Sandfields Pumping Station - condensing plant

Image: © Chris Allen Taken: 28 Feb 2020

The surviving brick engine house contains a Cornish beam pumping engine built in 1873. This is the upper part of the condensing plant that sits in a big iron tank that was filled with canal water that was being constantly returned to the canal by a pump on the other side of the wall to the left. The big pipe in the left background is the eduction (exhaust) pipe bringing spent steam from the cylinder into the top of the surface condenser that is bottom and slightly left of centre. The condensate and incondensable gases are removed from the condenser by the air pump in the foreground that is operated by a rod from the beam. Top left is the boiler feed pump that takes warm condensate from the hotwell and returns it to the boiler. So far, so good! But, the air pump has a large bore pipe to the right that returned to the canal and according to the original drawing it has been extended upward above the level of the hot well to accommodate this pipe. This has led to a very lively discussion both on site and via e-mail. A surface condenser only contains a volume of water corresponding to the steam used by the engine and all this should return to the boiler via the feed pump. As such, it needs a relatively modestly sized air pump and no need to return large volumes to the canal. On the other hand, a jet condenser needs (say) 20 times the weight of steam in injection water and would have a large excess to return to the canal. Furthermore part of the original specification refers to a surface condenser that could be converted to injection if found necessary. Therefore, our best guess is that this is arranged primarily as a surface condenser but could have an element of injection (jet) condensing if needed and that the air pump is therefore oversized relative to that required for pure surface condensing and has an overflow to return excess water to the canal. However, that is an element of conjecture based on available evidence. You may wake up now!

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