Coal Density and Consumption

[Ian J.]

A couple of questions:

 

1. What is the approximate average density of decent steam coal? By this, I mean the weight in tonnes per cubic metre (or if you prefer, tons per cubic yard)

 

2. What is a rough average coal consumption per mile for a steam locomotive? This of course has any number of variables to it, and I don't expect a single answer. Alternatively, are there any official tables from the days of steam that gave guidance to operational planners on the coal consumption of the locomotives they had to plan for?

 

TIA

[buffalo]

By no means a definitive answer, Ian, but I just happen to have some figures in front of me that will give some idea of an answer to your second question. These are from the 1927(?) trials by the LMS involving a Garratt, an S&DJR 7F, an LNWR 0-8-0 and an LMS 0-8-0 on coal trains over the Toton-Brent route. The coal consumption figures in lb/mile were respectively: 112.6, 80.6, 79.0 and 53.9. Taking load into account the figures in lb/ton.mile were 0.07, 0.078, 0.076 and 0.055.

Source: Bradley and Milton Somerset & Dorset Locomotive History

 

Any help?

 

Nick

[Ian J.]

By no means a definitive answer, Ian, but I just happen to have some figures in front of me that will give some idea of an answer to your second question. These are from the 1927(?) trials by the LMS involving a Garratt, an S&DJR 7F, an LNWR 0-8-0 and an LMS 0-8-0 on coal trains over the Toton-Brent route. The coal consumption figures in lb/mile were respectively: 112.6, 80.6, 79.0 and 53.9. Taking load into account the figures in lb/ton.mile were 0.07, 0.078, 0.076 and 0.055.

Source: Bradley and Milton Somerset & Dorset Locomotive History

 

Any help?

 

Nick

I can see that it would be helpful, thanks. The only thing I'm struggling with is what 'lb/ton.mile' means? lb = pounds, but ton.mile?

 

EDIT: Actually, there is also the weight of the train in this instance, which you haven't got by any chance have you?

[buffalo]

lbs of coal / (weight of train x distance in miles)

 

In other words, it is just the consumption in pounds per mile divided by the weight of the train. This gives the amount of coal needed to move one ton of train over one mile (a rather abstract concept but probably useful for comparisons).

 

So, for the Garratt in the above example, the average load in tons was 1452, the consumption in tons pounds per mile was 112.6. So, 112.6/1452 = 0.078 (by my calculation -- the original source said 0.07).

 

Nick

 

edit: tons corrected to pounds

[Adrian Wintle]

lb/ton.mile normalizes the value to take the weight of the train into account - lbs (of coal) per ton (pulled) per mile (travelled), or an indication of the efficiency of the loco rather than its gross coal consumption.

 

Note that the density of the coal will depend on the type of coal, and different railways used different types of coal in the pre-nationalization era, notably the GWR, which used Welsh coal which was softer (and presumably less dense) than that used by the others.

 

Adrian

[Ian J.]

lbs of coal / (weight of train x distance in miles)

 

In other words, it is just the consumption in pounds per mile divided by the weight of the train. This gives the amount of coal needed to move one ton of train over one mile (a rather abstract concept but probably useful for comparisons).

 

So, for the Garratt in the above example, the average load in tons was 1452, the consumption in tons per mile was 112.6. So, 112.6/1452 = 0.078 (by my calculation -- the original source said 0.07).

 

Nick

Thanks, that makes sense to me. Just one thing, you put 'the consumption in tons per mile was 112.6...', I sincerely hope you meant lbs...

[buffalo]

Thanks, that makes sense to me. Just one thing, you put 'the consumption in tons per mile was 112.6...', I sincerely hope you meant lbs...

I did indeed

 

Maybe it was just an excuse for me to post this followup as my 1000th post

 

Nick

[Ian J.]

Note that the density of the coal will depend on the type of coal, and different railways used different types of coal in the pre-nationalization era, notably the GWR, which used Welsh coal which was softer (and presumably less dense) than that used by the others.

 

Adrian

For arguments sake, I will think in terms of Welsh steam coal, unless there are available resources to hand to describe different average densities from different seams/pits.

[Ian J.]

An additional question for the preservationists, which is what is the general coal consumption (lb/ton.mile) of a given locomotive 'x' on a preserved line, where the loco is doing relatively light work (say five Mark 1s, approximately three-quarters loaded) and only travelling at 25mph maximum?

[asmay2002]

A couple of questions:

 

1. What is the approximate average density of decent steam coal? By this, I mean the weight in tonnes per cubic metre (or if you prefer, tons per cubic yard)

 

Not the density but the volume occupied by a ton of loose coal was about 40 cubic feet (that includes a fair bit of air as well as the coal) I think.

[Burkitt]

This table of material densities includes values for anthracite and bituminous coal in solid and broken forms http://www.simetric.co.uk/si_materials.htm

[Nick Holliday]

As usual Googling "Density of coal" provides [lenty of answers. Such as

Typical Bulk Density of Coal

• Anthracite Coal : 50 - 58 (lb/ft³), 800 - 929 (kg/m³)
  
• Bituminous Coal : 42 - 57 (lb/ft³), 673 - 913 (kg/m³)
  
• Lignite Coal : 40 - 54 (lb/ft³), 641 - 865 (kg/m³)
  

from the Engineering Toolbox website. Most British steam coal would have been bituminous, so the figures given equate to 0.5 - 0.7 tons per cubic yard.

[melmerby]

Now if you throw the calorific value of said coal into the equation you have yet more variables!

 

Keith

[Ian J.]

Thanks for all the replies so far. Now in the cases of the where the values are all in imperial I have to do a few tortuous conversions to my somewhat weird metric/imperial crossover measurements (I use mostly imperial for distances (millimetres/inches/feet/miles), but always metric for weight and volume! (g/kg/tonnes and cm³/metres³/tonnes))

[Blandford1969]

Ian

In termd of coal consumption you need to also take into account additional factors which influence consumption. Calorific value is more important than density. As you may know coal is made up of nitrogen, oxygen, carbon, ash, sulphur and hydrogen "no cash" as we were taught.

The next factor to be taken into account in terms of consumption is grate size, which really goes without saying.

Next is how well the fireman maintains high firebox temperatures. On the main line or on long non stop runs in steam days it is possible to get higher firebox temperatures and get engines into superheat which is where the because of the increase in pressure and temperature means the steam has less condensation within it is dryer and therefore will do more work in the cyliners per lbs.

The next point which links to temperature and consumption is how the fireman puts coal on , too much at once can significantly lower firebox temperatures. It will also mean more unburnt carbons being seen at the chimney so lowering consumption. Black smoke may look good for enthusiasts but is not good for economy. The LMS did research and a flim "little and often" which showed the best ecconomy, they said was about 6 to 9 shovels about every 3 minutes.

Linked to this we have also to consider the amount of oxygen the fire is getting, to burn most efficently coal needs about 20 percent extra oxygen above what you would theoreticly think.

Sticking with our exhust on effeciency, if we are not getting full combustion we will be getting carbon monoxide given off rather than carbon dioxide. The effect of this difference amounts to 60 percent difference in the amount to energy given off

 

Finally in considering consumption we have to look at the amount of blowinf off the fireman does. Based on a cost of 144.7 per tonne and 5.9p per 10 gallons of water it costs 5 ponds per minute

 

Having considered the firemans impact, we need to look at the drivers impact on consumtion rates . The speed and weight of the train will vary the consumption as at slower speeds it is likley more cut off will be needed. The easiest way of thinking about cut off is like the gears in a car at 30mph you will struggle in 4th gear on a hill.

A driver playing to the crowd and making more noise will reduce effecincy and also can damage the engine, its like thrshing a car in first gear.

Finally, the good driver will be able to improve consumption by using gradients to help him slow the train down and use less brake, the ejector of course using steam to pull the brakes off.

 

The condition of the engine will impact on consumption, leaking saftey valves, worn valves, damaged injector cones or oveheated feedwater will all reduce consumption.

 

We also need to consider the weather and time of year. Between October and April in steam heating season more coal will always be used ,again varying by the lenght of train and pressure put through the system.

Moving now to preservation effeciency will be lower because of the start stop nature of services and the long layovers at each end of lines. The longer the layover the more firebox temperatures fall which then means it takes longer to get it back.

What then of preserved railways? I can only talk of the SVR where I look at it on a monthly basis and we publish it to our crews.

Our average consumption is 33kgs per mile although this does vary by month. Running 6 coach trains rather than 8 coach ones saves around 3kgs per mile (sorry we buy in metric) last month as an example we were at 29.4kgs per mile. It will be higher this month as we use 8 coach trains in August.

 

Regards

 

Duncan

[Ian J.]

Duncan, many thanks for that.

 

I always knew that getting a single figure for consumption is pretty much impossible, but the kind of thing I was looking for was a general idea of how much coal a locomotive might use in a year, and therefore how much storage space that coal needs (hence the interest in density) and how often that area would need to be filled up by deliveries. The preservation aspect comes in as I want to model a preservation line and have a coal storage area. I 'need' to know roughly how much space would be reasonable to see reserved for storing the coal. There's no use in it just being a couple of staithes, if in reality it would need something the size of a football field. Arguably such an area could be 'off-stage', but I am hoping for it to be modelled to some degree. All the above answers are helping me to define what the storage area size is likely to be.

[Blandford1969]

Hi Ian,

 

To give you a better idea based on what you are doing, on the SVR, if you say on average for the 64 mile trip about 2 metric tonnes will have been used.

 

We have about 4 deliveries of coal each month of around 29 tonnes, with our storage at Bridgnorth able to take more. The storage area I would guess at being about 20 feet wide by about 40 feet long. Its not often full though apart from just before Gala or Christmas running.

 

Hope this additional bit is of use.

 

Kind regards

 

Duncan

[Fat Controller]

As usual Googling "Density of coal" provides [lenty of answers. Such as

Typical Bulk Density of Coal

• Anthracite Coal : 50 - 58 (lb/ft³), 800 - 929 (kg/m³)
  
• Bituminous Coal : 42 - 57 (lb/ft³), 673 - 913 (kg/m³)
  
• Lignite Coal : 40 - 54 (lb/ft³), 641 - 865 (kg/m³)
  

from the Engineering Toolbox website. Most British steam coal would have been bituminous, so the figures given equate to 0.5 - 0.7 tons per cubic yard.

 

I'd go further, and say that all steam coal used in the UK was bituminous; we have no deposits of lignite that I'm aware of, whilst even those railways that carried almost exclusively anthracite (the L&MMR and the BP&GVR) used bituminous coal to fire their locos.

[EddieB]

I'd go further, and say that all steam coal used in the UK was bituminous; we have no deposits of lignite that I'm aware of, whilst even those railways that carried almost exclusively anthracite (the L&MMR and the BP&GVR) used bituminous coal to fire their locos.

 

"Steam coal" usually refers to a grade of coal between bituminous coal and anthracite, and therefore is reasonably consistent in terms of carbon content and calorific value.