On Jul 24, 9:29*am, Matty F wrote:

Does an 1891 Baldwin Steam tram have a superheater?

I would doubt it. There are two reasons why not.

Firstly, not much in 1891 was superheated. Superheating in steam locos
appeared slowly, from 1900. It appeared according to the preference of
CMEs, some embracing it, others avoiding it. They mostly recognised
the efficiency advantages, but the problem was cylinder lubrication.
The high temperatures of superheating tended to break down the
lubricants of the period, leading to varnish buildup and sticking
pistong rings and valves. This was particularly a problem with slide
valves - why the piston valve also started to become popular around
this time.

Secondly, superheating still doesn't work well in trams or shunters,
even today. Superheating requires a hot superheater element, which
requires gasflow past it. Fine on a long-haul run, but hard to achieve
with stop-start work, or long periods standing idle. Some superheater
designs also suffer if cycled between hot & cold and may start to
leak. A more common arrangement for donkey engines (and this might
have applied to trams too) was the "steam drier". This was a very mild
superheater whose purpose wasn't to change efficiency by shifting the
enthalpy significantly, but merely to heat the steam enough to ensure
that thoroughly dry steam was delivered to the cylinders, and that it
would avoid condensation during expansion - even when these were
distant, or went cold between operations. For intermittent use,
condensation and wet carry-over (even though this wasn't as bad as
priming) was a problem. Steam driers were particularly common in small
vertical boilers, which otherwise tended to deliver wet steam.