Running the Bolier dry

J

John Morgan

Steam Traction
Hi Group,
Had a good steam up Friday, two sessions of 2 hours with Sabre Steam Annabel. The loco I was told by the late David Cooper was the first to be sold on the market after he had built one for himself. Great runner, steady speed, 40 psi on the gauge, pulling 5 heavy wagons.
Afraid to say I got a bit cocky and let the boiler run dry, my fault, mind wondered a bit. The thing is that after the boiler cooled down and I re steamed the clack valve would not seat right allowing steam and hot water into the side tank. Now to get the "shuttle" out of the main body of the clack is a problem because the by pass copper pipe runs over the top of the brass nut at the top of the clack valve. I sorted this by renewing the by pass copper pipe with a longer piece of pipe looping right over the clack so its out the way. Once the brass nut has been removed the "shuttle" with the black O ring can be lifted out with needle nosed pliers. Carefull not to drop it!. I gave it a wiggel and replaced it, but it still leaked a bit.
Now having contacted Tag Gorton and Steve Jackson re the leaking clack it seems the clack valve set up is as good as any you can get so I wont be replacing it with a clack with a ball therein.
Saturday. Removed the "shuttle" turned the black O ring around. Squirted a small drop of kettle descaler on a kitched towel and shoved it down the valve body for five minutes. Re assemble and steamed up. No leaks and the valve is working like new. I am now looking at obtaining spare O rings to replace any that get damaged due to the boiler running dry again.
Thank you Steve and Tag for your help.
 
It is not a good thing to let a coal fired boiler run dry, you will damage the firebox crownsheet and walls as the heat generated in a coal fired boiler far exceeds that of a gas fired engine, hence the use of an axle pump to keep the water level above the crown sheet at all times, if it does run dry happen then do not put cold water in but drop the fire immediatly.
I suggest you give the boiler a Hydraulic test before you run it again to ensure no damage has been done.
David Bailey DJB Model Engineering Ltd
 
David BaileyK27 said:
It is not a good thing to let a coal fired boiler run dry, you will damage the firebox crownsheet and walls as the heat generated in a coal fired boiler far exceeds that of a gas fired engine, hence the use of an axle pump to keep the water level above the crown sheet at all times, if it does run dry happen then do not put cold water in but drop the fire immediatly.
I suggest you give the boiler a Hydraulic test before you run it again to ensure no damage has been done.
David Bailey DJB Model Engineering Ltd
Click to expand...

Trouble is the water gauge on these Sabre locomotives is a little bit problematical in that it can be difficult to see exactly what is going on with the water level in the boiler. Several owners seem to have come across this problem. Very easy in this case for water levels to drop significantly. I have Shawe and DJB locomotives and the gauge glass on these little beasts these give a pretty good indication in my experience. I have found however, that like gas locomotives, coal locos also perform slightly differently when water levels are getting low and I use this observation in conjunction with a weather eye on the water gauge. The clack is, I suspect, a copy of the DJB type and these seem to work well on the locos that I have run and indeed my own 'Edrig' which has had many hours of running with no problem. I suspect that a new 0 ring would be worthwhile however.
 
Running the boiler dry seems to be an occupational hazard with the Annette. Fortunately the boilers are well made by Matt Johnson (who pops up on this forum from time to time). The water gauge on my Annette isn't very accurate and if I play it safe and run with the bypass valve closed for too long, the boiler overfills, pressure drops, and there's no way to get it back up again. I believe the clack valves on Annettes come from Steamfittings.co.uk, and are the same as those used by DJB. Although they aren't the conventional ball type, if they're good enough for David they must be OK.
Steve
 
Hi John, are you the one that I knew from the Beds Ridgmont Group?
Formery of Leagrave now Hemel Hempstead, if so when you comming to the Ruschbahn again?
JonD
 
Daniel,

All is well with the loco after the boiler ran dry. Thanks for your comments.

Just for the interested I bought a length of water gauge glass at the Large Scale Show a couple of months ago. This glass has a blue stripe down the back to show up the water level a bit better. John Shawe's loco has a 4mm glass so thats what I bought thinking they would all be the same. No chance, seems Sabre used 5mm. Now I am not to sure if I should use 4mm glass in a 5mm glass fitting, so I havn't. Having said that the water level sometimes drops like a stone leaving the boiler dry so a level gauge that is clearer to see may not be the answer. It needs to be watched all the while. Like you I shall run more with the by pass closed and the boiler fuller.
Has any one on the group suggestions about using 1mm undersized glass ?

John.
 
I would suspect that a difference of 1mm is probably a bit too much. One reason for the larger glass is that it should give a better (more accurate) reading. It is the small size that causes most of the problems due to the "stickyness" of the water. One solution to this that I have been told about, but not yet tried, is to insert a length of very thin fuse wire inside the glass to break up the meniscus.
 
John, I too have an early Annette [No. 6], and from the very first run I learned that it is a thirsty little beast. Also, my sight glass doesn't do the best job of letting you know the water level in the boiler. More often than not, water in the sight glass is actually bubbling/boiling. One of the first things I learned was that it is necessary to keep lots of water in the side tanks, and to do this, I use a "Long Reach" squeezable water bottle. It has a 32 oz. capacity and can squirt 4 oz. or more into the rectangular opening of the left side tank in a fraction of a second, so you do not have to stop the loco to add water. The next time around when the balancing tube has done its job another squirt will keep you going for a while. Here's a photo of the bottle, and best of all the cost is only $2.99.
CIMG8875.JPG


I've also learned that the Bypass Valve is not a true needle valve. As a result it is quite difficult to balance how much goes into the boiler, so I err on the cautious by trying to keep the boiler nearly full. Because of the load of the axle pump, this actulally improves slow speed running.

In addition, I'm finishing work on a Roundhouse Fowler tender to use with the Annette. In addition to carrying coal, I plan to install an 8 oz. model airplane fuel tank to serve as an additional onboard water resevoir. There will then be water in 3 tanks to feed the axle pump. Running low on water should be less problematic.

Good luck!
 
Lack of a blow down is certainly a factor because that allows you to clear the glass and see where the water returns to, but building a gauge glass that size with three cocks would be a work of art more than a working model. :bigsmile:
 
Tag, the main reason why these Water gauges do not work well is that the Water and steamways are far too small, our water gauges are fitted with the largest feeds possible in the size being used and give good results without a Blowdown Valve, I have fitted several Accucraft engines with a new top fitting to replace the Banjo Assembly currently being used, the holes in which are far to small and restrictive, I would suggest for 5mm glass that feed sizes should be at least 1/8" dia or larger for good results.
David Bailey DJB Model Engineering.
 
Q? could the bottom of the sight glass and the line to it be too close to the firebox, thereby causing water to boil while it's on its way to the sight glass.

I too thought about the surface tension of the water and added a drop of Water Wetter to the boiler water. Water Wetter is a commercially available product that is often used in automobile engine cooling systems. In "Big Block" engines in the 400 cubic inch range, the use of Water Wetter can result in a 30 degree lower coolant temperature as the coolant flows through the radiator with less friction.

My little test accomplished nothing as the water in the glass still appeared to be boiling. In this regard, if the tube to from the bottom of the sight glass is too close to the firebox it might result in significant heat transfer causing the water to boil [it is at 212 degrees to being with]. This tube runs the complete length of the firebox to the boiler.

If this is the real problem, installing a couple layers of ceramic paper insullation between the tube and the firebox may be a solution to the sight glass reading problem. I'm going to try this fix to see whether it solves the problem. I'll take photos.

Will
 
Regarding visual checks on sight glasses .... Several members ae my local model engineers use old barcodes from their shopping behind the glasss ;)
 
mmts said:
Regarding visual checks on sight glasses .... Several members ae my local model engineers use old barcodes from their shopping behind the glasss ;)
Click to expand...

Like that one! Good idea.

Full size glasses often have a frame with protector glasses and sometimes the back has a metal plate with black and white strips at an angle across it. Where the water is in the glass, the refraction, causes the lines to change angle and make the water more visible.
 
Thumper,
Thanks for the idea will give it a go. Members may find this interesting or not as the case may be regarding boiler level blow down. Bit of a ramble really.

My first coal fired loco was a John Shawe Roundhouse Jack. Could I get it to run, no chance. I tried and tried and was about to give up. The loco was second hand but had little sign of use. As my great friend the late Roger Goodall used to say, " When in doubt read the destructions". I read them, could not keep water in the boiler/fire kept going out and to top it all the steam whistle leaked and the blow down on the water glass leaked.
I took off the bottom elbow fixing of the water level valve. Silver soldered the leak, re drilled the water way and cleaned out the fixing and re fitted. Blanked off the steam whistle and WOW, off he went.

I spoke to John Shaw about the locomotive with a view of getting another water level gauge. John gave me the impression that it was not really needed but was nice to have. As it never worked when I had it I have not really missed having a blow down. Likewise on Sabre Locos I have not missed one either.
What is more interesting if you are still reading is that John Shawes Jack uses far less water per run than the Sabre Locos. My Annabel uses far more water on a run that Annette! I have no idea why.

John.

I have used plastic drinking straws, the ones with red or blue stripes theron on the back of the water gauge glass to read the water level easier, cut to size and push fit between the top and bottom nut.
 
John Morgan said:
What is more interesting if you are still reading is that John Shawes Jack uses far less water per run than the Sabre Locos. My Annabel uses far more water on a run that Annette! I have no idea why.
Click to expand...
Hard to tell without seeing the locos. How are you measuring the water consumption John? Do you find that the Sabre tanks empty quicker than the Shawe loco? Or are you just aware of the boiler level not being maintained on the Sabre locos?

I have found a number of problems that will cause excessive water usage on the two Annettes I have here for attention. The main culprit is the steam blower which uses an enormous amount of steam for very little effect, and this will destroy the boiler water level. A simple re-design of the blower pipe reduces the steam usage AND improves its efficiency. The axle pump on one loco does not work at all, and on the other only just works, so this too will cause the boiler to run out of water (both pumps to be replaced). Neither of these problems will occur on the Shawe loco.

Moving on to the tanks, the construction of the Sabre locos allows them to leak water from the tanks as the loco travels along. This is due to the tanks not actually being sealed to the bodywork in any way, so as the water sloshes around it can escape over the top of the tank and fall to the ground. The entry point for the bypass pipe is also not sealed, so allowing more water to escape from the tank. Both of these design problems give the appearance on high water usage, but it is actually just leaking away. Again, these issues do not occur on the Shawe loco.

Outline details of the work I am doing on these Sabre locos can be found here: http://www.rhoshelyg.me.uk/Sabre.html
 
You must log in or register to reply here.
Back
Top Bottom