3 replies to this topic

[Nageswar Kotari]

Dear Friends,
I got a question here while deciding the line rating using ASME B16.5.
The steps are like this
1) First material of construction should be decided according to fluid type and temperature of fluid
2) Line rating should be decided from B16.5 with tabular form of Pressure versus Rating.

My question is why these classes are decided as 150#, 300# and so on.
Does this 150 300 600 and all numbers have a logical meaning?
For example 150# line is safe for upto 150lbs pressure and all.

I'm sure that this is not random pick as such 150 300 and all are round figures and all. Please answer this question with some examples.
Thanks a lot.

[gvdlans]

See Pipe classes origin I
See Pipe classes origin II

[Nageswar Kotari]

Thanks Jedi,
But I did not get answer in these forums. Just a couple of funny abrevations and origins of roman and brotish rule and blah blah. I'm sorry to mention this but these forums have maximum answers which are of time pass type. Please give me your idea jedi. I would like to know the exact answer (If you have one).
Thanks
Nag

[gvdlans]

I did get the answers from the quoted discussions:

150#, pound or lbs is not correct anymore, it is Class 150, Class 300 etc. instead. This is to avoid confusions.

The original background of the pound rating is purely historical and probably "The origin of the numbers (150, 300, 600, etc) was the pressure in psig at the corresponding saturated steam temperature. The ratings are different today due to change in materials and flange design." or the 150 pound forged iron flanges that could withstand 150 psig of pressure at 500 degF according to another source (Pipe drafting and design)

Therefore, it is not true that "150# line is safe for upto 150lbs pressure and all". You have to look-up the safe temperature/pressure combinations in the ANSI B16.5 tables.