An Engineering Update

An Engineering Update – Cancelled Monday 28th August Steaming

Since a mechanical fault to the boiler feed pump ceased operations at our August Steaming weekend, our volunteers have been investigating the problem.

The boiler water feed valve next to the boiler acts as a non-return valve. When the pumps are working water is fed through this valve into the boiler. When the pumps aren’t working this valve stops the water flowing out of the boiler, therefore keeping the boiler full. We originally thought that this valve was stuck, meaning water couldn’t enter the boiler. Therefore the boiler wasn’t filling up and so as steam was being used by the engines the water level was falling, eventually to a level too low to allow us to continue.

The valve was taken apart, examined and rebuilt, however our volunteers couldn’t find anything dramatically wrong with it. There was a worry about a blockage in the pipe system between the boiler and the Header Pond. If there isn’t a need for water in the boiler while the pumps are working, this water is sent to the header pond instead. At the header pond there is a valve which lifts to allow the surplus water through. If this valve is lifting off at a lower pressure than the boiler it will always go to the header pond and never to the boiler. Our engineers connected a mains water pipe to the pipe that feeds water to the header pond which reached 30 pounds of pressure. This is higher than the 20 PSI working boiler pressure. This means that the weight on the valve in the header pond shouldn’t lift up until it’s got to a higher pressure than the boiler allowing water to enter. Also Proves nothing is stuck in the pipeline,

There was also a thought that there may be a leak in the pipeline somewhere, though no leaks were found.

So, although by dismantling the regulating valve and pressurising the pipe to clear a possible blockage we could have achieved a positive result, we could not identify a clear ’smoking gun’. So we decided to carry out a test run on both engines. This was successful with both engines delivering water to the boiler. We did notice though that whilst the valve in the header pond had lifted at a pressure higher than the boiler pressure in our static pressure test, it did not perform as well under operating conditions where it needs to lift and close around 10 times a minute with every stroke of the engine- some water was passing when in the ‘closed’ position, limiting flow to the boiler.

Before the last public steaming of the year on Saturday 23rd and Sunday 24th September we will strip down that valve and check its operation.