Андертон көтергіші: су жолдарының кереметі

Two caisson lift lock near Anderton, Cheshire, England

The Anderton Boat Lift is a two caisson lift lock near the village of Anderton, Cheshire, in North West England. It provides a 50 feet (15 m) vertical link between two navigable waterways: the River Weaver and the Trent and Mersey Canal. The structure is designated as a scheduled monument, and is included in the National Heritage List for England; it is also known as one of the Seven Wonders of the Waterways. Built in 1875, the boat lift was in use for over 100 years until it was closed in 1983 due to corrosion. Restoration started in 2001 and the boat lift was re opened in 2002. The lift and associated visitor centre and exhibition are operated by the Canal & River Trust. It is one of only two working boat lifts in the United Kingdom; the other is the Falkirk Wheel in Scotland.

Salt has been extracted from rock salt beds underneath the Cheshire Plain since Roman times. By the end of the 17th century a major salt mining industry had developed around the Cheshire "salt towns" of Northwich, Middlewich, Nantwich and Winsford. Completion of the River Weaver Navigation in 1734 provided a navigable route for transporting salt from Winsford, through Northwich, to Frodsham, where the Weaver joins the River Mersey. In 1759 the second Weaver Navigation Act appointed the Trustees of the Weaver Navigation and gave them responsibility for maintaining and operating the route. The opening of the Trent and Mersey Canal in 1777 provided a second route close to the Weaver Navigation for part of its length, but extended further south to the coal mining and pottery industries around Stoke on Trent. Rather than competing with each other the owners of the two waterways decided it would be more profitable to work together. In 1793 a basin was excavated on the north bank of the Weaver at Anderton that took the river to the foot of the escarpment of the canal – 50 feet (15 m) above. The Anderton Basin was owned and operated by the Weaver Navigation Trustees. Facilities were built to trans ship goods between the waterways including two cranes, two salt chutes and an inclined plane that was possibly inspired by the much larger Hay Inclined Plane at Coalport. The facilities were extended when a second quay was built in 1801 and a second entrance to the basin was constructed in 1831.

By 1870 the Anderton Basin was a major interchange for trans shipping goods in both directions, with extensive warehousing, three double inclined planes and four salt chutes. Trans shipment was time consuming and expensive, and the Trustees of the Weaver Navigation decided a link between the waterways was needed to allow boats to pass directly from one to the other. A flight of locks was considered but discarded, mainly because of the lack of a suitable site and the loss of water that would have resulted from using them. In 1870 the Trustees proposed a boat lift between the waterways at the Anderton Basin. The Trustees approached the North Staffordshire Railway Company, owners of the Trent and Mersey Canal, to ask for a contribution towards the cost. When this approach was unsuccessful the Trustees decided to fund the project themselves. The Trustees asked their Chief Engineer, Edward Leader Williams, to draw up plans for a boat lift. He settled on a design involving a pair of water filled caissons that would counterbalance one another and require relatively little power to lift boats up and down. A similar boat lift on the Grand Western Canal, completed in 1835, used chains to connect the caissons via an overhead balance wheel. It had a solid masonry superstructure to support the weight of the loaded caissons. Leader Williams realised that if he used water filled hydraulic rams to support the caissons their weight would be borne by the rams and their cylinders, buried underground and a much lighter superstructure could be used. He may have been inspired by inspecting a hydraulic ship lift and graving dock at the Royal Victoria Dock in London, designed by experienced hydraulic engineer Edwin Clark. In normal operation the cylinders of the hydraulic rams were connected by a diameter pipe that allowed water to pass between them, thus lowering the heavier caisson and raising the lighter one. To make adjustments at the start and end of a lift either cylinder could be operated independently, powered by an accumulator or pressure vessel at the top of the lift structure, which was kept primed by a steam engine. If necessary, the steam engine and accumulator could operate either hydraulic ram independently to raise the caissons, although in this mode it took about 30 minutes to raise a caisson, as opposed to three minutes in normal operation. The volume of traffic through the lift grew steadily through the 1880s and 90s but the hydraulic cylinders continued to cause problems. The gland of one cylinder (where the piston travelled through the cylinder wall) was temporarily repaired in 1887 and replaced in 1891, and the gland of the other cylinder was replaced in 1894. The main cause for concern was corrosion of the pistons. The use of canal water as a working fluid in the hydraulic system and the immersion of the pistons in the wet dock at river level led to corrosion and "grooving" of the pistons. Attempts to repair the grooves with copper made matters worse as it reacted electrolytically with the acidic canal water and hastened corrosion of the surrounding iron. In 1897 the lift was converted to use distilled water as its working fluid, slowing corrosion, but not stopping it completely. Over the next few years maintenance and repairs took place with increasing frequency, requiring complete closure of the lift for several weeks or a period of reduced and slower operation with a single caisson.

By 1904 the Weaver Navigation Trustees faced the prospect of closing the boat lift for a considerable period to repair the hydraulic rams. They asked their Chief Engineer Colonel J. A. Saner, to investigate alternatives to hydraulic operation. Saner proposed electric motors and a system of counterweights and overhead pulleys that would allow the caissons to operate independently of each other. Although this solution involved many more moving parts than the hydraulic system these would be above ground and accessible thus making maintenance easier and cheaper and have a longer working life. Other advantages of the conversion listed by Saner included a reduction in the number of operating attendants by one and the avoidance of costly boiler repairs. Saner promised to achieve the conversion with only three short periods of closure to traffic. This was important because it minimised disruption to traffic and the loss of revenue during conversion. As a result, the weight of the caissons and counterweights would now be borne by the lift superstructure instead of by the rams. The superstructure was therefore strengthened and put on stronger foundations. The new superstructure was built around the original lift frame in order to avoid the need to dismantle the original lift, which would have taken it out of service for a long period. The new superstructure consisted of ten steel A frames, five on each side, supporting a machinery deck 60 ft (18 m) above the river level where the electric motors, drive shafts and cast iron headgear pulleys were mounted. Wire ropes attached to both sides of each caisson passed over the pulleys to 36 cast iron counterweights weighing each, 18 on each side to balance the weight of each loaded caisson. The electric motor had to overcome friction between the pulleys and their bearings. A motor was installed, but normal operation only required about half of this power. In addition to the new foundations and superstructure, the wet dock at river level was also converted into a dry dock and the aqueduct between the lift and the canal was strengthened. The original caissons were retained but were modified to take the wire ropes that now supported them on each side. Conversion was carried out between 1906 and 1908. As Saner had promised, the lift was only closed for three periods during these two years, for a total of 49 days. The converted lift was formally opened on 29 July 1908 (although one caisson had been carrying traffic on electrical power since May 1908 while the second caisson was converted). During the 1950s and 1960s commercial traffic on British canals declined. By the 1970s the lift's traffic was almost entirely recreational and the lift was hardly used during winter months. The new superstructure was susceptible to corrosion and the entire lift was painted with a protective solution of tar and rubber that had to be renewed every eight years or so. In 1983, during repainting, extensive corrosion was found in the superstructure and it was declared structurally unsound and closed.

During the 1990s British Waterways carried out preliminary investigations before launching a restoration bid. It was originally intended to restore the lift to electrical operation but after consultation with English Heritage, in 1997 it was decided to restore the lift to hydraulic operation using hydraulic oil. To raise the £7 million restoration cost, a partnership was forged between the Waterways Trust, the Inland Waterways Association, the Anderton Boat Lift Trust, the Friends of Anderton Boat Lift, the Association of Waterways Cruising Clubs, British Waterways and the Trent and Mersey Canal Society. Heritage Lottery Funding contributed £3.3 million, and more than 2,000 individuals contributed to the scheme, raising a further £430,000. Restoration commenced in 2000 and the lift was re opened to boat traffic in March 2002. The site now includes a two storey visitor centre and exhibition building with a coffee shop and information and films about the history of the lift. The visitor centre incorporates the new lift control centre. Although a modified version of the original hydraulic system was reinstated, the 1906–08 external frame and pulleys have been retained in a non operational role. The weights that used to counterbalance the caissons were not rehung, but have been used to build a maze in the grounds of the visitor centre.