Panama Canal Locks - The Gates

The Gates

The gates which separate the chambers in each flight of locks must hold back a considerable weight of water, and must be both reliable and strong enough to withstand accidents, as the failure of a gate could unleash a catastrophic flood of water downstream.

These gates are of enormous size, ranging from 47 to 82 ft (14.3 to 25.0 m) high, depending on position, and are 7 ft (2.1 m) thick; the tallest gates are required at Miraflores, due to the large tidal range there. The heaviest leaves weigh 662 t (730 short tons; 652 long tons); the hinges themselves each weigh 16.7 t (36,800 lb). Each gate has two leaves, 65 ft (19.8 m) wide, which close to a V shape with the point upstream; this arrangement has the effect that the force of water from the higher side pushes the ends of the gates together firmly. The gates can only be opened when, in the operating cycle, water level on both sides is equal.

The original gate machinery consisted of a huge drive wheel, powered by an electric motor, to which was attached a connecting rod, which in turn attached to the middle of the gate. These mechanisms were replaced with hydraulic struts beginning in January 1998, after 84 years of service. The gates are hollow and buoyant, much like the hull of a ship, and are so well balanced that two 19 kW (25 hp) motors are enough to move each gate leaf; if one motor fails, the other can still operate the gate at reduced speed.

Each chamber also contains a pair of auxiliary gates which can be used to divide the chamber in two; this is designed to allow for the transit of smaller vessels — such as canal tugs — without using the full quantity of water. They were originally incorporated because the overwhelming majority of all ships of the early 1900s were less than 600 ft (183 m) in length, and would therefore not need the full length of the lock chamber. Nowadays these gates are rarely used; instead, small boats such as tour boats, tugs, and yachts are passed in groups.