Industries on Wadbury Vale

 
The Compressed Coal Company

The Compressed Coal Company is named after a rather unsuccessful briquette making company in the Forest Of Dean. In making briquettes the Compressed Coal Company uses a different technique to the Briquetting Company. Briquette are made by sticking dust and small pieces of coal together to convert small coal (also called duff, lime coal etc) into something more valuable.
In the model coal is bought in by rail screened, if oversized sold or crushed to size (technically granulated), the correct size coal is mixed with a binder, shaped, and put into an autoclave where steam is used to rapidly harden the raw briquettes. Steam comes from the power plant. The now solid briquettes go to bulk dispatch were they can be shipped out by rail or road - a National Coal Board truck can be seen loading briquettes. Briquettes for local delivery go to bagged dispatch were they are bagged and loaded onto trucks - a yellow truck can be seen loading bagged briquettes. From a modellers perspective all this explains why railway wagons come in and leave full (in bound coal & out bound briquette) and come in and leave empty (empty to collect briquettes & empty coal wagons returning to their colliery).

Sand-Lime Brickworks
 

In the late nineteenth century German experiments in making artificial stone resulted in a sand-lime brick process, patented in 1881. Production began there in 1894 but did not reach England until ten years later. The ingredients are silica sand, water and lime, which may be purchased already slaked or as quicklime to be slaked after mixing with the other materials. Slaking takes forty minutes in a rotary slaking drum or twenty-four hours by storage in silos and is following by batch mixing. Metallic oxide pigments may be added to yield pinks, greys, yellows and browns. The whole is then thoroughly mixed in a rod mill, a rotating cylinder with loose steel rods before being fed into powerful presses that form up to eight bricks at once under pressures of up to 200 tons. Two different coloured mixes fed into the same mould produce multicoloured bricks, if the faces are brushed after pressing, fine flint gravel in the mix creates texture. Steel trolleys carry a thousand bricks each to the autoclaves for curing, by saturated steam at 120 to 250 pounds per square inch. The curing lasts for four to twelve hours, depending on the strength and quality required. The pressure takes an hour or two to build up and release. At the end of the cycle the autoclave door is unbolted and the train of trolleys winched out. A weak hydrochloric acid dip removes surface scum; otherwise the bricks are ready for despatch.
Internet searches lead me to the site of the NRDC National Research Development Corporation (a Government of India Enterprise) who gave the following details: -
Calcium silicate bricks made from sand of siliceous waste and hydrated lime, generally known as sand lime bricks, are advanced building materials that give higher strength, uniform surface and sharp corners. These bricks can make beautiful walls that may eliminate plastering and painting, thus providing economical and superior alternative to conventional clay bricks. Manufacturing these bricks where sand or siliceous waste and lime are readily available, may, produce these bricks cheaper than clay bricks. Production of these bricks consumes about 30% less energy as compared to traditional clay bricks.
About 30,000 million calcium silicate bricks, solids as well as perforated, in different colours, are produced annually all over the world with the developed countries using completely automatic plants. Popularity of these bricks in developing nations has not picked up mainly due to ignorance, uneconomical local cost factors and non availability of raw materials at few places.
Process The process stipulates homogeneous raw mix preparation of sand and lime in a desired proportion with suitable quantity of water. The raw mix subjected to a suitable pressure in hydraulic press and cured under steam at design conditions yields beautifully coloured and fine finished ready to use bricks that give elegant walls without any need for plastering or painting.
Advantages; Accurate dimensions, sharp edges and no warpage, low coefficient of variation in strength, plastering on both sides of wall not required, mortar saving due to uniform shape and size, can be produced all round the year as no drying is involved, long durability, high strength and resistance to frost, conserves agricultural land as no clay required. Beautiful coloured bricks can be made, and utilises siliceous wastes.

My original concept was the brick works would run the entire length of the two base boards with an arrival (up) siding for lime and coal and a dispatch (down) siding for bricks. By jiggling components of the brick works I compressed it to the length of the dispatch (down) siding capable of holding 12 British wagons.

The plant is laid out as efficiently as possible with raw materials entering at appropriate points, staffing and mechanical help reduced to a minimum.

The process starts with sand arriving from the sandpit by narrow gauge industrial tram. On arrival the engine diver tips the sand out of the skips into the Conveyor House. The conveyor raises the sand and pours it into a storage bin. Augers move the sand from the storage bin to the rod mill. Wagonloads of lime arrive at the buffer end of the siding and are unloaded. Lime is stored then slaked in a silo and barrowed to the rod mill. Sand, slaked lime and water is mixed in the rod mill. A conveyor moves the mix to high level hoppers and drops into presses below. Raw bricks are loaded onto trolleys and pushed into the autoclave after several hours of steaming the trolleys are winched out and after cooling moved to the dispatch sidings. One siding is used to load rail wagons and the other serves a truck dock and storage area. Coals is delivered to a point just in front of the lime house where it is unloaded and fires the boilers proving the electricity and steam needed by the works. The brick works has three other structures. A corrugated iron building provides (55 @ 128-mm) facilities for staff working in dirty clothing. As the layout is set in the 1950’s social factors would require separate canteens and changing rooms for the technicians and labours. As there are ten technicians and eighteen labours on each shift the technicians would use about a third of the hut. The other building is a sweet of officers (55 @ 100-mm). I have assumed separate offices for the manager and accountant with a larger single office for the shift foreman and clerk. Both these buildings would have toilets and washing facilities. The other structure is the truck loading platform (107 @ 190-mm).
The building was built of Evergreen Styrene veneered in Slater’s corrugated iron, roof tiles and concrete block when strength is required. The building was painted in Humbrol paints I pour part of the thinner liquid away to get a higher proportion of the thicker grinds as this gives a matter finish. Gutters and down pipes are Slater’s rodding. I tested a number of glues to stick the building down and eventually used wood glue this has proved fine so far. The reason I used wood glue was that solvent-based glues attacked the expanded polystyrene often vigorously.

The Briquetting Company

Briquettes also know as briquets and breeze either turn waste products such as sawdust, wheat chaff, coal, and coke fines etc into a useable product or to coal into smokeless fuel (e.g. the Ancit, Maxiheat, Maxibrite, Mild Heat Treatment, Homefire and Taybrite processes). In Germany brown coal is briquetted.

Production of smokeless fuel briquettes uses several processes. Some use anthracite (itself a smokeless fuel) as feed; some use bituminous coal that is heated to a temperature just sufficient to soften it to allow compression to a briquette. Processes using only anthracite blend with a liquid binder (for example, phosphoric acid, coal tar, bitumen or molasses) before pressing to briquettes that are finally heat cured (to drive off "smoky" components) and quenched in water. There are usually no liquid or gaseous by-products from these processes - any fumes evolved are incinerated. For example Phumacite is a briquetted fuel produced by binding Welsh dry steam fines (10% - 15% volatile matter) coal with about 6% by weight coal-tar pitch, briquetting and carbonising the briquettes in batch ovens at about 800°C for around five hours, followed by water quenching. Its ash content is about 6% by weight. This side of the industry is not very modelable as the process is carried out in large plants. The same is true for the current Germany brown coal briquette industry.

In the Western Europe small scale briquetting has occurred in wartime and when the cost of fuel is high but has now largely stopped due to low fuel costs, high labour costs, and lack of a supply of coal fines as these are now happily burnt by power stations. Coal fines are coal with a maximum particle size usually less than one-sixteenth inch and rarely above one-eighth inch. Some firms made briquettes like small brick by mixing coal fines and cement at a ratio of twelve to one mould the mix, let it dry and sell the briquettes. The only problems are the cement gives a relatively high ash content and manufacture is labour intensive. This sort of firm is much more modelable. The requirements are:

Arriving coal needs to be unloaded and stored till used. Points to bear in mind are that coal fines are like sand so will blow away when dry, turn to slurry when wet and should not be adulterated these suggest use of storage bins.

Given the small amount of cement needed I assume it’s delivered in bags and stored out of the wet.

Coal fines and cement would be mixed on a mixing floor, in a cement mixer or batching plants. A convenient supply of water would be required.

Moulding could be carried out with hand moulds or a press. Mixing and moulding could be carried out in the same building.

Drying sheds that allowed a couple of days output to dry requiring an air flow over the briquettes while keeping them dry suggesting a roofed building with slatted walls.

A storage area would be need if the briquettes couldn’t be dispatch from the drying sheds.

Offices, staff room and of course don’t forget the toilet.

The various elements should be placed together to ease handling of the raw material and briquettes. Movement would be by barrow or possibly hand worked narrow-gauge railway. Briquettes will brake up if roughly handled due to the low proportion of cement. I feel that the labourers would like a roof and walls to keep the weather out these could be quite lightweight such as timber and/or corrugated iron.

In the UK most coal-cement briquettes were sold locally however during the Second World War the railways in Eire imported them from the UK on the basis that they were better than nothing. In Western Europe trade was much more extensive as the typical stove is more tolerant of briquettes.

My original concept was the briquette plant would be a small offshoot of the brick works processing a wagon or two of coal fines a day so all handling would be manual. By jiggling components of the brick works I compressed it to the length of the down siding. Giving the briquette plant use of the up siding capable of holding 7 British wagons. I also decided that coal fines would be delivered from the colliery by narrow gauge industrial tram. This had a number of advantages. Coal fines would be stored at the colliery removing the need for storage at the briquette plant. Except for incoming cement the up siding could be used to dispatch briquettes. The plant could be laid out more efficiently with raw materials entering at one end and briquettes leaving at the other. Staffing and mechanical help could be reduced to a minimum.

A couple of photographs I found on the Web suggested that the batching plant and press were quite small say 2 m³ each. This suggested that Incoming coal fines could arrive at a high level and be tipped out of skips into batching plant –only the cement would have to lifted. The batching plant could be placed at a medium level feeding directly into the press with the extruded briquettes coming out at a convenient height to load onto trolleys to move them to the drying area. Two days output would be about 200 m³ of briquettes adding space for skips, trolleys and labourers suggested a 300 m³ building. Given available space this suggested a 23-mm high @ 305-mm @ 120-mm building. Dried briquettes would be loaded into a skip and pushed to dispatch were a conveyor would load them into a high level bin. From the high level bin they could be tipped into; trucks, skips to load rail wagons or the bagging machine. Bagged briquettes for dispatch by rail would be moved by trolleys to the cement store for loading into vans or tarpaulined wagons. This arrangement would minimise staff with three salaried staff and ten peace rate workers. The salaried staff would be foreman (manager), clerk to keep the paperwork straight and a salesman. The peace rate workers comprising; a batcher and assistant to move the cement and look after the batching plant and press, a charge hand and six labourers to move the briquettes, and a dispatcher carrying out the loading and bagging. The split may seem dated but in the 1950s it would have been socially important and have practical implications. The peace rate workers would be covered in coal, cement and briquette dust so would need a canteen, changing room with lockers and washing facilities and separate toilets from the suited salaried staff.
I will only deal with the oddities. I used the same approach as the brick works. The only thing I would have changed is the slats on the side of the drying area. I wish I put in more uprights and painted the styrene behind the slats before gluing the slats in place. The low pitch roof is as my modelling hut.

Tedbury Quarry
 

The quarry is named after the Tedbury Camp Limestone Quarry to the south of the Mellis River near Mells. Limestone is normally sized before sale so the model assumes limestone is quarried, crushed and screened off scene. The crushed limestone is then moved by conveyor to the bunkers. If a mix such as ballast (3 parts pea to 2 parts fine crushed limestone) is required various sizes can be fed into the bunker. THe contents of the bunker is then dumped into railway wagons.

Coal Yard

Not normally treated as an industry none the less the coal yard should be a major generator of activity on the layout. Also the history of railways and the coal trade has been entwined - the coal trade begat the railways and the last goods traffic handled at stations was often coal.