X-mas tree and wellhead is the essential mechanical equipment used in oilfield as the main flow control devices. Wellhead assembly consist of wellhead and x-mass tree. Wellhead part of the assembly consist of casing stub, casing head, casing hanger, casing string, casing spool, tubing head, tubing strings, adapter. X-mass tree consist of cross, tee, choke, gate valves, pressure gauge, connectors, and, in some cases, cable port(s). Standards of design and fabrication varies from country to country, but widely applied standard is API.