I wanted some feedback on the style firing and running and coal quality that Hulson grates were truly intended for. Compared to table grates they bring in more air, but what are your thoughts when they are used with a low ash coal without an arch brick vs. high ash?

Has anyone fabricated table grates in-house? Since they are larger pieces, a broken corner from one can be a big deal. Have you resolved this without using new replacement stock?

Thanks!

John,

Great question! John, the 141R 568 in Switzerland has Hulson Grates. You may not be aware that there are actually different styles and types of Hulson Grates. Some have smaller air gaps, while others have larger air gaps. Additionally, the vent ways to the air gaps have different air ducts that direct the air to the ports. Some have thicker tops, or heads and yet others have thin or thinner sides.

The French did a lot of study on the proper use of the grates, as well as significant study on the effects of different types and or grades of coal.

The 141R 568, which can be seen in these videos;

http://wrrc.us/2011/05/video-06/

http://wrrc.us/2011/02/video-03/

(no need debating the videos.....they have been over-debated!)

Having been allowed to fire the locomotive a number of times, I have found the following to be true:

The grates respond best to very thin fires. Do not allow ash to build on the grates. Once you start to fire on the ash, or add coal on top of the ash, you end with problems. Shake the grates often. Once the grates clog up.....game over!

John, part of your question had to do with actual values of the coal. I am very sorry that I can not provide this information as I do not have it in front of me. I can tell you that good German Stoker coal works better than Czech "soft" lump coal. As for the values of each......?

We have had new castings of at least three different sizes and shapes of Hulson Grates made in England. Additionally, we here at WRC have had castings made of a variety of grates including rose buds and the traditional finger grates. We have also made and fabricated steel grates. My personal favorite when it comes to steel fabricated grates is the Rose Bud style with very long, deep tapered holes in very thick steel.

It is my personal belief that air flow in a rose bud style grate that has a long hole, large at the bottom, smaller at the top, is that the air velocity actually increases as it passes through the hole. This is also the premise behind the ducting in the Hulson Grate. Simply introducing air to a fire is not enough. The air must be introduced properly and in proper proportions to the flow of gasses being sucked through the boiler and fire box by what ever means are being used in the smoke box. There has been a great discussion about Lempor Exhaust systems on this page. The premise behind the Lempor exhaust system and other variations of the same is optimization of gas flow from the bottom of the grate, to the top of the stack, accounting for every aspect of combustion and gas flow along the way.

I like the Hulson Grates. They are hard to replace when they need replacing, they do break often, but properly used and cared for......a great fire results!

Kindly,

Hi John:
Our No. 97 has a "keyhole" firebox and no brick arch.
When I arrived in 1986, it was equipped with table grates, which were quite heavy and difficult to get in and out of the fire box.
When UP 3985 was converted to oil firing in the 1990s', I purchased all of the "Hulson" grate fingers. Then I borrowed Steamtown's Hulson grate carrier bar pattern, had it modified so it would make a variety of lengths, had new carriers cast up for both Nos. 97 & 40 and converted both to Hulson grates.
We like the Hulsons very much and have replaced few fingers over the years.
Over the years, we have used a variety of coals (including Anthracite on No. 40 for a while) without issue. The coal we are currently using is about 7.5% ash content.
J.David

David- I remember reading that article in Trains many years ago written by a summertime fireman on the VRR who mentioned the lack of a brick arch on 97.

Surely you've considered adding one? Too difficult or do you just think it wouldn't be worth the effort?

I have never had a drafting issue with Hulson grates, in fact just the opposite. My question regarding ash content and arch brick with these grates is asked because we fire very low ash content coal and the engines feature no brick. This is all the while working at all or most capacity so the draft is very intense.

Having fired western coal with lots of ash and on rosebud grates, I want to research a middle ground between the two ends of the spectrum. My initial theory is that the smaller amount of air available will cause less intense draft/less unnecessary waste. In turn this will save some fuel and hopefully smoke. I realize that oxygen is needed to aid combustion and reduce smoke, but remember that the engine is working very hard without any type of arch tube or brick to restrict the flow of gas, and in this case unburned material.

On the other hand, anyone considering grate styles for replacement gets my recommendation for the Hulsons. They are a good design with the increased air flow and I feel would be ideal for coals with a high ash content.

Reading used them on their anthracite culm burners with wide Wootten fireboxes, but I've seen them on plain old bituminous burners as well. I don't think they were adapted for any specific type of coal, and they had different designs for different amounts of air flow.

I think if you're lucky enough to fire with a reliable coal that burns well, you learn how to best use it on your locomotive no matter what grate or firebox features it may incorporate.

If you're getting a lot of unburnt particles of coal entraining in the draft, there's the possibility to consider of going to gas producer firing with a thick, deep fire with about 65-75% of the combustion air coming in over the fire, and a supply of steam to the bottom of the grate to prevent clinkering. In this system, the most heat comes from combustion of the volatiles driven off of the baking coal beneath. Or, you could expriment with the front end to see if you can diminish the effect of the draft without losing the necessary amount of air to sustain adequate combustion. Increasing the nozzle opening is a low tech thing to try to find the best balance for your particular conditions.

dave

Dave,

You mention supplying steam to an area below the grates of a firebox. I remember hearing of this setup before in past years. Would you care to elaborate on that specific part of the setup? For example, how is the steam supply set up? Is it run through a steam-water separator (I hope) so you don't rot the ashpan? How far is the steam spread among the area of the firing surface. How does this action prevent clinkering from a physics or chemistry standpoint?

I vaguely remember hearing that this was a possible Porta improvement. Is this a fact?


Best,
DC

Dear Hugh:
Actually, we did have a brick arch in No. 97 for a while.
We paid Christy Refractory (St.Louis, MO) to make patterns for a set of self supporting arch bricks and bought several sets of brick.
The arch worked great! Less smoke and an almost white fire under the arch.
The firebox (almost totally original from 1923) didn't like the change, dozens of staybolts in the "hot zone" began to leak.
Sadly, we removed the arch, caulked up the bolts and put everything back to the way it had been (and remains to this day).
It was an expensive experiment...
J.David

I'm not the engineering genius you need to answer a lot of the questions, just working on understanding it and sharing the knowledge I do find, but:

On the early South African conversions - think 1980s - part of the exhaust steam was piped to a sort of manifold under the grate but held above the ash pan. The addition of steam at this point prevented clinker formation by preventing the ash temperature at the grate from reaching the melting point. I'm picturing a waft of steam, not a blast of steam. A deeper ash pan was installed, and with the majority of combustion air entering over the thick firebed there wasn't much air space required between the mud ring and the ashpan sides.

The entire process is well covered in Wardale's "Red Devil" in greater detail than I can explain, and less completely but by those who better understand them than I do on some web sites such as Martyn Bane's and Hugh Odom's. You couldn't do better than to start at Hugh's Ultimate Steam Pages and link out from there.

If you check out the thread about the Welsh coal-oil-coal reconversions, I think that that locomotive - or maybe it was another on a Welsh line - had a Lempor and GPCS installed, removed and installed again or some such. The constant difficulty that seems to impact these conversions is human, it seems, from reading the literature and corresponding with people involved. These technologies are fired and run differently than the old standby ways, and not everybody wants to learn new tricks. As I mentioned in another thread, we can't be scared of trying something and being wrong and learning from the process, as JDC has outlined in his story about the brick arch experiment above, but some people refuse to try in case they get blamed, and failure and diversionary fingerpointing usually results.

I don't know if the steam application would help with a clinker problem on a traditional firebed design, but my guess is lowering the grate temperature could badly affect combustion in a thin firebed. Your best bet might be to simply not let ash build up and shake frequently if that's a problem on your line.

dave

Wow- never considered that as side-effect of an arch. I suppose it's related to the locomotive having been operated without one for all its previous life. Changing the heating of the firebox sheets probably radically changed the stresses on the firebox sheets.

I guess if you ever have to replace the complete firebox it'd be worth trying again.

Dave and Donald- Steam addition below the firebed is an integral portion of the Gas Producer Combustion System. It's interesting that Porta seemed to emphasize that the reason for it was to enhance the gas production of the coal bed, while Wardale in writing about it emphasizes that it was required with the deep firebed used with the GPCS to prevent rampant clinkering.

I think both Porta and Wardale tried several systems for distributing the exhaust steam evenly under the firebed. Another design goal was to keep the steam from wafting up in front of the cab where it would cause problems with visibility. One arrangement that works pretty well is a series of small-diameter pipes manifolded together below the grates with holes drilled along the sides to release the steam parallel to the firebed, where it can mix with the primary combustion air prior to being drawn up into the firebed.

IIRC, Wardale tried a simpler system with a single pipe along the gap between the ashpan and the bottom of the firebox on at least one engine, but this arrangement was much more likely to result in steam coming up around the cab.

I do recall that Wardale mentions a "poor man's GPCS conversion" he did on one SAR 4-8-4. IIRC, he provided a simplified system for the underfire steam and arranged something to keep the firedoors partially open (to admit secondary combustion air above the fire). I think the main goal of this system was to reduce clinkering. Guess I need to dig my copy of "the Red Devil..." out one more time...

In response to Dave, I do agree that in the current circumstances the draft could be reduced with the petticoat adjustment. At the time we are using very tired Hulson grates which will soon be replaced. I'd like to learn more about what affect others have experienced with the different coal grades and firebox set-ups for future use.

What size pipes and maximum steam pressure would you see used on an under bed system? Would the constant moisture content in the air affect the lifespan of the grates or otherwise? The "Red Devil" book and other documents written by Porta have been frequently referenced here and other threads, however I do not have access to these materials. Would you say a system like this could be gainfully utilized in most of the current operations in this country today? What is it exactly that makes the higher production of combustion? Is it similar to wetting coal?

John- As Dave alluded to earlier (maybe in a different thread) exact details of how to accomplish some of these steam improvements are difficult to find.

With the Gas Producer Combustion System (GPCS) exhaust steam from the cylinders is used to supply the under-bed steam system, so the pressure would be whatever the exhaust steam pressure upstream of the nozzle(s) is, say 5-15 PSIG. Using exhaust steam also makes the system self-regulating- the harder the engine is worked and the harder the engine is fired, the more underbed steam is fed to the fire.

A significant amount of technical information on Wardale's work (some from "the Red Devil", some from other sources) is available on the 5AT Project website. A section on the GPCS with links to more info is available here:

http://5at.co.uk/index.php/modern-steam ... /gpcs.html

These pages explain the chemical reactions involved in the GPCS. The reason for developing the GPCS is that it reduces unburned fuel carryover when burning solid fuels. Fuel carryover results in a huge loss in combustion efficiency when coal or wood-fired steam locomotives are worked at high combustion rates. By admitting more of the combustion air as secondary air above the fire rather than as primary air below it, the GPCS greatly reduces the carryover of unburned fuel. Much of the mass of the coal gasses off to form carbon monoxide, which is burned above the fire.

Trials with the GPCS by Wardale and Phil Girdlestone indicates some coals are more readily used with the GPCS than others. Porta was convinced that minor modifications could be made that would make the GPCS adaptable to practically any coal.

The GPCS has been successfully used on several tourist railways in the UK. Dig around on the 5AT website and you can find additional info.

Just read in Red Devil about the QJ improvements that never happened - Wardale was going to divert 8% of the exhaust steam to undergrate along with the feedwater heater exhaust and the stoker exhaust. Might try about 10% based on roughly copying his percentages. If you have the ash pan openings runnning along the sides below the mud ring, a pipe running alongside with holes spraying it sideways into the ash pan alongside the intake air would probably work. Losing 10% of the overly strong draft wouldn't hurt either, based on your posts above.

Also, he mentions QJ Hulson grates having about a 9.6% air opening ratio - or something like that, might be off a bit. He was more concerned about the cracks between grate sections being a variable factor.

Please let us know how this works out if you try it.

dave

These are roughly the proportions for GPCS
5 to 10% of exhaust steam for under the grate and it shold be sub divided to hole sizes of about 3/16 diameter. To be taken of the valve chest covers.
The air space of the grate should be about 5% of the grate area.
Top air can be as large as the tube area but using the door allows for ajustment.
The fire bed needs to be 15 coal partical deep for gas production.
Idealy a high volatile coal with a low ability to stick together.

The bit about a strong draught can be miss leading. The perseption of a high draught can be given if the air inlet is small ( like if the dampers are shut) or thickness of the fire gives a high gas flow resistance then there is high vacumm but little combustion gas flow. That is why Lempor type draughting is used for GCPS