{HEAD ~ The warped intermediate portion} of the pipe material is fixed to {TAIL ~ the supporting surface portion} of the head pipe by welding 
is fixed to
{ HEAD ~ The warped intermediate portion } of the pipe material is fixed to { TAIL ~ the supporting surface portion } of the head pipe by welding
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH