The ground water in this area is quite hard - up to 40 deg. - and must be softened before use to avoid scaling of the boilers and pipework. The build up of scale in the colliery boilers acted as a thermal insulator and had serious consequences, not only because it required more coal to heat the water, but because it could lead to the boiler plates actually being burnt by the flames.  The precipitation and deposition of scale is a function of the temperature of the water and, as the boiling point of the water will rise as the pressure increases, the problem of scaling will increase accordingly.

In the early years, although the water was filtered to remove suspended material, it’s doubtful whether the water was treated to reduce the hardness since the technology did not exist and the boiler pressures and temperatures were relatively low. If the water was treated at all it was usually by the addition of some organic material which would act in such a way as to cause any material precipitated to form a scum on the surface of the water, from where it could be blown out by means of a valve placed at water level.  The organic material used in some boiler plants in those days often took some strange forms - dead rats, dogs and, reputedly, even a donkey!

With the installation of more powerful winding engines in the early 1900s using steam at 90 - 100 psi the problem of scaling became a serious issue. Luckily, the chemistry was now much better understood and various technical solutions had begun to be developed. Around this time a water softening plant was constructed on the South pit-top near to the water reservoirs / cooling ponds and can be seen on the 1916 1:2500 map.

Water softener plant circa 1916 (JST)

In a photograph taken in 1919 there is a large Braithwaite sectional tank at this location with smaller tanks above it that have the appearance of a basic water softening treatement plant.  There is also a large amount of light discoloration both on the header tanks and in the general vicinity of the main tank The latter may be from spillage of the treatment powder - probably lime and soda ash - or it may be from the precipitate when the tanks were cleaned out.

This is to be the new Lassen and Mjort softener mentioned in the Stanton Ironworks monthly reports for February 1920.

Water softener tanks  circa 1922 (FoPP/JST)

Water softener treatment header tanks  circa 1922 (FoPP/JST)

Following the 1950s modernisation a new water-softener was installed on the south side of the cooling ponds. It consisted of a tall insulated cylindrical tower surmounted by a mechanism which tipped a measured amount of solution into the heated water column inside the tower.  The manufacturer of this plant is not known at present.

The softening minerals were supplied in powder form and mixed ready for use in a small building adjacent to the tower.  The solution was pumped to the top of the tower and held in a tank above the tipping bucket. The resultant precipitate from the softening process was then pumped into a pond formed on the old spoil heap between the Back Lane entrance and the sidings from the Great Northern railway.

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05 May, 2009