The valve is opened and closed by means of communicating bellows which are controlled by the pressure difference between {HEAD ~ two sections} in {TAIL ~ the valve} having different areas 
in
The valve is opened and closed by means of communicating bellows which are controlled by the pressure difference between { HEAD ~ two sections } in { TAIL ~ the valve } having different areas
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 OTH OTH