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Gretna Hm Factory Eastriggs Factory, Acids Section, Grillo Oleum Plant
Sulphuric Acid Plant (First World War)
Site Name Gretna Hm Factory Eastriggs Factory, Acids Section, Grillo Oleum Plant
Classification Sulphuric Acid Plant (First World War)
Canmore ID 373543
Site Number NY26SW 38.01
NGR NY 24527 65030
NGR Description Centred NY 24526 65030
Datum OSGB36 - NGR
Permalink http://canmore.org.uk/site/373543
- Council Dumfries And Galloway
- Parish Dornock
- Former Region Dumfries And Galloway
- Former District Annandale And Eskdale
- Former County Dumfries-shire
Field Visit (6 April 2022)
Canmore ID: 373543
Site Number NY26SW 38.1
NGR NY 24527 65030 (centred)
What survives of this complex plant is situated in dense deciduous scrub woodland immediately N of the road in the SW corner of HM Factory Gretna (Site 3). It is located between the modern sewage farm on the WNW (NY 24400 65050) and the remnants of the Mannheim Oleum Plant (NY26SW 38.2) on the ESE. These chemical works comprise the remains of four Grillo units, numbered 1-4 from ESE to WNW, the component buildings of each being spread over three ranges. Each range is symmetrical around a division running through the centre of the plant from NNE to SSW.
In the southern range each unit is made up of a single bank of twelve Sulphur Burners connected to a Heater-Cooler, a Sulphur Dioxide (SO2) Cooler, three Scrubbing Towers above a building containing acid tanks, pumps and coolers, and a block of five Coke filters. In addition, each pair of Grillo units shared a Converter House situated in the central range and a dedicated Sulphur Trioxide (SO3) Cooler in the northern range, where each pair also shared an Absorption House. All the machinery was removed soon after the First World War and only the foundations of the buildings and some associated structures survive.
Two Grillo units shared one of the two Sulphur Burner-Heater Cooler Houses (NY 24558 64980, NY 24472 65003) situated in the S range. The foundations of the house provided for Grillo Units 1 and 2 are situated in the ESE sector of the complex and are better preserved than the companion house provided for Grillo Units 3 and 4 to its WNW. The latter is partly buried under building debris and dense vegetation. Both buildings are T-shaped on plan and are outlined by square concrete footings for steel stanchions. These footings are linked centre to centre by a narrow brick skirting which buttressed the concrete floors, but this is visible only intermittently above the present ground surface. The SSW section of each T-shaped building originally contained the brick-built sulphur burning furnaces. The building associated with Grillo Units 1 and 2 measures about 23m from NNE to SSW by 17m transversely and encloses the remains of two grass-grown concrete floors which supported twelve furnaces to either side of a gap 3.5m wide. The furnaces on the ESE floor formed part of Grillo Unit 1, while those on the WNW floor formed part of Grillo Unit 2. No trace remains of these furnaces or the flues that transferred the sulphur dioxide to the brick-built Heater-Coolers from which a pure gas resulting from the burning of high-grade sulphur would be warmed in passing directly to the Heat Exchangers in the Converter House (see below). By contrast, less pure gasses from the burning of lower grade sulphur would be cooled in passing from the Heater-Coolers via a dust chamber to the Sulphur Dioxide Coolers (see below). The NNE section of the building which housed the Heater-Coolers is also rectangular on plan and measures about 33.5m from WNW to ESE by 9.5m transversely. Both buildings now enclose low swellings of debris where the Heater-Coolers once stood. There are also the remains of a small building immediately adjacent to their WNW ends, but their function is unclear.
The foundations of the four Sulphur Dioxide Coolers (NY 24571 64976, NY 24546 64983, NY 24486 65000, NY 24459 65007) are situated immediately to the ESE or WNW of the Sulphur Burner-Heater Cooler Houses. They were linked by pipework to the Heater-Coolers and their foundations are rectangular on plan, measuring about 10m from NNE to SSW by 6m transversely. Each comprises two rows of 11 concrete pillars, separated by a central concrete wall, with every pillar in a row linked to the next at ground level. The outer edges of their summits are stepped and there are bolts for a timber framework on their summits. At their NNE end is a low rectangular concrete slab, but although this is present at the site of the most westerly cooler associated with Grillo Unit 4, no clear traces were observed of the accompanying pillars that must have stood to its SSW.
Little remains of the Scrubbing Towers (NY 24579 64971, NY 24536 64983, NY 24499 64994, NY 24451 65007), with one trio being assigned to each unit. Each trio was located next to one of the Sulphur Dioxide Coolers and together with the buildings at their feet containing coolers, acid feed tanks and pumps, they were part of the system by which the impurities in the gas were gradually filtered through coke and removed with the aid of sulphuric acid. The nine brick walls running from WNW to ESE that formed the piers on which they were erected were arranged on a rectangular plan measuring about 17m from NNE to SSW by 6m transversely. These walls have all been demolished, but fragments of their lowest courses survive of those part of Grillo Units 1 and 2. The buildings situated at the foot of the towers (NY 24585 64971, NY 24530 64985, NY 24499 64994, NY 24445 65010) were rectangular on plan and measured about 20m from NNE to SSW by 8m transversely, although that associated with Grillo Unit 1 was narrower. All have left little trace apart from a few square concrete footings for steel stanchions marking fragmentary lengths of the outer walls of those in Grillo Units 1, 2 and 3. The few footings remaining at Grillo Unit 1 are consistent with a lean-to structure. Two distinct structures are visible within its outline. The more southerly comprises three rows of concrete dwarf walls, each aligned from WNW to ESE, with a single short buttress positioned centrally at its S end, while its companion to the N is double its length and has buttresses at both ends. It is possible that these supported the three circulating acid feed tanks, while a small rectangular plinth to their WNW may have supported a pump.
Although the Scrubbing Towers were situated next to the Sulphur Dioxide Coolers, in practice the impure gas passed directly from the latter, via an overhead pipe, to one of five Coke Filter blocks situated in a bank on the towers’ far side (NY 24593 64970, NY 24523 64990, NY 24507 64994, NY 24437 65012). The impure gas was first circulated through this filter and its immediate neighbour, before passing on to the Scrubbing Towers and then back again through the three remaining filter blocks. Their grass and moss-grown concrete foundations are rectangular on plan and measure about 28m from NNE to SSW by 9m transversely. The brick piers erected upon them are very poorly preserved, but some of their lowest courses survive in Grillo Units 1, 2 and 3.
A reserved space or alley (centred NY 24521 65013) about 8m wide is situated between the southern and central ranges of the plant. There is no trace of the path that once allowed the hand-pushed trolleys loaded with sulphur charges to run down this alley, enter the Heater-Cooler Houses and deliver the fuel to the furnaces. Indeed, this zone between the ranges is now interrupted only by the moss-grown, chamfer-edged platforms that formed the foundations of two chimney stacks (NY 24565 65003, NY 24479 65026). Each served a pair of Grillo Units and both are situated immediately SSW of one of the two Converter Houses (NY 24566 65012, NY 24482 65034) that occupied the central range. Their foundations measure 4.3m sq., while the circular apertures at their centres, reaching down to underground brick-built flues, measure 1.24m in diameter. One flue, which runs from ESE to WNW along the full length of the alley, has partially collapsed either side of the WNW chimney, where traces of a brick-built arch are visible on the surface within a grass-grown, ragged, linear hollow. Other flues run from each of the Sulphur Burner-Heater Cooler Houses and these enabled all the hot gases from the furnaces to be rapidly expelled from the plant in the event of an emergency. In addition, the chimneys also link with smaller flues that run from the SSW edge of the Preheater platforms inside the Converter Houses (see below).
One Converter House was provided for two Grillo Units and their foundations are also outlined at regular intervals by square concrete chamfered footings that supported steel stanchions. Each building is rectangular on plan and measures about 57m from WNW to ESE by 12m transversely. There are outshots at each end which housed four Roots Blowers. These are also rectangular on plan and measure 10.5m from WNW to ESE by 9.5m transversely. Each contains the two tall concrete blocks upon which the blowers were mounted, together with the smaller, lower L-shaped plinths that supported their belt-driven motors. However, the Suction-Presser Equalisers that minimised disruptive vibrations between the filter blocks and the blowers were attached to the pipework adjacent to the outshots’ gable-ends and have left no trace. The blower outshots are less broad than the rest of the Converter House and the extra space created externally on the SSW was filled in each case by a Grease Catcher (NY 24601 64997, NY 24529 65016, NY 24514 65020, NY 24444 65038). The locations of these cylinders are now marked only by the tumbled remains of their brick-built cradles, but originally the blowers drew the gases through the coke filters inside the Grease Catchers from whence they were passed through to the Heat Exchangers and the Sulphur Dioxide Converters situated inside the Converter Houses.
The internal arrangements of the two Converter Houses are similar, with each Grillo Unit being provided with two Preheaters, two Heat Exchangers and two Sulphur Dioxide Converters - these elements mirroring one another in each adjacent Grillo Unit. A grass and moss-grown concrete platform for a Preheater is situated next to each blower house, while a pair are also positioned next to one another in the centre of each building. They measure about 9.5m from NNE to SSW by 6.5m transversely and 0.2m in height, but apart from a small scatter of bricks on one of the platforms, no remains of their brick encased chambers or coal-fired furnaces survive. In most cases, at least two small flues are visible running from the SSW edge of these platforms into the main flue that expelled waste gases to the two chimneys. The Preheaters were only brought into play if the plant had to be restarted or the temperature of the gas that had passed through the Grease Catchers, the Heat Exchangers and back through the Heater-Coolers, was still too low to send directly to the Sulphur Dioxide Converters. The locations of the Heat Exchangers are marked by pairs of rectangular chamfer-edged plinths which are situated to the SSE of each Sulphur Dioxide Converter. These plinths, which measure 1.7m from NNE to SSW by 0.6m transversely and 0.15m in height, supported slender metal frames that raised these horizontal cylindrical vessels aloft. By circulating the hot gas from the Sulphur Dioxide Converters back through their tubing, the temperature of the gas from the Heater-Coolers could be raised sufficiently to send it straight to the Converters without resort to the Preheaters. The concrete foundations of the Sulphur Dioxide Converters can be likened to a ‘winged octagon’ on plan, each measuring 4.8m from NNE to SSW by 3.4m transversely and about 0.3m in height. No traces of their enclosing brick casings survive, but these tall vertical cylinders containing the platinum contact mass translated the sulphur dioxide to sulphur trioxide. Thereafter, the converted gas was conveyed from the Converter building by overhead pipework to one of the four Sulphur Trioxide Coolers situated in the NNE range.
The NNE range was divided from the central range by a Standard Gauge Railway Line (NY26NW 46.23), but all that remains of this is a terrace sloping gently downwards from ESE to WNW situated near the Sulphur Store (NY26NW 46.10). No trace survives of the four Sulphur Trioxide Coolers (NY 24579 65030, NY 24565 65033, NY 24495 65052, NY 24480 65056) which stood immediately N of the railway. One was provided for each Unit and each Cooler received gases from two Heat Exchangers in the Converter House. These coolers were used to regulate the temperature of the gas before it was conveyed to the two Absorption Houses (NY 24575 65042, NY 24492 65065) situated to their NNE. Each Absorption House was shared by two Units and this was where the oleum was produced by the interaction of the sulphur trioxide with sulphuric acid within tall towers packed with clean quartz. The main building also contained pumps, circulating tanks and acid coolers, while an outshot to the NNE held the weighing tanks and stock tanks into which the oleum was run before being pumped to the storage tanks (NY 24538 65081) located about 8m to the NNE. The Absorption Houses were originally rectangular on plan and measured about 33m from WNW to ESE by 17m transversely. Only traces of the foundations of that on the ESE survive and these are characterised by a grass-, moss- and scrub-grown concrete floor subdivided by low narrow concrete ribs orientated from NNE to SSW. The site of the oleum storage tanks is situated in a grass- and gorse-grown area, and all that remains are fragmented debris scattered over faint undulations.
The whole complex of buildings and ancillary installations that make up the Grillo Oleum Plant is described in the reports (Ministry of Munitions of War 1919, plan, 37-50; Ministry of Munitions and Department of Scientific and Industrial Science 1921, 46-65) outlining the processes involved in the manufacture of the cordite propellant at H.M. Factory, Gretna (Site 3). This was established by the Ministry of Munitions during the First World War. The character of the buildings and their components are illustrated by an undated plan (SUPP 10-39), descriptions of blueprints (SUPP 10-32 15011-12, 15015, 15022, 15024-6, 15043-4, 15065, 15071, 15140-1, 15184), blueprints (SUPP 10-34: 15157, 15167, 15255, 15257) and ground-based contemporary official photographs taken during and after construction (MUN 5-297 pt2 290-1, 310-12, 328, 342-6; MUN 5-297 pt3 362-4, 376-8, 386-8, 422-4, 434-6, 449, 451-451A, 468-9, 495-6, 501-2, 521-3, 539-40, 641; MUN5-297 pt4 641,643; MUN5-297 pt5, 710G) held by the National Archives at Kew.
The Sulphur Burner-Heater Cooler Houses were tall, single storey, steel framed structures with ridge roofs covered with boards overlain by a ruberoid membrane and capped with ventilators. They were clad with corrugated iron sheets, leaving open the bottom third that housed the furnaces. Nevertheless, one photograph taken in 1917 (MUN 5-297 pt3 496) shows that a stone wall was later constructed to fill this space at the S end of the building which served Grillo Units 1 and 2. The E and W elevations of the furnace sections contained seven equally spaced rectangular windows just below the eaves and a tall double window placed centrally close to the foot of the cladding on the S. The Heater Cooler sections situated at right angles were very similar, but their roofs lacked vents. They had three equally spaced windows below the eves in their E and W gable-ends.
By contrast, the twenty vertical cylinders arranged in two parallel banks that comprised Sulphur Dioxide Cooler were not covered over. They were supported instead by a tall timber framework bolted directly to the foundations. A wooden framework also encased the three tall, square, lead-lined Scrubbing Towers that were provided for each unit. They were built upon a concrete platform above the brick piers and each was surmounted by a two-storey, weatherboarded, ridge-roofed building capped with a long central vent. This building, which reached 14m in height and was accessed by a metal stairway at its NNE end, contained the circulating acid tanks in its upper section and distributors on the floor below. One elevation in the upper section contained four windows, while the opposite one contained four vents and there was a door in each gable-end that led out on to a broad railed viewing platform. The lower part of the building differed, with one elevation containing three vents interspersed with two windows, while the other contained similar vents interspersed with narrower windows. In addition, there was a single window in each of its gable-ends. The buildings at the foot of the towers which contained the other circulating acid tanks were of two kinds. Where space was limited (as with Grillo Units 1 and 3), they appear to have been narrow, lean-to structures with sloping roofs covered with a rubberoid membrane and containing three equally spaced skylights. Their SSW gable-ends were weatherboarded and there was a central doorway on the SSW, immediately above which were three rectangular windows. However, where space was less limited (Grillo Units 2 and 4) the buildings were broader with an off-set doorway in the SSW gable-ends and four rectangular windows. The five lead-lined filter blocks provided for each Unit to which the Scrubbing Towers were connected were encased within individual wooden frames that rested upon the outer edges of the concrete-capped brick piers.
The chimney stacks built in the alley between the southern and central ranges immediately adjacent to the Converter Houses were made of steel plates. They were almost 20m in height and towered over the nearby buildings. The Converter Houses were considerably taller than the Sulphur Burner-Heater Cooler Houses to their ESE. They were superficially similar, as they were also single storey, steel-framed structures clad with corrugated iron sheets. However, their pitched roofs and massive ventilator cowls extending the full length of the buildings were all included in the steel framing. Light was provided by continuous glazing either side of the cowl, while three outshots at a much lower elevation on the NNE covered the firing ends of the Preheater furnaces. These were also provided with skylights and contained broad sliding doors, while two wickets were provided in the SSW elevation of the building. The outshots enclosing the blowers at each end of the Converter Houses were much lower in height and screened from the latter by a partition. They were also single storey, steel framed structures, clad in corrugated iron sheets, with a ridge roof and a glazed strip to either side that provided light to their interiors. Each contained broad sliding doors facing NNE.
The Sulphur Trioxide Coolers (NY 24480 65056 and NY 24579 65030) were raised well above the ground by means of steel stanchions with square concrete chamfered footings. Their tubing was enclosed within a frame similar to that which supported the Sulphur Dioxide Coolers and they were also not covered over. The Absorption Houses, which rose to about 12m in height to their NNE, were single storey, steel framed structures clad in corrugated iron sheets, with pitched roofs and massive ventilator cowls extending their full length. Light was provided by continuous glazing immediately below the cowls, while there was at least one pair of sliding doors in the ESE gable-end adjacent to their SSW corners. The outshot was of similar construction, but its roof sloped down from SSW to NNE. The oleum that was produced was pumped to sixteen storage tanks divided between two parallel batteries situated on top of tall brick walls. These were linked on the ESE by two towers supporting a smaller tank linked by a platform which could be accessed via metal ladders and walkways.
The two site plans show some additional small buildings that were not observed during fieldwork. One (NY 24516 65005) was situated midway along the alley immediately NNE of the path in the S range by which the hand-pushed trolleys delivered the sulphur charges to the furnaces. This was rectangular on plan and measured about 11m from WNW to ESE by 2.5m transversely. Its character is otherwise unknown. Two similar buildings (NY 24419 65027, NY 24603 64971) were situated respectively about 8m WNW and ESE of the S range. Both were T-shaped on plan and the more westerly (now situated within the sewage farm) measured about 6m from NNE to SSW by 3m overall, while the more easterly was a little smaller. Two further buildings (NY 24517 65055, NY 24547 65045) were located about 22m apart between the Absorption Houses. The more westerly, which was rectangular on plan, measured about 8m from NNE to SSW by 6m transversely. A contemporary photograph shows that it was a single storey, brick-built structure with a slate ridge roof and a central ventilator cowl. There were three windows in its ESE elevation and two windows either side of a door in its NNE gable-end. Its easterly neighbour was more irregular on plan and measured about 11m from WNW to ESE by 7m overall.
The buildings comprising the Sulphur Burner Heater Cooler Houses, the Converter Houses and the Absorption Houses were offered for sale by auction as part of Lot 504 on 22-25 July 1924 (HM Treasury 1925, 96, items 3-8; Carlisle City Archives DX 170/38)), when they were purchased by Messrs. J. Jackson & Co. Ltd of St Vincent Street, Glasgow (Carlisle City Archives DX 2040/3). After their removal only the foundations were left in place and these are visible on an aerial photograph (M124/13 04127) flown on 19 August 1940. This photograph also shows the foundations of a small building (NY 24537 65037) situated about 20m WSW of the SW corner of the more easterly Absorption House.
Visited by HES Heritage Recording (MMD and ATW), 6 April 2022