6880 Betton Grange

Two gauge glasses are certainly not necessary. Just blow down the gauge and then raise the lever - the level should instantly return to its original level. If it doesn't, the water ways are blocked which is down to poor maintenance. There are also three test cocks.

If you (not you personally) cannot get one gauge frame to function correctly, how can you have any confidence in the second frame?

 

And when your one gauge glass blows?

 

Use the test cocks (that’s what they’re for) and replace glass.

 

Still better with two glasses. A test cock won’t tell you how high the water level is

 

It doesn’t really need to….just how low it is. You shouldn’t run with just one anyway so in practice I am not sure it makes a lot of difference, you just get on and change it.

 

If you have two glasses, any discrepancy between them is an immediate cause for concern which you can investigate further. If you only have one glass, your suspicions may not be raised by a fault.

https://www.railwaysarchive.co.uk/documents/MoT_Wheatsheaf1952.pdf is an example of an accident I would suggest could have been prevented by having two gauge glasses. As things stood, the crew noted that the water level shown in the one glass was at the top of the glass: half a mile further - perhaps just a minute - the firebox crown collapsed, indicating that the actual level was probably in the region of 8 inches lower than indicated. Two glasses would have shown an immediate discrepancy caused by one being faulty - unless you have the much less likely scenario that both glasses were faulty in the same manner.

It's also interesting how many people examined the loco and saw no fault:

• The apprentice fitter and his supervisor changed the glass on 18 December and deemed it to be working correctly. Another fitter who then examined their repairs in steam also deemed it fit to run.
• The crew on 19 December reported no fault
• The driver on 20 December thought the water was returning sluggishly., Accordingly, it was inspected by a fitter who, with the try cocks as his alternate method of testing, saw no reason to fail the engine.
• Three crews on 21 December noted the return was sluggish. A fitter who examined it deemed it was working correctly
• The crew on 22 December suffered a firebox collapse.

So over four days, five different fitters failed to find a problem which led to a firebox crown collapse.

Tom

 

If you shouldn't run with one glass, it hardly seems sensible that you would deliberately choose to go off shed with one glass! Yet that is what generations of GWR enginemen did ...

Tom

 

That’s the purpose of the test cocks.

I get the preference for two. Just never thought it a huge issue to only have one.

 

Except as I understand the GWR design, the test cocks come off the same passage ways as the gauge glass itself. So if (for example) the top passageway is partially blocked causing the water in etc glass to read falsely high, it will also affect the test cocks - which are therefore not an independent means of checking the level.

In the case I linked to, the fitter asked to investigate a suspect gauge glass saw the water was reading above half glass (above the level of the upper test cock); tried both test cocks and got steam/water from both, and concluded that the gauge glass was reading correctly when, as events subsequently showed, it wasn't.

Tom

 

Ok, but I’m not sure there was any greater incidence of boiler failure or low water incidents on the GW/WR than anywhere else, and locos with two glasses were not immune either. As I say, I get the reasoning behind having two and I probably wouldn’t specify a boiler without two glasses, but equally just having one doesn’t strike me with fear.

 

I did try looking into that, but I found so few instances of problems in the 20thC that no statistical analysis seemed possible.

 

The test cocks come off the pillar onto which the water gauge fittings themselves are attached. So yes they do get steam/water from the same openings into the boiler but not from the top/bottom gauge fittings holding the glass. In the report you posted the inspector found a constriction near the top of the glass. The test cocks would not show false readings by that particular defect.

 

Just to be clear, the gauge frame should be rodded through at every washout.

 

In my experience, a broken or blowing gauge glass is a very rare occurrence, usually caused by poor fitting. When it does fail, use the test cocks - that's what they are for.

 

I’ve had three go in my time on the footplate. One even broke the protector glass.

 

In the 70s I had a cab ride on Prairie 6106 at Didcot (cost 50p) and mentioned why only one gauge glass to the driver, it was one of the founders Graham Perry, and I think he was a bit put out!

 

Looks to be free of steam leaks (even small ones) at the front end. Well done to all involved.

 

Looks fabulous! Well done everyone.
Onto the SVR now?

 

That is the question.
Steam Railway quote as running in at the SVR during May, but with the diesel gala 16-19th and the GWSR the gala weekend after, I wonder if it will be used on passenger trains or not while there, maybe at best during the week ending Sunday 12th May?