The first tube sheet is mounted in {HEAD ~ the primary inner shell} while {TAIL ~ the second tube sheet} is connected to the secondary inner shell 
The first tube sheet is mounted in { HEAD ~ the primary inner shell } while { TAIL ~ the second tube sheet } is connected to the secondary inner shell
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH