[PSUBS-MAILIST] Valve part 2

Mon May 24 12:24:57 EDT 2021

Thanks everyone.

The thread is 2" BSPT on both obviously and I had the external one on the
pipe nipple cut at an engineering place with a powered pipe threader.
Agreed, ptfe tape will hopefully allow it to turn a little more.

I think with the advice given, im going to try and thread the male threads
on the pipe nipple a bit deeper.  Ive been having a quick look at pipe
threading machines.

Im going to see if i can hire one to start with.  Unlikely here i suspect.
Also i will go to the place i originally had it threaded and see if i can
borrow something.  I know them quite well there.

Did find some manual ones,

https://www.amazon.co.uk/Sealey-PTK992-Threading-8-inch-2-inch/dp/B000R9W1A6/ref=sr_1_3?dchild=1&keywords=2%22+pipe+threader&qid=1621872818&s=diy&sr=1-3

but they look a bit poor quality.  There are better, but look at the
price...But might just do it for this one job, especially as the threads
are cut mostly already.  Might need to get some better cutting dies?
Anyway, im not even quite sure how they work so will look at some videos
later.

Anyway, i have some options.  Keep any ideas coming, it really helps.
Thanks again.
James

On Mon, 24 May 2021 at 15:09, Sean T. Stevenson via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> First off, can you confirm that both the male and female thread are of the
> same thread standard (NPT, ISO / BSP, etc.)? These tapered thread forms are
> not all interchangeable.
>
> To get deeper engagement on a tapered pipe thread, you can run a tap in
> the female thread, or run a die over the male thread, or both. (Where the
> tools are available, it's never a bad idea to dress both sides of a tapered
> pipe thread connection prior to assembly just to avoid problems with fouled
> or damaged threads). In this case, I'd be inclined to try to dress the male
> thread with a die first, because it is likely out of true geometry due to
> the welding. A die that size won't be a cheap tool though if you don't
> already own it.
>
> Consider also the function of a PTFE (or similar) pipe thread sealant. The
> sealant actually serves three purposes, the first of which is, as expected,
> to seal the spiral thread gap. The second purpose is to prevent galling
> between similar alloys (particularly an issue with AISI Type 316 / 316L
> stainless and equivalents like CF-8M) during make up. The third, and
> arguably most important purpose is to act as a thread lubricant which
> facilitates greater engagement and interference of the tapered thread by
> reducing the rotating friction between the parts, ultimately resulting in a
> smaller gap to be sealed, and consequently a more successful seal.
>
> When working with tapered threads, I typically tighten them hand tight
> plus 1.5 to 3 full turns, but that is specifically with smaller diameter
> fittings. 2" and larger fittings may have different recommendations for
> number of turns as someone else already mentioned, and of course often
> tapered threads are used to make up fittings with a final required
> orientation, which isn't necessarily ideal for obtaining optimum assembly
> torque / engagement. Importantly though, "hand tight" applies to a
> connection which has first been lubricated with pipe thread sealant, and
> will typically be quite a bit further engaged than when test fit dry.
>
> Sean
>
> -------- Original Message --------
> On May 24, 2021, 02:05, James Frankland via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>
> Hi all.
> I didn’t get any responses to my valve dilemma.  I’ve made another video
> with the problem right at the start so you don’t have to watch it all.  I
> would really appreciate some advice here, I’m not sure what to do.
>
> https://youtu.be/qJhVeFrUwWI
>
> Thanks James
> _______________________________________________
> Personal_Submersibles mailing list
> Personal_Submersibles at psubs.org
> http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles
>
>
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