Temperature limit of sheroidal graphite cast iron valves and PED certification 1

[fabiobs]

Hello,
I have a simple question.
I know that many valves (gate, butterfly...) are casted in spheroidal graphite GJS 400-15 that is limited to -10°C but in the data sheet and PED certificate are marked up to -20°C. How is it possible?

 

[gerhardl]

I am afraid you will have to give the exact details (datasheet for the valve and regulation/text) before you will get an answer.

 

[fabiobs]

Many regulation like EN 12516-4 or EN 15776 indicate as low temperature limit for GJS 400-15 or GJS 450-10 -10°C. Many manufacturers of butterfly and gates valves indicate as low temperature limit -20°C. In Europe there is PED (pressure equipment directive) and use of material below the temperature indicated in the regulation must be justified. My question is easy: how can be use a casted spheroidal graphite below temperature limit?