Help me understand - thermometer bulkhead

[dkwolf]

So I'm in the process of converting a keggle; got the top cut and holes drilled for the thermometer and valve over the weekend. Got the valve and bulkhead installed with what I thought was no problems, until I tested it, and both fittings leaked. One of the o-rings had mashed out on the valve, so that was easily corrected. But the thermometer bulkhead, I fought with for an hour, and then called a buddy over to come help - and after another half hour, we were still losing the battle.

I noticed that the nut for the inside of the kettle didn't feel quite right when I threaded it on to the thermometer - it was a little bit 'loose' until you put tension on it, and then it felt like it locked down solid. So I started researching it, and found several discussions where it was mentioned that the thermometer has NPT (National Pipe Tapered) threads, and the bulkhead kit ships with a nut with NPS (National Pipe Straight) threads.

This makes absolutely no sense to me - why would anyone knowingly sell an adapter for a NPT threaded thermometer, with a NPS thread nut? Yeah, sure, it "works", but it seems like a big giant pain in the rear to me -- especially when the leak I was having wasn't through the o-rings, it was through the threads. Which is not surprising at ALL, given the two thread types.

I may give the bulkhead another try as-is, but I've also already ordered a NPT threaded nut to make it "right". Sadly, I paid as much for the nut and shipping as I did for the original bulkhead.

Can anyone offer some insight as to why they would do this in the first place????

 

[-CHRIS-]

Where did you buy it from? If it was from Brewhardware.com, it should tell you to wrap the threads with several wraps of teflon tape. That will stop the leak. I am not sure that they make NPT nuts honestly, there is not enough thickness for a useful taper.

Chris

 

[Scriv]

Several layers of thread tape will fix it right up. How will an NPT nut work? The thermometer has tapered threads, what if the nut stops short of the keggle wall?

 

[augiedoggy]

I have at least 10 nps nuts on my kettles bought from many venders for this use and many of my fittings are a mix of nps and npt threads with no issues at all... The silicone oring is supposed to go between the nut and kettle wall and the groove in it should make it compress against the NPT threads which should always be wrapped with Teflon tape because we all know npt threads are designed to be used with teflon tape to prevent Galling (Or something like that)

What do you mean orings?? There should only be one oring on the inside... that and maybe the lack of Teflon tape is your real issue.

I never even heard of an npt nut ? It was my understanding the male threads only were npt or nps (or BPS which many of the overseas suppliers pawn off without stating they are such)

 

[dkwolf]

Where did you buy it from? If it was from Brewhardware.com, it should tell you to wrap the threads with several wraps of teflon tape. That will stop the leak. I am not sure that they make NPT nuts honestly, there is not enough thickness for a useful taper.

Chris

Got everything (in that order) from Austin Homebrew - coworker and I were putting in an order for a couple recipe kits, so I got the hardware I needed from them too.

The nut I ordered this afternoon is from Adventures In Homebrewing - same coworker has ordered stuff from them this afternoon. If in reality, it's the same nut I already have, I'll add it to my spare parts jar(s) and hopefully remember it the next time I need something like this. Maybe tomorrow night I'll try assembling it with some teflon and see what happens.

 

[dkwolf]

I have at least 10 nps nuts on my kettles bought from many venders for this use and many of my fittings are a mix of nps and npt threads with no issues at all... The silicone oring is supposed to go between the nut and kettle wall and the groove in it should make it compress against the NPT threads which should always be wrapped with Teflon tape because we all know npt threads are designed to be used with teflon tape to prevent Galling (Or something like that)

What do you mean orings?? There should only be one oring on the inside... that and maybe the lack of Teflon tape is your real issue.

I never even heard of an npt nut ? It was my understanding the male threads only were npt or nps (or BPS which many of the overseas suppliers pawn off without stating they are such)

The bulkhead kit from Austin has a washer that fits over the thermometer threads, then an o-ring up against that, with a larger washer (washer ID = o-ring OD) that acts as a retainer to keep the ring from squashing out all on the outside of the kettle, then another o-ring and the nut on the inside. When I mess with it tomorrow, I was planning to try installing the o-ring on just one side of the bulkhead to see what kind of difference that made -- I know only having one ring instead of the two will give me more thread to work with, which has been an issue so far.

 

[-CHRIS-]

Got everything (in that order) from Austin Homebrew - coworker and I were putting in an order for a couple recipe kits, so I got the hardware I needed from them too.

The nut I ordered this afternoon is from Adventures In Homebrewing - same coworker has ordered stuff from them this afternoon. If in reality, it's the same nut I already have, I'll add it to my spare parts jar(s) and hopefully remember it the next time I need something like this. Maybe tomorrow night I'll try assembling it with some teflon and see what happens.

Teflon tape will seal it right up. My entire keggle brewery uses Brewhardware.com fittings and none of them leaked follwing his directions. Just wrap the threads with teflon tape and place the o-ring on the inside.

Chris

 

[dkwolf]

Figured I'd post an update. The new "NPT" nut that I ordered showed up Thursday or Friday, but I didn't have time to mess with it until tonight. Wouldn't you know...when I compared it to the nut shipped with the bulkhead kit.... EXACTLY the same. So, yeah...labeled as NPT, actually NPS. Oh well.

Took the advice above, pulled everything off, wrapped the thermometer threads with teflon, and only put a washer (no o-ring) on the outside of the kettle. That alone gave the inside nut more threads to bite on. Started filling the keggle for a leak check, and spraying water directly on the inside of the fitting from the garden hose to give it a certain element of a 'pressure' test. No leaks whatsoever.

....except for that little one on the ball valve. Drained the keggle, removed the ball valve and bulkhead, put fresh teflon tape on that fitting, and re-assembled it - again, without the o-ring on the outside of the keg. Filled the keg all the way to overflowing without the slightest hint of a drip on the outside. Thanks for all the help!

And now, with the extra nut that I ordered and the 'spare' parts I'm not using from the two bulkhead assemblies, I've got enough spares for a third fitting should I so desire.