BSPP vs BSPT - comparison and which applications?

[Rdpere]

I know that BSPP is parallel and BSPT is tapered.

I also know that the basic advantage of BSPT is that it doesnt need shoulder to be fixed with the object to which it is screwed,
and that with some BSPT you dont need additional sealing as it cuts into material and seals by itself.

Are there any more advantages of BSPT vs. BSPP, what are the most common applications of each?




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Also one more question, that isnt directly connected ... can you define the start of a thread , so you always have the correct angular position of a bolt
regarding to the nut?


Thank you for any information in advance!

 

[TugboatEng]

BSPT is inexpensive (one step machining). It does not require elastomer seals which simplifies chemical compatibility and allows for use at higher temperatures. There is no age deterioration. It can be clocked during assembly.

BSPP is lower emission. The elastomer seal resists vibration. It does not require the use of messy sealants. BSPP provides a more reliable seal in mass production (less skill required).

 

[Rdpere]

BSPT is cheaper to manufacture that BSPP? And what do you mean with that BSPP is lower emission?

Also, is there any downside to screwing BSPT bolt into BSPP hole (in comparison to BSPP bolt)?

 

[TugboatEng]

BSPT requires only a single threading operating and no additional labor such as installing o-rings. BSPP requires a counter bore or some type of support washer for the o-ring and these parts are assembled by hand. BSPP fittings that require clocking have an additional jam nut as well.

As for emission, BSPP fittings are less likely to leak or seep oils and such in my experience.

As for mixing systems, that's not the intention. Why would you want to do that?

 

[XL83NL]

We use BSPP acc. ISO 1179 for a lot of our high pressure/temperature applications where NPT (or SBPT, if you like) doesn't work anymore since 1179 has the advantage of a metal sealing ring. The female part requires a lot of attention during manufacture, mistakes are easily made and will have a big impact on the joint's ability to properly seal. Swagelok Rs-fittings can be used off-the-shelf to connect tubing and so forth.

Huub
- You never get what you expect, you only get what you inspect.