ISO 15590 Flange Ratings

[rneill]

Has anyone looked at the flange rating table in Part 3 of ISO 15590 ...

Can anyone explain the high temperature ratings of Class 1500 and 2500 ...

Questions:
1. The 250 C rating (225 bar) of Class 1500 is higher than both the 175 and 200 C ratings which are 219 and 225 bar respectively.
2. The 200 C rating (365 bar) of Class 2500 is higher than the 175 C rating which is 341 bar.
3. If you calculate the temperature derating factor used, it varies significantly between pressure classes. For example, at 150 C, derating is as follows:
Class 150 - 96.9%
Class 300 - 96.4%
Class 600 - 96.6%
Class 900 - 96.7%
Class 1500 - 88.6%
Class 2500 - 88.5%

I assume that there is some problem with the ISO 15590 published ratings for Class 1500 and 2500 but a google search did not reveal any errata, or corrigendums and I was unable to find any mention of this issue?

I'm also curious that thru Class 900, the ratings are almost identical to MSS SP-44 except for the 200 C ratings which tend to be significantly different.

 

[BigInch]

Looks like an EUSNAFU
use the ANSI rating. Interpolste for 250C, Convert to barg and C
It seems that it should be around 216, 7 or 8 barg

If it ain't broke, don't fix it. If it's not safe ... make it that way.

 

[rneill]

I'm pretty sure there is a SNAFU in the standard but the standard has been out for a long time ( 8 or 9 years ) and I can't find any evidense of a correction being published.

Regarding ANSI ratings, I'm not sure ... ANSI starts to derate at 38 C whereas pipeline flange ratings in many pipeline flange standards (CSA Z662/Z245.1, MSS SP-44, and ISO 15590) don't start to derate until 120 C. In Classes 150 to 900, ISO 15590 and MSS SP-44 have very similiar flange ratings but these are quite a bit higher than the ANSI ratings between 38 C and 250 C.

 

[SJones]

ISO did start to look at edition 2 of 15590-3 in April 2009. It doesn't appear to have made a lot of headway. I guess that people aren't much bothered about the potential for error as they use the ASME ratings or bespoke designs. As far as I am aware, the only pipeline standards that call the ISO document up are ISO 13623 and DNV-OS-F101.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04