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-   -   Gate valves and why we don't use them... (http://www.sailnet.com/forums/gear-maintenance/48785-gate-valves-why-we-dont-use-them.html)

sailboy21 11-09-2008 03:20 PM

Gate valves and why we don't use them...
 
I know I know... But I haven't had a haulout other than to cradle ship my boat and I still have one gate valve for the galley sink drain. It finally gave up the ghost today. You can turn the handle all you want forever and ever and ever :eek: I think the gate is lodged about 1/4 shut but of course there is no way to tell. So now I have to either schedule a haulout ASAP or hope the tides are right to dry out on the grid. Temps are around freezing so I can't do any glass work or painting. What a waste of a haulout...

Let this be a lesson to all you procrastinators!!! I know you are out there...

Replace crappy substandard valves ASAP!!!

Don't wait, DO IT NOW!

CS271409 11-09-2008 04:00 PM

Do I understand correctly from your comments that you are in Alaska but don't haul your boat for the winter?
I changed all my gate valves in my 1978 27 footer this spring. It was a time consuming and fairly expensive venture but worth it in my mind. The gate valves looked brand new when I took them off but I still like the piece of mind I get from proper seacocks. They were in fresh water only.
Wait for Maine Sail to chip in here on this subject... it should only be a few minutes or so. He has an excellent site providing great instructions on how to do this. You shouldn't need to do any painting or fibreglass work but I used some West System epoxy to set my new bedding / backing plates.

sailboy21 11-09-2008 05:00 PM

Year round sailing in Alaska... What sucks is I had plans (always got plans...) to replace all the mushrooms and backing plates and install real flanged seacocks for every thru-hull. Now I get to just band-aid the problem and save it for later by putting a new NPT ball valve on the old mushroom.

SEMIJim 11-09-2008 05:37 PM

At least it isn't on an engine cooling intake. Had a fellow sail club member recently tell me about the time a gate valve failed on a boat he was on, on the engine raw water intake. IIRC, the alternator bracket failed, the alternator fell off and broke off the raw water intake's gate valve's handle. They jury-rigged an alternator bracket (they were "at sea"), but did not realize that when the gate valve's handle was broken off, the gate fell closed. Luckily, it turns out impellers are usually tougher than we give them credit for.

Jim

xort 11-09-2008 06:52 PM

"proper" seacocks are better but not perfect! i have several that are stuck, frozen. and they are in extremely difficult areas to reach.

you MUST excersize all valves

sailaway21 11-09-2008 07:37 PM

There is nothing inherently wrong with using gate valves on a boat as a sea ****. The problem arises with the quality and design of valve used. What is commonly seen is a brass valve suitable for home use. There are high quality gate valves available in a variety of materials and construction methods. and they'll work just fine properly installed.

Small boat sea cocks serve their purpose well if maintained. Ball valves work easily but sometimes too easily if they're mounted to something that is subject to vibration and movement, like a boat. They can be either closed or opened inadvertently. Most of them commonly found are of no better construction than the lowly gate valve from the hardware store. Being a ball valve does not inherently make it safer...just easier to use.

There are no ships that use the same type sea cocks you'll see on boats; there's no effective way of operating them absent power. Gate valves are used almost exclusively, with the telescoping thread type being most common. Butterfly valves are often used but not for sea cocks. Butterflys are commonly power driven and suffer the same weakness that most, other than gate valves, suffer; a potential inability to close by manpower alone. Those long stems you see on gate valves are what gives them their mechanical advantage. Thus one man can easily open or close a valve that may be serving a 36" diameter pipe.

Here's a site I found buy simply googling gate valves: http://www.velan.com/products/pdfs/v...603-99-web.pdf
Further research will reveal the tremendous variety of suitable gate valves, even for your thru-hulls.

countrybumpkin 11-09-2008 07:54 PM

Quote:

Originally Posted by sailboy21 (Post 399086)
I know I know... But I haven't had a haulout other than to cradle ship my boat and I still have one gate valve for the galley sink drain. It finally gave up the ghost today. You can turn the handle all you want forever and ever and ever :eek: I think the gate is lodged about 1/4 shut but of course there is no way to tell. So now I have to either schedule a haulout ASAP or hope the tides are right to dry out on the grid. Temps are around freezing so I can't do any glass work or painting. What a waste of a haulout...

Let this be a lesson to all you procrastinators!!! I know you are out there...

Replace crappy substandard valves ASAP!!!

Don't wait, DO IT NOW!


yep! still trying to figure out the best way to fix my situation. I can sail, but the cooling system is closed for now: http://www.sailnet.com/forums/gear-m...ould-i-do.html

sailboy21 11-09-2008 08:15 PM

Quote:

Originally Posted by sailaway21 (Post 399175)
There is nothing inherently wrong with using gate valves on a boat as a sea ****.

There are several inhearant reasons not to use gate valves where a Teflon seated ball valve is available:

-No definite position indication
-mating surfaces will leak if damaged
-takes a lot longer to open or close
-prone to jam on backseat
-damage from freezing more likely
-more corrosion prone (more wear surfaces)
-more parts involved (more point of failures, as in my case)

http://www.mcmaster.com/catalog/114/...l/c03ga1fs.gif
http://www.mcmaster.com/catalog/114/.../c03aga21l.gif

sailaway21 11-09-2008 08:30 PM

I think you'll find that subs use butterfly valves that are backed up by gate valves. Double valving thru-hulls is common practice on ships. I've never seen a square head **** or a ball valve on any ship..at least in a major piping system.

Valiente 11-10-2008 12:15 AM

Someone needs to review the automatic word censoring on a site in which the word for a male chicken is both legitimate and frequent.


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