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Note: This is a sub-section of 1874 Institution of Mechanical Engineers
Visits to Works (Excursions) in South Wales
In the afternoon an Excursion was made by the Members by special train to the Bute Docks, where the working of the hydraulic tips and balance tips for shipping coal, together with the portable hydraulic cranes, hydraulic hauling engines, and other machinery described in the paper read at the meeting, was shown by Mr. McConnochie; and the new basin and large entrance gates were seen.
The Penarth Docks were then visited, where there is a tidal dock 2100 ft. long and 370 ft. wide, having an area of about 18 acres, with an entrance basin of 3 acres area. The entrance gates are 60 ft. wide, and are opened only at high tide for the passage of vessels, the depth of water in the dock and basin being 25 ft. at neap tides and 35 ft. at spring tides. The coal shipping is on the high-level system by balance tips, of which there are ten at the dock and a double one at the basin, with hydraulic cranes for discharging ballast, and hydraulic power for working the dock gates. The mouth of the river Ely forms a tidal harbour, extending 1.5 mile with an average width for the first 4 mile of 600 ft. at high water and 280 ft. at low water; the depth for this length is 5 ft. in the centre of the channel at low water. The tidal harbour has twelve balance tips for shipping coal; the depth of water in the berths at high water is 20 ft. at neap tides, and 30 ft. at spring tides. The dock and harbour are in communication with the different railways.
The Meeting then terminated.
In the afternoon the Members were entertained at luncheon in Cardiff by the Rhondda Valley Colliery Owners; and an Excursion was made by special train to visit some of the principal Collieries in the Rhondda and Aberdare Valleys.
On the way to the Rhondda, Valley, the celebrated Pontypridd Bridge was seen, the train slackening speed in passing it. This singular bridge, from which the place derives its name (Pont-y-typridd, "bridge of the earthen house"), was the work of a self-taught mason and architect, William Edwards, who became one of the most famous bridge builders of the last century. He failed twice in his attempt at Pontypridd; first in 1746, when at the age of only twenty-seven he built a bridge of three arches which was swept away by a flood; and secondly in 1751, when he constructed a single-arch bridge with. too thin a crown and overloaded at the haunches.
His third attempt in 1755 succeeded perfectly; by introducing three circular openings in each of the haunches, the weight was reduced, and the keystones relieved. The span of the bridge is 140 ft., its arch forming the segment of a circle of 87.5 ft. radius; the height of the crown from the water is 34 ft., and the width of the roadway 11 ft. From the form of the bridge, the rise of the roadway on each side towards the centre is very steep, and this, together with the narrowness of the bridge, has rendered it inconvenient for the accommodation of the present traffic; another bridge at a lower level and with a flatter and wider roadway has accordingly been built close to it; but the old bridge still remains in a sound condition.
Glamorgan Coal Co
The Glamorgan Coal Co.'s Llwynypia Colliery in the Rhondda Valley was then visited, where the Members were received by the Managing Director, Mr. Archibald Hood. The steam-coal pit is 380 yards deep, and the winding is done by a pair of horizontal engines with 34 in. cylinders and 6 ft. stroke, coupled at right angles, and working direct upon the shaft of the conical winding drum, which tapers from 25 to 15 ft. diameter. The time of each lift varies from 45 to 47 sec., giving a mean speed of aboutt 17 miles per hour in the shaft; the total time between the cages alternately coming to bank in regular working averages 1.25 min., including the time occupied in changing the trams.
The cages have two decks, each holding one tram; and the trams contain each from 20 to 22 cwt. of coal. There is another winding pit 111 yards deep for bituminous coal; and a third pit 370 yards deep fitted with a Guibal ventilating fan of 30 ft. diameter and 10 ft. width, which at 50 rev. per min. exhausts 95,000 cub. ft. of air per min. An extensive range of coke ovens is employed in making coke from small coal; the coal is ground under edge-runners, and sifted, and is so clean as not to require washing before coking.
Messrs. Nixon's Navigation Colliery in the Aberdare Valley was then visited, the Members being received by the Manager, Mr. George Brown. A pair of oscillating engines are employed for winding from one of the pits of 365 yards depth, having cylinders 33 in. diameter and 6 ft. stroke, and reversed by a donkey engine; and at another pit of 286 yards depth a pair of side-lever marine engines, with cylinders 33 in. diameter and 5 ft. stroke, are adapted as winding engines. Both pairs of engines have conical winding drums tapering from 22 ft. extreme diameter to 10 ft. diameter at each side; they wind at a mean speed of about 17 miles per hour in the shaft, raising each time about 40 cwt. of coal.
The ventilation of the colliery is effected by a Waddle fan of 40 ft. diameter and 1 ft. 5 in. width at the circumference, driven at 40 rev. per min. by a horizontal non-condensing engine with 32 in. cylinder and 4 ft. stroke; at that speed the fan exhausts 89,000 cub. ft. of air per min., producing a vacuum of 1.35 in. of water. At 45 rev. per min. the fan is calculated to discharge 100,000 cub. ft. per min., and at 50 rev. 120,000 cub. ft. The air-compressing engine at Middle Duffryn Colliery, described in the paper read at the meeting, was seen at work, supplying compressed air to the underground hauling machines. The Members were invited to luncheon at Aberaman House by Sir George Elliot, Bart., M.P.; and returned to Cardiff in the evening.
On Thursday, 6th August, an Excursion was made by the Members by special train from Cardiff to Merthyr Vale Colliery, the Merthyr Sewage Farm, and the Cyfarthfa and Dowlais Iron Works.
Merthyr Vale Colliery
At Messrs. Nixon's Merthyr Vale Colliery, where the Members were received by the Manager, Mr. George Brown, two shafts of 16 ft. diameter are in progress of sinking, and have at present reached a depth of 380 yards, being lined with cast-iron tubbing through 212 yards depth; the total ultimate depth is expected to be about 490 yards. During the sinking the water is being raised from the shafts in large tubs. The pit-bead gear is being constructed entirely of iron, the pulley frames being made of flange rails riveted together in sets of four, around hoops of 2 ft. diameter. The conical winding drum is 24 ft. extreme diameter, tapering to 10 ft. diameter on each side. The winding engines are a pair of marine engines with return connecting-rods, having 83 in. cylinders with 4 ft. stroke, and are to raise each time 80 cwt. of coal, and to be reversed by a donkey engine; they are coupled direct to the shaft of the winding drum, and with it are mounted on the top of a foundation 30 ft. high, consisting of a mass of concrete enclosed within thick masonry walls. Adjoining the colliery are some substantial cottages erected of concrete, for the use of the workmen.
Merthyr Sewage Farm
At the Merthyr Sewage Farm the Members were received by the Chairman of the Merthyr Board of Health, Mr. William Jones, and the Surveyor to the Board, Mr. Samuel Harper, by whom they were conducted over the works. The sewage of Merthyr is conveyed from the town to the farm at Troedyrhiew, a distance of four miles, is a brick culvert, 24 in. by 18 in. The sewage is strained before it is allowed to flow on the land, by means of two straining tanks, one working while the other is being cleaned. Each tank is 200 ft. long, 5 ft. wide, and 5 ft. deep, the bottom paved with stone, and the top covered with planking; and the interior is filled with broken furnace-cinder, coarse at the bottom, but small and fine at top. The tanks are changed for cleaning every four or five days; and the solid material extracted is carted on the land.
There are four "downward filtration" areas, of about five acres each, which are drained from 6 to 7 ft. deep; the sewage is allowed to flow on one area at a time for six hours, and is then passed on to the next; so that each area works six hours and rests eighteen out of the twenty-four, Mr. Bailey Denton's arrangement being that each area of five acres should contain about 48,400 cubic yards of earth, and that every cubic yard should have a maximum quantity of 7.5 gallons of sewage per day to cleanse. These downward intermittent filtration areas were first used in February 1871, and cover altogether 20 acres; there are also 56 acres laid out for "wide irrigation," making 76 acres total on the farm at Troedyrhiew. Five miles further down the same valley, near Navigation, about 160 acres in addition are laid out for wide irrigation, to which the sewage is conveyed from Troedyrhiew in a brick culvert, 24 in. diameter, and in some places wooden pipes are used; there are thus altogether nearly 220 acres of irrigated land, besides the 20 acres of filtration ground.
As regards the condition of the effluent water from these downward filtration areas, it is stated by the Rivers Pollution Commission that "the result is highly satisfactory, more so even than that which had been obtained in the laboratory of the Rivers Commission. Indeed on the 10th June 1871 the water entering the Taff from the Merthyr intermittent filters was considerably purer than the Thames water which we are often compelled to drink in London."
At that time the whole of the sewage from a population of 25,000 was cleansed -upon these 20 acres of filtration ground; and the cost of under-draining and laying out the ground was in this instance about £220 per acre. The commercial results have been that 40 tons per acre of Italian rye grass have been cut, and cabbage has been sold from the farm as high as £43 per acre.
Where land is dear and difficult to be obtained, downward filtration answers well as a means of disposing of sewage on a small area; but where sufficient land can be obtained at a fair agricultural value, and situated so that the sewage will flow over it by gravitation, needing no expensive main carriers, wide irrigation is more profitable, as utilising the sewage to a far greater extent than can be done by the downward filtration process; for experience has shown that on irrigated land as heavy crops can be raised as on an equal area of filtration land with five times the quantity of sewage. The area required for irrigation is found to be about one acre per hundred of the population producing the sewage.
The present sewage of Merthyr is produced by a population of about 40,000, and exceeds one million gallons per day, of which one twelfth is sent to the filtration areas, and the remainder to the irrigated lands. With the exception of the 20 acres of filtration areas, the whole of the works have been designed and laid out by Mr. Harpur.
Castle Pit, Troedyrhiew
At the Castle Pit, Troedyrhiew, the Members were received by Mr. William T. Crawshay, and the large pumping and winding engines were seen at work. The pumping engine is of very massive construction, having a cylinder 68 in. diameter and 8 ft. stroke, placed inverted over the pit, with the piston-rod coupled direct to the pump plunger-pole, and also to one end of a beam, the other end of which is connected by a massive cast-iron connecting-rod to a crank on the flywheel shaft above; the crank is 6.6 ft. radius, and the flywheel, shaft, and crank weigh together 60 tons. The engine was making 4 rev. per min., and raising water from a depth of 265 yards in three lifts, the pump plunger being 15 in. diameter; the speed can be increased to 12 rev. per min. if necessary. The pair of vertical winding engines have overhead cylinders 36 in. diameter and 4.5 ft. stroke, and wind from a depth of 263 yards in 37 seconds, giving a mean speed of 14 miles per hour. The winding drums are cylindrical, 12 ft. diameter, with flanges 16 ft. diameter.
At the Cyfarthfa Iron Works, over which the Members were conducted by Mr. William T. Crawshay, the first blast furnace was built in 1770, and there are now seven furnaces of 52 ft. height and 14.5 to 16 ft. diameter at the boshes. Five of them are blown with cold blast and two with hot, and all except one have closed tops fitted with bell and hopper, the gases being employed to heat the boilers.
These furnaces being built in a row against the hill side, the coal and ore are brought direct by rail to the level of the furnace tops, where the coke ovens and calcining kilns are situated in convenient proximity for charging the furnaces. The extensive ranges of coke ovens are discharged by steam power, the charge being pushed out at the front by means of a ram at the back, which is forced through the oven by a small traveling steam engine running between two rows of ovens. The puddling mills are driven by two water wheels and two non-condensing engines, and the bar mills by two condensing beam engines and an oscillating non-condensing engine. There is also a non-condensing beam pumping engine with cylinder 30 in. diameter and 8 ft. stroke, which is used in times of short water to return the water from the river to the top of the water wheels; it works two single-acting lift pumps of 72 in. diameter and 4 ft. stroke, connected on opposite sides of the beam, the usual rate being 8 rev. per min., and the height of lift about 30 ft.
Proceeding by the special train via Vaynor Valley and Pontsticill to the Dowlais Iron Works, the Members were there received by Mr. George T. Clark and Mr. Menelaus, and were first shown the new Ivor blast furnace recently started, of 55 ft. height and 18 ft. diameter at the boshes, which is intended to run 300 tons of Bessemer pig per week. It has a closed top, and is supplied with hot blast at a temperature of about 1200° Fahr. by four regenerative firebrick stoves of 29 ft. height and 22.5 ft. diameter, heated by the waste gas from the furnace. The materials are raised to the furnace top by a water-balance hoist.
In the steel works are four regenerative gas furnaces for the Siemens-Martin process, in which steel-scrap and crop ends of steel rails are used up; a bath is first made by melting about 30 cwt. of pig iron, into which the steel scrap is gradually fed; and finally spiegel is added to bring the metal to the desired quality. The charge of steel ultimately obtained is about 6 tons, and the time occupied in working it about 10 hours. The four steel furnaces are arranged along the straight side of a D shaped pit containing a ladle-crane large enough to receive the entire charge from one furnace; the ingots are cast in moulds in the same way as in the Bessemer process.
Adjoining these furnaces are six of the ordinary Bessemer converters, blown by a pair of vertical blowing engines. The cogging of the steel ingots is done in a reversing mill driven by a pair of engines on Ramsbottom's reversing principle; and from the togging mill to the circular saw which cuts them in two the ingots are conveyed along the floor by means of a series of rollers driven by an engine. In the rail mill the blooms are hauled out of the heating furnace by hydraulic gear; the tongs attached to the bloom are hooked to a chain that is wound up on a drum by means of a hydraulic cylinder, the ram of which carries a rack gearing into a pinion on the drum shaft. The pair of non-condensing engines driving the rolling mill, having 45 in. cylinders with 10 ft. stroke, coupled at right angles and making 24 rev. per min., with their massive framing and gearing, were described at a former meeting (see Proceedings Inst. M. E. 1857 page 112); also the largo non-condensing blowing engine, which has a steam cylinder of 55 in. diameter and 13 ft. stroke, and a blowing cylinder of 144 in. diameter and 12 ft. stroke, making 20 rev. per min. and delivering about 44,000 cub. ft. of air per min. at a pressure of 3.25 lb. per sq. in. For conveying heavy loads of materials from one part of the works to another at a slow speed and over steep gradients of 1 is 40, small geared locomotive engines are employed, having a single cylinder mounted on the top of the boiler, and driving the trailing axle by gearing from an independent crankshaft.
The Dowlais Iron Works were established about 1750, and the number of persons now employed in the ironworks and collieries is between 11,000 and 12,000. The Members were entertained at luncheon at Dowlais by Mr. George T. Clark; and returned to Cardiff in the evening via Bargoed and Rhymney Valleys, visiting on the way the ruins of Caerphilly Castle.
On Friday, 7th August, an Excursion was made by the Members by special train from Cardiff to visit the Landore Siemens-Steel Works, the Morfa Copper Works, and the Landore Tinplate Works, near Swansea, and the Mwyndy Iron Ore Mine near Llantrissant.
The regenerative gas furnaces for the Siemens-Martin process of steel manufacture are arranged in two rows of eight each, along the opposite sides of the casting pit, over which works a steam travelling crane; and along the centre of the pit is an elevated railway, on which run the wagons that receive the ingots, and also a portable steam crane. On the floor of the pit are laid rails for running the casting ladle under the mouth of each furnace and conveying it thence over the ingot moulds, which are arranged in straight rows in the bottom of the pit. Each furnace is capable of working 6-ton charges; and the old works adjoining contain eight similar furnaces. The charge consists of about 6 tons of pig iron and scrap, the proportion varying from 2 to 4 tons of either; sometimes the quantity of pig is the greater, and sometimes the quantity of scrap, according as they happen to be available.
To this is added iron ore sufficient to oxidise the carbon and silicon in the pig iron (African ore was used at the time of the visit), after which about 8 per cent. of spiegel is added, and the charge cast; the result is generally a quantity of steel equal to or slightly exceeding the weight of the pig, scrap, and spiegel together, the iron from the ore replacing the loss of the impurities in the pig &c. When working without scrap, the charge consists of about 5-1- tons of pig iron, with sufficient ore as before to oxidise the carbon and silicon; after which spiegel is added, as in the mixed charges. The melting of the bath of pig iron previous to charging the steel scrap occupies from 3 to 4 hours, and the whole time of working off a charge is about 10 hours. In the rolling mill the reheating furnaces are all on the regenerative principle, heated by gas, those for the rail mill being 21 ft. long inside, with four doors for charging and withdrawing the blooms.
There are five 8-ton single-acting blooming hammers with 32 in. cylinders and 7 ft. stroke. The rail mill is driven by a reversing engine having a pair of 35 in. cylinders with 4 ft. stroke, geared to make 3.25 rev. to 1 rev. of the rolls. The tyre mill on the floor level is driven by gearing from a pair of vertical engines half sunk below the floor. The bar mill and wire mill are driven by a pair of vertical engines with 30 in. cylinders and 4 ft. stroke.
In the wire mill the steel wire is brought down from 1 1/8 in. to 1/4 in. diameter in fourteen passes through the rolls, and the handling of the wire is managed with as much dexterity by the men that during the latter part of the rolling there are five bends in between the rolls at once, so that the single wire is undergoing five different degrees of reduction simultaneously at five different points of its length. Two close-topped blast furnaces supply the pig-iron for the steel-making furnaces; one is 66 ft. high and 19 ft. diameter at the bashes, and the other 65 ft. high and 18 ft. diameter. They are supplied with hot blast by three regenerative firebrick stoves 50 ft. high, heated by gas obtained from separate gas producers, which contains much less dust than the gas taken off from the blast furnaces, and by its use therefore the stoves are more easily kept clean; the furnace gas is used for heating the steam boilers only, for which purpose a dearer description of coal would have to be used than suffices for the producers.
Each of the three hot-blast stoves in succession is kept on blast for 1.5 hour at a time, and is then heated up again by the gas for 3 hours. The furnaces are blown with six tuyeres each, by a pair of vertical condensing engines having 45 in. steam cylinders, 100 in. blowing cylinders, and 5 ft. stroke, working with 40 lb. steam and giving a pressure of blast of 41 lb. per sq. in.; the steam cylinders have double-beat Cornish valves worked by cams.
The coke ovens and ore heaps are on high ground at the level of the railway, about 12 ft. below the tops of the blast furnaces, to which the materials are raised by a direct steam lift with 24 in. ram, worked with 30 lb. steam. The coke ovens are arranged in double rows, between which runs an endless chain worked by an engine; and any oven is drawn by attaching the rake to a chain passing round a sheave in front of the oven and hooked to the endless chain. The charging of the ovens is at present done by hand, but arrangements for charging from the top are in progress; and the usual charge in each oven is 4.5 tons of coal, which is kept in the oven three days and nights, the loss amounting to only 20 per cent. of the weight charged into the ovens; smaller charges are burnt two days and nights, with a loss sometimes reaching 27 per cent.
The coke produced is of a superior quality, containing only 8 per cent. of ash. The bricks for lining the steelmaking furnaces are made from selected stones consisting of almost pure silica, and contain 98 per cent. of silica, the remaining 2 per cent. being alkaline matter. The stones are first broken in a stone-breaking machine, and then crushed between rolls. Carr's disintegrator is also used for reducing the stone delivered from the stone-breaker, but the material thus pulverised is too fine for brick-making by itself, and is only used for mixing with the coarser crushed stone from the rolls. This mixture is then further mixed with lime-water, and pressed in moulds worked by hand. The bricks thus made being very tender are carefully placed in a drying shed heated by flues under the floor, and are afterwards stacked and burnt for about five days in beehive kilns, each containing about 33,000 bricks; they are then sufficiently hard and tenacious to stand much rough usage.
The Members were entertained at luncheon at the Works by Mr. Siemens.
The principal ore smelted is the ordinary yellow copper ore (copper pyrites), which is the most abundant ore of copper, and is a sulphide of copper and iron, the purest qualities containing about 35 per cent. of copper with 35 per cent. of sulphur and 30 per cent. of iron; but the usual proportion of copper is not more than from 5 to 13 per cent., and the ore generally contains more or less sulphur, with arsenic, quartz, and other impurities. The smelting of the ore involves six successive processes of calcining and melting, some of which have at times to be repeated.
In the first process a charge of about 80 cwt. of clean ore in a rough powdered state is roasted in a reverberatory furnace or calciner, having a hearth about 18 ft. long and 15 ft. wide; after being exposed to a gentle heat for about 12 hours, during which it is stirred at intervals of 2 hours, the roasted ore, having now lost much of its sulphur and arsenic, is raked out of the furnace to cool, and wetted with water.
In the second process a charge of 22 cwt. of this roasted ore is smelted in another reverberatory furnace having a hearth of coarse sand, 11 ft. long and 7 ft. wide, sloping towards the door; the smelting takes about 4 hours, slags and fluxes being added as required, according to the quality of the ore. When the charge is all melted, the slag on the top of the metal, which contains earthy matter, quartz, and the chief part of the iron, and also from 0.25 to 0.5 per cent. of copper, is skimmed off by a rabble and drawn out into a sand bed; the melted metal is allowed to remain in the furnace, and repeated charges of roasted ore are put in and treated in the same way, until the melted metal rises as high as the bridge at the door; the tap hole at the side is then opened, and the melted metal run off direct into a tank of water, whereby it becomes granulated. The metal thus obtained, called "coarse metal" or "mat," is an alloy of all the metals in the ore with sulphur, and contains about 33 per cent. of copper, or about four times the original proportion of copper in the ore, the remaining 67 per cent. being chiefly iron and sulphur.
In the third process the mat is roasted in a large furnace like that used in the first process; the charge consists of 80 cwt. of granulated metal or mat, and is kept in the furnace 24 hours, being repeatedly stirred; the metal is afterwards drawn out into a vault under the furnace and oxidised by exposure, the rest of the iron contained in it being thus converted into oxide.
The fourth process consists in smelting this metal in charges of 46 cwt. at a time, each charge occupying from 5 to 6 hours; the metal is run out at every second charge into sand beds, and is now a very rich mat, called "fine metal," containing about 66 per cent. of copper.
In the fifth process the fine metal is roasted and smelted in a large furnace to get rid of the remainder of the sulphur; a charge of 50 to 60 cwt. after being melted is exposed for 4 hours to a gentle heat, which is afterwards increased to drive off the remainder of the sulphur; the slag is repeatedly skimmed off the melted metal, which is run out into sand moulds, and is called "rotten" or "blistered copper," containing 94 to 96 per cent. of copper.
This is then refined and toughened in the sixth process, a charge of about 8 tons being exposed in a smelting furnace for 12 or 16 hours to a roasting heat, then melted, skimmed of slag, and worked as clean as possible. After it has been about 24 hours in the furnace, samples for testing are taken at frequent intervals in small iron ladles; if the metal is fine enough, it settles down considerably in the ladle on cooling; but if it swells up and shows dark veins or marks, it requires further "fining."
When sufficiently refined, the toughening is effected by covering the surface of the melted copper with powdered charcoal or anthracite coal; and in order to accelerate the process and to get rid of the last traces of oxide, the metal is also "poled" or stirred diligently for about half an hour with a pole of green wood; this produces a strong ebullition, thereby raising any remaining impurities to the surface, where they are skimmed off, leaving the metal soft, tough, and of a light red colour. The duration of the poling has to be carefully regulated, for if continued too long or not long enough, the copper is of brittle quality in either case, and is said to be "ovorpoled " or "underpoled " respectively; when a test sample of the copper hammered cold on the anvil does not crack on the edges, and the colour and grain are good, it is considered sufficiently refined and toughened.
The finished metal is ladled out of the furnace by iron ladles, and is poured into cast-iron moulds to form cakes, bars, or ingots of "fine copper," for rolling or casting. The copper rolling-mill is supplied with cakes varying from 1 cwt. to nearly 20 cwt., the smaller sizes for making copper sheathing for ships, and the heavier cakes for making large plates for locomotive fireboxes &c. The copper hammer-mill contains a steam hammer, by which these locomotive plates are hammered and flanged, and large bottoms for breweries and distilleries are made, as also largo bowls and sugar pans. The yellow-metal mill is principally engaged in the rolling of ships' sheathing, and of large square sheets for export. There is also a train of rolls for making bars and bolts of both copper and yellow metal.
Landore Tinplate Works
At the Landore Tinplate Works, where the Members were received by the Manager, Mr. Richard Hughes, the iron, which is required to be of very uniform and specially good quality, is all made on the premises from the best pig iron; this is fused in a coke refinery, then remelted and worked in a charcoal refinery, and then stamped out under a steam hammer into large cakes or "stamps" of about 4 to 2 in. thickness; these are reheated in hollow fires, forged under heavy helves, and rolled into bars, which after being cut to the proper length are rolled down into very thin plates, eight times the thickness of those ultimately required. Each plate is then folded into eight, and reheated, and the whole pile is rolled again down to the same thickness as before; the ends being sheared, the thin sheets are separated, pickled in dilute sulphuric acid, washed, annealed in closed boxes in a furnace at a dull red heat, and planished by rolling cold.
After a second annealing, pickling, and washing, they are placed in a bath of melted palm oil, and then dipped successively into three baths of melted tin; the last of these contains a purer quality of tin, and has a pair of finely finished rollers immersed in it, between which each plate passes in quitting the bath; by this means the superfluous tin which formerly used to collect along the bottom edges of the plates is wiped off and saved.
The tinplates are then dipped in bran or "sharps" and wiped, which gives them a final polish; and they are packed in boxes according to size and quality. "Terme " plates are made in the same manner, but are coated with a mixture of about 3 lead ands tin. To show the extreme tenuity to which the iron plates can be reduced by the rolling, specimens were exhibited of plates rolled cold in the planishing rolls, of the following dimensions and weights:-
[See table in image]
The thinnest of these plates was consequently not more than 0.00011 in. or 1-8900th in. thick, while the largest plate, of 45 in. length, was 0.00166 in. or 1-600th in. thick, which was a sample of ordinary manufacture.
Mwyndy Iron Ore Mine
In returning from Landore to Cardiff, the Members visited the Mwyndy Iron Ore Mine, near Llantrissant, where they were received by the Manager, Mr. William Vivian, who gave a description of the mine, and an account of the early opencast mining for iron ore and the manufacture of iron with charcoal, which were carried on in that locality several hundred years ago, until prohibited by an act of parliament forbidding the further use of the neighbouring woods for the requisite supplies of fuel; and a specimen of iron of excellent quality was shown, which had been produced at the time of those early workings, the name "Mwyn-dy" meaning "mineral house."
About sixteen years ago a discovery of ore in the adjoining property led to the finding of ore in this mine also, and workings were commenced upon it. The deposit consists of brown haematite iron ore, occurring in a large bed or mass, between the carboniferous limestone on which it rests, and a bed of conglomerate. It lies immediately south of the edge of the South Wales coal basin, the thin shales overlapping the limestone close to the ore. The bed of ore was in some places from 35 to 40 ft. thick, and it dips north at an angle of about 45 degrees.
Like most other deposits of hematite iron ore in the same formation, it is found to be very irregular, large masses of ore being suddenly cut off by intervening bosses of limestone. This necessitates the employment of not less than one third of the miners upon "dead work," exploring, and making communications for ventilation and for the conveyance of the ore; the total number of men employed is about 280.
The mine is worked both opencast and by mining underground, the extent of the workings being very considerable. The vertical depth to the present deepest point is 280 ft. from surface; and the water is pumped by two engines, each of which in winter raises upwards of 1,000 gall. per min., one of them being arranged to work on the dip. The ore is very variable in hardness, and a great deal of it requires blasting; from the levels it is brought out by horses to the vertical shafts and inclined planes, and on reaching the surface is tipped direct into the railway wagons, if sufficiently pure; but if not, it is first dressed by hand labour, being broken by hammers and then picked by hand to separate the iron pyrites and other impurities.
The total quantity of iron ore raised and sold has been over 620,000 tons, and the mine is at present in active work, yielding about 5,000 tons of ore per month. The quality of the ore is useful, yielding from 45 to 48 per cent. of metallic iron; it contains some silica. This and the Bute mine adjoining are the only hematite iron mines of importance in the district, and they possess the advantage of being within easy distance by rail from many of the South Wales blast furnaces. The Members were invited to refreshments at the mine by the Mwyndy Iron Ore Company; and returned in the evening by special train to Cardiff.
Brown and Adams
On Saturday, 8th August, an Excursion was made by the Members by special train from Cardiff to Harris' Navigation Coal Co.'s Pits, near Quaker's Yard, where the diamond rock-drilling machine is being employed for sinking two shafts. They were received by the Managing Director, Mr. Frederick W. Harris, and the other Directors, and by Messrs. Brown and Adams, under whose direction the works are being carried out.
The pits are being sunk for the purpose of working a coalfield of about 2,800 acres, and the coal expected to be worked is the Aberdare Upper 4 Feet seam and the other White-Ash coal measures of South Wales, the estimated depth to the former being over 600 yards. The two pits are 17 ft. diameter and 60 yards apart, and have reached a depth of 128 yards since first starting fifteen months ago; the sinking is at present in the Pennant rock, the thickness of which is estimated to be from 300 to 400 yards. At about 200 yards depth a workable bituminous seam is expected, called the Brithdir seam, which is one of the blackband or lower Pennant series.
The rock-drilling machine consists of a long rectangular cast-iron framing, extending across the pit, and mounted on a vertical centre bar, on which it can be turned round to face in different directions. The two opposite sides of the framing form vertical slide-beds, each carrying four revolving vertical drill spindles placed at any desired distance apart, so that eight drills can be at work simultaneously if required, the spindles being driven by bevil gearing from a central engine worked by compressed air. The lower end of each spindle is enlarged to 2.25 in. diameter and is made tubular, the bottom annular face having four diamonds embedded in it.
The machine was shown at work above ground on a block of Pennant stone 11.5 in. thick, through which a 2.25 in. hole with 0.75 in. core was drilled in 4.5 min. In sinking the pits the practice is to bore a set of thirty holes at the bottom of one pit to a depth of about 4.5 ft., and then remove the machine to bore in the other pit while the holes in the first are charged and fired, dynamite being employed for the blasting.
The compressed air at 40 lb. per sq. in. is supplied by a compressor having a pair of vertical overhead cylinders, the inlet valves being placed in the pistons; the compressor is driven by a horizontal engine with 25 in. cylinder geared 2 to 1. A pair of locomotive engines suitably fixed, of 50 H. P. each, are employed to drive the temporary winding gear, their driving axles being extended and coupled direct to the drums.
The Members were invited to luncheon at the works by the Directors of the Company.
The special train then proceeded to Newport, stopping on the way at the Crumlin Viaduct, and the Members were conducted through the whole length of the viaduct underneath the roadway by the District Superintendent of the Great Western Railway, Mr. Peter Donaldson.
The viaduct crosses the valley of the river Ebbw in seven spans of 150 ft. each, the total length being 1,050 ft. and the greatest height 200 ft. The piers are formed of hollow cast-iron columns, 17 ft. high and 1 ft. diameter, built up in successive tiers, with fourteen columns in each tier, and the piers taper upwards from an area of 27 ft. by 60 ft. at the base of the highest pier to 18 ft. by 30 ft. at the summit of each; the columns are fitted into one another by socket joints, and are connected in each tier by horizontal cast-iron girders, and by horizontal and vertical wrought-iron tie-rods tightened by wedges.
The main girders are Warren trusses, each 150 ft. long and 141 ft. deep; the compression beam, forming the top member of the girder, is a riveted box-girder 14 in. deep and 9 in. wide, formed of plates of varying thicknesses; the tension member consists of four wrought-iron bars, of 6 in. x s in. average section. There are four girders in each span, carrying a double line of rails; they are supported by the ends of the compression beam resting upon a sliding block in a saddle casting on the top of the piers, to allow for expansion and contraction; the extreme difference of length in each span between summer and winter does not exceed 11 in.
The viaduct was completed in 1856 at a cost of £60,000, including three additional spans of the same length in the adjoining smaller viaduct; but the subsequent further expenditure in 1868, for strengthening the girders, and substituting a wrought-iron floor with cross girders and rail bearers, in place of the timber with which the viaduct was originally covered, amounted to about £15,000, including painting.