Comparison between American standard and German standard. 1

[lhwingking]

If I say the rating of a Ball valve is PN 25 (DIN standard), what is the equivalent rating in American standard (150#, 300#, etc..)?

 

[XL83NL]

There's no equivalent. Some PN-classes closely match Class-ratings, some dont. Furthermore it's material dependent.
This article gives you a rough idea on where the best matches are, although it gives a few PN-ratings that dont exist.
Here's my best guess;
Cl. --=-- PN
150 ---- 16
300 ---- 40
400 ---- 63
600 ---- 100
900 ---- 160
1500 --- 250
2500 --- 420

 

[ione]

Just to add to XL83NL's post that not only material, but also temerpature plays a role.

 

[LittleInch]

see also

http://www.eng-tips.com/viewthread.cfm?qid=341213,

but be careful when looking at the ratings - some of them seem to be made up, i.e. the PN ratings I can find for flanges are 6,10, 16, 25, 40, 63, 100, 160, 250, 320, so I don't know where some of these weird 20 bar and 50 bar rated valves come from....

a few times I've put PN 16 valves / equipment in a #150 system, just that the lowest rated bit of kit (in this case 16bar) sets your design pressure.

So the valve rating doesn't change - its a max 25 bar valve - that could go into any piping class system, but it would set the design pressure of that system to 25 bar if it was the lowest rated bit of kit. If you don't need any pressure higher than 25 bar then you're Ok, if you do choose a higher rated valve.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[XL83NL]

... ratings I can find for flanges are 6,10, 16, 25, 40, 63, 100, 160, 250, 320, so I don't know ...

If you dig into EN 1092-1, you'll find the rest in (e.g.) table 7. For weldnecks (type 11) this also includes PN 2.5 and PN 400.

Availability of a certain PN-rating, as a first, depends on flange type. E.g. type 05 flange (weirdly) go up to P N100 max.
Second, market demands counts (even more). I can tell you you'll have a hard time sourcing a PN 2.5 flange of any class.

/edt; my 1st post lists PN 420, this should be PN 400.

 

[LittleInch]

I just didn't bother with PN 2.5... My point is that the OP and lots of others all work on maximum flange rating when in fact any system can be designed for any design pressure so long as it doesn't exceed the lowest rated part of that system. That might be the flange, but might be the pipe or some other package (e.g. heat exchanger, separator etc) so the obsession with rating is not helpful.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way