Geograph - photograph every grid square

As built the lift was water hydraulic powered. In 1908 it was converted to electric operation. Following its expensive rebuild at the end of the 20th century it reverted to hydraulic power but with oil as the operating medium and electricity driving the pumps rather than steam. This is the plant seen on a special open day from behind a barrier in the doorway. There are multiple high pressure pumps that I think were working at about 70 bar (c1000 psi). The closest pumps are of smaller capacity and used to operate the lift in balance (one caisson descending while the other is rising) while in the left background are the booster pumps that are used to raise a caisson on its own (out of balance). The lift is usually operated in balance but to start it in the morning it is necessary to raise one caisson on its own. On this occasion both caissons had been raised to the mid position to allow the public access to staging in the dry well. As such, the system was pressurised and the public couldn't wander among the pumps in case there was to be a high pressure leak (unlikely). There is insufficient oil to raise both caissons to the upper position together and I'm not sure why they would want to do that anyway.