A piston is disposed in each cylinder for reciprocal movement therein in {HEAD ~ order} to pump {TAIL ~ the fluuid} from the inlet to the outlet 
to pump
A piston is disposed in each cylinder for reciprocal movement therein in { HEAD ~ order } to pump { TAIL ~ the fluuid } from the inlet to the outlet
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH