[PSUBS-MAILIST] Swagelock needle valve

[Private]

"Integral bonnet non-rotating stem valves". As you rotate the handle, the stem itself does not turn but is drawn out by a thread on the inside of the handle. This non-rotating stem allows the valves to have no packing. The reason I picked them was that I'd found the packing to be a frequent source of minor air leaks. Nothing serious, but an irritant. As for how the seal is accomplished, on the inside end of the stem there's a little flat disk of some elastomer that comes down over a hole. They are like needle valves only in that the thread that pulls the stem up is quite fine, so they give you more turns than a ball valve. Not that the application of blowing a ballast tank requires that fine a control -- it's the lack of packing that's appealing to me.


Best,

Alec



> On Mar 24, 2014, at 12:06 AM, swaters <swaters at waters-ks.com> wrote:
> 
> Yea. I remember you saying they are not true needle valves. What kind of valves are they technically?
> Thanks,
> Scott Waters
> 
> 
> 
> 
> Sent from my U.S. Cellular© Smartphone
> 
> Private <alecsmyth at gmail.com> wrote:
> You know these are not actually needle valves? And they have no packing to tighten.
> 
> 
> 
>> On Mar 23, 2014, at 11:59 AM, swaters <swaters at waters-ks.com> wrote:
>> 
>> Thanks for the info Sean.  My valve that failed had a ever so slight leak from the get go. Over the winter it was in the closed position and when I charged the system, it had a pretty noticable leak. The other two valves work great. I am going to order another valve and run it this season with alot of dives and see how she works.
>> Thanks,
>> Scott Waters
>> 
>> 
>> 
>> 
>> Sent from my U.S. Cellular© Smartphone
>> 
>> "Sean T. Stevenson" <cast55 at telus.net> wrote:
>> Needle valves are designed as fine metering / flow control valves. While they can be used as shut off valves, maximum stem / seat life is obtained by incorporating an on / off valve upstream of the metering valve, and using this for shutoff so you don't ever have to torque down the needle valve to reliably cut flow to zero. Most automatically operated flow control valves fail open in their standard configurations for this reason, as it improves repeatability.
>> 
>> Also, be aware of the tightness of the packing nut around the valve stem, as leaks often occur here. If you want to get fancy, you can use a fine resolution / low range torque wrench on the stem, but for these small Swagelok valves it is usually sufficient to just feel the resistance to turning the knob.  You want enough compression on the packing to eliminate leaks and prevent vibration from possibly moving the valve out of position. Any more than that just increases wear on the packing and friction on the stem, making it more difficult to perform fine adjustments.
>> 
>> Sean
>> 
>> 
>> 
>> Private <alecsmyth at gmail.com> wrote:
>>> 
>>> Hi Scott,
>>> 
>>> My valve issue was entirely sloppiness. I had added a port to the little HP manifold, and didn't clean the inside of the manifold properly after cutting the thread on that extra port. Metal chips got into the valves and interfered with proper seating. Two of the valves I was able to clean, but one I think got its seat damaged because I was just never able to make a good seal on it again. I currently have the manifold out of the sub for cleaning, and got a replacement valve on eBay. 
>>> 
>>> I would suggest taking the problem valve apart to see whether something has got in there. What you say about storing them open makes sense, and I'll do that in the future, but I haven't yet had a valve issue after winter storage. I have had issues with the electricals. Last winter a speed controller blew after it's first minute or so of spring running, and this year I had one that wouldn't work at all for the first few minu! tes but has acted normally once it came on. Maybe the cold made some relays "sticky" to begin with.
>>> 
>>> We must be doing very similar things on our boats right now!
>>> 
>>> Best,
>>> 
>>> Alec
>>> 
>>> 
>>> 
>>>> On Mar 23, 2014, at 12:23 AM, swaters <swaters at waters-ks.com> wrote:
>>>> 
>>>> Alec,
>>>> I remember at the psubs conference in Islamorada you had a malfunction on the needle valve from Swagelock. I am preping my sub for this season and noticed a air leak. It is comming from one of the same needle valves. Did you end up just buying a new one or did you repair it? I am thinking based on the way these work they need to be stored in the open position. Do you think that is correct?
>>>> Thanks,
>>>> Scott Waters
>>>> 
>>>> 
>>>> 
>>>> 
>>>> Sent from my U.S. Cellular© Smartphone
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>> 
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>> -- 
>> Sent from Kaiten Mail. Please excuse my brevity.
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