dear sak9,
for condensate recovery schemes, you may look the site of GESTRA.
www.gestra.de
and also you must keep in mind that the condensta flow must be calculated in max. conditions - during starting up and stop of the boilers.
Dear Tom,
for sure i can say that that ND 40 is the nominal pressure for the flange equivalent PN 40 responds ANSI class 300. C32- C38 means chapter 32-38. C22.8 means forged steel DIN No 1.0460 or ASTM A-105.
The diameters according to DIN are the following:
1/2" - DN15; 3/4" - DN...