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Live steam engine boilers

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sbwhart:
Hi Nick

Good advice thats one reason I've stayed a member of our local club even though they P*****d me off by not being very welcoming.

And your quit right about Old Curly's methods being a bit out of date it took me a while to get to grips with design / method I,ve read quiet a few book on boiler making:- Curly's, Martin Evans, Model Engineer mag etc , and they all seam to have their own methods, Curly calls for screwed stays sealed with soft solder which is a no no by todays standards, the prefered method of fixing fire box stays nowadays seems to be rivets with the heads on the inside with the diameter sticking out that are simply silver soldered in place. I supose whats happend is that technology as moved on with new/better solder and fluxes and a better understanding of requirements. Talking to the boiler inspector at the club an Ex Crewe works copper smith who swears by easy flow flux but I know that there are now available tenasity fluxes that are more tolerant of sustained periods at temperature.

Interesting point about the blower needing to be fixed hadn't picked that one up, its filed away.

With the supper heaters I want to make the tubes from stainless steel and extend them back into the fire box, have any of your guys at your club any exparience of this.

On a similar point with Curleys designs, his water level gauges, the screw valves can be screwed right out alowing the steam to escape, I,ve heard that this is a No No as well, you have to use screw cock type valves fitted now, is this correct ?.

Up to now I've slavishly followed the drawings but from now on I'll start to deviate, boiler feed pump design I'm going to change as well as the cylinder lubricator pump

Thanks for your imput much apreciated

Stew

Bernd:
Nick,

It was a disscusion that I just picked off the Live Steam news site. If I remember correctly the 1 1/2" scale engines run around 100 to 125 psi. The disscusion was based around boiler explosions between the real ones and the models.

I just thought it would make for some good disscusion here.

I read a while ago about hdro testing of pressure vessels, such as boilers. There are acutally two methods used. One is were the said vessel is placed in a tank of water and is then pressurized. The volume of water is messaured to see how far the vessel has acutally expanded. The other test is what is done on model boilers were the boiler is put under pressure while being totaly full of water at 2 or 2.5 times the normal operating pressure.

Some have said that such checks will actually weaken the boiler as time goes on because you are stressing the material at 2 to 2.5 times it's operating pressure every time you put the boiler through this check.


Bernd
 

NickG:
Bernd,

We do it as per southern federation code of practice, for copper boilers that is water pumped in to 1.5 x working pressure to be held for 20mins. So much drop is allowed, I forget how much but can get the info at our next meeting. This happens every 2 years I think, the boiler has to be stripped right down out of frames, lagging removed every 4 years. Steam test is required every year to ensure no leaks from fittings and safety valves do not let pressure rise so much above working pressure with the blower fully on and a large fire.

I would imagine the copper stretches and work hardens the first time due to being annealed during soldering.

I think steel boilers call for 2 x working pressure.

Stew,

Sounds like you've already done a lot of research on this, you need to these days, it could end up being the most expensive part of your engine whether you build it yourself or buy it!

Not sure about the stainless superheaters, if there is anybody that's done it I haven't heard about or seen them but will ask around. I think stainless welding is one of those things people are probably fearful of, it's out of their comfort zone!

I can't quite remember what the water level gauge is like on mine. I thought you just needed a water drain, but you might be right, I think i'd heard somethign about being able to shut off top and bottom incase the glass breaks. Will find out these details next time I'm down and post an update.

Nick

bogstandard:
Nick & Stew,

There are so many federations this and society of that's, it causes a lot of confusion. Each one seems to have their own regulations, and none of them like to think that anyone else is better than them.

If only all these people could come together and agree on a solid set of rules and regulations, then there would be no questioning then. Everyone would be happy because a standard set of rules would be in force. Comply with those rules, and you can steam anywhere.

I still think, at the moment, the steam fraternity is mainly self governing, but it only has to show one tiny bit of weakness or tragic mistake, and the H&SE will be in like a shot, and get more involved than they already are. Then everyone will be in deep trouble.

What has happened in the model boat fraternity is everyone accepted the 3 bar litre rule for boilers in model boats. That made everything clear to everyone what was expected of them. The government were happy, the insurers were happy, and the steam lads now had a set of rules they could work to.
There is just one fly in the ointment, the MPBA (Model Power Boat Assoc.). They have not accepted the new rules (all because I think they were asked to contribute, but declined, saying that they want to make up their own). So a bunch of fuddy duddy old farts, still living in the Victorian era, has thrown the whole lot into chaos again. So if you want to sail in any of their organised events, you have to have a boiler certified to their specs, and any other sailing event, the great 3 bar litre rule is in force. As you can guess, the MPBA is now losing membership at a high rate of knots.

John

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