A seal is installed in the groove on the open end of the cup to seal to {HEAD ~ the primary face} of {TAIL ~ a tubesheet} around the tested rib plug 
A seal is installed in the groove on the open end of the cup to seal to { HEAD ~ the primary face } of { TAIL ~ a tubesheet } around the tested rib plug
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH