Sentinel 7109's Mechanical Lubricator - A Second Mystery Solved

The first mystery was solved in my previous article on the subject. I'd been wondering why there should be a short pipe leading from one of the exhaust pipes to the base of the mechanical lubricator.

Pipe ends highlighted

I'd heard that the pipe was to help heat the lubricator using exhaust steam; however, I could not see how this worked as there did not seem to be anywhere for the steam to escape at the lubricator end.

I was told recently that there should be a hole for the steam to escape but wasn't told where it was likely to be located. On previous occasions, I'd not found anything resembling a hole anywhere. However, as I am currently in the process of refitting the exhaust pipe concerned, I decided that I would have to look a good deal harder.

I detached the pipe from the lubricator. Initially, I still couldn't find a hole but then I began to unscrew the lubricator fitting and spotted what looked like a centre punch indent. I scraped at it with a piece of wire and a hole appeared.

Lubricator pipe fitting

There it is!

Blowing in some air demonstrated that there really was a route for the steam from the pipe to the little orifice.

So a mystery solved and yet another of a Sentinel's peculiar steam outlets found.