Ladies and Gentlemen,
American Society of Testing Materials has ASTM A536-84(2009) - Standard Specification for Ductile Iron Castings
http://www.techstreet.com/cgi-bin/detail?doc_no=ASTM%7CA536_84_2009_;product_id=1642773 . If it is a code job then go to ASTM or ASME for direction. If not what the other respender says seems reasonable I have run on similar before. I am a CWI graduate engineer. I hope this is helpful.
Sincerely
Len Andersen weld@spemail.org
914-536-7101 , 212-839-6599 8-4 New York Time , 914-237-7689 (H)
www.lenadersen.com