Boiler Fitting Tapered Seal

[electrosteam]

My first post from sunny Sydney.

Many of the boiler fittings on the Climax use a taper on the plug to contact a sharp right angle on the mating housing.
Eg: the banjo plug and water column drain for the water gauge.

I am a new builder and all my UK reference data use flat surfaces with an interposing gasket, thread tape or paste to achieve the seal.

Just wondering how reliable the tapered metal/metal seal has proven in service.

Thanks in advance,
John.

[Ed Hume]

I've had some years of running my locos with light usage - perhaps 4 to 8 times a year. My experience is that the metal to metal (crush) seals do fine without tightening. It has been more often that I have seen paper gasket seals needing to be tightened. Maybe it is because the paper swells and shrinks so there is more joint motion to create uneven sealing.

I have noticed that in the new Shay book (his latest book), Kozo specifies phosphor bronze for the tubing nipples instead of brass as specified in the older books. I am thinking there are beneficial reasons for this - the bronze is easier to silver solder and it will be stronger and more resilient to keep its shape with usage. Also if there is exposure to steam, bronze does not have zinc which can degrade with steam exposure.

[electrosteam]

Ed,
Thanks for the response.
The only publication by Kozo that I have access to is the Climax, but I will be subscribing to Live Steam & O. R. to monitor the latest design - unlikely that I would be tempted to build a K27.

In the Climax book, the pipe/nipple design appears to be almost flat/flat contact, although the contact surface is at 45 degrees to the pipe axis.
This is virtually the same as an industrial loose olive, a proven approach.

My interest is specifically the flat/edge design in applications not directly associated with piping - the water gauge previously referenced.

I know that the flat/edge approach can work.
About 50 years ago I participated in the development of a similar design for use in the manufacture of high power vacuum valves.
These valves had copper anodes with a brazed evacuation copper tube that extended to a brazed flat copper flange.
The flange then contacted a circular ring on the vacuum pump side.
The ring provided a sharp edge (of about 90 degrees included) to the flange.
We could clamp up the system, bake at a high temperature (by gas burners), cool to room temperature, re-tighten and operate an electronic gas absorption system to achieve an extremely good vacuum.
A one-off use, no vibration and only one temperature cycle.

Valve separation from the pump utilized double hard rollers squeezed together with a hydraulic cylinder achieving a cold weld of the internal copper surfaces and pinch-off from the mounting flange.
The sharp pinch-off was carefully protected and then potted in soft solder when the valve was mated with its heat-exchanger (air or fluid).

The interest is whether the flat/edge design operates for extended periods in a locomotive environment.

John.

[electrosteam]

Ed,
I got it wrong above, my apologies.

I went back and re-read the Climax book and the steam pipe fittings are indeed a flat/edge design, similar to the larger fittings used on the water gauge.

I will take your comments as the real-world experience that I was seeking, thank you.

John.