Seacock - Mixed metals?

It's a pity that the full facts have not been made known. It seems from what you say that Seahope even withheld relevant information when he posted his tale of woe on here
He didn't withhold. At the time of posting on here he had misunderstood what had happened. It was only later after seeing the fine detail of the insurer's surveyor's report that I got the full facts and was able to construct the case that ultimately defeated Towergate. It was a bizarre set of facts that won't be repeated and doesn't affect any discussion on seacock bonding, so is kinda irrelevant
 
OK,with respect to your knowledge. Why did Bene not bond the seacocks on my 351 and 381? If I was to bond them now and something were to happen due to seacocks fizzing, who would be to blame? Would the best advice be, keep the system as the manufacturer made it?
S
Bene are expert cost cutters. You don't have to bond seacocks and the boat is likely CE cerifiable without bonded seacocks. If you bond them now that cannot cause seacock fizzing. My own boat is sitting in the sea in Antibes right at this minute with bonded seacocks and nothing is fizzing. (She is being lifted next Monday so I'll make sure 2x on that!).

If you don't bond them and get a local galvanic cell scenario or my failed pump scenario, not bonding them could sink your boat. Alternatively if you do bond them then introduce a positive potential to your earth circuit by some duff electrics a la Random Harvest AND have ineffective anodes, then bonding them could cause your boat to sink. So the correct answer has to be bond your seacocks and have good electrics+anodes I suppose!
 
Perhaps that's to be expected: the reality is that the world's best engineers and weigher-uppers of evidence do not faff about doing reports on sunken 25 foot fishing boats in which nobody died and seacocks. When you have your own knowledge and perhaps a degree plus lots of experience in engineering matters you take a report like RH with a healthy pinch of salt.

What a ridiculous and arrogant statement. Do you suppose that the MAIB keeps a list of second division investigators specifically to produce slapdash reports? In a long career spent carrying out engineering failure diagnosis I have investigated items varying in price from less than £1 to £several hundred millions. I believe that I carried out every one of them to the full capability of my degree and considerable experience. I know nothing of the MAIB but since they are charged with investigating all types of failure I assume that they contract in specialists in the various scientific and engineering disciplines necessary for each job. If I was responsible for this activity and reporting to the UK government I would employ the best people I could find and see no reason why MAIB would not do the same. The cost of the failed item has absolutely nothing to do with the quality of the report.
 
What a ridiculous and arrogant statement. Do you suppose that the MAIB keeps a list of second division investigators specifically to produce slapdash reports? In a long career spent carrying out engineering failure diagnosis I have investigated items varying in price from less than £1 to £several hundred millions. I believe that I carried out every one of them to the full capability of my degree and considerable experience. I know nothing of the MAIB but since they are charged with investigating all types of failure I assume that they contract in specialists in the various scientific and engineering disciplines necessary for each job. If I was responsible for this activity and reporting to the UK government I would employ the best people I could find and see no reason why MAIB would not do the same. The cost of the failed item has absolutely nothing to do with the quality of the report.
Hang on there! You've read the RH report and you can see that the statements I referred to are utterly unsubstantiated. That makes the report second rate on that score, though of course it was a good report in bringing to folks attention dezincification of brass. As regards your sentences 3+4, I wasn't talking about you. As regards MAIB it would be nice to think they used the best experts out there but they are a government department with costs to keep under control, and your view that they would use a top expert to look at a seacock on day boat that got wet without anyone drowning might be a bit out of kilter with reality. Fact remains that we have on the one hand internet momentum behind the "don't bond seacocks" view which I think stems from the RH MAIB report (and, in my book, some mis-reading of that report) while on the other hand plenty of engineers and the world's quality yachtbuilders bond their seacocks.
 
How are you "sure"? Do you really think that the best engineers in the world would be in business as small second hand boat surveyors? The fact they are small boat surveyors is frankly a strong indication that they are not the sharpest tools in any box. They might even have read Random Harvest and not read it particularly well! The world's best yacht makers bond their seacocks.

The "day job" of one of the surveyors I referred is to survey large commercial ships, small boats are his hobby. Surveyors in associations have access to databases listing faults found on different boats and areas of particular concern to which they can refer.

You are an expert in some areas of law, but presumably not the sharpest tool in the box in others. At least give qualified surveyors some credit for knowing what they are talking about in their particular area of expertise.
 
Fact remains that we have on the one hand internet momentum behind the "don't bond seacocks" view which I think stems from the RH MAIB report (and, in my book, some mis-reading of that report) while on the other hand plenty of engineers and the world's quality yachtbuilders bond their seacocks.

OTOH there are millions of boats out there without bonded seacocks that have not suffered seacock failures, or even, in my own case, 30 years with no visible dezincification. As I posted earlier, when I looked into the reasons for bonding I could only find USA practice that seemed to be more to do with lightning strikes than corrosion protection.
 
You are an expert in some areas of law, but presumably not the sharpest tool in the box in others.
Yikes, I'm not sure where you got my CV from (:)) but I have a degree in engineering. From Imperial. You, and your surveyor?
Anyway I'm happy to disagree as I said earlier. Also as said earlier, my main concern is that this forum is "right": there is a string of posts above saying it is generally accepted that seacocks shouldn't be bonded, and for the benefit of folks who might read this in the future I wanted that balanced by mention of the facts that there is a considerable weight to the opposing view, and many (perhaps most, but I don't know that) serious yachtbuilders including just for example Oyster always bond their seacocks. Folks can decide for themselves of course (and hey, thanks to various collective efforts including yours we're all insured for this nowadays :D)
 
Yikes, I'm not sure where you got my CV from (:)) but I have a degree in engineering. From Imperial. You, and your surveyor?
Anyway I'm happy to disagree as I said earlier. Also as said earlier, my main concern is that this forum is "right": there is a string of posts above saying it is generally accepted that seacocks shouldn't be bonded, and for the benefit of folks who might read this in the future I wanted that balanced by mention of the facts that there is a considerable weight to the opposing view, and many (perhaps most, but I don't know that) serious yachtbuilders including just for example Oyster always bond their seacocks. Folks can decide for themselves of course (and hey, thanks to various collective efforts including yours we're all insured for this nowadays :D)

I think it's best if we just agree to disagree on bonding, too many experts (and amateurs like most of us on the forum) with differing views but little in the way of definitive science. It's not worth falling out about.

Yes, we have managed to persuade at least one insurer to change their policy wording regarding corrosion but I've still replaced all but one of my underwater fittings with composite:)
 
I think it's best if we just agree to disagree on bonding, too many experts (and amateurs like most of us on the forum) with differing views but little in the way of definitive science. It's not worth falling out about.

Yes, we have managed to persuade at least one insurer to change their policy wording regarding corrosion but I've still replaced all but one of my underwater fittings with composite:)
Wot you need is Male Bonding :)
 
Yikes, I'm not sure where you got my CV from (:)) but I have a degree in engineering. From Imperial. You, and your surveyor?
Anyway I'm happy to disagree as I said earlier. Also as said earlier, my main concern is that this forum is "right": there is a string of posts above saying it is generally accepted that seacocks shouldn't be bonded, and for the benefit of folks who might read this in the future I wanted that balanced by mention of the facts that there is a considerable weight to the opposing view, and many (perhaps most, but I don't know that) serious yachtbuilders including just for example Oyster always bond their seacocks. Folks can decide for themselves of course (and hey, thanks to various collective efforts including yours we're all insured for this nowadays :D)

Historically it was often, if not usually, recommended that all underwater fittings were bonded to the anodes but thinking seems to have slowly shifted away from this. MG Duffs website used to include the recommendation to bond all underwater fittings however the section has fairly recently been rewritten and no longer includes this.

Not sure of the relevance of a qualification in Engineering. My son has a Masters degree in engineering. If I remember I'll ask him about all this on the weekend, although his priority job is do deal with a leaky ballcock for me. Something to do with a "washer" I believe.

What we really need is someone with experience and expertise in electrochemistry and/or sea water corrosion. I used to work alongside a small team of Chemists who were experts on seawater corrosion but sadly I have lost contact with them all.
 
I don't mean to drag this thread back to the top but maybe I can bring it back in line with the original question which was to do with different metals at a seacock. Originally I posted a Stainless valve attached to a bronze elbow. Here is a new question:

Below is a large stainless holding pot attached to a large inlet manifold seacock. From that I have 6 x 3/4 bronze ball valves that go to various areas of the boat. I have now removed them all to service and clean but should I really be considering replacing them for all stainless valves given that that are attached to a stainless thread? That said, the valves look ok with no signs of corrosion after 18 years apart from the usual crud and ground up limpet shells.

10968416_10153033302228162_8317834394687943282_n.jpg
 
I don't mean to drag this thread back to the top but maybe I can bring it back in line with the original question which was to do with different metals at a seacock. Originally I posted a Stainless valve attached to a bronze elbow. Here is a new question:

Below is a large stainless holding pot attached to a large inlet manifold seacock. From that I have 6 x 3/4 bronze ball valves that go to various areas of the boat. I have now removed them all to service and clean but should I really be considering replacing them for all stainless valves given that that are attached to a stainless thread? That said, the valves look ok with no signs of corrosion after 18 years apart from the usual crud and ground up limpet shells.

I think you have answered your own question.

If there is no problem after 18 years there is no problem.
 
Well this is true. Oh by the way, they were all bonded during that time :disgust:

your choice now whether to keep or remove the bonding. You've read the debate.

presumably your disgust indicates that you will remove it but if you do keep it be sure to maintain the boat's electrical wiring in good order. :)
 
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maintain the boat's electrical wiring in good order. :)

Well that is a whole different story. Once I've renewed all my valves I intend to go around and figure out where all the bonding wire goes and the condition of it. Back in 96 Ian Anderson certainly ensured things were done best practice but still it is 18 years old.
 
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