Retired Section Swansea Docks


Lock Gates, Kings Dock Lock, Swansea

 There are three pairs of lock gates installed in the Kings Dock Lock at Swansea – the inner gates, the middle gates and the outer gates. The middle and outer gates are identical in size, but the inner gates are shorter in length to accommodate the inner cill of the lock. The original lock gates were manufactured in 1907 by the Thames Ironworks Shipbuilding & Engineering Co. Ltd. at a cost of  £38,503 5s 0d., and the contract for the lock gate operating machinery was awarded in the same year to Sir W G Armstrong, Whitworth & Co. Ltd. in the sum of £4,250 0s 0d. There are also two reserve pairs of lock gates, one for the inner position and the other for either the middle or outer position. The reserve gates for the inner position were manufactured in1928 by Vickers Engineering of Barrow in Furness, and those for the middle/outer position by Fairfield Engineering of Glasgow in 1947. 

Each lock gate is essentially a steel tank divided into internal chambers by horizontal and vertical bulkheads. The bottom chambers are normally maintained dry, although a determined amount of water ballast is added on occasions to increase the stability of the gate during stormy weather conditions or very high tides. The upper chambers have scupper openings which allow water to enter and exit the structure as the lock is filled and lowered, so that the neutral buoyancy of the gate can be maintained at all times. The level of water in the lower chamber of each gate was initially controlled by hydraulic ejectors, but in later years these were superseded by electric pumps. Access to the various gate chambers is gained through four “trunk” tubes – two short ones to the upper chambers and two long ones to the bottom of the gate. These tubes were just large enough for a man to traverse, and can clearly be seen in the video below.

Overall each lock gate was manufactured to a high degree of accuracy and, to allow the gates to make a good seal, the mitre, heel and cill - i.e. the outer edge, inner edge and bottom - are finished with massive sections of precision-cut greenheart timber. Each gate is hinged in position by a pintle and socket at the bottom and a link plate, heel pin and "U" strap at the top. Originally the mitre end was also supported by a large hinged roller which ran along a purpose-built roller path at the bottom of the lock, and which could be adjusted from above by a “spear rod” mechanism.

When a gate required major maintenance or repair it was released from its position by removing any water from the lower chambers and blanking off the scupper openings, thus sealing the gate and making it buoyant so that it could be floated off its mountings. The replacement gate would then be brought into position in a similar manner with the procedure reversed. Repairs were carried out on a purpose-built slipway in the River Tawe – this being a sloping ramp of approx. 30 degrees which was wide enough to accommodate a pair of lock gates side by side. On the slipway were two robust rail-mounted carriages which would be positioned at the bottom of the ramp at low tide. At high tide the floating lock gate would be towed up-river, positioned over one of the carriages, and allowed to settle as the tide receded. It was then hauled to the top of the ramp, well clear of the tidal reach, by air-operated winches and multi-purchase pulleys, and finally jacked up onto the concrete support pillars mounted on the top end of the slipway. The carriage could then be lowered away to allow access to the underside of the gate (see photo of slipway, carriages and pillars below).

In this position, major refurbishment work could be undertaken over an extended period. Thorough cleaning, both internal and external, was followed by a detailed inspection and the subsequent replacement of any internal structural members that might have deteriorated over time. Damaged external plating was repaired or replaced by the Boilermakers. The next step was to renew the mitre, heel and cill timbers after these had been carefully prepared in the Carpenters’ Workshop to very fine specifications. After checking the overall dimensions, the gate would then receive several coats of bitumastic paint, and replacement timber fenders would be fitted. Finally, all access manholes and scuppers would be blanked off, an air compressor attached, and the gate would be pressure-tested for leaks. Job done!

Full credit must be given to the Edwardian engineers responsible for the design and construction of the lock gates and operating machinery, and of the lock structure itself which was built with materials such as granite worked to a high degree of accuracy, and without the use of modern-day lifting and cutting machinery.

View of installation of outer lock gates

The finished lock - view from the sea and ready for shipping - showing swing bridge that
 gave access to Queens Dock and Palmers Dry Dock.

Maintenance fitters ''repacking'' the hydraulic piston that operated the lock gates. This was a regular job that had
to be completed between the ''tides'' at low water when the lock was inoperative, whatever the weather.



Floating lock gate being towed away by tugs from the lock after removal.

View of Slipway and carriages used for the maintenance of the lock gates

Lock gate resting on concrete pillars with the carriage clear of the gate.




The water hydraulic system was replaced by oil hydraulic and electrical control in the late 1990s

Photo showing new lock gate control room


Left to right
1/ Cyril Jones, 2/ xxx xxx, 3/ Malcolm Easthope, 4/ G Rees, 5/ Arthur Eynon, 6/ Bryn Lloyd,
7/ S Pitts, 8/ Capt' Jack White, Dockmaster, 9/ Capt' Tucker,10/ Capt' Terry Chappell,
11/ Cyril Croot, 12/ C Wright, 13/ Joe Mages, 14/ A Webster, 15/ David Crowley, 16/ S Mayo,
17/ J Davies and 18/ Capt' Gerry Grenfell