So – What IS a Coal Washery?

The following is taken from “Surface arrangements at bituminous mines” Copyright 1907. from the Chapter titled “Coal Washing”

“As coal is never found pure … the impurities contained need to be removed. The impurities such as slate, bone, iron and sulfur (in the form of iron pyrites), and the clay or dirt that is found with the coal. If the slate, bone, and pyrites are not too intimately mixed with the coal, they may be separated from it by the use of water, after the lumps have been broken into small pieces. The coal being lighter will float off, while the bone, slate, and pyrites will settle. This method of separating the impurities is called coal washing.”

What that basically means is that there were many different ways of making what was essentially a giant washing machine. There was a need to crush the coal prior to washing it – but that is another subject altogether.

On page 67 there is a sectional view and a side view of a ‘Stewart Jig’. The diagrams gave me enough information to start to re-create the structure in Sketchup.

Stewart Coal Washery

Click image for a larger version

In another book titled “Coke: A treatise on the manufacture of coke and other prepared fuels ..” Copyright 1905, I hit the jackpot as there are even better drawings and description of the Stewart type washery.

The drawing to the left shows what I started with. This along with the text allowed me to pretty much figure out where all the bits fit.


Click the image for a larger version

Here is the washery as modeled in Sketchup. I left off all of the various machinery bits as I was concerned with the construction of the washery itself.

None of the joints are butt-joints but are jointed as they would have been in ‘real life’.

I’m going to sub-divide the Washery build into probably four sections. This is simply so I can make sense of what I am attempting and have no basis in anything other then that:

  • Section I – Consists of two parts: Overflow tank – what it says .. overflow of water from the Jig tank and Settling tank – Where the coal and shale separate. From this tank the cleaned coal will moved to a coal tipple where a larry, truck etc. can be filled from.
  • Section II – Consists of two parts: A Supply tank – Filled with water continuously (recycled from the settling tank) and the Jig tank – an agitator. This is the working part of the Washery .. the agitation separates the coal and shale.
  • Section III – At the very top of the structure is the Unwashed Coal Bin – this receives the coal from the breaker via a conveyor belt. It will contain crushed and broken coal, shale, dirt and clay. A door and chute will allow the material to be processed as needed.
  • Section IV – All of the mechanicals. I may expand this to a fifth section depending on how complex this gets.

Logic and Guesses

For the next while I’m going to post up what I modeled in Sketchup. I used the drawing from the book and then to the best of my ability how I interpreted that drawing. Where I couldn’t transfer that drawing to the 3d model I tried use logic. Not being in any way an engineer that ‘logic’ may be suspect. Feel free to comment on that point if you wish.

I expect at some point someone will point out that I have ‘Widget A’ incorrectly connected to ‘Widget B’. Be nice. I’m just a hobbyist doing my best and not .. as I said an Engineer. Simply explain why ‘Widget A’ should be connected to ‘Widget B’ and if I agree I will change it. See. Simple.

I haven’t started the model yet .. I’m just laying out the plan for it now. This will then be a guide for when I actually start building the model. When I do that I will update each section with photos and text. If/when I make changes based on the hands on – I will then correct the ‘plan’ to reflect those changes.

There are a multitude of flat belt pulleys, belts, sprockets and chain represented. The diameters of the pulleys and sprockets can be fairly well deducted from the drawings. The ratios between these various pulleys and sprockets then can be calculated. Given a speed for the engine we can then calculate the RPM for each pulley or sprocket. The only remaining variable is the HP. Given this we can then find the needed width for each belt (and therefore the flat belt pulley width) and I suspect the width of the sprockets/chains (that last bit still needs researching).

  • Crusher requires 45 HP
  • a five-jig washer require abouts 100 HP. It might be taken from that number then that a single-jig might only require 20 HP maximum as elsewhere it states that it requires about 10 HP per jig.
  • if a steam engine produces 45 HP at 250 RPM then it would produce 20 HP at 111 RPM and 10 HP at 56 RPM



I have nothing to go on other than I would guess the timbers would undergo the same procedure as bridge timbers from the same time period. Bridge timbers that are new are dark brown from creosote. When they have weathered over the years they are gray. I could *pressume* (close to an assumption with all the baggage that can have) .. that this will fall somewhere in between.
A little research shows that railroads used zinc chloride to treat ties in the late 1800’s, switching over to creosote in the first decade of the 1900’s. Since the references to a coal washery were published in 1905/1907 then we could suppose that either the wood wasn’t treated at all or if it were, zinc chloride could have been used. I did find where attempts were made to add a dye to zinc chloride treated wood to enable telling how deep the preservative had pentratiated .. which tells me that there must be little color change. I suspect that I will just .. make the wood gray after all and forget all of the ‘guesstamation’.

I was thinking about this a bit and with no supporting evidence at all I would bet that the parts that are in constant contact with water such as the tanks would have been tarred. If you think about it .. boat hulls were tarred .. joints between boards stuffed with oakum and then covered in pitch. I would be willing to bet that the insides of the tanks were mopped with hot tar/pitch.

Milling Stop

No few pieces of the timbers will require a notch cut into the end. A simple stop as shown would enable me to run a 1/4″ Dremel Router Bit to make the notch. Since the only difference will be the distance the notch is from the end and the depth (which honestly will probably be the same 0.042″) I will need to note which timbers need to be grouped for the same cut. Let’s call this .. ummm .. NG or Notch Group(ing). So .. say a notch 0.042″ deep, 1/4″ wide that is 1/8″ from the end will be NG-1. I will annotate the drawings with that.

I used a milliling stop similar to this to notch the timbers for my Ore Bin.

Prototype Stuff

Overview The following was provided by John Stewart of the Newcastle Coal Company's No.2 Mine Tipple, Newcastle Alabama Photos Aerial View To the left center we have four rows of coke ovens. Just the ones in the photo represent something like 112 ovens - no telling how many more are outside the view. Center bottom...

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Coal Washery – Section I

Section I - Overflow and settling tanks Overflow and Settling Tanks Here in Section I we have the Overflow Tank – what it says .. overflow of water from the Jig tank. It is at this point that the water is pumped back to the Supply Tank to the start of the cycle. Settling tank...

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Coal Washery – Section II

Section II - Supply and Jig Tanks Supply and Jig Tanks Section II – Consists of two major parts: A Supply Tank – Filled with water continuously (recycled from the Settling Tank) and the Jig tank – an agitator. This is the working part of the Washery .. the agitation separates the coal and shale....

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Coal Washery – Section III

Section III - Unwashed Coal Bin Unwashed Coal Bin At the very top of the structure is the Unwashed Coal Bin – this receives the coal from the breaker via a conveyor belt. It will contain crushed and broken coal, shale, dirt and clay. A door and chute will allow the material to be processed...

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Coal Washery – Section IV

    Section IV - Mechanicals There is quite an assortment of "mechanicals". I put that in quote as some items are more like what could be called infrastructure .. but .. mechanicals is good enough for now: two Belt Elevators a Chain Elevator sprockets with chains pulleys of various sizes with belts the jig...

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