RCAHMS SURVEY
Date 2007 - 2009
Event ID 605898
Category Recording
Type Standing Building Recording
Permalink http://canmore.org.uk/event/605898
1. Background
(See Ground plan DC51320/ SC1156469, elevation and section DC51339/ SC1156500 and RCAHMS photographic survey of 2008)
Biggar gasworks was opened in 1839 (1) and is named and depicted on the Ordnance Survey 1st Edition 25-inch map (Lanarkshire, 1864, sheet XXXIV.9). The retort house (now the coal store) at NT03880 37696, a range to the N (NT03882 37704, now gone) and a now demolished gas holder (partially overlain by the current exhauster house, centred NT03868 37697) are shown. The manager's house is also depicted (NT03NW 248).
The Ordnance Survey 2nd Edition 25-inch map (Lanarkshire, 1897, sheet XXXIV.9) map shows the original retort house, but the N range has been mostly demolished and replaced by the buildings now visible on the site (showroom/office block, originally a cottage of 1858) and the now demolished coal/coke Store at NT03884 37713 which served the original retort house. Two gasholders (NT03876 37705 and NT03865 37686) are depicted and correspond to the current layout. These date from 1858 and 1879 but have been rebuilt. (2) The Ordnance Survey 25-inch map of 1911 (Lanarkshire, sheet XXXIV.9) shows the addition of the current retort house (NT03882 37686).
The Ordnance Survey 25-inch map of 1940 (Lanarkshire, sheet XXXIV.9) shows the meter house (NT03873 37690) and the lime store (NT03887 37693) more clearly. Lime was originally used in the purifiers but presumably iron oxide was also used. The exhauster house is also depicted on the 1940 map (built circa 1914, NT03869 37701).
Friedrich Christian Accrum’s ‘A Practical Treatise on Gas Light’ (1815) shows the typical layout of a gasworks some 20 years prior to the opening of Biggar. (3) The linear layout is noticeable in both the Treatise and the Ordnance Survey 1st Edition 25-inch map (Lanarkshire, 1864, sheet XXXIV.9) depiction of Biggar with the chimney and the gas holder either side of the retort house and condenser and outbuildings and stores away from the main process buildings. The gasworks itself is away from the town centre and on the outskirts due to the smoke, odours (from the spent purifier material) and danger of explosion (from the coal yard) that town-gas production entails. It is also situated on deliberately chosen, lower-lying ground near the Biggar Burn. Town gas, along with other gaseous substances, rises and so it is easier and cheaper to distribute as it does not need to be pumped.
John Ritchie of Lanark was hired to provide specification and plans for the original gas works in 1839. Robertson and Wilson of the Gorbals Foundry, Glasgow was the chosen contractor to build the gas making apparatus. The building work was carried out by a local firm, Watson and Robertson. The first gas maker was a cooper named Ramsay who was sent to Carluke gasworks to learn gas making. (4)
Biggar Gas works is operated as a heritage site by the Biggar Gas Works Trust and the Royal Museum of Scotland and is open throughout the summer months.
2. The Process
Coal was taken from the coal store by barrow and hand shovelled into the retort. The retort door was then closed (and sometimes sealed with ‘pug’ and clay and lime mixture, but at Biggar the doors were self-sealing). The retorts were then heated by the furnace. Three gases were driven off in the retort: hydrogen, carbon monoxide and methane. These were ‘sucked’ through the system by the exhauster (at Biggar this is located next to the washer/scrubber and was electrically driven using a belt drive). The gas bubbled through the hydraulic main and passed through the pipes to the condenser. The gas bubbled through water in a base tank. Tar and ammonia was extracted and cooled in the pipes. The gas was then drawn through the Livesey washer and rotary ‘scrubber’ to remove further ammonia and tar. The gas was then pumped to the purifiers where the hydrogen sulphide was extracted. The now ‘clean’ gas was measured (by the meter situated in the meter house) and pumped to the gas holders. From the water-sealed holders, the gas was distributed to the town users.
The retorts were emptied and the coke (coal with gases and impurities driven off) was then used to heat the retorts or in some cases could be sold on as a smokeless fuel. Ammonia and coal tar by-products could be re-used in other industries, although the smaller gas works did not tend to sell on ammoniacal liquor as it was not cost effective.
3. The Site
Coal Store (original retort house)
The original retort house (latterly the coal store) is a masonry, one-storey building with three blind walls, a concrete floor raised at the N end and a corrugated roof. The N wall has two windows either side of a double door and it has been rebuilt above its right hand window and door openings (see DP013425). The Ordnance Survey 1st Edition 25-inch map (Lanarkshire, 1864, sheet XXXIV.9) shows a vestibule area which is now gone. The E and S walls butt onto the square chimney base (which is of good quality masonry build) and the walls are either later or for ease of chimney repair/rebuild. The W elevation is of rubble and has a ‘bow’ in it suggesting rebuilding. There are significant brick inserts probably from the time of the building of the new retort house which was in existence by 1911(Ordnance Survey 25-inch map, Lanarkshire, 1911, sheet XXXIV.9).
The original S elevation (the original exterior wall, see SC1036045) is now an internal wall. The original retort bench could possibly have run along the S wall to allow access to the chimney as well as access to the condensers and purifiers to the W. The W wall also has a blocking which corresponds to the current position of the condenser apparatus. This wall could also have supported the original retort bench and there are signs of blackening on the wall.
The roof has been replaced at least three times (5) but the wrought iron roof truss appears to be original and may, therefore, have been re-used from the earlier roof structure. There is evidence of it having been re-fitted at the chimney breast where there are ‘notches’ in the iron with no corresponding obstructions or members for which they were cut. A fuller survey of this wrought-iron roof structure will be carried out in 2010. The 1974 image taken by John Hume (SC434402) shows the replaced roof of the original retort house. This appears to be at a lower level than that shown in the 1865 illustration. The condenser pipes may have been replaced or remodelled (heightened), when the new retort house was built.
It was common for small gas works retort houses to have louvered roofs to allow steam to escape when the carbonised coal was quenched on removal from the retorts. Small town gas works retort houses generally resembled brewery buildings as a result. (6)
Retort House
The brick-built, wet-harled, single-storey retort house, butts onto the ashlar S wall of the former retort house (current coal store) and was built about 1911 (it appears on the Ordnance Survey 25-inch map edition of 1911, surveyed in 1909). A door has been inserted into the S wall to allow access to the retort house from the coal store. The floor is of concrete. The ‘new’ retort house shared wall shows the original gable of the original retort house when viewed from the S. It has a corrugated (original) asbestos roof of the ‘Belfast’ type.
The retort bench has nine retorts (DC51339 and SC103604, five and four retort arrangement) with cast iron retort doors and ascension pipes installed circa 1912 (date shown on the retort doors). The arrangements of retorts allowed for the maximisation of the circulation of the hot flue gases which heated them. The current silica retort (introduced into gas making in the early 1920s, life span about 10 years) and the brick bench would have replaced the original fireclay retorts due to the wear and tear on the ceramic linings (they would have been replaced every 3 years or so). The adoption of fireclay retorts (displacing cast-iron from the early 1850s) increased the yield of gas produced per ton of coal and each charge was carbonised at a greater speed, thus making it a more efficient and cheaper material for retort linings. (7) The furnace which heated the retorts is of the Klonne recuperator type or regenerator setting (or arrangement of retorts). The hot gases from the coke passed through a number of brick passages in the retort bench (DC 51339) allowing for secondary air to combust around the retorts set into the bench. (8)
The cast iron ascension pipes carried the flue gases and tar to the hydraulic main (DC 51339 E). Hydraulic mains were the first stage of tar/water trap which ensured that a large proportion of the tar was removed and the flue gas cooled as well as eliminating the possibility of ‘blow back’ of explosive gases when the retort doors were opened for re-charging with coal. (9) This gas was then ‘sucked’ through two pipes, one at either end of the hydraulic main (see DC 51339 F; SC1036041) to the condenser situated at NT03878 37696 (see DC51320 and DP013429).
Condenser
The Condenser (annular layout) is of cast-iron and considered to be original (LAR 4/1) although the drawing of 1865 does show condenser pipes of a different style in the same location but this may be artist’s licence. (10) The condenser pipes may have been replaced or remodelled (heightened), when the new retort house was built and the new hydraulic main pipes were installed to increase the area of pipe condensing the gas. The gas was bubbled through the water tank at the bottom (DP013429) to remove the tar. The condenser would then cool the flue gas (to atmospheric temperature) in the annular tubes above.
Exhauster House
The exhauster house was built in 1914 and is a one storey building of brick construction with a slate roof (DP013418).This building still houses the exhauster and the Livesey washer/rotary scrubber (Henry Balfour and Co ltd, Leven, Fife, 1914), which removed the rest of the tar and ammonia from the gas. The washer consists of a tank with water in which the gas is drawn through pipes with holes, which act as a wire pulling action, the gas bubbling through the water. The tar then runs down the pipes into a tar pit below. The gas then passes into the rotary washer and scrubber above to remove more tar (with brushes) and to dissolve the ammonia in water (resulting in ammoniacal liquor). From here the gas was pumped back to the purifier house adjacent to the coal store and the condenser. The ‘pull’ on the exhauster (which affected the calorific value of the gas) was controlled by a governor which would have resembled a small gas holder.
Purifiers
The purifiers are by the Barrowfield Iron Works (DP013431) date unknown, although they probably date from around the 1911 expansion.
The lean-to building which houses the purifiers may in part date from the original 1839 buildings. The walls are of ashlar and rebuilt in some areas, with a slate and wooden roof. The W wall and part of the S wall (masonry in its lower course, see SC1036045) which backs onto the ‘new’ retort house of 1911 is original and has a later blocking allowing ingress to the retort house. It has a later roof line and its shared back wall (with the meter house) was probably substantially rebuilt when the new retort house was built. The current wall shared with the ‘new’ retort house (see DC51320) may be the original and as seen in the c.1865 drawing. (11) It is clear from this drawing and the current evidence (the original roofline is visible in the purifier house) that the roof has been raised to accommodate the pipes coming from the hydraulic main. It could also be conjectured that the purifier house was extended to accommodate changes in purifiers when the exhauster house and the new retort house was built. Bricks set into the area in front of the purifier house are marked ‘Morningside’ and so date from c.1920s-1940s. (12)
Meter House
The meter house has rubble walls and an asbestos roof. It utilises rubble walls from the original gas work as shown on a drawing of the works from c.1865. (13) The depiction of the meter house in this drawing however, suggests that it has been inserted with the S wall when the meter was inserted in the early 1920s. Its current N wall is original to the depiction on the Ordnance Survey 1st Edition 25-inch map (Lanarkshire, 1864, sheet XXXIV.9).
The meter itself is a ‘wet meter’. It takes the form of a horizontal drum half filled with water. The interior is divided into compartments (tin was usually used) which revolved around an axle. The compartments rotate as the water is displaced by gas. The turning compartments are attached to geared pointers in the dials. The meter house contains a desk on which the ledger would have been kept to record the dial reading every few hours.
Gas Holders
The water sealed, wrought-iron, telescopic, column-guided gas holders date from 1858 and 1879 respectively. (14) They have been rebuilt but the gasholder to the N (the oldest) retains its original lattice tri-form frame and cast-iron tank, although the original counterbalancing weights have been removed. Its present capacity dates from 1918. (15) Both have runners between the tank and the external columns.
Showroom and Offices
These were built sometime circa 1858 (14) with later addition of a brick offices and toilet block onto site boundary wall at NT03890 37709. The original coal store area was on an adjacent paved area (see DC51320 and DP013424).
Chimney
This square base with circular stalk (SC434402) has been partially demolished for safety reasons. The chimney is visible on the Ordnance Survey 25-inch map of 1911 (Lanarkshire, sheet XXXIV.9) and is built of finely tooled and dressed masonry (see SC1036047). There is a lean-to Lime Store adjacent to the original retort house (later coal store), next to boundary wall and chimney base at NT 03886 37695 (see DP013425).
Transport
The gasworks is situated some 379 m (1240 feet) from the now demolished railway goods yard and railway station (NT03NW 108). Coal would have been brought in by rail and carted/driven to the site. The carbonised coal (coke) removed from the retorts would wither be used in the furnace as fuel to heat the retorts or sent out by rail as smokeless fuel to be used in other industries.
Glossary
Ammonia: colourless gas by-product of manufacture of coke and gas from coal
Coal Gas (aka Town Gas): produced by heating coal in a retort to about 1350 degrees centigrade. This was then processed and distributed for heating, cooking and lighting to homes and businesses.
Condenser: enabled gas from retorts to be reduced in heat, water in a tank removing tar and ammonia before being pumped to the washer and scrubber for further decontamination
Exhauster: a pump which drew the gas from the hydraulic main and condenser and pushed it through the rest of the process
Exhauster House: a building housing the exhauster or pump. At Biggar, the scrubber and washer was also housed in this building.
Gas Holder: a telescopic tank (known as the ‘bell’) sealed with water which stored town gas ready for distribution. The gas holders at Biggar are kept fully extended for ease of painting and cleaning.
Gas Meter: measured the amount of gas produced in a gasworks
Hydraulic Main: a pipe filled with water through which retort flue gas drawn to cool, remove tar and ammonia from the gas bubbling through it
Livesey Washer: this removed tar from the gas using water and perforated pipework
Producer Gas: gas of carbon monoxide and nitrogen mix and made cheaply in gasworks from passing heat through coke. Used to heat retorts and mixed with Town Gas. Originally developed by C.W. Siemens in the 1850s but not successfully taken up until the 1880s.
Purifier: a cast iron vessel containing iron oxide and hydrated lime to remove toxic hydrogen sulphide from gas once it had been pushed through the scrubber
Retort: vessel closed at both ends in which coal was heated to produce gas. Early 19th century retorts were made of cast iron and latterly from fireclay (1850s on) and silica from the 1920s.
Retort Bench: this was usually brick-built and housed the horizontal retorts and incorporated the flues which carried the producer gas around the retorts
Retort House: the building that housed the retort benches and associated plant
Scrubber: removed ammonia by bringing the gas in contact with large wetted surfaces in the case of Biggar, using brushes in a rotary scrubber
Tar: viscous by-product collected from hydraulic main, condenser and scrubber
Tar Pit: collected tar from the condenser. Washers also have one.
Town Gas (aka Coal Gas): produced by heating coal in a retort to about 1350 degrees centigrade. This was then processed and distributed for heating, cooking and lighting to homes and businesses.
Notes
1. Wood, J.L., ‘Early Gas Making’ (The Royal Scottish Museum, Chamber s Street, Edinburgh, 1982, Leaflet 5), 3
2. Wood, J.L., ‘Early Gas Making’ (The Royal Scottish Museum, Chamber s Street, Edinburgh, 1982, Leaflet 5), 3
3. Friedrich Christian Accrum’s ‘A Practical Treatise on Gas Light’ (1815)
4. Gentle, I., Biggar Gasworks 1839-1989 150 Years of Industrial History, (The Newcomen Bulletin, December 1989), 9
5. See Wood, J.L., Early Gas Making, (The Royal Scottish Museum, Chamber s Street, Edinburgh, 1982, Leaflet 5), 1. See also SC 434402 and DP013432. The lithograph of Biggar with the gasworks in the foreground was produced by the engraver Robert Paterson, Edinburgh from photographs taken by Thomas Annan. It was published in 1873 by David Lockhart, printer, Biggar.
6. Wilson, G.B.L., The Small Country Gasworks, (Transactions of the Newcomen Society, 1973), 33
7. Cotterill, M.S., The Development of Scottish Gas Technology 1817-1914: Inspiration and Motivation (Industrial Archaeology Review 5, 1980-1), 25
8. Vincent, C. (Ed.), Chemistry as Applied to the Arts and Manufactures, (London, [1880]), 1010
9. Cotterill, M.S., The Development of Scottish Gas Technology 1817-1914: Inspiration and Motivation, (Industrial Archaeology Review 5, 1980-1), 20
10. although the rest of the image looks to be accurate see Wood, J.L., Early Gas Making, (The Royal Scottish Museum, Chambers Street, Edinburgh, 1982, Leaflet 5), 1
11. Wood, J.L., Early Gas Making’,(The Royal Scottish Museum, Chambers Street, Edinburgh, 1982, Leaflet 5), 1
12. Douglas, G.J., Hume, J.R., Moir, L., Oglethorpe, M.K., A Survey of Scottish Brickmarks, (Scottish Industrial Archaeology Survey, 1985), 31
13. Wood, J.L., Early Gas Making, (The Royal Scottish Museum, Chambers Street, Edinburgh, 1982, Leaflet 5), 1
14. Trinder, B. (Ed.), The Blackwell Encyclopedia of Industrial Archaeology, (Oxford,1992), 82
15. Gentle, I., Biggar Gasworks 1839-1989 150 Years of Industrial History, (The Newcomen Bulletin, December 1989), 9
16. Gentle, I., Biggar Gasworks 1839-1989 150 Years of Industrial History, (The Newcomen Bulletin, December 1989), 9
Visited by RCAHMS (MMD), 2009.
