Clinker and tube blockages

[JonL]

If my clunky maths is correct, between myself and my sons today we managed six miles of our little club track. However we started to struggle to get maintain steam about halfway through the morning, which I suspected was to do with airflow through the fire. We pricked it through multiple times but I ended up admitting defeat, dropping the fire and starting again. We did ok for a while, then it happened again. We were finding lumps of flattish clinker the size of a 50p piece in the firebox. As you can imagine, on a 3.5" William that is quite a big lump. (The grate is 1 3/4 in x 3 11/16 in).

I've got it home, started to clean out all the ash and I've found the bottom three tubes were blocked (william doesn't have that many tubes to begin with). This explains quite a lot, but it's not happened to me before. I'd appreciate some help in analysing what I have done wrong? Some of the facts:

1) I've recently changed from Anthracite beans to anthracite grains, from the same supplier. I was advised I would need less blower. It hasn't changed things a huge amount, but I'm still getting to grips with things. Also I've steamed before using these grains and didn't have these issues. 

2) We were cruising at around 5mph most of the time. Very slight incline and equal descent (obviously, its a loop) where the locomotive was working harder, then coasting.

3) Only load was a single person at a time, varying from fatty me, to medium son, to smallest son.

4) As usual the smokebox had a good layer of ash and grit in it, less than usual (despite this being the furthest we have ever driven in one session). 

5) We were using the blower quite hard just to try to keep steam up. Dropping the blower dropped the steam production.

6) Total time in steam was around 4.5 hours.

So did I just build up the fire too high? Have the blower on too hard? Is it the coal at fault?

If anyone has any advice I would be very glad to hear it.

[smallbrother]

On a long run I look periodically in the firebox to get an idea of the build up of ash which could block the lower tubes.

Not always the same outcome - coal varies, so does my driving and firing.

If the coal is forming clinker then I would tend to use more blower - this would drag more particles into the tubes and make the situation worse.

What I am trying to say is that the sure way to beat clinker is to drop the fire every 2 hours say. If you are well practiced you can get back on the track in under 30 minutes I reckon.

I've never driven 3.5" but I think 2 hours good running would be a decent outcome for a small firebox.

Pete.

[JonL]

Ok, thats interesting. I hadn't considered dropping the grate before I called it quits. I'll need to come up with a slick way of doing it, it is a faff to get it back up.

[JonL]

Someone suggested a rosebud grate, I'm not sure that would fix it but it a fun experiment anyway

[Gary L]

May 15, 2021 19:53:56 GMT JonL said:

If my clunky maths is correct, between myself and my sons today we managed six miles of our little club track. However we started to struggle to get maintain steam about halfway through the morning, which I suspected was to do with airflow through the fire. We pricked it through multiple times but I ended up admitting defeat, dropping the fire and starting again. We did ok for a while, then it happened again. We were finding lumps of flattish clinker the size of a 50p piece in the firebox. As you can imagine, on a 3.5" William that is quite a big lump. (The grate is 1 3/4 in x 3 11/16 in).

I've got it home, started to clean out all the ash and I've found the bottom three tubes were blocked (william doesn't have that many tubes to begin with). This explains quite a lot, but it's not happened to me before. I'd appreciate some help in analysing what I have done wrong? [Snip]

My Bridget will run well for a couple of hours, and then quite suddenly become very shy of steam. I now know what to look for, and invariably the lowest pair of tubes are blocked with char. It seems beyond comprehension that just two tubes in the coolest part of the boiler should make such a difference but they do. There is not much spare room for char in the smokebox, because the tubes are only a little higher than the bottom of the smokebox; though this is not at all an unusual feature. I think the truth is that the total tube area in the Bridget boiler is only just sufficient. It isn't difficult to cure; just brush out the smokebox and the two tubes; though doing this quickly enough to avoid the fire dying for lack of draught with the door open is something else.

I'm not sure there exists a definitive answer to clinker. It is formed from impurities in the coal, which is very variable. People say that different bags from the same supplier can perform differently in respect of clinkering, and I've no reason to doubt what they say. Someone in another thread said recently that in full size, rapid cooling of a very hot fire by closing the dampers was regarded as a sure-fire invitation to clinkering; maybe the alternation between high and low steam rates that you describe is a similar cause. There are certainly many other ways of creating clinker, if only we knew...

The remedy Smallbrother suggested, of routinely dropping the fire after a couple of hours running makes a lot of sense, (depending on how easy it is to reinstate the grate with everything hot of course). With a boiler already full of hot water, re-lighting the fire and getting back to full pressure shouldn't take long. The trouble is, we tend to hang on for too long, thinking we might just coax another lap or two... but it doesn't work and then you find yourself stuck with no pressure and blocking the track miles from the steaming bays. Not a way to win popularity contests; nor is it a quick way of getting back into steam with a clean fire!

Gary

[steamer5]

Hi Gary / Nobby,
Interesting discussion, Gary reference to closing the damper on a hot fire.....maybe as Nobby described with a track that rises, power on great draft hot fire lots of steam, then the track falls, regulator closed, hot fire, not so much air, safety lifts, then injector on cold water to the boiler & or the driver opens the fire door to cool the fire. Rinse & repeat....only a thought

Cheers Kerrin

[David]

I had the same thing over the weekend, although my tubes were not blocked. About 2 or 3 hours seems to be the limit I can get before the steaming goes way off.

If you are going to drop the fire, fill the boiler right up, get the pressure right up with the blower, and then you'll have hot water rather than cold, and steam for the blower to bring the new fire up. Shouldn't take too long.

[smallbrother]

A year or two ago I think Alan (Delaplume) described such a routine that he used, might have been on a Simplex.

He clearly had it well rehearsed and was back on the track in little time, and as said above, took action BEFORE the problem arose.

My Bridget (sold to Paul on here) was the same. About 2 hours running and needed a clean. My Holmside also 2 hours when I am pulling about 6-8 adults.

Due to my creaking bones I actually welcome the opportunity to change activity. I can hardly stand after an hour or 2 of running anyway.

Pete.

[JonL]

I suspect the lower tubes being blocked is the biggest issue here looking at this discussion. It wasn't a great heartache dropping the grate, but now I know I'm going to be doing it hot I can devise a tool or two to help and get it sorted more easily.

More than anything I'm now thinking that the grate design on Britannia must be a pain with being non-removable and only dropping. Or maybe that's actually easier?

I'm glad I finished this loco before carrying on with the Britannia, Its really going to guide my build.

Thanks for everyone's help, every bit has been very useful.

[andyhigham]

The beauty of a sweet pea is you can pull the fire, sort it out and shove it back

[smallbrother]

Jon,

Once the pin, ashpan and grate have dropped I separate them from the coal/ash/clinker and let them cool off while cleaning the tubes. There is usually a puddle of water in the steaming bay to put them in.

If they are still too hot to handle after that then I sprinkle some water over them. Not sure how much space is under your William but I don't have to touch anything hot when putting the grate back and shoving the pin back through the frames.

My main trouble is having to get myself back up off the floor after lying under the engine.

Pete.

[flyingfox]

Greetings Mr Sideways, as an experiment, is it worth just stopping, cleaning the bottom row of tubes, and having another go, in case blocked tubes is causing the problem, rather than clinker?
just a thought>
Regards
Brian B

[dhamblin]

With 'Netta' we tend to give it a good rake through of the fire after each run, stick some more anthracite beans in and a good bit of blower and the fire builds quickly. Agree with other posts regarding cleaning out the smokebox every so often during a running day - that lesson was learnt very quickly during my first day helping run it in 2017.

Regards,

Dan

[JonL]

I don't think the smokebox is backing up too much; I think its the tubes as mentioned before.

Do you think I'd get less trouble with the blockages if I went back to beans? I've got half a bag of each left (using grains at the moment).

I'd like to get hold of some proper steam coal but that hasn't proven easy so far.

I think I'll improve the location of the grate in the ashpan; at the moment the biggest issue is keeping it centred while fitting it. It's easy on the bench because its upside down.

[coniston]

My Speedy built to the original boiler drawings always suffered from poor steaming after a couple of hours running loaded, the answer was to clear the bottom row of tubes. This was accomplished in the time it took to offload and reload passengers by simply closing the blower, opening the smokebox door and using a well worn bronze tube brush poke the bottom row through. Literally a couple of minutes, then on with the blower to get he fire bright again before the off.

I always keep a check on the clinker by raking through to the fire bars every now and again, if I spot anything building up I have a pair of suitably modified BBQ tongs (the stainless steel wire type) that I can grab any big bits off the top of the fire through the fire hole door. It is surprising with a bit of practise how easy it is to bring the clinker to the top to get access. This can usually be done in the station without holding up anyone unnecessarily.

Just keep practising, you'll soon get the hang of it.

Chris

[Gary L]

May 16, 2021 20:25:35 GMT JonL said:

I don't think the smokebox is backing up too much; I think its the tubes as mentioned before.

Do you think I'd get less trouble with the blockages if I went back to beans? I've got half a bag of each left (using grains at the moment).

I'd like to get hold of some proper steam coal but that hasn't proven easy so far.

I think I'll improve the location of the grate in the ashpan; at the moment the biggest issue is keeping it centred while fitting it. It's easy on the bench because its upside down.

My impression is that the char gathers first in the smokebox, then the level rises until it backs up into the lower tubes. Once the airflow through the tubes is partly blocked, the speed decreases and the char is dropped in the tubes instead. The net effect of course, is the same.

I don’t think the size of the fuel is likely to make a lot of difference to char production. Welsh steam coal swells when heated and splits into quite fine grains about the size of Grape Nuts only lighter. If you have a fierce blast these get quickly lifted into the smokebox without burning first. Amongst the modifications I had to make to improve Bridget’s steaming, at least two involved (counter-intuitively) softening the blast. There has been a noticeable reduction in this unburnt char in the tubes and smokebox, which translates to longer running time.

I was given to understand that anthracite doesn’t share this property, though your experience seems different. It makes me wonder if what you are being sold is the genuine stuff... I’ve heard that coals are being sold under generic names these days, which might not relate to traditional mining locations at all, and only in passing to traditional coal properties. It is not so much “passing off” as “nearest available substitute”. So it might be worth trying a different fuel supplier (or a softer blast) if you are having a lot of trouble from blockages.

Gary

[smallbrother]

Hi Jon,

I don't think steam coal is the answer. I have tried several batches on 5" and 7.25" locos and sometimes it is as good as anthracite but generally worse. You would also have to break it down to small sizes which is very wasteful. However, worth an experiment just for interest if nothing else, you won't harm anything.

As for beans/grains, I don't think the difficulty lies in the size either, from my experience.

As Gary says, if you can extract any clinker it will help enormously.

Pete.

[andyhigham]

Another thought on this.
The bottom row of tubes are furthest from the chimney so the gasses have to travel further. I wonder if the gas flow through the bottom row is slower even when clean allowing soot to settle in the tubes?

[simplyloco]

I must admit that when I saw this thread title I was reminded of how many of us squaddies felt after two weeks on exercise, living off tinned food and no showers! 

[ejparrott]

A constant use of blower to maintain steam indicates there is probably an issue with the front end which needs resolving first.

You might find a brick arch will help both with tubes clogging and extracting heat from the fire.