Brass Seacocks

Chris_Robb

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I was looking over the weekend for replacement seacocks - the ball type rather than the good old blakes cone shaped ones.

I could only find ones made of BRASS. Everything you read about, says don't use brass. All the chandlers seem to stock the same type, and no Bronze or Phosphor Bronze appear to be available.
 
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Ball valves are not particularly good news as seacocks. If immersed and when closed they trap a cylindrical plug of water withing the valve ball which, if it freezes, can fracture the rather thin body casting. This is more of a risk if the valve is close to the waterline, or in fresh water. There are some heavy duty types about but I have not come across any made in anything other than brass.
 

Chris_Robb

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However, they do seem to be fitted as standard now.
Re freezing - I always leave them open when ashore, but closed in the water. - I am an avid seacock closer, so all, get opened and closed virtually every time we sail.

I am mainly concerned about Brass below the waterline and de-zincing.
 

oldjohnnyb

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The www.asap-supplies.com website and their catalogue lists brass and bronze ball valves as two seperate items.
How can you tell a Brass ball valve from a Marine Bronze ball valve?
Also how do you overhaul the type of ball valve commonly sold in yacht chandlers, or are they maintenance free?
John

<P ID="edit"><FONT SIZE=-1>Edited by oldjohnnyb on Mon Nov 26 12:42:04 2001 (server time).</FONT></P>
 

brianhumber

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The Galvanic Series controls what metals you should choose. The more NOBLE the metal the better, thus use Nickel-Aluminium Bronze or Silicon Bronze. Never, never use Brass or manganese bronze, they are towards the BASE metals ie readily corroding type.
Once sailed on a VLCC with base metal pipework just before the seawater valves. Yes the rest of the pipework did not corrode being more noble, but boy were we kept busy making up new base pipework sections as it corroded faster then you could drink pints. Holed 10in seawater piping 70 feet below the surface still gives bad dreams.
 

ccscott49

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Bronze ball valves are available, with stainless balls and teflon seals, they usually come plated, but I have seen some italian ones and dutch, but no Brit ones. The main chandlers should be able to help, or cleghorn waring, ASAP supplies etc.
 

Chris_Robb

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So why are chandleries selling Brass ones which are clearly not fit for the purpose??? There is nothing on the packages to say what they are made of, - only the brochure says brass.
 

Chris_Robb

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West Marine has one of the most informative catalogues going. I must see what they say.

I am however appalled by the lack of knowledge in chandleries, and the fack that using Brass could be potentially life threatening.
 

vyv_cox

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I think there is a risk of going over the top here. Brass has been used for centuries in sewater systems. Ok, it's not ideal and for yachting use you could not expect indefinite life for brass in the way that you might for bronze. Brass seacocks could reasonably be expected to last for 5 - 10 years. I have brass fittings on my engine raw water system that are unchanged in 15 years, with no sign of corrosion. It just needs a little owner input from time to time to ensure that fittings remain in good condition. Dezincification is pretty obvious and the strength remaining in the fitting can be tested quite easily.
 

Plum

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If you hunt around you will find suppliers of ball valves made of a de-zinc-resistant brass. I bought mine from Auafax (they are a wholesaler, I beleive, but supply many chandlers) http://www.aquafax.co.uk/. They are very reasonably priced and therefore you can, if in any doubt, replace them after, say, 6, or even 10, years. Yes, most chandlers do not understand the differences and often tell you that the brass ones on the shelf are made of bronze! When you fit ballvalves please ensure you do not use a sealer that sets as you will have a big proble when you need to remove them again.
 

Chris_Robb

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Been away for a couple of days - Thanks for your response, at a practical rather than theoretical level.

What are the obvious signs of dezinking? I jnow on a propellor, it will give a pimk copper look, is this the same for skin fittings? If the plating remains intack (which most of them have) it may be difficult to see the state of the metal.
 

ccscott49

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you will see the de-zincing around the plating and through it, the plating will probably go first, it is the same as a prop. Those marelon ones, glass re-inforced plastic, are the dogs bits, next to blakes that is! They are really strong, need to be, somebody is bound to stand on one on its side, they are designed to take that kind of abuse! I shouldn't be saying this, if the classic boat lot hear, me I'll have to start using an alias! If you knew my boat you would understand!
 
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