When a fluid pressure in the extension chamber exceeds a certain level, {HEAD ~ the plug} disengages the valve seat such that fluid may flow from the extension chamber, in {TAIL ~ the entry port}, along the relief passageway, and out the exit port 
When a fluid pressure in the extension chamber exceeds a certain level , { HEAD ~ the plug } disengages the valve seat such that fluid may flow from the extension chamber , in { TAIL ~ the entry port } , along the relief passageway , and out the exit port
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH