Cutting BSP fitting to size?

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I bought a 1/2 bsp to 3/8 push fit to go on an lpg regulator which is to be used as a secondary regulator to supply CO2 to my keg for connection to beer engine. The 1/2 inch bsp doesn't go all the way in, though by eye the female thread on the regulator is much deeper, so I expected it would. Is it ok to cut down the thread on the John Guest fitting?
 

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I personally wouldnt, I'd replace the o ring with a thicker one or thick gasket.
I hadn't thought of doing that. Is there any particular material I should be looking for in a thicker o ring??


It doesn’t have too, as long as it’s sealed. Use tape or some kind of gas rated liquid thread sealant.
Thanks. Would PTFE tape be ok fo this?
 

peebee

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Thanks @Buffers brewery - I didn't realise there was such a thing as parallel and tapered. Good to know!
That fitting has an O-ring, therefore most certainly is a parallel thread. Tapered threads seal anyway, although I'll still put on some PTFE tape to make sure (all UK BSP female threads are parallel, only very occasionally you can get tapered female but they will probably have a "Rc" designation).

I stopped using JG fittings, one of the reasons being; put PTFE tape on will created a seal, but also encourages a bit more tightening, at which point the JG fitting easily shears off!


[EDIT: BTW, I think that's a 1/4"BSP thread; the other side - output - is 3/8"BSP.]
 
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peebee

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Thanks @Buffers brewery , but the "conundrum" was only caused by the OP only showing half the regulator so I was judging 1/4" by eye alone. I'm rather familiar with those regulators 'cos I recommend them for "cask conditioning" style beers ("Cleese" are the makers).

You can get them without those bits and bobs screwed into the ports like the above picture (horrible POL adapters for one) because removing them can be really tough. You can get the 20-300mbar variants in this country but you have to look hard. The 50-150mbar commonly available variant is all you need for cask emulation.

For anyone wondering, 1000mbar is 14.7 PSI (PSIG to be properly correct), so 50mbar is not very much. Hence you must use LPG regulators as secondary regulators, commonly available secondary regulators will not come anywhere near close and precision low-pressure regulators cost a small fortune.
 
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Thank you both. I should have provided more info.
[EDIT: BTW, I think that's a 1/4"BSP thread; the other side - output - is 3/8"BSP.]
Yes, that's correct. I have the 50-150mbar as I found a link to it (likely by you @peebee ?) in a thread on using a beer engine, which I found very informative (thanks!).
This is the reg:
These are the JG:
 

Buffers brewery

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According to the chart I found the inlet thread is specified as FEM-Rp1/4 which is female 1/4” BSPT, and the outlet thread is FEM-Rp3/8 which is female 3/8” BSPT, I think :confused.:

These fittings might be an alternative to plastic…
 
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peebee

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According to the chart I found the inlet thread is specified as FEM-Rp1/4 which is female 1/4” BSPT, and the outlet thread is FEM-Rp3/8 which is female 3/8” BSPT, I think :confused.:
Rp = R = "parallel". Rc = tapered. Flippin' mumbo-jumbo, it's far easier not looking too closely!
 

peebee

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Thanks everyone. I'll crack out the PTFE tape rather than the hacksaw and see how it goes.
Remember what I said about over-tightening (and if they do shear, you might say "but I didn't over-tighten" - I'll believe you!).

If it does shear, @Buffers brewery posted a link above to some metal adapters (1/4" out-of-stock at this moment). From my favoured supplier too (Context Pneumatics) but their catalogue is devoid of "Kelm" stuff at the moment because of some daft issue further down the line (but they still have the stock if you ask). The metal adapters still use "push fit" whereas I prefer something more secure (and all sorts of other alternatives which can create cerebral aneurisms if you dig about too deep).

[EDIT: BTW, tapered male fittings will be fine into the parallel threaded regulator, they will just tighten before screwing all the way in - that's what creates a seal.]
 

peebee

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Rp = R = "parallel". Rc = tapered. Flippin' mumbo-jumbo, it's far easier not looking too closely!
@Buffers brewery : Told you it was "mumbo-jumbo"! "Rp = G..." not "R". My slipup, "R" covers tapers, but Rp means "cylindrical" or parallel if you prefer. "Rs" is apparently external tapered or BSPT as opposed to internal thread (Rc). Gawd knows what the "c" in Rc stands for. I've seen some suggestion that tapered and parallel have different pitch, but not that I've experienced.

Had enough? I have 🥴
 

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