An additional tubular insert member is held within {HEAD ~ the principal conduit member} to open and close the secondary conduit connected directly to {TAIL ~ a work station} 
An additional tubular insert member is held within { HEAD ~ the principal conduit member } to open and close the secondary conduit connected directly to { TAIL ~ a work station }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL