Kempton Park Pumping Station - turbine detail

Image: © Chris Allen Taken: 17 Apr 2011

I'm sure that many will recognise this as a labyrinth packing. This is the main turbine shaft at the exhaust end of the turbine and the shaft has a series of very finely machine concentric grooves with a knife edge finish. These are designed to keep steam in or (at the exhaust end of a condensing set) air out. They work on the principle that as the gas trying to move along the shaft passes from space to space it expands until is quite literally runs out of pressure and can go no further. This gland was actually steam sealed with a little visible wisp of steam at the vapour pipe to show that all was well. There is an oil thrower on the shaft to the left to stop lubricating oil ingress. This is all incredibly elegant (and invisible) engineering.

Images are licensed for reuse under creativecommons.org/licenses/by-sa/2.0