Discharge valve 12 can be moved by an adjustment mechanism 15 in such a way that either of the apertures 13 or 14 is positioned in the flow passageway to {HEAD ~ the outlet} of {TAIL ~ exhaust line} 11 
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Discharge valve 12 can be moved by an adjustment mechanism 15 in such a way that either of the apertures 13 or 14 is positioned in the flow passageway to { HEAD ~ the outlet } of { TAIL ~ exhaust line } 11
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH