... -140Mpa wellhead christmas treenorm : design and manufac ture as per api The wellhead christmas tree ,oil gas production tree produced by ... , it consists of casing head, casing spool,tubing spool,tubing head adapter,studded cross, threaded flanges,adapter spool,gate valve,choke valve and the tree ... assembled of threaded nippe,solid bull plug,tree cap,cap flange,top connector, valves,cross and spool