pressure gauge – what happened before 1850?

[Roger HartParticipant @rogerhart88496]

The bourdon gauge was invented about 1849 but steam locomotives were around long before. So how was the pressure in the boiler measured? How did you know when 'enough was enough'?

[Roger HartParticipant @rogerhart88496]

[Anonymous]

It probably wasn't measured which, along with no safety valves, meant that boilers regularly exploded as working pressures increased, until legislation stepped in.

Andrew

[BazyleParticipant @bazyle]

The Newcomen engine was operated at only about 5psi and the Watt engines not a lot more so a mercury manometer was sufficient. I have a book from about 1890 showing an automatic feed system using a water tank about 30 feet above the boiler since the 15psi over pressure was enough.

[Bob Brown 1Participant @bobbrown1]

Do not need a bourdon tube to measure pressure so may be they used something different before 1849 like a piston and spring.

[Neil WyattModerator @neilwyatt]

Stevenson's Rocket used a mercury manometer – you can see it in most pictures. Many early safety valves used weights and levers so they could operate a=tr an easily calculated pressure. they were also vulnerable to being tied down by the engineman.

Neil

[Neil WyattModerator @neilwyatt]

Running in front of the chimney on this 'replica':

[LambtonParticipant @lambton]

. The Stipulations and Conditions of the Rainhill Trials (1829) required for each engine:

"There must be a Mercurial Gauge affixed to the Machine, with Index Rod, showing the Steam Pressure above 45 Pounds per square inch; and constructed to blow out a Pressure of 60 Pounds per inch".

One fitted to Rocket was 9 feet high and was braced against the side of the tall chimney. It was made from copper tube with a wooden float projecting out to enable the driver to read the boiler pressure.

[Roger HartParticipant @rogerhart88496]

Thanks very much everyone. I guess a bit of mercury slopping about was a small danger compared to all the other dangers. Nice to see what practical folk our forbears were.

[DMBParticipant @dmb]

Have a good Stoke and run!!

[DMBParticipant @dmb]

I heard a story about an early engine in Brighton Station which had a steel bucket of fish plates hung on the SV lever because of the heavy train. Boiler went bang and steam dome was found in New England Street 300 yards away.

[Howard LewisParticipant @howardlewis46836]

In USA, the hissing of the Safety Valve annoyed the crew of "The Best Friend of Charleston" . So they tied it down, with predictable (to us now) results.

Even with reliable pressure gauges, boiler explosions still happen. Only a few years ago, in USA, a traction engine exploded killing the crew and spectators, at a vintage fair.

In the latter days of steam in USA, a Baltimore and Ohio EM8 (a large articulated loco) boiler exploded. The pictures of the aftermath are terrifying, with the remains of the huge boiler torn open and thrown down what remains of the track.

All these things explain why we have regular boiler tests, and check Safety Valves and Pressure Gauge calibration.

Much as I dislike much of what the EU does, the "bar litres" regs do make sense. Even a small boiler, contains a lot of heat and potential energy, that no one wants meet head on!

If the flying metal does not injure, the condensing steam WILL.

Howard

[Neil WyattModerator @neilwyatt]

Posted by DMB on 06/12/2015 13:19:12:
I heard a story about an early engine in Brighton Station which had a steel bucket of fish plates hung on the SV lever because of the heavy train. Boiler went bang and steam dome was found in New England Street 300 yards away.

And it rained boiled fish in Hove

Neil

[Neil WyattModerator @neilwyatt]

Posted by Howard Lewis on 07/12/2015 12:29:04:

Even with reliable pressure gauges, boiler explosions still happen. Only a few years ago, in USA, a traction engine exploded killing the crew and spectators, at a vintage fair.

As I recall the water level dropped and the firebox crown (which was corroded to 23% thickness) overheated and then caused a massive increase in pressure probably when the boiler was topped up.

Hmm – my recollection isn't far off – a detailed report is HERE

The engine jumped ten feet into the air and finished up in a tree, and five people died.

Neil

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