Don Young's Black 5

[runner42]

As a consequence of changing the boiler design to meet he AMBSC Code Part 1 requirements, i.e. replacing the girder stay with a number of rod stays, the spacing of the rod stays at the sides of the outer wrapper/firebox had to be arranged judiciously to prevent fouling of the stays with the regulator operating mechanism and the blower tube running from the backhead to the smokebox tubeplate. The gap between the top row and next to top row is at the limit of the stay spacing allowed dependent on the rod diameter, material thickness and operating pressure. Generally the stay spacing in all other situations exceed the AMBSC Code Part 1 requirements, viz spacing is 27.5 mm, requirement is 31.5 mm, stay diameter 6.35 mm, (1/4"), requirement 6 mm. The photo shows the spacing in question indicated by a red line.


boiler stay spacing by Brian Leach, on Flickr

The lower stays needs to be cut back as short as possible to allow the boiler to sit between the frames.

boiler stay spacing1 by Brian Leach, on Flickr 


Brian

[Jim]

Looking good Brian. Well done.

Jim

[runner42]

In silver soldering the stays in the outer wrapper and firebox was easy because of the access to the stays to readily heat them to silver soldering temperature. This was not so for the stays on the vertical sides because of the smaller space between the outer wrapper and firebox. Because the heat could only be applied to the outer wrapper heating the stays was limited to the length of stay protruding, more protrusion enabled more surface area was heated. So the best approach is to have the stay as long as possible balanced against more wasted material that has to be removed. This raises an important point on the length of stays in the firebox will heating in of the water be improved by having a long stay.

Brian

[uuu]

The danger in heating from one side only is that you'll have the stay and plate on the heated side up to temp, and (possibly) the stay on the other side, but it will be the devil's own job to get the remote plate hot enough, just with conducted heat. That's if I've understood what you're trying to do correctly.

Wilf

[runner42]

Jul 10, 2021 9:26:11 GMT uuu said:

The danger in heating from one side only is that you'll have the stay and plate on the heated side up to temp, and (possibly) the stay on the other side, but it will be the devil's own job to get the remote plate hot enough, just with conducted heat. That's if I've understood what you're trying to do correctly.

Wilf

I used my mobile and without spectacles so it was difficult to know what I had written in the last post, so it was not clear what I was trying to say. The approach is to silver solder the protruding stays on the outer wrapper first and then the same stays in the firebox, a two pass operation. Because access to the stays between the outer wrapper and firebox is limited heat can only be applied to the outer wrapper during the first pass. Similarly heat can only be applied to the firebox during the second pass. Because both the stays and outer wrapper need to be at silver soldering temperature the greater the protrusion the more stay can be heated.The same for the second pass in the firebox. The long protrusion on the outside will be cut off to accommodate the boiler cleading, but the long protrusion in the firebox might assist heat transfer to the water.

Brian

[uuu]

I see, thank you.

Wilf

[Jim]

Just a suggestion Brian, my boiler inspector suggested I not trim the stays until after the pressure test as the 'tails' made it easier silver solder any leaks should there be any round the stays. You probably already are already aware of this so please ignore if you are.

The boiler is looking very good I must say.

Cheers

Jim.

[runner42]

Jul 11, 2021 10:26:05 GMT uuu said:

I see, thank you.

Wilf

But what's your thoughts on leaving the stays long in the firebox, would it assist heat transfer and make the boiler more efficient?

Brian 

[uuu]

I don't think it will make any difference. If the heat transfer process was mainly conductive, hot gas to metal, then the extra surface area might make a difference. But the stays are so thin, that the extra area is not very big. And in the radiant environment, the rays will all meet a surface one way or another.

All theoretical of course, let's see if anyone has any practical experience.

Wilf

[mbrown]

I think there may be a danger of the protruding stays burning away. In full size practice, stay nuts in the firebox did burn away and their deterioration was a sign the boiler needed overhauling. They will also make it harder to keep the firebox sides clean and may promote the build up of soot and clag - all of which will reduce conductivity.

In some vertical boilers, there were hollow protrusions into the firebox which greatly increased the heating surface - I think they are called Field Tubes - but solid stays in the firebox add nothing to the heating surface.

I guess in a wide firebox you could try the idea and trim off the extra stay length if it was unhelpful. But in a narrow box that might be a challenge.

It seems a big gamble on an expensive item to me....

Malcolm

[runner42]

I am envious of ME's who make boilers without hiccups, fitting the smokebox tubeplate to the barrel with 21 tubes and 4 flues was for me exceedingly challenging. The difficulty lied in overcoming the taper in the barrel which was smallest diameter at the entry, so the diameter of the smokebox tubeplate had to be a little bigger than this to fit correctly in its inward position. My boiler is different to DY's who had a parallel section at the smokebox tubeplate end. Although I used bullets to guide the alignment of the tubes through the holes in smokebox tubeplate, because the smokebox tubeplate had to be canted to overcome the taper the bullets kept jumping out when hitting the smokebox tubeplate. I tried for over a week trying to get the smokebox tubeplate in position and had a sleepless night wondering if I would eventually succeed. Thoughts of not finishing the boiler crossed my mind. Eventually I succeeded and the answer was knowing where to hit and how hard. Little taps was the answer starting at the 12 o'clock position going clockwise. 


smokebox tubeplate in situ by Brian Leach, on Flickr

The bullets I used,

bullets by Brian Leach, on Flickr

Having completed the stays in the outer wrapper/firebox I added 4 to the throatplate, 


throatplate stays by Brian Leach, on Flickr

In the citric acid bath ready for the next operation/

Brian

[runner42]

The boiler is nearing completion, awaiting some additional silver solder to complete the area around the foundation ring, small voids nothing of significance. A proviso is that there is further rework required to address the invariably expected leaks in unplanned areas, which for me at least is par for the course. Anyway, it indicates that my thoughts are now directed to the pressure test and preparation for submitting it to the BI for final inspection and formal pressure test.  At this inspection stage, depending on the results it will receive a serial number which will be stamped on a copper plate and affixed to the backhead.

boiler by Brian Leach, on Flickr

The longitudinal stays will have to be removed prior to further silver soldering iaw AMBSC Code Part 1 para 3.4.3.1, they are type 2 of para 3.4.3. At the moment I have kept the stays over length to better enable it to be located. Once all silver soldering operations are complete I shall cut them to their proper length.

boiler1 by Brian Leach, on Flickr

boiler2 by Brian Leach, on Flickr

boiler3 by Brian Leach, on Flickr

boiler4 by Brian Leach, on Flickr

Brian

  

[runner42]

I suppose I am in that sort of mood wanting to air my mistakes. In trial fitting the regulator to the boiler it has a connection to the wet header by a transfer tube that relies on a threaded bush on the smokebox tubeplate. This threaded bush red circled in the photograph is required to be absolutely square to the boiler centreline because any small deviation at this point is greatly magnified by the length of the transfer tube and therefore will not engage the regulator's threaded output. When I silver soldered this threaded bush to the smokebox tubeplate I was totally unaware of this need so did not check if it was so. It is way out due to the smokebox tubeplate not being totally flat at this point due to the required curvature towards the flange and the fact that the threaded bush needs to be positioned close to the top edge of the smokebox tubeplate.

I cannot ease the threaded bush into a better position because there is no unsupported area in the copper to achieve this. So my fix is to produce a long bar that has the required thread form that screws into the bush and heat the bush so that the silver solder is liquid and then use the bar to alter the position of the bush so that it is correct to the boiler's centreline. It will mean that the bush will not sit plumb with the smokebox tubeplate, but canted slightly. This will not affect the boiler in anyway.

The brass threaded plug obscures the threaded bush in question and should have been removed for better visibility, but I used a previous photo instead.

Brian

boiler3.1 by Brian Leach, on Flickr

   

[runner42]

Well that fix worked out well. I made the rod which was screwed into the bush and depending on the direction that was required to align it with the boiler's centreline I positioned the boiler so that gravity was working for me. The weight of the rod which was made out of stainless was quite heavy and exerted sufficient force to re-align the bush. Manual intervention was unnecessary. It took little movement of the bush to correct the misalignment and I don't think it required a lot of heating to achieve this. Maybe the silver solder releases its hold on the bush before the liquid state is reached.

Brian 

Correction by Brian Leach, on Flickr

Correction1 by Brian Leach, on Flickr 

[keith1500]

I guess if only the drawings had little notes or markers that indicated this part to align with part xx etc you might not be caught out by such a minor error.

Good result.

Keith

[runner42]

Aug 17, 2021 9:38:01 GMT keith1500 said:

I guess if only the drawings had little notes or markers that indicated this part to align with part xx etc you might not be caught out by such a minor error.

Good result.

Keith

Yes Keith I agree, but in my case I would have forgotten about any such note when the time came to undertake the silver soldering. But, one thing to my credit I did orientate the bush such that when the steam pipe that carries the transfer tube is screwed hard up against the bush so that the 4 tapped holes that mates the wet header are correctly positioned so the wet header distribution pipe is horizontally aligned.

Brian 

[runner42]

I trial fitted the regulator mated it with the transfer tube and wet header. Locating it was a bit tricky until I let the regulator float so there was some wiggle room. Everything went in OK. I was glad that the wet header distribution tube was correctly oriented and horizontal to the flues. The length of the transfer tube was just the right length so I am pleased that this can be ticked off. The regulator actuating rod mates OK but is a bit too long l must have lost an 1/8th inch in the length of the boiler because it was OK before soldering the backhead.

Brian
.

[runner42]

My first inroads to verifying the boiler's water tight integrity failed miserably due to the problems with the foundation ring. It being the lowest point didn't allow for progression beyond that. So I attempted to add more silver solder, so that a good coverage would provide sealing in the small pathways around the corners of the foundation ring where the profile is multi-faceted to accommodate the flanges on the end plates. However, although the backhead end was reasonably straightforward the throat plate end was another matter entirely. A few attempts using different manufacturers 45% silver solder made me conclude that these had higher melting points  than the silver solder used up to that point, ie blue tip silver solder. So I had to purchase another 500g, the minimum quantity order, this took some time to receive delivery. Having received this I was surprised that the same problem existed with this silver solder. I received an Eureka moment when I noticed how hot the barrel was getting and concluded that it was a heat dump drawing the heat away from the point of interest. So, it required some means of preventing this and covering the barrel with some heat retaining material. Pink batts came to mind, but local suppliers didn't accommodate small quantities. Having pink batts in the loft space, thought was given to raising the roof tiles to borrow a small piece or two. But the thought of SWMBO asking pointed questions on why I would be on the roof put paid to that. I found a material ceramic fibre blanket to be ideal and cheap enough on e-Bay, However, two weeks delivery was specified. So think again! Not a very ME solution but it did the trick and that was to pile bits of broken house bricks around the barrel. 

The red circle indicates the problem area of the foundation ring
 
Foundation Ring problem by Brian Leach, on Flickr  


Foundation Ring problem1 by Brian Leach, on Flickr

Many would say that it was obvious that the barrel would be the cause of the problem and cater for it in the first instance, not after some failed attempts. 

Brian 

[runner42]

Using a very large propane burner (114 kW) it was impossible to use the preferred method of applying the silver solder to foundation ring once the flux exhibited the watery appearance indicating that it was close to the required temperature, so the silver solder had to be positioned on the foundation ring at the outset and the heat applied to both the silver solder and foundation ring. The first attempt was to to lay strips of silver solder along the foundation ring but this was not that successful. The problem was two-fold, one the silver solder strips was dislodged due to the blast from the propane burner when placed at the edge of the foundation ring when trying to seal the join between the outer wrapper and foundation ring. Two the silver solder often melted before the copper reached temperature and tended to change from strips to nodules and as a consequence areas were not covered. This was overcome by producing small rings of silver solder in the same way when soldering rod stays and these were placed on the foundation ring side by side. The was possibly uneconomical in use of silver solder but I wanted a good coverage and the newly acquired 500g had to be put to use. I am not going to build another boiler.

Brian

[Roger]

Sept 2, 2021 23:38:38 GMT runner42 said:

Using a very large propane burner (114 kW) it was impossible to use the preferred method of applying the silver solder to foundation ring once the flux exhibited the watery appearance indicating that it was close to the required temperature, so the silver solder had to be positioned on the foundation ring at the outset and the heat applied to both the silver solder and foundation ring. The first attempt was to to lay strips of silver solder along the foundation ring but this was not that successful. The problem was two-fold, one the silver solder strips was dislodged due to the blast from the propane burner when placed at the edge of the foundation ring when trying to seal the join between the outer wrapper and foundation ring. Two the silver solder often melted before the copper reached temperature and tended to change from strips to nodules and as a consequence areas were not covered. This was overcome by producing small rings of silver solder in the same way when soldering rod stays and these were placed on the foundation ring side by side. The was possibly uneconomical in use of silver solder but I wanted a good coverage and the newly acquired 500g had to be put to use. I am not going to build another boiler.

Brian

Hi Brian,
That worked out well in the end though, it's not the easiest of jobs.

I'm not a fan of adding Silver Solder to a hot joint, you need to get it much hotter than necessary. 55% Silver Solder melts when it's hardly showing Red heat, so it's not necessary to get it all that hot. Anything that's unnecessarily hot just exhausts the flux more quickly than needed, and you end up with corrosion that you don't want.

I've done a lot of jobs now with the Silver Solder being rested on the job, and there are a few things that make it work well.

1) I use a lot of thick creamy flux to completely cover the Silver Solder.
2) I form the Silver Solder to go right around the job if possible, so it stays where I put it.
3) I use a piece of Titanium wire to keep nudging errant Silver Solder in place. It always moves as the flux boils off the excess water, but it stays put once that's happened.

If you do these things, you won't have the Silver Solder turn into balls because it's always submerged in flux which keeps the heat even.