Taper fittings

[G&M]

If a valve is marked as having a 1/4" BSPT fitting, is that a taper fitting ? Must one be used or is a normal fitting OK ?

[John Stumbles]

If it's for gas (which a lot of taper fittings are for) then I'd say yes it must be taper. Ditto for steam, compressed air or anything else dangerous.

Otherwise if it fits and works, OK.

[Chris]

BSPT is indeed a taper thread - BSPP is a parallel thread (though often both get referred to as BSP). I was always taught:

BSPT female with BSPT male = ok (with sealant on thread) BSPP female with BSPP male = ok (uses bonded seal or fibre washer or similar to seal) BSPP male with BSPT female = ok (with sealant on thread)

Anything else = not ok

That's what the guys that taught me hydraulic systems design said anyway. The guy that taught me plumbing said that anything will seal with enough hemp and snot ;-)

HTH,

Chris.

[G&M]

It's for oil. BSPP male into BSPT female which you seem to say is OK.

Thanks.

[Chris]

Agggh!! Sorry, what my brain meant to type was BSPP female with BSPT male is ok. Unfortunately my hands weren't listening. It wasn't til I saw your reply that I realised. Apologies.

BSPP male with BSPT female is not recommended because you do not get very many threads engaging, particularly a problem with harder materials (eg plated steel) / higher pressures.

Apologies again for the confusion.

Chris.

[Chris]

Agggh!! Sorry, what my brain meant to type was BSPP female with BSPT male is ok. Unfortunately my hands weren't listening. It wasn't til I saw your reply that I realised. Apologies.

BSPP male with BSPT female is not recommended because you do not get very many threads engaging, particularly a problem with harder materials (eg plated steel) / higher pressures.

Apologies again for the confusion.

Chris.

[G&M]

As you say agggh. But many thanks for pointing it out before I made a potentially fatal mistake.