Swanscombe

Swanscombe Logo
White's Brand.

Snowcrete Logo
APCM's Snowcrete Brand.

Location:

Clinker manufacture operational: 1845 to 1990

Approximate clinker production: 40 million tonnes (11th)

Raw materials:

Ownership:

From the historical point of view, this is the most important of plant descriptions. Swanscombe's combination of size and longevity makes it uniquely important. However, like the comparable West Thurrock plant, it has proved extraordinarily difficult to obtain reliable technical information, and the article is likely to remain "work in progress" with much conjectural content for some time. Plans, photographs, data and firm dates are desperately sought! Please contact me with any relevant information or corrections.

Often known as White’s Works, and in earlier times, as Frost’s Works. Swanscombe was the longest-operating cement plant, and for much of its life, the biggest in the UK, from around 1846 to 1926, when it was overtaken by Bevans. It began life as a cement plant in October 1825, when James Frost commenced making his “British Cement” using wet process bottle kilns. The plant was acquired from Frost by Francis and White in 1833 and continued manufacturing the same product. The Francis / White partnership was dissolved in 1836 and John Bazley White and Sons commenced as a business on 1/1/1837, making both Roman and Frost’s cements at the Swanscombe site. I. C. Johnson was engaged as manager in 1838. His emulation of William Aspdin's cement (then made at Rotherhithe) was complete by October 1845, and the company advertised Portland cement for sale. By 1850, production was around 250 t/week of which more than half went for export to France where the first large scale use of Portland cement was for concrete in harbour work. Thanks to this market, Swanscombe became the largest plant. Large scale use in the UK only started around 1860, when the plant was capable of making around 640 t/week, using 23 bottle kilns. In 1864 there were 26 (688 t/week). In 1870 use of the “thick slurry” process began, in combination with an inefficient form of chamber kiln fed with partially pre-dried material. An 1872 valuation counted 32 kilns (870 t/week). From 1877, three Hoffman rings were installed, with 25, 28 and 30 compartments (output 625, 700 and 750 t/week). Although launched with some fanfare, they seem to have been phased out by the end of the century. The old bottle kilns were replaced with standard chamber kilns in the 1880s, and by 1898 there were 127 of these (3800 t/week at ~14 MJ/kg), plus 16 shaft kilns (Dietzsch kilns? 1200 t/week at ~4.4 MJ/kg) burning surplus dried slurry.

Following the establishment of APCM, the largest rotary kiln installation took place. APCM contracted for rights to install 32 kilns of standard Hurry & Seaman design: sixteen at Swanscombe, eight at Bevans, six at Wouldham and two at Arlesey. The Swanscombe kilns were installed first, in 1901-1902, although competitors' kilns were already in operation at Martin Earles and Shoreham (see article). In addition to the large number installed, the kilns were lengthened in two stages between 1905 and 1907 to keep them ahead of most competing installations, although Sundon A2 became the largest kiln in 1909. Most of the static kilns were decommissioned in 1901, but the most recent set of 14 chamber kilns was kept in reserve and used intermittently until the Bevans rotaries came on line in 1904. The rotary kiln system yielded around 7000 t/week by 1907, as confirmed by Davis, who gives a good photograph of the kiln installation. Some time between 1912 and 1922, kilns 1 & 2 were converted to coal dryers, and an extra stack was added between kilns 9 and 10. In 1923, kiln 6 was fitted with a waste heat boiler. The plant was described in detail in the APCM 1924 schedule.

The first rotary kiln set was replaced in 1929 with new “state of the art” kilns. The first three installed in 1929 together equalled the output of all the old kilns and the latter were decommissioned. The “good bits” of the old kilns were then re-assembled and augmented to construct the white cement kilns. The first two started in 1932, allowing the initial much smaller white kilns at Beddington to be shut down. A dedicated grinding and storage plant for white cement was constructed at the north end of the kiln house.

The plant ran through WWII making grey cement without interruption. On 2/3/1958, kiln B1 ceased grey clinker production and was converted for white production and renamed S5. This replaced the small white kilns, which were then used as make-up capacity for grey clinker, except in 1967-1970 and 1975-1976 when S3 and S4 were briefly used for top-up white production. Grey production was earmarked for closure with the start-up of Northfleet in 1970, but because of the poor performance of the latter, the Swanscombe grey kilns struggled on. They shut down in 1981, but B2 and B3 re-opened to take on sulfate resisting clinker following the closure of Holborough. The final shut-down in 1990 (white production being replaced by imported Aalborg white cement) ended 145 years of Portland cement production at this plant. The site has been entirely cleared and partially re-developed. Foundations are still visible.

Please contact me with any relevant information or corrections. I am particularly interested in firmer dates and statistics, pictures, plans.

Power Supply

The original plant was directly driven by steam engines. These were augmented with gas engines during the 1890s. At the time of the 1900 rebuild, the kiln section was electrically powered using generators driven by three double-expansion steam engines - two of 1000 HP and one of 800 HP. At the same time a central gas plant was installed to feed the gas engines driving the raw- and finish mills. With the 1929 rebuild, the plant finally switched to purchased electric power, from Barking, the Kent grid in 1933 and the National grid in 1938.

Rawmills

Washmills were always used. The 1901 plant had washmills in the worked out quarry south of London Road. There were three parallel lines, each consisting of two rough mills, two fine washmills and two screening mills. The plant was driven by gas engines supplied with gas from the plant's gas works. In the 1929 plant, new larger washmills were constructed in the same place, fed with chalk brought by rail from the quarry and clay slurry washmilled at Alkerden and pumped from there (~2 km). The main washmill system consisted of two 186 kW rough mills elevated to allow dumping flint from the base, used alternately. These were followed by two parallel lines, each consisting of a secondary washmill and three screening mills, powered by common 298 kW drives. Two larger washmills were added later. From 1976, these mills were used only for white cement, grey cement slurry (OPC and SRPC) being supplied by the Northfleet Swanscombe Park rawmills.

24 rotary kilns were installed in three stages:

Note: the 16 A-series kilns all went through two stages of modification, all having similar dimensions, but at slightly different dates. The modifications involved first removing the Hurry & Seaman two-stage coolers and extending the kilns forward, then adding an expanded back-end section.

Kiln A1

Supplier: Fellner & Ziegler
Operated: 15/3/1901-2/1912: subsequently (from 1919) used as a coal drier
Process: Wet
Location: hot end 560274,175097: cold end 560313,175103: entirely enclosed.
Dimensions:

Rotation (viewed from firing end): clockwise
Slope: 1/13.751 (4.170° = 7/8" per horizontal ft as per Hurry & Seaman)
Speed: 0.86 rpm
Drive: 30 kW
Kiln profile:

Cooler:

Cooler profile (states 2 & 3): 0×1486: 16154×1486: tyres at 2692, 13462: turning gear at 8077
Fuel: Coal
Coal Mill: all sixteen kilns indirect fired using common coal milling system - 8 Griffin mills, supplemented by (1907?) 3 Krupp tube mills for re-grind.
Exhaust:

Typical Output: state 1 - 33 t/d: state 2 - 45 t/d: state 3 - 70 t/d
Typical Heat Consumption: state 1 - 10.5 MJ/kg: state 2 - 10.2 MJ/kg: state 3 - 9.2 MJ/kg

Kiln A2

Operated: 3/1901-3/1912, from 1919 used as coal drier
Location: hot end 560275,175091: cold end 560314,175097: entirely enclosed.
Dates: state 1: 3/1901-4/1906: state 2: 6/1906-7/1907: state 3: 9/1907-3/1912
Identical in all other respects to A1

Kiln A3

Operated: 3/1901-12/1924
Location: hot end 560276,175085: cold end 560315,175091: entirely enclosed.
Dates: state 1: 3/1901-4/1906: state 2: 6/1906-7/1907: state 3: 9/1907-12/1924
Identical in all other respects to A1

Kiln A4

Operated: 3/1901-6/1928
Location: hot end 560277,175079: cold end 560316,175085: entirely enclosed.
Dates: state 1: 3/1901-4/1906: state 2: 6/1906-7/1907: state 3: 9/1907-6/1928
Identical in all other respects to A1

Kiln A5

Operated: 4/1901-11/1928
Location: hot end 560278,175073: cold end 560317,175079: entirely enclosed.
Dates: state 1: 4/1901-3/1906: state 2: 7/5/1906-7/1907: state 3: 9/1907-11/1928
Identical in all other respects to A4

Kiln A6

Operated: 5/1901-1/1929
Location: hot end 560279,175067: cold end 560318,175073: entirely enclosed.
Dates: state 1: 5/1901-3/1906: state 2: 7/5/1906-6/1907: state 3: 8/1907-1/1929
Exhaust: as other kilns but 1923-1929 a waste heat boiler was placed between kiln and flue.
Identical in all other respects to A4

Kiln A7

Operated: 6/1901-4/1929
Location: hot end 560280,175061: cold end 560319,175067: entirely enclosed.
Dates: state 1: 6/1901-12/1905: state 2: 2/1906-6/1907: state 3: 8/1907-4/1929
Identical in all other respects to A4

Kiln A8

Operated: 8/1901-7/1929
Location: hot end 560281,175055: cold end 560320,175061: entirely enclosed.
Dates: state 1: 8/1901-12/1905: state 2: 2/1906-5/1907: state 3: 7/1907-7/1929
Identical in all other respects to A4

Kiln A9

Operated: 9/1901-7/1929
Location: hot end 560282,175049: cold end 560321,175055: entirely enclosed.
Dates: state 1: 9/1901-12/1905: state 2: 2/1906-5/1907: state 3: 7/1907-7/1929
Identical in all other respects to A4

Kiln A10

Operated: 11/1901-7/1929
Location: hot end 560283,175043: cold end 560322,175049: entirely enclosed.
Dates: state 1: 11/1901-12/1905: state 2: 2/1906-4/1907: state 3: 6/1907-7/1929
Identical in all other respects to A4

Kiln A11

Operated: 1/1902-7/1929
Location: hot end 560284,175037: cold end 560323,175043: entirely enclosed.
Dates: state 1: 1/1902-10/1905: state 2: 12/1905-3/1907: state 3: 5/1907-7/1929
Identical in all other respects to A4

Kiln A12

Operated: 1/1902-7/1929
Location: hot end 560285,175031: cold end 560324,175037: entirely enclosed.
Dates: state 1: 1/1902-10/1905: state 2: 12/1905-3/1907: state 3: 5/1907-7/1929
Identical in all other respects to A4

Kiln A13

Operated: 2/1902-7/1929
Location: hot end 560286,175025: cold end 560325,175031: entirely enclosed.
Dates: state 1: 2/1902-10/1905: state 2: 12/1905-2/1907: state 3: 4/1907-7/1929
Identical in all other respects to A4

Kiln A14

Operated: 4/1902-6/1929
Location: hot end 560287,175019: cold end 560326,175025: entirely enclosed.
Dates: state 1: 4/1902-10/1905: state 2: 12/1905-1/1907: state 3: 3/1907-6/1929
Identical in all other respects to A4

Kiln A15

Operated: 5/1902-6/1929
Location: hot end 560288,175013: cold end 560327,175019: entirely enclosed.
Dates: state 1: 6/1902-10/1905: state 2: 12/1905-12/1906: state 3: 2/1907-6/1929
Identical in all other respects to A4

Kiln A16

Operated: 6/1902-6/1929
Location: hot end 560289,175007: cold end 560328,175013: entirely enclosed.
Dates: state 1: 5/1901-9/1905: state 2: 11/1905-11/1906: state 3: 1/1907-6/1929
Identical in all other respects to A4

Kiln B1 (=S5)

Supplier: FLS
Operated: 24/6//1929 to ?12/1990
Process: Wet
Location: hot end 560299,174971: cold end 560417,174991: hot end enclosed.
Dimensions: (metric)

Rotation (viewed from firing end): clockwise
Slope: 1/25 (2.292°)
Speed: 0.426-1.23 rpm: in 1958 slowed to 0.343-0.99 rpm
Drive: 90 kW
Kiln profile:

Cooler:

Fuel: 1929-1958 coal: 1958-1990 oil: from 1985, some landfill gas was used, and some petcoke was used from 1990.
Coal Mill: Initially direct fired with a British Rema ring-roll mill. Subsequently, direct: 2 Atritors.
Exhaust: originally to stack via ID fan. An electrostatic precipitator was added before the ID fan in 1935.
Typical Output: 1929-1937 358 t/d: 1937-1945 365 t/d: 1945-1952 372 t/d: 1952-1958 370 t/d: 1958-1990 (white) 317 t/d
Typical Heat Consumption: 1929-1937 7.34 MJ/kg: 1937-1945 6.94 MJ/kg: 1945-1952 6.83 MJ/kg: 1952-1958 7.17 MJ/kg: 1958-1990 (white) 8.49 MJ/kg


Kiln B2

Supplier: FLS
Operated: 22/7/1929-3/1981, 4/8/1984-?11/1990
Process: Wet
Location: hot end 560297,174980: cold end 560416,175000: hot end enclosed.
Dimensions (from cooler ports): metric 120.00 × 3.450B / 2.850CD
Rotation (viewed from firing end): clockwise
Slope: 1/25 (2.292°)
Speed: 0.426-1.23 rpm
Drive: 90 kW
Kiln profile (from cooler ports): -2800×3450: 33200×3450: 36000×2850: 120000×2850: tyres at 2000, 12800, 27200, 44400, 66000, 87600, 109200: turning gear at 47250
Cooler: Unax planetary 12 × 5.67 × 1.200
Fuel: Coal, except 2/1960-4/1968 Oil, 4/1968-2/1974 mixed coal/oil (average 40% oil). From 1987, coal partially replaced by up to 45% petcoke and some landfill gas.
Coal mill: as B1 until ?1974, then direct: PHI 75 kW MPS 100 roller mill
Exhaust: originally to stack via ID fan. An electrostatic precipitator was added before the ID fan in 1935.
Typical Output: 1929-1933 358 t/d: 1933-1946 367 t/d: 1946-1960 369 t/d: 1960-1968 387 t/d: 1968-1971 350 t/d: 1971-1974 401 t/d: 1974-1978 369 t/d: 1978-1990 345 t/d
Typical Heat Consumption: 1929-1933 7.44 MJ/kg: 1933-1946 7.01 MJ/kg: 1946-1960 7.04 MJ/kg: 1960-1968 7.75 MJ/kg: 1968-1971 8.03 MJ/kg: 1971-1974 7.36 MJ/kg: 1974-1978 7.13 MJ/kg: 1978-1990 7.43 MJ/kg


Kiln B3

Operated: 8/7/1929-3/1981, 19/8/1984-?12/1990
Location: hot end 560296,174989: cold end 560414,175009: hot end enclosed.
Typical Output: 1929-1933 358 t/d: 1933-1946 367 t/d: 1946-1960 370 t/d: 1960-1968 376 t/d: 1968-1971 346 t/d: 1971-1974 368 t/d: 1974-1978 363 t/d: 1978-1990 351 t/d
Typical Heat Consumption: 1929-1933 7.52 MJ/kg: 1933-1946 7.01 MJ/kg: 1946-1960 7.03 MJ/kg: 1960-1968 7.85 MJ/kg: 1968-1971 8.04 MJ/kg: 1971-1974 7.33 MJ/kg: 1974-1978 7.10 MJ/kg: 1978-1990 7.47 MJ/kg
Identical in all other respects to B2


Kiln B4

Supplier: Vickers Armstrong
Operated: 15/09/1935-3/1981
Process: Wet
Location: hot end 560286,174997: cold end 560376,175012: hot end enclosed.
Dimensions:

Rotation (viewed from firing end): clockwise
Slope: 1/20 (2.866°)
Speed: 1.00 rpm
Drive: 172 kW
Kiln profile:

Cooler: Reflex “Recuperator” planetary 12 × 15’6”× 3’11⅜” (metric 12 × 4.72 × 1.203)
Fuel: Coal, except 2/1960-4/1968 Oil, 4/1968-2/1974 mixed coal/oil (average 40% oil)
Coal Mill: direct: Ernest Newell 150 kW ball mill
Exhaust: to stack via ID fan and electrostatic precipitator.
Typical Output: 1935-1939 471 t/d: 1939-1954 449 t/d: 1954-1960 428 t/d: 1960-1968 404 t/d: 1968-1971 373 t/d: 1971-1974 448 t/d: 1974-1981 478 t/d
Typical Heat Consumption: 1935-1939 7.43 MJ/kg: 1939-1954 7.38 MJ/kg: 1954-1960 7.78 MJ/kg: 1960-1968 8.54 MJ/kg: 1968-1971 7.62 MJ/kg: 1971-1974 7.79 MJ/kg: 1974-1981 7.53 MJ/kg


Kiln S1

Supplier: made up from A-kilns, with new nose and burning zone from Vickers Armstrong. It was not Kiln A1.
Operated: 1932-1939, 1947-1958, 1960-21/6/1966
Process: Wet
Location: hot end 560274,175097: cold end 560313,175103: entirely enclosed.
Dimensions: 132’8½”× 8’10¼”B / 6’3½”C / 7’10½”D (metric 40.45 × 2.699 / 1.918 / 2.400)
Rotation (viewed from firing end): clockwise
Slope: 1/13.8 (4.156°)
Speed: 0.86 rpm
Drive: 30 kW
Kiln profile: 0×1734: 1118×1734: 4229×2699: 9782×2699: 12243×1918: 31864×1918: 33236×2400: 40450×2400: Tyres at 1651, 12852, 21082, 28473, 36398: turning gear at 17234.
Cooler: quencher then centre-discharge rotary shared with S2: 23’0” × 3’1½” (metric 7.01 × 0.953)
Cooler profile: 0×724: 1092×953: 3505 outlet: 5918×953: 7010×724: Tyres at 1372, 5638.
Fuel: Oil on white, Coal on grey
Exhaust: direct to common flue, suction being provided solely by the stack.
Typical Output: 1932-1939 (white) 66 t/d, 1947-1958 (white) 73 t/d, 1960-1966 (grey) 83 t/d
Typical Heat Consumption: 1932-1939 (white) 14.7 MJ/kg: 1947-1958 (white) 13.6 MJ/kg: 1960-1966 (grey) 10.4 MJ/kg


Kiln S2

Operated: 1932-1939, 1946-1958, 1960-22/8/1966
Location: hot end 560275,175091: cold end 560314,175097: entirely enclosed.
Identical in all other respects to S1


Kiln S3

Operated: 1937-1940, 1946-1962, 1964-1970, 1975-1976
Location: hot end 560276,175085: cold end 560315,175091: entirely enclosed.
Cooler: quencher then rotary cooler: 14’0”× 3’1½” (metric 4.27 × 0.953)
Cooler profile: 0×953, 3658×953, 4267×826: Tyres at 914, 3353.
Typical Output: 1937-1940 (white) 68 t/d: 1946-1958 (white) 75 t/d: 1959-1966 (mainly grey) 86 t/d: 1967-1970 (white) 75 t/d
Typical Heat Consumption: 1937-1940 (white) 14.5 MJ/kg: 1946-1958 (white) 13.5 MJ/kg: 1959-1966 (mainly grey) 10.65 MJ/kg: 1967-1970 (white) 13.3 MJ/kg
Identical in all other respects to S1


Kiln S4

Operated: 1949-1962, 1964-1970, 1975-1976
Location: hot end 560277,175079: cold end 560316,175085: entirely enclosed.
Identical in all other respects to S3



Sources:

The following is a transcript of an anonymous article that appeared in the London Standard on Monday, 24 August 1874, page 6.

By 1874, the overwhelming majority of people of the region between Dartford and Gravesend were employed in the cement industry. The largest producer and employer was the Swanscombe plant of John Bazley White & Brothers. As at many other locations, long after the establishment of extractive industries, relatively well-heeled commuters started to move into the area, and began to complain about the local industry, bringing to bear legal resources that the earlier working-class residents could never have afforded. As it turned out, their efforts to curtail the industry failed, and the plant continued in operation for another 116 years.

The demonstration was also described in The Building News on 28 August, and the article is quoted by Francis. It says that the complainant was S. C. Umfreville of Ingress Abbey. It says that the foreman (here called Walkland) stated the object of the proceedings was to "shut up all the cement works in the county".

THE SWANSCOMBE PORTLAND CEMENT WORKS.

The high road running through Northfleet, Stone, and Galley-hill, was, on Saturday, the scene of an unwonted demonstration. A procession of bloused workmen, their wives and children, to the number of between four and five thousand, accompanied by bands, and carrying numerous flags and banners, was on the march to the Rectory Grounds, Swanscombe. The main body of these people consisted of the employees of Messrs. J. B. White Bros. Portland Cement Manufactory, Swanscombe, and their friends. The occasion of the display needs a word of explanation. Certain of the inhabitants of Swanscombe and Northfleet state that their health is seriously affected by the smoke from the chimneys of the cement manufactory; others, that the vicinity of these works deteriorates the value of their property. Those finding reason for complaint have taken legal proceedings with a view to entirely suppressing the manufacture of Portland cement in the neighbourhood. To consider their position then, under this aspect of affairs, the workers belonging to Messrs. White's firm, and the tradespeople and residents of the several immediate parishes, turned out to enter their solemn protest against any disturbance of the existing state of things. The country for several miles round was profusely decorated with flags, many of which bore inscriptions, such as " Honest labour should be well protected," "Live and let live", "Success to all cement manufacturers". Before the procession marched a man bearing a loaf aloft on a spear, behind came several with paintings representing the cement factories, over which were written the significant words— "Our daily bread". The occupations of some of those depending for their livelihood upon the manufactories were brought very visibly before the eye. The boatmen were drawn along the road in an immense boat with sails unfurled and pennons flying; the carrier had his van. Those trades which did not admit of so forcible a representation as the foregoing were depicted, in their leading characteristics, upon canvas. Northfleet and Swanscombe contain a population of about 6500 inhabitants (Note A01), the majority of whom, either directly or indirectly, derive their sustenance from cement manufactories. In the one establishment of the Messrs. White 800 men and boys are employed, and the number of souls depending upon the exertions of these is 4000. The average earning for a man is 30s. a week; the total weekly wages paid is upwards of £1000 (Note A02).

Shortly after four o'clock in the evening the processionists assembled in the meadow appointed for the purpose at Swanscombe, and the Rev. T. H. Candy, rector of the parish, was called upon to preside. His testimony with regard to the alleged nuisance was that during the six years of his residence the number of deaths had been steadily diminishing, even although the population was increasing. At present it is about eleven or twelve in 1000 (Note A03). The parish of Swanscombe numbers 2000 people, which is double what it was 20 years ago (Note A04). After the reverend chairman, a host of working men came to testify their soundness in wind and limb. John Bardoe, a bricklayer, had been employed in the cement works for 36 years. He was as healthy as could be desired, and knew no cause of complaint in the neighbourhood, save one— that cement workers were universally troubled with large families. This sally produced a good deal of mirth, which rather increased when the philosophic bricklayer reproved the audience in the following terms: — "It's no laughing matter, mind you, I've got the trouble to bear on my own shoulders". James Walkley, a man of about 24 stones (Note A05) weight, remarked that he was "one of the sick ones". He had been engaged in cement making since 1830, during which time he had not been a day either sick or idle. Before the factories had been established in the district ague had been very common (Note A06); but, owing to the smoke from the furnaces heating the air, the disease did not amount to one-fourth its former prevalence. Hugh Mitchell, the secretary to the working men's benefit club, had been engaged in the works for seventeen years. The health and comfort of the men and their families were shown in the fact that at Christmas there was a balance of £123 14s. to the credit of the club, which sum was apportioned among the men in shares of 8s. 6d. each. The Rev. Mr. Odell, Wesleyan minister, explained that an application had been made to the attorney for the prosecution of the indictments to allow the case to stand from October till the following sessions, in order that there might be an opportunity to judge of the effect of the extensive improvements in process of being carried out at the manufactories. The reply was that no alterations or improvements would satisfy the complainants, who believed the nuisance to be irremediable (groans) (Note A07). Nearly £4,000,000 had been paid for labour in the various cement works since they were commenced. Fathers had placed their sons in the factories, and the latter, in their turn, brought their children up to the same employment. They could not consent to the wishes of those who wanted the position of the works changed; as the manufacture could be only carried on where nature had provided a suitable place (Note A08). The Rev. Mr. Shrewsbury, Congregationalist, said the experiment which had been made within the last two years for diminishing the smoke had proved satisfactory. He lived a great deal nearer the chimneys than some of those who complained, and only once or twice in the period of the four years of his residence had he noticed anything like smoke in his neighbourhood. It had never in the slightest degree injured his health. With regard to the deterioration of property, three or four years ago there were 18 empty houses worth from £40 to £80 per annum to the landlord. These were now all let except two. A portion of land near the factories of the Messrs. White had been offered eight years ago for £500 per acre; only a short time since it was valued at £1000 per acre (Note A09). Those chronically sick persons who were affected by the smoke, and their number could be counted upon the fingers, would have to leave the vicinity. Large interests could not be disturbed because a few people murmured. James Ward, aged 60 years, had been employed 40 years in the cement works. He was now "open to run or jump with the best of them". Mr. Heys proposed a resolution to the effect that the proceedings against Messrs. White were unjustifiable. He had an experience of fifteen years, close under the chimneys, and neither he nor his family during that time had been affected by the smoke. The only nuisance in the neighbourhood was the marshes, the owners of which, he thought, should be compelled to drain them. The resolution was adopted. Mr. D. Pearse moved a resolution to the effect that the meeting regarded with anxiety the misery that would ensue should opponents succeed in closing Messrs. White's establishment. The resolution was adopted. The Rev. Mr. Shrewsbury moved a resolution to the effect that the meeting was cheered by the idea that those who figured in the prosecution would considerably modify their mode of procedure on maturer reflection. The Rev. Mr. Odell, in seconding the resolution, maintained that if the manufactory were to be closed "some 20,000 Kentish men would know the reason why" (great cheering). The testimony of the masters of the ships in the river was, that health of the boys on board the Goliath, Chichester, or the other vessel, had not been in any way affected by the smoke from the factories. The resolution was adopted. A protest against the pending proceedings, signed by a great number of those who were prevented from attending the meeting, was read; and a protest of a somewhat similar character was extensively signed in the field. Votes of thanks to the chairman and principal speakers brought the proceedings to a close.

The following slightly sardonic plant description comes from the Kent and Sussex Times, 17/03/1877, p6, apparently a re-print from the Dartford Chronicle (reference unknown). It depicts the plant at a transition point, with the old Goreham/White patent bottle kilns being replaced by Hoffman kilns. The dispute described above ended in a court case that was finally resolved three weeks before this article, in favour of White's, the installation of the new kilns being a major factor in their favour, although it is interesting to note that they had not yet been commissioned.

A VISIT TO MESSRS. WHITE'S SWANSCOMBE CEMENT WORKS.

In continuation of our tour through the scenes and manufactures of the Dartford district, we present our readers this week with a sketch of the vast cement works carried on by Messrs. White and Bros., at Swanscombe. We shall confine our observations entirely to the technical and mechanical aspects of the manufactory, which will, we think, by their strong local and scientific interest, sufficiently commend themselves to our readers. The works lie between Greenhithe and Northfleet, in the parish of Swanscombe, and were, we believe, commenced in a much humbler form by Mr. Frost in 1823, from whom they were purchased by Mr. White in 1833, attaining their present magnitude by a steady development of the cement trade both at home and abroad.

The approach from the river slope, past Ingress Abbey, shews the whole of the works, at a coup d'œil, snugly ensconced in a hollow, from which 18 tall chimneys shoot up into the sky. The upper air around the spot is at times smoky, but below, or on approach, very little is perceptible. Arrived at the entrance we are soon busily occupied in keeping a watchful eye, with a view to personal security, on the loaded cars, which shoot to and fro over the interlaced railways leading to the river and about the works. Our passport presented and approved, we find ourselves confided to the care of Mr. Glover (Note B01), the manager, whose technical knowledge renders him an excellent cicerone and moreover a good companion. Winding our way through the kiln passages, with which the works are tunnelled everywhere, in rabbit-burrow fashion, behold us standing at the foot of the cliff, which to cut well back inland, and presents a perpendicular scarp, from 70 to 80 feet deep. Thence the freshly cut chalk, snowy white in the light, dimly blue in the shadow, is being cut at mid-level, and lowered into wagons by means of slots cut in the cliff, the passages and apparatus going under the name of mills. The material is then conveyed to the mixing mills, with any flints which may happen to have escaped notice, as these latter are by no means looked upon as desirable accompaniments, and are consequently picked out. The portion excavated forms a large pit, some 20 acres in extent; the entire works, chalk-land, &c., covering 60 or 70 acres. Before we leave to follow the chalk cars, we must give parting glance at the fine new Hoffman kiln, which is now nearly completed, and occupies a central position in the pit. It is a raised oblong structure, 250 feet by 90, with 16 compartments, through which the fumes are drawn off by a colossal shaft 260 feet high. The structure was built under the superintendence of Mr. Glover (Note B02). Passing on to the chalk cars, which have, no doubt, been waiting for us too long, we ascend a few steps and find ourselves gazing down into a huge circular receptacle, in which, with hideous discordant clangour, the chalk we have seen, is being mixed with the other requisite - the clay - by a revolving wheel furnished with tines, the passage of which latter over the floor amongst the stray flints which have found their way in, causes the noise, which is, to say the least, considerable. These same flints afford an interesting illustration of the formation of pebbles by waves &c., for, by dint of rolling about during two or three days, and incessant friction against each other and the tines, they become changed from the well-known large angular flints of the chalk, into most respectably polished pebbles. Mingled with little of the mixture in which they lie, they form an excellent concrete. The clay lies beside us: it is an alluvial deposit from the estuaries and creeks of the Medway, and is of a dark gray colour, very different from our ochreous tertiary soils. It has moreover, a greasy soapy feel, suggestive of a large percentage of alumina.

The wash mill or mixing apparatus we were examining (which is only one of several) is worked by a compound engine of 250 horse power, and the "slurry", as the grey slushy-looking mixture is called, after flowing through into an adjoining house, is lifted by elevating wheels to an upper storey, whence it is passed between horizontal millstones and comminuted to a further extent by a process of rapid revolution until ready to be pumped away. As eight pairs of these stones here combine to produce a deafening roar, we are only too delighted to pass on to the next point of interest - the engine room. We learn that there are three other of these mill houses with six stones each. The engine also drives a machine for drawing the tramway cars up the inclines. We should state that the engines in each house are very powerful: this one is supplied with steam by three boilers, and works on the composite principle, with steam at 40 lbs pressure. The cylinders are short, but of great breadth; the piston has three feet stroke, and the crank a throw if eighteen inches. In the centre of the crankshaft is a huge fly-wheel weighing 14 tons, and 16 feet in diameter. Some of the cement has been utilized to form a capital concrete flooring outside the engine house. Pass we on now to the drying process. The "slurry" or mixture of chalk and clay, is pumped, by a motion obtained from the engine, into a large central pipe, from which radiating branches carry the mixture to all parts of the works. By an excellent and economical adaptation, the waste heat from the kilns is drawn through flues beneath and around the drying floor (Note B03), on which the compound flows in thick treacly stream from the pipe. It speedily solidifies and cracks in every direction until, a sufficient dryness having been obtained, the stuff is removed into masses about a foot square. It has now the appearance of a number of fire bricks fused together, and is vesicular in structure. My guide informs me that it has acquired a new name, and that the old one must be heard of no more, so we will follow the "dried slip", as it is now called, on its way to the kilns. It put into barrows with a sufficient quantity of coke and burned at nearly a white beat. The product is semi-vitrified and of a dark grey colour. Once more the name is changed, and we now have to deal with the product as "clinker". In this last operation, the material has undergone a great chemical change. Originally we had a mechanical mixture of chalk, which is almost entirely carbonate of lime, and clay, which we may call silicate of alumina. At the intense heat to which the mixture is subjected in the kilns, the lime parts with the carbonic acid, which with a varying proportion of carbonic oxide and watery vapour passes up the tall shaft. It then unites with a portion of the silicic acid in the clay, so as to form a double silicate of lime and alumina with an excess of caustic lime. It only now remains to grind up the contents of the kiln, for which purpose a quantity of the crude material is transferred to crushers, worked by the ubiquitous steam-power. The product is the raised by chain elevators to a series of smaller mills, whose rapidly revolving stones subject it to a still further process of attrition. The chamber is filled with a dun-coloured cloud, and the floor is deeply covered with the fine particles; but, though the visitor speculates as to irritated lungs and blocked wind cells, the workmen, one and all, seem healthy enough, and assure us that they experience no inconvenience. Below, the final process of packing is being carried on. The fine powder passes down a shoot and to received into sacks or casks. The sacks are filled at once; if, however, the cement is to be stored in the casks, it is allowed to cool, for, in the friction of the final grinding, it has attained a temperature of 140 degrees or even more. It is so fine that 95 per cent passes through a sieve having 2,500 holes to the square inch. This concludes the details of the manufacture, and nothing now remains but to notice the means by which the establishment is made, like some we have described elsewhere, self contained and independent of accident or delay from causes operating from without.

These portions of our tour are, in themselves, of great interest and more than worthy of a separate descriptive chapter, of far greater length that we are able to give in the brief record we have proposed. First as to the means of internal transit. Besides the tram cars and inclines, there are 3 little locomotives busily puffing and drawing loads varying from 30 to 60 tons. For the repairs, which the cars sometimes require, there is a "hospital", in which we find five or six men very busily employed. The engines have also a place of resort in case of accident, and in the engine factory we observe powerful drills, lathes, &c. at work, replacing broken guides, screws, shafts, bearings, &c. In the adjoining smithy are a number of forges, all worked by Giant Vaporifer. Yonder is a steam hammer, and on one side are small but powerful wind furnaces with crucibles and tongs, for any minor brass or iron-castings that may be required. We are inclined to think it is time to cry "Hold enough" - but no, not even yet is the end nigh. Here is the carpenter's shop, with its distinct lathes and appliances, and now we enter the cooperage. Any wonder we might have had, as to where the thousands of casks about the works came from, vanishes at once. The staves are first shown us in the rough - quite unshaped, and, to all intents and purposes, mere pieces of board. The cask heads lie round us in hundreds of piles. How are they fashioned into such symmetrical curves? Surely by some slow and tedious process. But no! We are to be shown the making of the tops and bottoms, all at once, and in an instant. Six of these rough boards are put into a circular grip. A handle is turned by a small boy, and we stand aloof for a moment. There is a whir of wheels, a blinding shower of shavings and fragments for three or four seconds, the machinery is stopped, and there are our casks-head and bottom complete. Now for the staves. The same marvellous ingenuity has not failed here. The contracting cooper, Mr. Hewitt, shews us, with just pride, an apparatus he has invented, which fashions each stave without risk or danger to the limb, in a single second. A "cam" gives the required approximation and separation to a pair of circular saws; half-a-dozen of the boards are passed through and come out perfect staves, shaped at both ends. We are lost in admiration at this, really one of the most ingenious appliances we have seen. It will fashion 60 staves a minute, and yet we are told that the invention, which has been very properly patented, is, in the present form, a mere rough piece of experimental apparatus (Note B04).

And now to conclude. Looking at the present and past condition of this centre of human ingenuity and energy, not only as a whole, but in its smallest detail, we can see the secret of its success. Steady, plodding perseverance at the head, and a readiness to further the ideas and suggestions of the subordinate workmen, have borne their fruit in conception and consummation of the schemes, by which this vast establishment has attained its present proportions and prosperity.

I have not found a description of the plant as re-built in 1900. However, the 1929 rebuild was described in a 1929 APCM publicity handout, subsequently re-printed in Cement and Cement Manufacture, 3, 1930, pp 6-18. It is believed to be out of copyright.

Values of imperial units (as of 1930) used in the text (alphabetical order): 1 inch = 25.399956 mm: 1 ft = 0.30479947 m: 1 yard = 0.91439841 m: 1 acre = 0.40468424 Ha: 1 cubic ft = 0.0283167 m3: 1 gallon = 4.5460756 dm3: 1 lb = 0.45359234 kg: 1 cwt (hundredweight) = 50.802342 kg: 1 ton = 1.01604684 tonne: 1 HP (horse-power) = 0.7456998 kW: 1 psi (pound-force per square inch) = 6.89478 kPa.

The Swanscombe Works of the Associated Portland Cement Manufacturers, Ltd.

About a hundred years ago a factory was established at Swanscombe, Kent, for the manufacture of Frost's cement, one of several cements of similar character which were approximately contemporary with Aspdin's Portland cement. This factory had on its staff in the early days the late I. C. Johnson, one of the pioneers in the development of Portland cement, and it has kept in the forefront of progress in cement manufacture throughout its century of existence. The factory was in the possession of the White family for very many years until the formation of the Associated Portland Cement Manufacturers, Ltd., in 1900. Some of the earliest rotary kilns erected at cement works in Europe were put in at Swanscombe (Note C01), sixteen kilns 60 ft. long being in process of erection in 1900. These units were afterwards lengthened to 130 ft., and other alterations and improvements introduced from time to time as the technique of their use was developed.

With the accelerated progress made in rotary-kiln design during recent years, however, it became clear that the Swanscombe kilns, with their numerous alterations and additions, had served their useful life. It was therefore decided to scrap them entirely (Note C02) and build new rotary kilns of the very latest design, and at the same time to reconstruct and modernise the whole factory to give an output of about 400,000 tons of cement per annum, of the very highest quality, including the well-known "Ferrocrete" rapid-hardening Portland cement.

In this reconstruction work difficulty was occasioned by the fact that the site was very limited and the works had to be kept running. A considerable amount of clearing had to be done, and the necessity for continuing manufacture involved delays and temporary expedients in order to prevent the stoppage of essential portions of the plant (Note C03). The work was, however, facilitated by the fact that no power plant was required, the necessary electric power being taken from the County of London Company's generating station at Barking.

Raw Materials

Ample supplies of chalk and clay are available to supply the output named for very many years (Note C04).

Dealing first with the clay, a deposit about a mile from the plant is now being worked (Note C05). This is washed in the pit and pumped to the works in the form of slurry, and discharged into storage and mixing tanks. This clay slurry is fed to the main washmills in the correct proportion by means of a large elevator 60 ft. long, with a rubber belt 30 in. wide, and fitted with two lines of buckets. The motor driving this elevator is controlled by a special electrical timing device in such a way that when the operator at the washmill pushes a button to start the hoist-tippler handling the chalk (referred to later) the same movement also starts the clay elevator and allows it to run for a pre-determined period, after which it automatically stops and remains so until the operator again pushes the button. Arrangements are, of course, included so that when necessary clay can be added independently of the operation of the chalk-tippler, and similarly the tippler can be worked, if necessary, without any clay being delivered (Note C06).

Washmills

The chalk was formerly brought to the washmills in 3-ton tippler-trucks running on 3 ft. gauge track with outside flanges, and it was decided to substitute standard-gauge trucks and track and to make arrangements for 10 to 12 tons of chalk to be tipped direct to the washmill at one time, and for at least 120 tons of chalk to be washed per hour.

Two new heavy preliminary washmills are each 30 ft. diameter revolving at 11 r.p.m. and driven by a 250-HP motor through a totally-enclosed spur reduction gear which gives a speed reduction from 730 to 95 r.p.m. on the line shaft. These roughing-mills are each fitted with heavy cast-steel gratings, and are built on piers so that when they are washed out the flints can be swept through a hole in the bottom of the mill direct into railway trucks. A special slow-motion gear is fitted to the mill motor to enable this sweeping operation to be satisfactorily performed. One of the mills maintains the full output, so that the other may be stood by for cleaning and repairs. Owing to the site arrangements it was impossible to tip the chalk trucks to these mills without first elevating them, and for this purpose a hoist-tippler was installed. This tippler lifts the trucks 23 ft., and is arranged so that by means of a heavy steel change-over flap it can deliver to either mill.

The slurry flows by gravity to either of two intermediate mills, but from the intermediate mills a slurry-wheel distributes the slurry equally over the finishing mills. This slurry wheel is 24-ft. diameter, and is fitted with two lines of buckets to enable it to deal with the full capacity of the mill. The two lines of mills each consist of one intermediate mill 20 ft. diameter with a speed of 23 r.p.m. and fitted with perforated plates, followed (after the elevator) by three 20-ft. diameter finishing mills running at 25½ r.p.m. and fitted with finer perforated plates (Note C07). Arrangements have been made for continually extracting, elevating, and washing the fine flint grit from the intermediate and finishing mills in spiral conveyor washers.

Each line of mills is driven by a 400-HP motor through totally-enclosed spur reduction gearing, giving a ratio of 485 down to 70 r.p.m. Each line has its own pump-house containing three sets of 12 in. by 15 in. plunger pumps, which are each direct-coupled through a worm-reduction gear to a 20-HP motor, the speed of the pumps being 9.5 revolutions per minute. These pumps work at a pressure of from 60 to 80 lbs. per sq. in. and deliver the slurry to four reinforced concrete air-agitated correction tanks, each 17 ft. diameter and 30 ft. deep and each capable of holding 6,500 cu. ft. of slurry (Note C08). An air-blowing system is installed, and when working according to the original design a complete cycle of operations takes about 22 hours, so that on this basis each tank is in the mixing period for just over half an hour, during which time it is "blown" six times consecutively (each "blow" lasting about 15 seconds). With this system of blowing, the size of the receiver is important, as it is "blown" empty each time, and the pressure at which the "blow" takes place is governed by the height of the slurry in the tank.

This arrangement is advantageous when the tanks are used for storage, but at Swanscombe they are only used for adjusting purposes and in order to make sure that the slurry is correct before it enters the main mixers. It has, therefore, been found more convenient to give each tank four or five consecutive "blows" as soon as it has been filled from the washmill so as to ensure thorough mixing of the slurry before it is passed to the storage mixers. These consist of one rectangular tank 250 ft. by 66 ft. fitted with travelling mechanical stirrers, and four circular tanks 66 ft. diameter; the latter fitted with air agitating jets. This has given entire satisfaction (Note C09).

The pump-houses for the mixers have been reconstructed and the pumps grouped into two separate houses, one group drawing from the rectangular mixer and one from the four circular mixers. Each pump-house contains three standard 12 in. by 15 in. slurry pumps directly-coupled through worm gear to 10-HP motors which pump direct to the kiln back-ends.

Rotary Kilns

The rotary kilns, three in number, have a capacity of 16 tons each per hour. They are 403 ft. long, the burning zone being 11 ft. 3 in. diameter by 127 ft. long, and the remainder of the kiln 9 ft. 4 in. diameter. Each kiln is mounted on seven sets of roller rings and bearings, the ring at the firing end being 25 in. wide and the others 15½ in.; they are all 6 in. thick. The rollers vary in diameter from 3 ft. 3 in. to 3 ft. 11 in. (Note C10)

The main driving spur-ring is 17 ft. 9 in. diameter, and gears with a 19-tooth pinion to which is coupled a further machine-cut spur reduction of 3.3 to 1 ratio. The remainder of the gear reduction is by means of a totally-enclosed gear which at the high-speed end is direct-coupled to a 120-HP variable-speed A.C. motor. The total speed ratio is 1 to 777.25, and is arranged to give a kiln speed of from 0.28 revolutions to 0.84 revolutions per minute.

The feed of slurry to the kilns is controlled by a "spoon-feed" gear coupled through totally-enclosed worm reduction to a 5-HP variable-speed D.C. motor (Note C11).

The coolers are of the "integral" type fitted around the firing end, and consist of twelve tubes per kiln, each 19 ft. 6 in. long by 3 ft. 11 in. diameter. About one-quarter of the length of each cooler, at the hot end, is brick lined, the remainder being fitted with chains (Note C12).

All three kilns are coupled through fans and by-passes to one reinforced-concrete chimney 250 ft. high. The induced-draught fans are capable of handling 6,000,000 cu. ft. of gas (Note C13), each with a water gauge of 3 in.

Coal Firing Arrangements

Unit coal pulverizers of the ring-roll type with classifiers are installed, each being capable of grinding up to six tons of coal per hour. Owing to the very high suction which the system of classification requires, combined with the high air velocity required in the burner pipe with this type of kiln and cooler, the fan installed for this purpose is of special construction. In addition to the main fan, which can give an air pressure of 10 in. in the delivery pipe (Note C14), a booster fan has also been provided.

The feed from the hoppers, each of which has a capacity of 90 tons, is by a cubimeter, with which has been incorporated a drum-type magnetic separator to ensure that all tramp iron is removed.

The main coal supply comes by water to the wharf, and in order to handle this a 5-ton electric crane has been installed capable of unloading coal from steamers at the rate of 100 tons per hour to a hopper mounted on travelling wheels, which in turn delivers to a bi-cable ropeway, also of a capacity of 100 tons per hour. This ropeway is 3,500 ft. long and delivers the coal either direct to steel bunkers over the mills or into a reserve store at ground level.

For handling the coal from the reserve store to the overhead hoppers, a 3½-ton travelling crane with a 35-cwt. grab has been installed, which can run the full length of the store and also over the pulverizer hoppers. The runway for this crane has also been extended so that coal can be grabbed straight from railway trucks and delivered to the hoppers. Advantage has been taken of the ropeway to provide for handling the gypsum to store; arrangements are also installed for feeding this gypsum direct to the tail ends of the clinker band-conveyors.

The clinker from the coolers is elevated and conveyed to the clinker hoppers entirely by troughed band-conveyors. These conveyors are in duplicate throughout, and are each 24 in. wide running about 250 ft. per minute. There are first a pair of level conveyors running underneath the coolers delivering to two pairs of inclined bands in series, which take the material to the top of the clinker hopper and then deliver through cubimeters on to a pair of shuttle conveyors each 115 ft. long which can be arranged to fill any portion of the clinker hoppers. This arrangement dispenses entirely with elevators for handling the clinker. The clinker hoppers, two in number, are of reinforced concrete, and each has a capacity of 1,400 tons; the hoppers are at such an elevation that the clinker can be delivered direct through table feed-gears to the ball-mills. The grinding-mill consists of 14 sets of ball-mills and tube-mills, the ball-mills being supported by a steel and concrete platform at such an elevation that the grit can be delivered through a short screw straight to the tube mills (Note C15). Each ball-mill and tube-mill is an independent unit driven by a 250-HP motor through totally-enclosed spur-reduction gearing. The spur-ring on the mill itself is also machine-cut and totally enclosed. All the motors and gears for these mills are contained in two separate rooms underneath the clinker hoppers. These motor rooms are ventilated and cooled by air washers working on the "plenum" system. The mills deliver to duplicate 18-in. spiral conveyors placed flush with the floor, which in turn deliver to a group of four elevators in the centre of the building. Any two of these elevators are capable of taking the full output of the mill, namely, about 100 tons per hour.

The ball-mills are ventilated first to the enclosed space over the clinker hoppers so as to settle the major proportion of the dust, and thence through the roof to the atmosphere. The tube mills and all the cement conveyors are ventilated by two cyclone bag-filter combinations. The whole of the system, including pipes, cyclone, filter, etc., is wrapped with felt, and so far has given complete satisfaction.

The cement is stored in warehouses which occupy an area of 37,200 sq. ft. and are capable of holding 20,000 tons of cement. The elevators mentioned in connection with the grinding-mill deliver the cement to duplicate band-conveyors which carry straight across the centre of the warehouse and in turn deliver to four similar conveyors running over the centre of the bins. The delivery from these bands to the bins is by means of throw-off carriages.

The bins, which are 68 ft. long, are arranged in two parallel rows with a 24-ft. space up the centre, which has a ground-screw on each side flush with the floor and just clear of the bin doors. A set of rails runs down the centre of the space, on which four sets of electrically-driven haulage gears, each with a 20-HP motor, can move for operating the drag scrapers by which the bins are emptied into the ground screws. These in turn deliver to a system of inclined band-conveyors and screw-conveyors delivering to hoppers over the packing machines. All these conveyors are direct-coupled through worm-reduction-gears to independent motors (Note C16).

Three lines of rails run parallel with the warehouse just outside the bin walls, and the packing plants are arranged on each side of these rails—bag packing on one side and cask and drum packing on the other.

The bag-packing plant consists of four two-spout machines fed from a 50-ton overhead hopper by means of an extracting-screw and circulating-elevator, thus securing a regular feed to the machines. The circulating elevator also deals with the spill. The packing machines are fitted with dust-collecting plant. After discharge from the filling machine the bags drop on to a short wire-belt conveyor, which in turn delivers them to a turntable 17 ft. diameter. Five loading points are brought successively under the end of conveyors, thereby reducing to a minimum the labour of stacking on the slings. From these turntables the cement is loaded on to trucks for transport to the wharf in heaps of 30 cwts. in slings by overhead cranes. Further rotation of the turntables brings the stacks round underneath two 30-cwt. overhead electric cranes. These are arranged so that they span the outer half of the turntable, and also the nearest line of rails, and the stacks of bags with sling complete are lifted from the turntable direct on the trucks. The trucks are standard gauge with a special flat platform, and are capable of carrying up to 15 tons of cement per truck.

In the cask and drum-packing plant the chief feature is six groups of mechanical jarring machines. Each pair of machines is fed by an overhead dial weighing machine, the platform of which carries a small hopper of about 5-cwts. capacity fitted with a gate-valve at the bottom. The supply of cement to each group—consisting of six machines—is from a hopper underneath one of the previously-mentioned screw conveyors, and is controlled by a pair of flow-and-return screws, each flow screw being fitted with three outlets and gate valves delivering to the hoppers on the weighing machines. The casks or drums after packing are lifted by similar cranes to those used for the bags and deposited on platform trucks for transport to the wharf.

Wharf

The works are situated some distance from the river, and the loaded cement is transported to the wharf in train loads of about 200 tons (Note C17). A reinforced-concrete jetty was constructed at this works over twenty years ago and is still in excellent condition. It was, however, inadequate for the duty now required. A new reinforced-concrete approach 128 ft. by 34 ft. has therefore been built; the original structure has also been strengthened and lengthened from 258 ft. to 468 ft., the extended portion being 54 ft. 9 in. wide so as to accommodate three lines of rails with two lines of track to carry portal-type cranes. The older portion of the pier is only 40 ft. wide, so that it will accommodate only two lines of rails and one line of crane track.

Two electric cranes have been installed, each of 30-cwt. capacity and capable of loading at the rate of 80 to 100 tons per hour. The depth of the water available at low-water spring tides will be 23 ft. The old coal wharf, which is 500 ft. long, has also been remodelled and deepened, and, as previously mentioned, a 5-ton portal electric crane has been installed for handling coal and gypsum on to the ropeway.

Electrical Plant

As stated earlier, the whole of the power used on the works is purchased. The additional supplies required in connection with the reorganisation necessitated an extension of the sub-station in order to provide for the total load of 5,000 kW now required. The Supply Company's transmission system operates at 33,000 volts and the reduction to 3,000 volts—at which the supply is taken—is by transformers in the Power Company's sub-station on the works.

The works' installation commences at the 3,000 kV switchgear controlling the supply to the factory. This is an eight-panel switchboard built up of air-insulated truck-type units. This switchgear is housed in a switchroom adjacent to the Supply Company's 3-kV switches, and so arranged that the bus-bars of the two equipments are in line so that with this arrangement the bus-bars are continuous for the two switchboards whilst each is separately housed. The feeder panels in the sub-station control seven radial feeders so interconnected that a duplicate 3,000-volt supply is delivered to six local sub-stations.

The outputs of the motors vary from 400 HP to ½HP, and, with the exception of the 500-volts 120/40-H.P. variable-speed A.C. commutator driving the kiln motors, 3,000 volts are used direct on motors of 100 H.P. and above and 500-volts (obtained through 3,000/500 transformers) on motors below this power. Lighting is carried out at 110-volts, 3-phase, obtained through transformers at each sub-station.

Each of the sub-stations is equipped with the necessary switchgear and transformers to give the power and lighting requirements of its own section of the factory. This lay-out permits of the isolation of the supply to any section without interfering with others, and facilitates the obtaining of power consumption and costs of each manufacturing process. The sub-stations are designed on the same lines, the type of equipment in each being identical. The largest is the grinding-mill and packing plant sub-station which is equipped with a 3,000-volt truck-type switchboard, a 500-volt ironclad switchboard of the draw-out type, and the necessary transformers. Space available for the site of this and other sub-stations was limited, and the transformers are mounted on the roof of the sub-station, which is a reinforced concrete building built on the grinding mill.

All motors are of the enclosed protected type, the large motors down to 100 H.P. being 3,000-volt slip-ring machines of standard design controlled by truck cubicles and heavily rated liquid starters. Motors under 100 H.P. are 500-volt end-shield roller and ball-bearing machines of special enclosure, with all ventilating openings on the vertical, and fitted with fans passing a high-velocity cooling air through the windings and cores; the effect of the enclosure and the ventilating system is to prevent the settlement of dust in motors in atmospheres laden with cement-dust. Motors from 100 H.P. down to 30 H.P. are of slip-ring type controlled by floor-mounted oil-immersed stator switches with separate heavily-rated oil-immersed face-plate starters, oil switch and starter being assembled as one unit. Seventy per cent. of the 500-volt motors are under 30 H.P. and are high-torque squirrel-cage machines controlled by oil-immersed starters of either the squirrel-cage or direct-switching type. High-torque squirrel-cage motors were limited to 30 H.P. on account of the large starting currents involved above this power; disturbing line voltage, and increasing the cost of control gear beyond an economical figure.

All motors and control gear are of simple and robust construction, designed for continuous duty. The type and sizes of control gear and outputs and speeds of motors have been standardised as far as possible, and all similar equipments are mechanically and electrically interchangeable, resulting in spares and spare parts being reduced to a minimum.

Final distribution to each 500-volt motor is made from a separate way on a distribution-board fitted with fuses of 50,000 kVA rupturing capacity, which give instantaneous interruption of a circuit under short circuit. The fuses fully protect control gear on large power circuits, and the separate fuse-links efficiently permit of the ready isolation of each motor circuit for inspection or repair.

Distribution on main 3,000-volt and 500-volt circuits is carried out by means of 3-core P.I.L.C.A.-served cables (Note C18) laid direct between sub-station and buildings and in cable racks or cable trenches under cover. From distribution boards to motor starters, and from starters to motors, 3-core V.I.R. armoured and served cable is used, while all lighting is carried out with V.I.R. (Note C19) in galvanised conduit with heavy galvanised fittings. All cables and apparatus are securely bonded, and the electrical installation is iron-clad throughout and efficiently earthed to duplicate earth-plates at each sub-station.

Communication is provided between all parts of the works by a 70-line automatic telephone installation housed with batteries in duplicate and charging set in the main sub-station. An emergency lighting supply for the main sub-station and the indicating lamps on the Supply Company's switchgear are obtained from the telephone batteries in the event of failure of the 33-kV supply.

The rotary kilns are by F. L. Smidth & Co., Ltd.; cables by W. T. Henley's Telegraph Works Co., Ltd.; coal grinding plant by British Rema Manufacturing Co., Ltd.; aerial ropeway by British Ropeway Engineering Co., Ltd.; clay excavator by Priestman Bros., Ltd.; wagon tippler-hoist by Mitchell Conveyor and Transporter Co., Ltd.; electric cranes by Stothert & Pitt, Ltd.; regulating valves by G. Polysius A.G.; fans by Sturtevant Engineering Co., Ltd.; weighing machines by W. & T. Avery, Ltd.; locomotives by Hawthorn, Leslie & Co., Ltd.; electrical equipment by Metropolitan-Vickers Electrical Co., Ltd., and the English Electric Co., Ltd.; switchgear by A. Reyrolle & Co., Ltd.; cement cooler by Vickers-Armstrongs, Ltd.; reduction gears by H. Wallwork & Co., Ltd., and the Power Plant Co., Ltd.; band conveyors by Fraser & Chalmers, Ltd.; Bates sack-filling machines.

NOTES

Note A01. The actual census data are of interest:

YearStoneSwanscombeNorthfleetTotal
182151490819643386
1831719116621244009
18411066170336216390
1851829176350387630
18611013232357439079
187116173105651511237
188125504541879015881
1891378165771171722075
1901513169751290625012

In subsequent censuses the number directly employed in cement manufacture declined, reaching zero in 2011.

Note A02. £1 (1874) = £95 (2015)

Note A03. The crude death rate for England as a whole was around 21 per thousand in 1873. However, crude death rate is irrelevant, since a low and falling death rate is to be expected in a rapidly-expanding population consisting mainly of young people.

Note A04. He probably means the ecclesiastical parish, excluding Greenhithe.

Note A05. 1 stone = 6.35 kg. James Walkling (born in Horton Kirby, Kent, 1814) was listed as "labourer" in the 1841 and 1851 censuses. In 1861 he was "superintendent" and in 1871 "sampler". He died in 1880.

Note A06. Malaria had been an endemic scourge, and the principal cause of death, around the Thames estuary. Mosquitoes are attracted by carbon dioxide, and kilns kill them! The reduction in malaria in places with lime kilns is frequently claimed in 19th century texts.

Note A07. There is a degree of logic in this point of view, in that the "improvements" probably consisted mainly of "being seen to be doing something" rather than actual remedies. The installation of chamber kilns with high stacks would have improved things, but White's were reluctant to do that. Swanscombe's next move was actually to instal Hoffman kilns, with 80 m stacks.

Note A08. Mother Nature provided the Thames Estuary with the perfect raw materials for a cement industry of exquisite inefficiency.

Note A09. Strictly speaking, of course, this is the price - not the value.

Note B01. Arthur Glover (b Westminster, 1839: d Gravesend, 1910) was Swanscombe plant manager approximately 1875-1895. One of his sons (Edward Arthur Glover) founded the Lewes plant.

Note B02. The dimensions given seem wrong. A 16-compartment kiln would be about 70 × 150 ft. On the other hand, other sources suggest the first kiln had 25 compartments.

Note B03. Modifications of bottle kilns under the previous manager, William Goreham, ducted hot gas from the kiln dome into the adjacent drying flats. Similar arrangements were also developed at Bevans

Note B04. The extraordinary mechanisation of cooperage is described elsewhere.

Note C01. They were preceded by kilns in Germany and Denmark, and by kilns at Martin Earles and Shoreham in Britain.

Note C02. Not entirely, since parts of the old kilns were re-assembled as the white cement kilns as soon as the new kilns were in operation.

Note C03. The re-build of Bevans involved an expensive 5-year shutdown - an experience not to be repeated.

Note C04. The quarry went on to supply the Northfleet plant, which had nine times the capacity.

Note C05. The Alkerden pit had been opened in 1909 and also served the Bevans plant. Located mainly in Swanscombe Park, it was operated alongside other clay sources in order to remove Tertiary beds overlying the Swanscombe Park chalk reserve.

Note C06. The normal method of chemistry control was to vary the length of the burst of clay added per truck of chalk. The mill handled about 8 trucks per hour.

Note C07. The 1900 arrangement had three lines of mills, each consisting of a washmill and three screeners. One line was removed, and the washmills became the "intermediate" mills in the new system.

Note C08. The slurry line ran 200 m, under the London Road and under the kilns to the blending silos.

Note C09. The storage tanks were all part of the 1900 installation: only the blending tanks were new. The storage tanks when full contained sufficient for a generous 4½ days' kiln run. However, the blending tanks were small, filling in less than two hours, so there was little opportunity to control individual tanks; chemistry was controlled by blending pairs of tanks.

Note C10. The dimensions of these FLS kilns were entirely metric. As always in these articles, the dimensions are rendered, inexactly, in Imperial units. FLS conventionally produced tube dimensions in units of 0.15 m. The length of the kiln (the distance between closure plates), given as 403', was 122.8 m (402' 10.65"), and was rendered as 402' 10⅝" in the Blue Circle kiln schedule. The actual kiln length, measured from the centre lines of the cooler ports, was 120 m exactly. The burning zone internal diameter, given as 11' 3", was 3.45 m (11' 3.83") and was given as 11' 3⅞" in the schedule. The length of the burning zone (from the front closure to the rear of the taper), given as 127', was 38.8 m (127' 3.56") and was given as 127' 3⅝" in the schedule. The cold end internal diameter, given as 9' 4", was 2.85 m (9' 4.20") and was given as 9' 4¼" in the schedule. The hot end tyre was 630 mm wide, and the rest were 400 mm. The hot end rollers were 1.2 m in diameter, and the rest were 1.0 m. The kilns were the largest on offer from FLS at the time, eventually exceeded in 1934 by the 150 m kilns installed by FLS in their own plants at Aalborg, West Thurrock and Helwan.

Note C11. No mention is made of kiln heat exchangers. Although in 1929 chain heat exchangers were available, and were installed at the FLS plants at Ketton and West Thurrock, they were apparently not offered to Blue Circle's Swanscombe and Hope. The Swanscombe kilns had 12 flights of channel lifters, extending 35 m (29% of effective length) from the cold end. The kilns were soon converted to chain heat exchangers, as information leaked out from West Thurrock. Of course, it is quite possible that Blue Circle insisted on the more archaic technology.

Note C12. The cooler tubes were 6 m long (5.678 m effective) and 1.2 m internal diameter.

Note C13. This presumably means 6 million cubic feet per hour. A calculation shows that at 16 ton/hr, 7.5 MJ/kg heat consumption and 1% BE oxygen, the exhaust flowrate would be 34.6 m3/s (4,400,000 ft3/hr) at 270°C. Add to this some back end seal inleak.

Note C14. This implies a nozzle velocity of about 60 m/s.

Note C15. The fourteen ball-and-tube sets were the original 1900 installation, uprated only in that the original flint tube mill media had been replaced with steel, and the motors uprated accordingly.

Note C16. The old fashioned cement bins were also the original 1900 installation. They were replaced with silos in the mid 1930s.

Note C17. The double handling made Swanscombe more expensive than many of the other Thames plants, and it subsequently re-focussed on landward despatch by road and rail.

Note C18. PILCA = paper-insulated, lead cable-armour

Note C19. VIR = vulcanised india-rubber