Ball valves

ghostlymoron

ghostlymoron

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I have to replace one of my seacocks on the cockpit drain. The existing is a 1.5" stainless steel. The ball no longer responds to the lever!
I am bewildered by the choice of material. I would have thought that stainless 316 would be best but other information suggests bronze/DZR and even plated brass may be OK.
What do you recommend?
 
the use of stainless steel below the water line has many question marks hanging over it. 316 is the correct grade if you go that route.

Bronze may be the best choice but expensive, DZR brass is an alternative but you must be sure that it really is DZR. Beware of a material known as Tonval!

I think I am right in saying don't use plated brass.


But check your existing valves. It may be just the handle that is at fault.
 
The usual (cheap) ones in chandleries are usually plated brass ones, often Italian. Proper bronze ones are about 3 times the price of brass ones, you can get them from ASAP supplies. As VicS says, steer clear of TONVAL - they are only brass and will dezinctify.
 
I'm currently wondering whether to use a ball valve or replace the 20 year old gate valve on a heads outlet.

As I have had mixed results when changing a ball valve on the other heads (why Moody fitted two different types, I don't know) I've come to the conclusion as I can't afford to replace them all with traditional Blakes valves, I might just as well stick to a gate valve.
The one I saw in Port Solent at least looked and felt like Bronze. The ball valves are so light, I wonder what the material is?

Cheers
 
Why not banish the corrosion altogether and go for a plastic ball valve?
(sound of running for cover...)
 
I'll add another vote for plastic, we are changing over to plastic pipework and fittings wherever possible on the rigs and ships I work on.
However if you have bronze skin fittings, it might be advisable to connect them to the anodes in case the original electrical continuity was through the metal valve body...
 
[ QUOTE ]
However if you have bronze skin fittings, it might be advisable to connect them to the anodes in case the original electrical continuity was through the metal valve body...

[/ QUOTE ] Bronze (and DZR brass) fittings should not need cathodic protection from sacrificial anodes. Any non ferrous (ordinary brass) fittings that do require it should not be connected to the main anode system.

I dont understand what you mean by "original electrical continuity was through the metal valve body"
 
[ QUOTE ]
... I've come to the conclusion as I can't afford to replace them all with traditional Blakes valves, I might just as well stick to a gate valve...

[/ QUOTE ]
I was always given to understand that gate valves have no place on boats - something to do with the risk of them not closing fully due to corrosion etc. The first thing I did on buying 'ur boat was to replace the heads sink outlet gate valve with a ball-valve. Wasn't difficult or expensive, just access was a bit fiddly.

Yes blakes valves are expensive, but I don't like the idea of holes in hulls.
 
I'm just in the process of changing out the seacocks on our joint owned Rival 32. The original Gate valves (yes, Gatevalves) were Brass (not DZR, not plated, just ordinary brass) and have lasted 30 years. There is some slight evidence of dezincification (where the zinc disappears from the brass leaving only copper), but only a slight pinking, and not deep, easily removed with a single stroke of a file.
Only one valve failed, and that only in the stem, which appears to have been overtorqued. One was stuck fast to the skin fitting thread, requiring hacksawing the thread on the skinfitting thread, (and a replacement skinfitting as a result).
The boat has no electrolytic protection. The engine has standard Volvo gearbox to block insulation, but thats the only concesssion to corrosion.
Skin fittings (also 30 years old) seem in good order, so will stay put (except the sawn one). Heads Blakes valve is likewise in good order.
Seems amazing that all this brass is in such good order after so long, but makes me wonder how necessary DZR (dezincification resistant) brass really is. I'm sure there are some horror stories, but wonder if theyre all related to using shore power?
Replacement cockpit drains and sink drain valves will be 316 SS ballvalves. The old brass gate valves (except for the damaged one) are too good to throw away, but I'm not prepared to risk another 30 years!
Boat is wintered dry, and marina berthed in summers.
 
Hi Vic, I normally work on steel hulls and am not sure about the earthing requirements in fibreglass, wooden, or ferro cement hulls, that was why I wrote " might be advised". Quite happy to accept advice from those more knowledgable than myself...
(However I'll still recommend modern good quality plastic ball valves! (As long as they aren't mechanically stressed))
 
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