Basic construction and operation Lock (water navigation)

a plan , side view of generic, empty canal lock. lock chamber separated rest of canal upper pair , lower pair of mitre gates. gates in each pair close against each other @ 18° angle approximate arch against water pressure on upstream side of gates when water level on downstream side lower.

all pound locks have 3 elements:

a watertight chamber connecting upper , lower canals, , large enough enclose 1 or more boats. position of chamber fixed, water level can vary.
a gate (often pair of pointing half-gates) @ each end of chamber. gate opened allow boat enter or leave chamber; when closed, gate watertight.
a set of lock gear empty or fill chamber required. simple valve (traditionally, flat panel (paddle) lifted manually winding rack , pinion mechanism) allows water drain or out of chamber; larger locks may use pumps.

the principle of operating lock simple. instance, if boat travelling downstream finds lock full of water:

the entrance gates opened , boat moves in.
the entrance gates closed.
a valve opened, lowers boat draining water chamber.
the exit gates opened , boat moves out.

if lock empty, boat have had wait 5 10 minutes while lock filled. boat travelling upstream, process reversed; boat enters empty lock, , chamber filled opening valve allows water enter chamber upper level. whole operation take between 10 , 20 minutes, depending on size of lock , whether water in lock set @ boat s level.

boaters approaching lock pleased meet boat coming towards them, because boat have exited lock on level , therefore set lock in favour – saving 5 10 minutes. however, not true staircase locks, quicker boats go through in convoy.

operation of canal lock

1–3. boat enters empty lock

4. bottom gates closed, bottom paddles closed, top paddles opened, lock starts fill

5. lock filling water, lifting boat higher level