Leaky whistle valve

[timg]

I have a leaking whistle valve that even when closed makes the whistle sound like it smokes 40 a day and has just run the Brighton marathon. I haven't seen this design before and not sure how to make it steam tight?

[jem]

Perhaps a little valve paist to make the mating surfaces mate?

best wishes

Jem

[weary]

Depending on valve mating surface condition and overall length of the valve spindle can you p'raps slip a suitably sized 'O-ring' down the shaft of the valve and onto the valve face?

Phil

[mbrown]

The whistle valve I made for 99 3462 is similar in that the valve is rigidly fixed to the operating pin. It leaks....probably because the valve, its spindle and the valve seat are not absolutely concentric.

Two possible sutions: replace the valve with a ball, held up to the seat by the spring, and a loose pin to push the ball off its seat. The ball should self-centre on the seat if the seat is truly round.

Second, put a small O ring over the existing valve so that it seats between the valve and its seat. The problem here might be that the operating pin is then too short, but it would be a quick and easy initial option.

On mine, the design precludes a loose ball so I am going for the second solution.

Hope that helps.

Malcolm

[chris vine]

Hi Tim,

There is also a small shoulder on the valve rod, just where it gets to the valve proper. Is it possible that this is catching on the hole and stopping it from seating. This might happen if the spring is sitting in such a way as to push it off to one side a little.

I also have one of the whistle valves and it leaks when you blow it. Hot fingers prevent over-enthusiastic whistle blowing!!

Chris.

[timg]

Thanks all,
Decided to use some valve paste and a 3mm nitrile o ring as well. and first signs look like that should have sorted the problem.

[JonL]

I'm reliably informed there is no such thing as a stupid question... is it connected up the right way round? It's the sort of mistake I'd make and kick myself over.

[timg]

Apr 15, 2024 13:04:20 GMT JonL said:

I'm reliably informed there is no such thing as a stupid question... is it connected up the right way round? It's the sort of mistake I'd make and kick myself over.

That's OK. I'm not quite sure what you mean

[JonL]

If steam enters from one side the pressure will hold the valve shut, if supplied from the other side it will leak.

[timg]

Ran the loco at the club on Saturday and as soon as I tested the whistle it continued to remain slightly open. Could the spring need replacing?

[timg]

Apr 20, 2024 11:35:52 GMT JonL said:

If steam enters from one side the pressure will hold the valve shut, if supplied from the other side it will leak.

The steam comes through behind the valve so should keep it shut until it's released

[chris vine]

I think there is a discontinuity in the diameter, or a notch if you prefer, just below the valve part of the spindle. This could easily catch in the bore at the step.
Also, the spring has an unfinished end, in your photo. This will tend to load up the valve sideways and may be causing it to catch on that notchy bit.

A bit of careful observation and experimenting will soon have you fixed up...
Chris.

[jma1009]

Quite a lot to consider here.

A whistle valve ought to be able to deal with the stringent requirements of subsequent boiler hydraulic tests.

The valve ‘Rod’ ought to be very good fit between the exit of steam to the whistle pipe connection and the whistle ‘handle’ to move the rod to open the valve to boiler pressure. The seating of the whistle valve on the boiler supply side ought to be ‘perfect’ and not leak. To obtain a decent seat on valve, whether a valve head on the ‘rod’ as here, or a ‘rod’ onto a ball valve, requires (as Malcolm states) absolute concentricity. And a well machined seat for the valve head or a ball. A solid valve head combined with a rod will also require to be perfectly concentric.

Those are prerequisites.

As to a spring that keeps the valve ‘shut’ in addition to boiler pressure, these springs are often short and stiff which is challenging so as to ensure that the spring does not impose anything but a ‘centralising’ effect on the ball or valve head. If the spring has the effect of forcing the valve head or ball to one side, then avoiding a leak is always going to be a problem.

Great care ought to be had in the choice of the spring, and the finishing of the cut ends so that they do not impart anything other than a central ‘push’ force, and avoid any force to one side.

There are various ways to try and achieve this. The first is to keep the distance between the valve seat and the steam exit to the whistle pipe exit as short as possible. This requires very accurate silver soldering and machining. It reduces the unsupported length of the ‘rod’ in the cavity from the valve seat to the exit, and the tendency of a poor spring to upset the seating.

The second is to finish the spring ends correctly. And at this point may I comment that the section within which the spring works and ultimately compresses should allow sufficient steam to get to the exit to operate the whistle. So the ends of the spring need to be ‘flattened’. And correctly. So as to minimise any sideways force. (The same could equally be said of safety valve springs, and springs in mechanical lubricator check valves).

I’ve bought many stainless springs over the years. And wound my own, and also in phos bronze wire. You have to grind the ends and flatten the ends. After grinding (which might be just a whisker on the grinder) immediately flatten when still hot, or add a cigarette lighter to the end to immediately flatten.

Apologies for the lengthy reply.

[simon6200]

Mine had been leaking lately and a spot of oil on the spindle seems to have fixed it, at least for now. I made one with a Viton O-ring seat for a Gauge 1 Eric I made.