. In your case I would spend a bit more and buy an inverter welder. That is DC, with much better results especially if the welder is inexperienced.

[LyndonJ]

The UK usesa MEN system (multiple earthed nuetral ) so the nuetral is tied to ground at every substation, switching point and meter.

However there's no amperage going into the water. It's a circuit from and back to the welder itself. You will only get problems if there's an electric field already in the water from someone elses faulty wiring. Then when you earth your boat their leakage will give you very minor electrolyisis unless it's a major fault.

You can measure for an electric field in the water simply by dropping a meter lead into the water and one in the earth socket of an extension lead (on ac volts) if its more than 2 or 3 volts there's a problem around.

If the neutral disconnects and the phase shorts to the csae than the fuse will blow immediately, the problem can occur with poorly wired devices where the netral and earth wores have been swapped. But if you run the device in a residual current device breaker and it doesn't trip its ok.

Other solutions are to run the welder through an isolating transformer

[troy2000]

I much prefer DC welders, partly for safety reasons. My dad and I spent a fall and winter around Montrose, Colorado one year, welding together feed yard fences out of old oil well pipe and sucker rod.

In the middle of the day, things tended to get soggy in the sunshine. We lined our leather gloves with cloth gloves, and welded until they got wet enough to start stinging us more than we cared to put up with. At which time we'd swap the wet ones for the ones we had drying on the exhausts of our Lincoln welders, and carry on.

A guy came out one day with an AC welder, and tried to keep up with us. In the first place, his welds weren't deep enough to hold; we wound up redoing most of his work. And along about the middle of the day when his gloves got wet, his welder knocked him down.

We checked to make sure he was still breathing, picked him up and set him in the passenger seat of his truck, and told his wife to skedaddle to the emergency room with him. He heard he came out of it OK, but he never returned to the job.

As LyndonJ points out, the ground leg of a circuit doesn't dissipate into the water, or into any other ground. It just uses it as a path back to the welder. So there shouldn't be any electrolysis worth noticing, or eating of anodes.

[capt littlelegs]

The UK power supply is earthed at the substation transformer, some more modern supplies use PME (positive multiple earth) systems combining the earth and neutral but they are not allowed in certain places including marina and shore supplies where a separate earth wire is required.

The supply to any metal boat should be earthed to the hull for safety and checked that all conductors are connected properly. You should also have an RCD (residual current device) in the shore supply to give fast protection in the event of electric shock.

Properly earthed there will be no significant AC current between the hull and the nearest earth point. Any AC current leakage is more dangerous to life than your boat. A boat floating in water is not properly connected to earth due to the resistance in water, only a solid earth cable can do that. You cannot tell if there is a current flowing in water by checking for voltage!

Electrolysis or galvanic erosion is not caused by faulty wiring but by the earth wire completing the circuit to earth for the small current produced by the sea water and metal boat parts. If this is a problem then an isolation transformer is required.

The voltage on welders is enough to kill in certain circumstances so do not weld in wet conditions. The best welder for your use is an inverter type with a light sensitive face shield.

[CDK]

Originally Posted by capt littlelegs

Properly earthed there will be no significant AC current between the hull and the nearest earth point. Any AC current leakage is more dangerous to life than your boat. A boat floating in water is not properly connected to earth due to the resistance in water, only a solid earth cable can do that. You cannot tell if there is a current flowing in water by checking for voltage!

Why do you continue to convey rubbish? People are looking for answers, not confusion.
Grounding a large object by putting it in a pond or lake is the correct way to do it, better than the average earth electrode which also depends on humidity. The resistance of natural water is almost ZERO for a large surface.

Connecting shore ground to your boat is stupid, unnecessary and may even kill you! You should never rely on other peoples work, badly maintained wiring etc. if you have a choice.
A new concrete pole was wired by a dumb ass electrician with the phase connected to the pole ground lug and left that way for nearly a year. The concrete was too hot to touch and the yellow green earth wires in the area carried sometimes nearly a 100 volts.
This happened 100 meters from my house. I complained immediately but no one came; they said it was impossible that such mistakes were made....

[capt littlelegs]

Originally Posted by CDK

Why do you continue to convey rubbish? People are looking for answers, not confusion.
Grounding a large object by putting it in a pond or lake is the correct way to do it, better than the average earth electrode which also depends on humidity. The resistance of natural water is almost ZERO for a large surface.

Connecting shore ground to your boat is stupid, unnecessary and may even kill you! You should never rely on other peoples work, badly maintained wiring etc. if you have a choice.
A new concrete pole was wired by a dumb ass electrician with the phase connected to the pole ground lug and left that way for nearly a year. The concrete was too hot to touch and the yellow green earth wires in the area carried sometimes nearly a 100 volts.
This happened 100 meters from my house. I complained immediately but no one came; they said it was impossible that such mistakes were made....

Despite having this explained to you previously you still persist in your silly view that electrical engineers are wrong. You obviously have no idea about electricity, the supply, installation or the safety regulations applied to it. Your comments are ridiculous, unsubstantiated, completely wrong and very dangerous. Please leave electrical subjects to those qualified to comment before you cause someone to be killed.

[Wynand N]

Originally Posted by CDK

Put the welder on a sheet of rubber or plastic so it is isolated and keep the area dry. Treat the outside shell of the welder as hostile..

Actually, the earth welding cable is already earthed to the welding machine casing...

But all welding machines, transformer AC/DC or inverter DC can kill and should be treated with utmost respect, moreso in and around water or damp conditions and would not hurt to take any type of precaution, such as CDK suggested, to make it safe for yourself and others.

[capt littlelegs]

Originally Posted by Wynand N

Actually, the earth welding cable is already earthed to the welding machine casing...

But all welding machines, transformer AC/DC or inverter DC can kill and should be treated with utmost respect, moreso in and around water or damp conditions and would not hurt to take any type of precaution, such as CDK suggested, to make it safe for yourself and others.

Of course the incoming cable is already earthed to the welder that is why it should also be bonded to the hull to prevent any possible potential difference so there would be no need to isolate it. The welding cable is not necessarily earthed to the casing. A fault to the welder case for example could still cause sufficient voltage difference to be fatal. CDK is suggesting no earth to the hull, there is no reason for this. If the hull become live because of a cable fault for example it can kill anyone in the water or stepping on to shore. The resistance of the water will definitely be too high to blow the fuse and maybe too high to activate the RCD, assuming it works, many don't in a marine environment. The UK electrical regulations demand the hull be earthed, end of argument.

[capt littlelegs]

A bit about welding onboard.

http://www.mcga.gov.uk/c4mca/mcga-mn...F91F009E3ACB72

[CDK]

Originally Posted by capt littlelegs

Despite having this explained to you previously you still persist in your silly view that electrical engineers are wrong. You obviously have no idea about electricity, the supply, installation or the safety regulations applied to it. Your comments are ridiculous, unsubstantiated, completely wrong and very dangerous. Please leave electrical subjects to those qualified to comment before you cause someone to be killed.

Littlelegs you're a nuisance, a nail in my coffin.
I probably have forgotten more about electricity than you ever had the chance of learning. Nowhere did I write that I didn't trust electrical engineers.

The electricians are the ones I do not trust. Fifty years of chasing cables in buildings and boats (your words) make you very experienced but not an expert.

I claim no such experience. In fact the only boat I ever worked on besides my own was the sailing yacht of a friend of mine, an Austrian movie director. I did that for fun because he paid the marina incredible sums and still had an unreliable electric system. For 1000 Brazilian cigars and 200 Cubans I designed, built and installed him a state of art system with monitoring display, automatic battery bank switching, fold-back current limiting instead of fuses and an audio alarm that never worked because nothing ever failed. I didn't chase any wires, just ripped out the old stuff and replaced it with a control/monitoring cable running from stern to bow and two supply wires.

You wrote somewhere that you are in the process of winding up your business, so you have a lot of spare time. Go visit the customers where you have connected shore ground to the hull, tell them you acquired advanced knowledge and cut that wire.

Below you see a picture of two Berkeley jets, approximately 6 weeks after being subjected to the effects of seawater and shore ground connected to ship ground.

I can also explain why shore ground must be isolated, show you the oscilloscope pictures and calculate the currents involved, but this picture says it all.

[capt littlelegs]

Originally Posted by CDK

Littlelegs you're a nuisance, a nail in my coffin.
I probably have forgotten more about electricity than you ever had the chance of learning. Nowhere did I write that I didn't trust electrical engineers.

The electricians are the ones I do not trust. Fifty years of chasing cables in buildings and boats (your words) make you very experienced but not an expert.

I claim no such experience. In fact the only boat I ever worked on besides my own was the sailing yacht of a friend of mine, an Austrian movie director. I did that for fun because he paid the marina incredible sums and still had an unreliable electric system. For 1000 Brazilian cigars and 200 Cubans I designed, built and installed him a state of art system with monitoring display, automatic battery bank switching, fold-back current limiting instead of fuses and an audio alarm that never worked because nothing ever failed. I didn't chase any wires, just ripped out the old stuff and replaced it with a control/monitoring cable running from stern to bow and two supply wires.

You wrote somewhere that you are in the process of winding up your business, so you have a lot of spare time. Go visit the customers where you have connected shore ground to the hull, tell them you acquired advanced knowledge and cut that wire.

Below you see a picture of two Berkeley jets, approximately 6 weeks after being subjected to the effects of seawater and shore ground connected to ship ground.

I can also explain why shore ground must be isolated, show you the oscilloscope pictures and calculate the currents involved, but this picture says it all.

I have plenty of nails! Electrical engineers make the regulations that we all with a legal responsibility should be following for safety if you carry out electrical work. You don't trust them because you think you know better and would remove the ships safety earth wire. You certainly don't know or understand the reasons for regulations, therefore I doubt you know more than me! Galvanic isolation is a secondary consideration but easily dealt without being dangerous. I have no intention of removing any earth wire, my customers are always advised of how to prevent errosion problems, it is their choice if they follow it... better a dead boat than a dead person!

[CDK]

Originally Posted by capt littlelegs

I have plenty of nails! Electrical engineers make the regulations that we all with a legal responsibility should be following for safety if you carry out electrical work. You don't trust them because you think you know better and would remove the ships safety earth wire. You certainly don't know or understand the reasons for regulations, therefore I doubt you know more than me! Galvanic isolation is a secondary consideration but easily dealt without being dangerous. I have no intention of removing any earth wire, my customers are always advised of how to prevent errosion problems, it is their choice if they follow it... better a dead boat than a dead person!

Once again, I have a lot of faith in electrical engineers, although not in all of them. The ones that needed 7 or 8 years to graduate instead of 4 eventually landed in government jobs making regulations and amending them.

Of course regulations are a necessity, they are the guidelines for the industry and save the average Joe a lot of headaches. I've never seen a regulation where it said that connecting a boat to shore ground is mandatory, but if you insist there is one in the UK, I believe you.

I have no knowledge of UK regulations because I never worked there, but I briefly studied in London to finish mechanical engineering long ago because my native country's government paid the bills and I had served my country in another way. I tasted the atmosphere, so I believe you without proof.

If such a regulation exists, it should be reconsidered.

I once wrote a book about a very specialized electronics topic. Several 1000's of copies were sold, which was quite amazing considering the limited market. An author normally does not read his own books because he knows what's in it, so it took over a year before I accidentally saw an embarrassing error, repeated several times in different chapters. Yet the book was praised and nobody ever complained.
Not everything printed is true, yet it is often taken for granted.

In an ideal case, the shore ground is an independent electrode or group of electrodes, isolated from the grid. If you connect your boat to that, I have no objection, but it is not very useful as a safety feature because your boat's hull has a much larger surface area and provides better ground contact than a copper or galvanized bar.
Perhaps that is the way it is installed in the UK.

But in the country I live in, the power company connects its neutral to the ground electrodes as well and that is asking for trouble. In bone dry rock, the electrodes do not provide the safety they suggest and the uneven load distribution over the 3 phases pull the neutral away from ground potential. On an oscilloscope screen you see a totally unpredictable jitter with spikes high enough to fast-charge your batteries with.

You do not want to connect that to your boat's hull, certainly not without a fuse (the regulations stipulate not to use a fuse there I presume). The average boat owner has no means to check if the ground connection offered is really at 0 potential and certainly not if it will stay there, so to be isolated is his best option.

*While I wrote this, the computer's UPS has cut in twice because the grid voltage was momentarily under 210 or over 250 VAC. What do you think happens with the neutral wire during such events?

[capt littlelegs]

You do not want to connect that to your boat's hull, certainly not without a fuse (the regulations stipulate not to use a fuse there I presume). The average boat owner has no means to check if the ground connection offered is really at 0 potential and certainly not if it will stay there, so to be isolated is his best option.

This is like saying the car owner has no means of checking if his brakes will work or for how long so removing them is the best option!!!

I suggest you do a little studying on earthing systems, then we might be able have a sensible discussion. The whole point in having a good low resistance wired earth is to dump fault currents and blow the appropriate fuse quickly before a dangerous voltage can be reached. It would be nonsense to put a fuse in the earth wire and for what purpose?

That is the basic system in use around the world before we get to the belt and braces of earth leakage trips that still require as good an earth as is possible and that is still an earth wire all the way back to a neutral/earth termination if possible and/or a local earth point. I know they are not all perfect but it is still the best system. You could only isolate completely from the supply earth if the supply is isolated as in an isolation transformer or onboard generator but you still need an onboard earth system for the same reasons especialy on a metal hull.

You could conceiviably have a shore supply with earth to a non conductive hull but not connected to any metal hull parts that could possible be touched but that would have to be risk assessed. There has to be a standard that suits every situation as far as practicable.

I have never had a problem where a customer has ever been in danger because I follow the regulations as the accepted standard even where it could be argued because I understand them. If I did not do that I risk being sued and having someone's death on my conscience!

People involved with electronics are the very worst for challenging supply earthing systems and other conventional systems, they only see why an isolated system makes sense to them but never see the wider picture and the safety and practical reasons that are beyond their field. A well trained electrician still has to study electrical engineering to understand it even if he doesn't have to be fully qualified in every aspect. As I have said he is still legally required to follow best practice.

[jonr]

> Properly earthed there will be no significant AC current between the hull and the nearest earth point.

There can certainly be enough to corrode your boat. I consider that significant and so do all the people who buy galvanic isolators (a way to connect your boat to ground and prevent small stray currents).


> You cannot tell if there is a current flowing in water by checking for voltage!

Sure you can. And if there is no voltage then there will be no current.