Hydraulic Power Stations & Ring-Main
System, Swansea Docks
At one time all mechanical appliances such as cranes, coal hoists, swingbridges, lock gates, turntables & capstans on Swansea Docks were operated by pressurised salt water pumped into an 8” underground hydraulic ring-main by steam-powered pumping stations, each housing a large coal-fired steam engine coupled to double-ram reciprocating pumps generating a water pressure of 800 psi and operating to the demand of the system's hydraulic accumulators
The western power station stood alongside the old Prince of Wales Dock tidal basin in the River Tawe and operated around the clock, while the eastern power station at the east end of Kings Dock operated for 16 hours per day. Both power stations were identical in layout and design, and were magnificent examples of early 20th century engineering. Adjacent to each engine house was a pump rooms equipped with horizontal double-ram reciprocating pumps, each incorporating a large flywheel, and in the basement below was an impressive array of auxiliary equipment.
Hydraulic power was distributed around the Kings Dock and the Prince of Wales Dock via an 8” diameter ring main fabricated with 36ft sections of cast-iron pipe, passing under the Kings Dock locks and the Scherzer passage en route. Shut-down valves at strategic points in the ring-main circuit allowed leaks and bursts to be isolated for repair while pressure in the circuit was maintained.
Hydraulic accumulators were constructed alongside each power station and at strategic locations around the docks to maintain water pressure whenever demands were high. (see below for further information on hydraulic accumulators)
The 8” ring-main also powered a separate 4” inch hydraulic system that operated the lock gates, swingbridge, capstans & sluices etc., at the Kings Dock lock entrance. The 4” system included a two inch auxiliary back-up circuit with so many interlinking valves that, when fully identified and mapped out, looked more like a map of the London underground! (Viv Howells)
The South Dock hydraulic power station, now the Pump House Restaurant, was similar to the Kings Dock power stations in layout and equipment and, in the mid 1950s, was the first to be converted to electricity with the installation of four Chester three-ram electric pumps and a standby Blackstone diesel engine coupled to a Sulzer pump. A Paxman Ricardo low lift pump was also installed on the quayside to pump water from the dock into station's elevated header tank which, in turn, supplied water to the pumping equipment down below.
In winter when the temperature dropped to or below freezing point a set of defrosting measures were put in place on coal hoists, hydraulic cranes, accumulators, lock machinery, etc., using braziers and blow-lamps to prevent appliances freezing up. Maintenance work would be suspended with staff split into two twelve hour shifts to provide round the clock cover. When the hydraulic ring main was discontinued, the remaining much smaller circuit around the locks was changed from salt to fresh water. Although this came at a cost, it was less corrosive to the valves and other moving parts of the system. In very cold weather the supply was temporarily changed back to salt water which has a lower freezing point.
Hydraulic Accumulators
Hydraulic accumulators on Swansea Docks consisted of a large vertical cast-iron cylinder containing a column of water held under pressure at 800 psi by a weighted ram. A circular (annular?) ballast tank containing pig iron or other heavy material suspended from the ram cross-head provided the precise weight needed to maintain the requisite water pressure in the cylinder.
When the ring-main was at its maximum pressurise of 800psi it automatically maintained the same pressure in the accumulator's cylinder, forcing the weighted ram up to its maximum height. When high demands on the system caused a drop in ring-main pressure, the weighted ram would automatically force water from the cylinder into the hydraulic main to balance out the pressure in the system.
Before the accumulator's ram could bottom out, the power station's pumps (first steam then electric) activated (were activated?) to pump more water into the system and, in doing so, raise the accumulator's ram back up to its maximum operational height. Thus the pumps would work intermittently, depending on load, but the accumulator was always working to mitigate load fluctuations and thereby maintain a constant operational pressure of 800psi throughout the ring-main system.
Note: The South Dock hydraulic power station's accumulator came to an unfortunate end around 1960 when the ballast tank counterweight parted company from the ram crosshead and crashed down from some considerable height, causing the unrestrained, hydraulically-charged ram to rocket upwards and lodge itself in the accumulator tower roof. From then on the South Dock lock gates were operated indirectly by hydraulic capstans and wire ropes rather than by direct hydraulic pressure.
Compiled from information provided by Viv Howells Mechanical Engineering Supervisor Swansea & Port Talbot Docks