{HEAD ~ The vessel} and the seal cover have {TAIL ~ respective surfaces} that, when engaged, define a circumferential interior passage between the vessel and the seal cover 
have
{ HEAD ~ The vessel } and the seal cover have { TAIL ~ respective surfaces } that , when engaged , define a circumferential interior passage between the vessel and the seal cover
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH