harry wrote:

If you look at a guage glass it has diagonal stripes behind it.

If the glass is full of water they are refracted to the horizontal as
seen through te sight glass.
If the glass is full of steam, they remain diagonal.
So you know whether the water level is above or below the glass.

When the first main transformer to be built for the Class 357
stock was delivered, we noticed that, unlike previous UK
practice, the oil level sight glass was plain, rather than
prismatic, and the oil was almost clear, so the level was
difficult to see.

I suggested diagonal stripes behind the tube, an idea that was
initially regarded as, at best, strange. I persevered, and
quickly produced a suitably marked piece of card. The result was
as I had anticipated, much to the amazement of all around.

Sometimes steam can help electrics!

Chris
--
Chris J Dixon Nottingham UK


Have dancing shoes, will ceilidh.