The valve element also has {HEAD ~ a through passage} 23 which, when arranged in an open position as shown in FIG 1, enables {TAIL ~ passage} of gas through the valve 
The valve element also has { HEAD ~ a through passage } 23 which , when arranged in an open position as shown in FIG 1 , enables { TAIL ~ passage } of gas through the valve
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH