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Old 15-06-2012, 17:37   #16
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Re: Sea Cock Won't Open or Close

Replace it with a Spartan and be done with the headache.
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Old 15-06-2012, 18:00   #17
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Re: Sea Cock Won't Open or Close

Am I correct that you've the question, "How fast does a material degrade?" to how much it degrades? I like it.

In the right conditions some plastics, in the right circumstances, can degrade as much as 70% in 24 hours. Others in the same environment, will degrade 6% in 4 days then flatline for the next 24 days of the test.

The question for boat owners is what is the environments these parts are subjected to, what is a maximum acceptable level of degradation, and what is an an acceptable minimum base line.
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Old 15-06-2012, 18:05   #18
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Re: Sea Cock Won't Open or Close

Cburger,

I had Spartan's on my old Shannon. I'd consider them an excellent option, but not the only one. Is there some basic standards that you can think of that can fit the criteria to define a really good seacock.
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Old 15-06-2012, 18:31   #19
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Re: Sea Cock Won't Open or Close

ball valves just dont have that big a shaft at the smallest cross section.... I'm surprised there arent more stories of them failing..... I'm a big proponant of tapered seacocks....
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Old 15-06-2012, 19:05   #20
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Re: Sea Cock Won't Open or Close

A good ball valve doesn't really have a shaft it has a key arrangement that meshes with a slot in the ball. As I said My Shannon had old Spartan seacocks and they were great. Or Benford had ball valves and they worked great. The boats were of the same vintage and had similar usage. I checked all the valves regularly. The only problem I had was on one of the Spartans. The cone was severely pitted and had to be replaced. I don't attribute that problem to the design or quality of the of the product.

Design preference aside, if someone you knew said that they really preferred a ball valve, what good general advice as to the qualities to look for in a seacock?
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Old 15-06-2012, 21:08   #21
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Re: Sea Cock Won't Open or Close

I've been selling seacocks for a long time. I've seen both Marlon and bronze ball type seacocks with broken stems. They were frozen and people just twisted them off. I've seen tapered plug seacocks frozen so badly they had to be disassembled and the taper pollished and greased before you could move them. With ball valve type seacocks the solution is very simple, just exercise them a couple of times a year. For tapered plug seacocks, exercise and a little grease once a year and they will never freeze. A lot of people put grease fittings in one of the drain holes of tapered plug seacocks. This makes it very easy to give it a shot of grease once in a while. Never do that on a ball valve seacock as the pressure of the grease can blow out the seals.
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Old 15-06-2012, 21:14   #22
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Re: Sea Cock Won't Open or Close

Jedg, If I were buying seacocks for a boat today, I'd probably not buy seacocks. I'd use Groco Flanged Adapters and ball valves. Groco Flanged Adapter IBVF
That makes it real easy to change the valve if you need to, but gives you the strength of a seacock.
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Old 15-06-2012, 22:25   #23
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Re: Sea Cock Won't Open or Close

HopCar - I just sent you a response to the other thread post. I'm not trying to diss the Groco flanged unit and I agree with you on the issues of maintenance. I'm trying to find out what people really think in important regarding that most critical part of their boat, those holes in their hull.

There just seems to be a disconnect between our concerns for safety and what we're willing to accept. Here's an example. You mentioned on the other thread that you saw a thru-hull/ball valve combination get impacted by something and sheer off. I suggested that the mechanical weakness properties of the thru-hull/ ball valve combo are similar to the Groco flange.

So, we set an impact standard, let's say we make it simple, something we all can relate to. We take a regular 8 lb splitting maul with 36" handle. We make a pendulum. We affix a thru-hull/ball valve combo to a fixed platform. We then take the maul and pull it back 90 degrees and let it go. We do the same for the Groco unit. And we do a control unit, a regular Spartan tapered and a Groco top line seacock.

This needs to be impartial, so we need to arrive at a minimum number of hits that defines a safe assembly. How many hits would you deem acceptable before either assembly sheered of.

1 4 6 10

Let's say that a reasonable number of hits is 6. So let's say that the ball valve combo goes to 8 and the Groco flange goes to 9. But the two seacocks go to 12. The issue to me is, what is the appropriate standard to use.

Let me throw in a ringer. At the time of the test someone comes up with a new plastic thru-hull/ball valve system that withstands 25 hits.

Do we raise the standard? Or do we keep the one we established and just let people decide which level of risk they're willing to take?

Interestingly, I don't believe there is an ABYC impact standard for thru-hulls and seacocks.
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Old 16-06-2012, 00:03   #24
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Re: Sea Cock Won't Open or Close

Quote:
Originally Posted by Jedg View Post
Am I correct that you've the question, "How fast does a material degrade?" to how much it degrades? I like it.

In the right conditions some plastics, in the right circumstances, can degrade as much as 70% in 24 hours. Others in the same environment, will degrade 6% in 4 days then flatline for the next 24 days of the test.

The question for boat owners is what is the environments these parts are subjected to, what is a maximum acceptable level of degradation, and what is an an acceptable minimum base line.
From my limited experience the one big enemy of any plastic or plastic cousin is sunlight.
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Old 16-06-2012, 02:54   #25
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Re: Sea Cock Won't Open or Close

I use Use black (poly valves)
& have some in use 10 yrs

The bore water that they carry
Can be more corrosive than sea water
Black grey & engine they have all performed
Well.
Value $$$ 5*****

Goggle Philmac poly ball valve
Rural poly irrigation
They work for me!!!!
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Old 16-06-2012, 10:02   #26
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Re: Sea Cock Won't Open or Close

"I've been selling seacocks for a long time. I've seen both Marlon and bronze ball type seacocks with broken stems. They were frozen and people just twisted them off. "
Yep, In fact broke at least one myself. To my thinking the weak point is the shaft, or possibly the threaded end on the shaft. Some shafts have an o ring on them, so the oring slot is the smallest diameter part... The ball can be a lot bigger than the wimpy shaft. I'd feel a lot better if they made the shaft about half the diameter of the ball!
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Old 16-06-2012, 20:04   #27
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Re: Sea Cock Won't Open or Close

Jedg, It would be a fun experiment. We should use 3/4" test samples as that is the smallest commonly available seacock. I suspect that your 8 pound maul wouldn't have much effect on a traditional seacock with properly secured flange. I think it would knock the ball valve off of a thru-hull. I don't know what would happen with a ball valve on a Groco Flanged Adapter. My gut is that the better thread engagement and flange would allow it to survive.
In my opinion, traditional seacocks have stood the test of time and there is no need for any thing stronger. Where there is room for improvement would be to make them lighter, cheaper or require less maintenance.
Come on down to Miami and we'll break some thru-hulls!
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Old 16-06-2012, 21:46   #28
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Re: Sea Cock Won't Open or Close

I just wrote you a long note on my thoughts on the Groco flange/ thru-hull valve issue. I think we got off on the wrong track re. the Groco flange. I have nothing against the flange, in fact I think it's a better solution than the thru-hull one.

The issue really is the broad range of "acceptable thru-hull/seacock products and installations." One group of experts recommends only bronze seacocks and no more than three components (seacock and two fittings.) and thru bolted. These same people give Forespars Marelon plastics a pass because it meets an ABYC standard. Others say that the thru-hull/ball valve system is fine, but don't like plastic. Almost everyone agrees that impact is the most critical concern regarding thru-hulls. But there's no impact standard, in particular for non-metal fittings. Additionally, everyone has fits about metal corrosion, yet gives plastics a pass because they don't corrode. The fact is that every plastic degrades, depending on the environment, like hot, cold, moisture, dry. The de facto standard for plastic degradation for tensile strength and flexural modulusis 30%, and thats only for UV. But it does set a benchmark.

I personally feel that the degradation maximum is to high. But what should the number be? That's why I'm looking for some responses.

The same think applies to the seacock / thru-hull issue. Think about it. What would your comfort level be, 2 hits, 6 hits, 10? You can send it to me direct. I;m simply going to tally the info and post it as food for thought.

Then I'll let you do the testing?

Fair winds,

jed
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Old 16-06-2012, 23:14   #29
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Re: Sea Cock Won't Open or Close

Bronze is copper and tin or a variety of alloys of copper, including alloys with arsenic, phosphorus, aluminium, manganese, and silicon, are commonly termed "bronze. yellow bronze is copper / zinc, also know as brass

The trick is that the alloy material, say aluminum or manganese can leach out of the bronze over time. In leaching ,the less noble metal is removed from the alloy by microscopic-scale galvanic corrosion. Its a slow process, but it happens. Salt water helps that process along nicely too.

When the alloy material leaches from the bronze, whats left is structurally weaker. This is one reason, OK one of the main reasons that stems shear off on ball valves. It's not a flaw, its a feature that tells you its time to replace the ball valve.

If your using the typical ball valves, just plan on replacing them every 5-7 years. The alloys used, pretty much makes it a consumable item...One reason the groco flanged adaptor works.

Oh Bonding all the seacocks works well too. If the bonding is done correctly and your always on top of your zinc replacements. This assumes that none of your bronze valves has magnesium as a alloy material. Magnesium is lower galvanic potential them zinc, so the magnesium sacrifices/leaches first... Lovely..

I'm not a big fan of bonding for that one reason. Oh it works great, but if the prop zinc erodes too fast say due to stray currents, next to go would be the aluminum and tin alloys in the bronze. One reason valves snap off now and then...

Just fyi.
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Old 17-06-2012, 10:09   #30
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Re: Sea Cock Won't Open or Close

I think the Marelon valves are pretty amazing as far as material strength goes. Unfortunately, they seem to have taken the design and just left it pretty much as it started... didnt improve it along the way. The handles break off and the ball seizes up . Not sure why, maybe because the plastic swells over time.? Pick one up in your hand at West Marine.... almost impossible to turn the handle when it's new. A more robust handle, shaft and maybe a stainless ball and it would be unbeatable. I had to remove one (broken stem!) in my catamaran... and i can tell you, that stuff is tough! It took a saw, chisel and file to get it out of there. Impossible to "break" the plastic, even with a hammer. A good idea, poorly implemented.
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