The piping Code in Europe is EN 13480 (several volumes: Materials / design/ testing/ etc..)
I believe you can find it in this site.
Part one of this standard: Title: General. Deals also with PED ( Pressure European Directive)matters, with which you must comply within Europe.
With PED, and depending on the Nominal diameter + the design pressure and type of fluid (Liquid or gas) then you make some classification which defines the type calculations , inspection , etc...
Again you can find on intern free software for making this type of classification
You have always to work with a NOBO (notified body) which is approved to conduct checking as per PED.
For instance in Holland or UK, the NOBO is Lloyds, in Germany is TUV, in Belgium Vincotte, in France DNV or Service des mines, etc..you may also have several NOBOs working in one country

In each part of EN 13480 you have at the end appendices , I believe termed Z, mandatory , which tells how compliant you are with PED.

I disagree a but ( and my apologies) DIN is not leading , that is why we have EN ..it is endorsed by every one in Europe. EN was st up to break the monopoly of one country...and to keep the market open and get rid of nationalism and national preference, all suppliers and manufactures must be equally treated providing compliance with PED.

For instance Shell in Holland and UK , have all their materials according to ASTM , and piping and flange sizes are in in inches which are according to B31.3 and B31.1 ( thus in inches and ASTM), etc..they do not comply with DIN, and the DIN flanges ( rated in PN, ex. PN 16 )are somewhat thinner than the ones in B16.5 ( which are rated in Pounds (ex. 300 #) ..still Shell uses now the whole PED procedures.
Same for BP, Total. And it foolish to imagine those major oil company changing all their assets , stock and existing systems to DIN

Above is also valid for vessels/ columns/ heat exchangers ...but the code is then EN 13445