Why 2000# threaded fitting are not covered in ASME B16.11

With ref. to your query on 2000 class fittings, I would like to highlight that those low pressure fittings have become more absolute in application.
Those fittings are finding very less use in low pressure drainage/sewer systems.

Answering yours and additional questions,

1) The 9000 lb fittings in NPT threading is beyond the permissible leakage allowance and so is why NPT threaded fittings are not available in that range. But other threading type can withstand higher pressure, which is how compression/threaded fittings work, like swagelok.

2) For 2000 lb fittings, socket welding is not available, as threaded fittings are sufficient enough for that pressure class. And socket welding such thin pipes is not economical/recommended due to the special care/skill required or the practical difficulty on alignment issues.

3) Cap & coupling were not convered in B16.11even when the MSS SP 49/50 was first encompassed into it and 4000 lb was eliminated due to the lack of support in the Americal industry. If you are using 2000 lb piping fitting, plugs are to be used against caps and unions against couplings.

Above all these, the most important fact to be considered is of the market trend and industry acceptance. For instance, min. pipe sch is STD / 2.24mm for 1/4". The pressure it can withstand is around 2000 lb discounting NPT threading. But it has become a practice to use 3000 lb and not 2000 lb.

Moreover to what I have seen, the prices difference is nearly nil between 3000 and 6000. 9000 is around 5 to 10 % higher than 6000. ofcourse it depends on the quantum you purchase.

Regards,
Kannan.


Dear all,

 could anyone explain that threaded fitting i.e. cap & coupling of class 2000  are covered in which standards?
 
because ASME B 16.11 , covered the forged threaded fitting (i.e. Tee, elbow and cross) of class 2000, 3000 and 6000.
But threaded cap,half coupling and coupling are covered from class 3000 and 6000.  
 
Regards,
Vinayak