Geograph - photograph every grid square

This vast machine that weighs about 100 tons was built in 1892 in Hayle and installed secondhand in this new engine house by 1924. It worked until 1954 and is now preserved by the National Trust.
This shows the top of the 90" diameter cylinder with its piston rod rising to the beam above. There is a displacement lubricator feeding steam oil to the cylinder - the brass object on the left. Arrayed across the front of the cylinder are three valves in a box called the 'top nozzles'. The nearest is the governor valve, which is a hand worked throttle that controls how much steam passes. Next is the steam valve that actually puts steam on top of the piston to push it down to raise the pump rods at the other end of the beam. This valve is closed part way through the stroke to allow the steam to expand and be used more efficiently. On the right is the equilibrium valve that opens at the end of the downwards stroke to allow steam to pass to the lower side of the piston, so that it ascends under the weight of the pumps. If you want to see this for real, I would recommend Kew Bridge Steam Museum or Crofton Pumping Station.