Over the last two and a half years the trust has been carefully monitoring and measuring the temperature and humidity at Sandfields Pumping Station. The aim of this study is to gain a fuller understanding of how best to preserve the bright works on the Cornish engine and to understand the factor that cause rust along with the idea conditions and treatment to prevent it.
Here is the latest report form the engineering team:
The one working humidity/temperature data logger was left ticking over in the ground floor of the engine house from mid-March until a couple of weeks ago when I returned to active service. I’ve attached a screenshot of the data- at least it makes a change from graphs of Covid-19 infection rates. It’s interesting(ish) because it shows the pattern of variation over an extended period (nearly 6 months), whereas previously I’d been looking at chunks of time of only 2 or 3 weeks.
As can be seen, for much of the time the %RH was in the range 60-70%, with values above and below this range mainly coinciding with spells of particularly warm or cold weather. Keen observers will also notice that there was another incidence around the end of March when a temperature spike of 60+ degrees was recorded- the spirit’s still about.
60-70%RH is in the range where some atmospheric corrosion of iron/steel would be expected. However most of the engine remains relatively unaffected, helped I’m sure by the Steelguard we’ve applied.
I’ve also included “then and now” photos of three areas I taped off in October 2018 (is it really two years ago?) and left untreated. In two cases there’s very little difference, whereas where the pump rod attaches to the beam there’s noticeable corrosion. I think this is more likely to be down to differences in material (eg chemical composition) rather than in location. I’ll leave the data logger to record for the next 6 months to get a comparable picture over winter.