RAVENSCRAIG STEEL WORKS 1954 - 1992

More photographs of Ravenscraig keep emerging and I plan to add them to the website.

Beginnings

After WWII Colvilles considered various plans for expansion. This included - increasing pig iron production and updating rolling mill equipment and concentrating steel-making into fewer, larger sites.

A fourth blast furnace at Clyde Iron Works was proposed and approved for construction in 1951. But a shortage of coking coal in Scotland meant that concentrating iron production at Clyde Iron would stop the other Colvilles works in Motherwell from being converted to hot metal working. By 1952 the plans had changed to installing the blast furnace, as one of a pair, at a "new works" in Motherwell, beside Dalzell works.

Colvilles had the new site surveyed in January 1953. The name Ravenscraig was suggested (it was formally used from September 1954). Work started on the site in 1953, the coke ovens were lit on 3 June 1957, and the blast furnace was lit on 6 September 1957.

In 1952 there was a plan for a melting shop and a slabbing mill at Ravenscraig to supply Dalzell works. The plan also included a 4-high plate mill, plus a 4 stand 4-high Steckel semi-continuous light plate and sheet mill at Clydebridge to replace the hand operated mills of Smith & McLean. A wide plate mill was proposed for Ravenscraig to replace the Dalzell mill, which was on a cramped site.

By 1955 Colvilles decided to install a second blast furnace at Ravenscraig, plus coke ovens, an increased melting shop and a slabbing mill to replace the one at Dalzell. The Dalzell 2-high plate mill was to be replaced with a 4-high plate mill, and the Clydebridge 3-high plate mill was to be replaced with two 4-high stands with room for further stands in future for producing light plate and sheet. A third blast furnace at Ravenscraig was also being considered, to allow the old blast furnaces at Dixons Blazes to be closed.

There was much political debate, around this time, about the growing UK demand for strip steel. There were 3 continuous strip mills in the UK (Ebbw Vale, Margam and Shotton), plus a number of small hand mills, and a fourth strip mill was needed to meet UK demand. Various areas in the UK were competing for this. In Scotland the political impetus was to reduce unemployment. Scottish politicians wanted the mill in order to create a source of strip that would in turn lead to car building and other industries within Scotland. A site at Grangemouth, operated by Richard Thomas & Baldwins was proposed.

Colvilles was not interested in the strip mill, believing that the market for strip would not be in Scotland and that, with high transport costs, the mill would not be economic. However, politicians considered that any losses would be less that the unemployment costs. Colvilles was persuaded to reconsider, and proposed a reduced size of strip mill at Ravenscraig, since this would not starve the supply of iron and ingots to the plate mills. Following discussions at the Iron & Steel Board, with Richard Thomas & Baldwins, it was proposed that two semi-continuous 6 stand 4-high strip mills ( i.e. including a roughing mill to reduce the number of continuous mill stands), one in Scotland and one in Wales, would best meet demand around the UK. This solution was finally announced by the Prime Minister in November 1958.

To support the strip mill, a third blast furnace was required for Ravenscraig, plus an increaseed melting shop with a fourth open hearth furnace and LD blowers. Cold rolling mills at Gartcosh were also adopted, to allow different strip gauges to be derived, following discussions with the mill manufacturers, Davy-United.

The Gartcosh mills started in November 1961. The Ravenscraig roughing mill started in February 1962, and the strip mill rolled the first coil on 4 December 1962.

Description of Ravenscraig Works

This description is from a leaflet for visitors to the works that was produced by Colvilles just prior to Nationalisation in 1967. Thanks to Ron Mullett, Blast Furnace Manager, for providing this.

Introduction

In 1954, when the first phase of development was begun, Ravenscraig was a green field site. By 1957 a new steelworks, consisting of coke ovens, by-products plant, one blast furnace and an open hearth melting shop with three steelmaking furnaces had been built. At the same time, new iron ore unloading facilities had been installed at General Terminus Quay, Glasgow.

The object of this initial development was to lessen the dependence of the Colville Group on imported steel scrap by increasing the production of pig iron.

In 1959 work began on the construction of a strip mill, the main aim of which was to broaden the basis of the Scottish economy and, by providing a source of supply of sheet steel, to encourage the establishment and expansion in Scotland of the lighter industries which use this product.

The sixty-eight inch hot strip mill has a potential annual output of one and a half million tons of hot rolled sheets and light plates and the primary slabbing mill, which has a potential annual capacity of over two million tons, can roll bigger ingots than any other mill of its type in the world.

The addition of the rolling mills at Ravenscraig necessitated increasing the iron and steel making capacity of the works. On the ironmaking side, two more blast furnaces were installed, making three in all, together with associated coke ovens, by-product plant and facilities for handling increased tonnages of coal and iron ore.

For steelmaking, a fourth 250 ton furnace was built in the existing open hearth melting shop and a new basic oxygen steelmaking plant, consisting of two 100 ton LD converters, was constructed.

Associated with the hot strip mill at Ravenscraig is the new cold reduction mill at the nearby Gartcosh Works. At this works cold reduced sheet and coil are produced from the hot rolled strip supplied by Ravenscraig.

These two mills, with their modern equipment, produce, a wide range of strip mill products of the very highest quality identified by the trade name `Colcrest'.

Power Station

The power station is the control centre for all power and fuel distribution throughout the works.

BOILER PLANT

4 X 125,000 lb/hr and 1 x 200,000 lb/hr blast furnace gas/coke oven gas/oil fired bi-drum units. Stop valve conditions of 420 psig at 820°F. Automatic temperature and combustion control.

TURBINE PLANT

1 x 20 MW/30 MVA; 1 x 12.5 MW/28 MVA; 3 x 10 MW/ 11.6 MVA generators with automatic voltage control.

2 x 90,000 cfm / 32 psig and 2 x 90,000 cfm / 40 psig turbo blowers.

AUXILIARY PLANT

3 back pressure turbine pumping units exhausting steam at 160 psig into works process steam system and driving main power station circulating pumps and blast furnace cooling water pumps in tandem. 4 sets water treatment plant - filtration and zeolite base exchange units.

SWITCHGEAR

3 main 33 KV switchboards and 27 x 11,000 volt substations. Grid supply to plant - 275,000 volts, 180 MVA capacity.

Coke Ovens and By-Products

The coke oven installation consists of the following -

COAL HANDLING

Coal is received by rail and conveyed from two forty-five ton wagon tipplers to twelve blending bunkers, each of 500 tons capacity. Coal is blended from the bunkers and passed to one of three hammer mill crushers and thence to the battery service bunkers. Facilities exist for stocking and reclaiming blended coal.

BATTERIES

There are 210 Becker combination gas-gun ovens in six batteries of thirty-five ovens with a total capacity of 33,000 tons of coal per week. Each pair of batteries has a coal service bunker of 3,500 tons capacity and its own quenching tower and coke wharf. The ovens can be fired on coke oven or blast furnace gas. The oven chambers have an average width of 16 inches with 2 inches taper, and are 14 feet high

by 42 feet 4.75 inches between door linings.

BY-PRODUCT PLANTS

The by-product plants are based on the indirect method of ammonia recovery and extract from the gas, tar, ammonia, crude benzole and naphthalene. The ammonia is used to produce sulphate of ammonia and the crude benzole is distilled to refined products, while the cleaned coke oven gas is used as a fuel gas.

Ironmaking

ORE RECEPTION

All ore is imported, coming from such places as Canada, Sweden, South America and West Africa. The ore is discharged from ships at General Terminus Quay, Glasgow, and brought to Ravenscraig by rail in special trains consisting of bottom discharge wagons of 32 tons capacity.

On arrival at Ravenscraig, it is dropped into a 350 foot long slot discharge bunker and thence via two 1,500 ton/ hour rotary plough feeders and conveyor belts, is fed to ore screenhouses or to the stockyard (1,200 feet long by 170 feet wide). The ore is reclaimed from the stockyard by an ore bridge crane with a grab of 12.5 tons capacity.

SINTER PLANT

Sinter is an agglomerate made from fine ore and limestone, and by combining these materials in the sinter it is possible to reduce blast furnace coke consumption considerably. The sinter emerges from the sinter plant in porous lumps, and the relatively large internal and external area of these lumps means that correspondingly less fuel is required to process them in the blast furnace. The use of lime-sinter is thus an important part of modern iron making techniques.

There are two sinter plants, each with a single strand.

No. 1 Plant. The machine is 72 inches wide with grate area of 720 square feet, has 20 windboxes and a fan rated at 220,000 cfm at 30 inches wg and 350°F. Sinter is hot screened and delivered to blast furnaces by transfer car.

No. 2 Plant. The machine is 144 inches wide with grate area of 1,890 square feet, has 18 bifurcated windboxes and a fan rated at 450,000 cfm at 32 inches wg and 350°F. The rotary cooler is 70 feet in diameter. Sinter is cold screened and delivered to the blast furnaces by conveyor belt

LIMESTONE

The limestone required for the blast furnaces and also by the basic oxygen steelmaking shop is transported by a special shuttle rail service from Colvilles' new limestone quarry at Shap, Westmorland.

BLAST FURNACES

Coke, iron ore and limestone are charged into the blast furnace to produce molten pig iron. The three blast furnaces at Ravenscraig have a total capacity of some 30,000 tons per week.

They are equipped for high top pressure operation up to 1 atmosphere.

No. 1 Blast Furnace, 25 feet 9 inches hearth diameter. Three hot blast stoves at 110 feet high by 25 feet 1 inch diameter.

No. 2 Blast Furnace. 25 feet 9 inches hearth diameter. Three hot blast stoves at 130 feet high by 25 feet 1 inch diameter.

No. 3 Blast Furnace. 26 feet hearth diameter. Three hot blast stoves at 116 feet high by 26 feet 9 inches diameter.

Hot metal is taken to steelworks in 200 ton capacity mixer cars, or 75 ton capacity Kling ladles.

Steelmaking

Steel is made by melting scrap with molten pig iron from the blast furnaces together with fluxes and oxidising materials. At Ravenscraig, steel can be made either in the open hearth melting shop or in the basic oxygen steelmaking plant.

OPEN HEARTH MELTING SHOP

This consists of five bays - the box filling, charge holding, furnace, casting and mould preparation bays.

Ore, limestone, etc., are handled in the raw materials plant which consists of a 50 ton wagon tippler feeding 8 storage bunkers of 35 tons capacity. An ore stockyard of 12,000 tons capacity serviced by a 3 ton capacity MonoTelpher crane is also provided.

The furnace bay contains three 250 ton open hearth furnaces of conventional design with silica roofs and basic linings and uptakes, and one 250 ton all-basic furnace of Maerz-Bollens design. Two 800 ton capacity inactive mixers provide storage for the molten iron which constitutes approximately 65 per cent of the furnace charge. The charging boxes which carry the scrap, ore, limestone, etc., are moved on bogies which are pushed across the front of the furnaces, the boxes being emptied into the furnaces by a 10 ton non-rotating charging machine.

The open hearth furnaces are fired with fuel oil and are equipped with shell-type fire-tube waste heat boilers which each produce 35,000-50,000 lb/hr steam at 300 psig and 720°F.

The steel from the furnaces is tapped into a single 250 ton capacity ladle which is carried by one of the two 375 casting bay cranes. The charge is teemed into a train of ingot moulds set on casting cars; the ingot size varies from 7 to 34 tons.

The moulds are removed in the stripping bay by a 40 ton stripper crane with 400 ton stripping capacity and the ingots are despatched to the slabbing mill.

BASIC OXYGEN STEELMAKING

In the basic oxygen process, oxidation is effected by injecting a stream of pure oxygen containing finely powdered lime, produced in the lime burning plant, on to the surface of the molten iron in the steelmaking vessel. This operation results in the oxidation of the impurities out of the iron and in doing so generates the great heat necessary to complete the steelmaking process.

The basic oxygen process is very rapid and a 100 ton charge of high quality steel is made in less than an hour. In an open hearth furnace, on the other hand, about eight hours are needed to make a 250 ton charge of steel. To prevent atmospheric pollution in this process, the exhaust fumes are treated in an electrostatic gas cleaning plant.

BASIC OXYGEN STEELMAKING SHOP

This consists of four bays - the charging, converter, casting and stripping bays. The steelmaking process employed is the LD/AC, or lime-injection, process and can operate with a hot metal/scrap or hot metal/ore charge.

The charging bay is 78 feet wide by 488 feet long. At one end is the pouring station for 200 ton hot metal mixer ladles and at the other end the scrap area where the scrap is loaded into the 25 foot long by 4 feet 6 inches wide scrap chutes. Both hot metal and scrap are weighed and the bay is serviced by a 160/50/20 ton capacity hot metal crane, a coupled twin hoist 40/30 ton capacity scrap charging crane and a 12 ton capacity scrap filling magnet crane.

The converter bay is 62 feet wide by 488 feet long and houses the two 100 ton converters, with space for a third vessel. Vessels are lined with unfired tar dolomite blocks and equipped with a two-speed electric tilting drive. The injection lances are 46 feet long and the 8 inch diameter lance consists of an outer water cooling jacket, an annular space through which the main oxygen stream is injected at about 140 psi and a central bore through which the powdered lime is injected, carried by low pressure oxygen. The waste heat boiler has a peak capacity of 120 tons/ hour at 1,200 psig which passes to accumulators and then to the superheaters which produce steam at 600 psig and 870°F. After leaving the boiler, the gases are electrostatically cleaned and the recovered dust is pelletised. The converter bay also houses the raw materials conveying, storage and weighing system and the lime-crushing and conveying system.

The casting bay is 105 feet wide by 488 feet long and includes five independent transverse teeming platforms, serviced by two 400/50/10 ton capacity stripping cranes. After stripping, the ingots are loaded into articulated trailers for transfer to the slabbing mill.

TONNAGE OXYGEN PLANT

The oxygen for this process is produced in a tonnage plant consisting of one 200 ton/day Tonnox plant and one 200 ton/day Rescol plant. In addition to supplying the requirements of the basic oxygen steelmaking shop, oxygen is distributed to Colvilles' works in the Motherwell area at 600 psi pressure.

LIME BURNING PLANT

Stone handling and storage: Minus 8 inch plus 4 inch limestone is fed by conveyor belt from a track hopper below ground level to the three 680 tons capacity kiln bunkers, passing over a 2 inch 350 tons/hour Gyrex screen en route. A separate 300 ton capacity storage bunker is provided from which limestone can be stocked-out by dumper truck.

Kilns: There are three vertical shaft, skip charged kilns, each with six tuyeres. The hot exhaust gases are used in a heat exchanger to preheat the fuel gas of 130 BTU/cubic feet. The kilns are charged with minus 8 inch plus 2 inch stone and each kiln produces 5 tons/hour of burnt lime. Lime processing: The burnt lime from the kilns passes over a 2 inch grizzly screen whence the oversize passes to a 24 inch by 40 inch single roll crusher for reduction to minus 2 inches. The combined product is then fed by conveyor to the basic oxygen steelmaking plant, while rail loading facilities are available for transporting the lime to other processes.

The combination of open hearth and basic oxygen techniques at Ravenscraig allows extreme flexibility in steelmaking.

SLABBING MILL

From the melting shops the ingots are conveyed to the 2 high slabbing mill. Here, after reheating, they are rolled into slabs either for Ravenscraig hot strip mill or for the heavy plate mill at the adjacent Dalzell Works. For strip making the slabs are about 25 feet long and 8 inches thick, but before being rolled in the strip mill the slabs are allowed to go cold. They are then examined carefully and any surface imperfections are removed by means of an oxygen/propane torch. In the slabbing mill run-out line a special machine is installed which can perform this dressing operation automatically on four sides of the slab as it passes through the mill.

The slabbing mill bay is 95 feet wide and the total length occupied by the mill and main units is approximately 900 feet. In the adjoining bay, which is also 95 feet wide and over 1,000 feet long, all slab cooling, examination, hand scarfing and despatch are carried out.

SOAKING PITS

There are 8 coke oven gas/oil one-way top fired soaking pits each 28 feet long by 11 feet wide by 14 feet 6 inches deep with normal holding capacity of 145 tons; the pits are not equipped with recuperators ; each pit is equipped with a water-tube type waste heat boiler, with a capacity of 10,000 lb/hr and a stop valve condition of 600 psig at 870°F.

There are two 12-cell electric soaking pits, each cell measuring I o feet 6 inches by 4 feet 6 inches wide and able to accommodate ingots of up to 2 1 tons, giving a maximum holding capacity of 250 tons. Heating is by means of resistors in coke-filled troughs which run the full length of the pit.

The soaking pit bay is served by two cranes designed to handle ingots up to 40 tons.

ROLLING MILL

The mill is a 2-high, high lift reversing mill, with each roll individually driven by a 7,250 hp motor at 50/80 rpm. The cast steel rolls operate in roller bearings and are 50 inches in diameter by 138 inches long with a maximum opening of 80 inches and a barrel length of 68 inches.

The mill is equipped with sideguard manipulators on both of its sides, and five lifting fingers on the ingoing side. The screws for the top roll are not coupled mechanically but each is driven by a 600 hp directly coupled motor, vertically mounted on the housing top. These motors are electrically synchronised.

Automatic four-sided hot scarfing equipment can be inserted in the production line. It operates at 40 psi and a table speed of 100 ft/min using an oxygen/propane flame.

SLAB SHEAR

Slab shear is an air-hydraulic 3,000 ton down and up cut shear and can shear any section up to 72 inches wide and/or 1,296 square inches. The maximum opening of the shear blades is 26 inches. The stop-measuring gear can measure up to 360 inches long.

Slabs are transferred to the cooling, dressing and despatch bay via a piling table and rope hauled transfer carriage with a capacity of 40 tons.

Strip Mill

RE-HEATING FURNACES

Before being rolled in the hot strip mill the slabs are brought up to rolling temperature in one of two continuous furnaces.

VERTICAL SCALE BREAKER

From the slab reheating furnace, the slabs proceed down the roller tables to the vertical scale breaker. Here they pass through a pair of vertical rolls which squeeze the slab sideways and crack the furnace scale across the surface of the slab; the scale is then washed off by high pressure jets of water.

HORIZONTAL SCALE BREAKER

After the vertical scale breaker, the slabs pass through a pair of horizontal rolls and the process of scale cracking and removal is completed. In this stand, a limited degree of reduction takes place and the slabs, now a little longer, pass down the next set of roller tables to the 4-high reversing roughing mill.

THE 4-HIGH REVERSING ROUGHING MILL

The object of this mill is to prepare for the finishing stands a piece of steel of about one inch thick and, on the full slab size, about 200 feet long. This reduction is achieved by means of from three to seven passes backwards and forwards: horizontal rolls effect the reduction and vertical rolls control the width. The mill is wholly automatic, each operation controlling the succeeding operation.

6 STAND 4-HIGH FINISHING MILL

After leaving the reversing roughing mill, the slabs are conveyed down the roller table to a crop shear which cuts off the front end of the slab in order to present a straight leading edge to the finishing mill. In these six finishing stands, the slabs are progressively reduced in thickness to the gauge required. The reductions in thickness are quite severe, being from approximately one inch to as thin as 0.0495 inch. In reduction, the strip is elongated as it goes through each set of rolls and each set of rolls therefore revolves faster than the one preceding. By the time the steel leaves the sixth stand of the finishing mill, the piece can be up to 4,000 feet long and travels at a speed of up to 2,750 feet per minute (31mph). On the run-out tables the strip is cooled under water sprays and then caught in a coiler. These hot rolled coils are the finished product of the actual hot strip mill.

FINISHING

The first function of the hot strip mill is to produce hot rolled coils of suitable gauge to go to the Gartcosh mill for cold reduction. Hot rolled coils not being cold reduced can be sold in coil form, or as light plates in the thickness range 3/8 inch to 1/8 inch, or as hot rolled sheets under 1/8 inch. To produce hot rolled light plates or sheets, the coils are taken to the adjacent finishing bays where they are uncoiled and cut to length. Special flattening arrangements are incorporated in the shearing lines. Further equipment includes a temper mill designed to impart the required degree of flatness and surface hardness, a slitting line to enable coils to be slit from a wide coil into several coils of narrower width, and facilities for pickling.

AUTOMATION

Among the most interesting and useful applications of automation at Ravenscraig is the control of the 4-high reversing roughing mill. Here the process is entirely automatic from the time the hot slab arrives at the entry side of the mill from the re-heating furnace until it leaves the mill after anything between three and seven passes backwards and forwards through the rolls. Once the mill has been set for the particular size of slab to be rolled, roll adjustments and the reversing of the mill motors follow a programme pre-set in the control cabin. It is largely because of the speed of operation made possible by automation that this single-stand reversing mill can perform a job which, in a fully continuous mill, would require five or six separate stands.

The 6-stand finishing mill has been engineered with full automation in view, and the six continuous stands which are at present not fully automatic in operation have been designed so that they can be controlled by a simple electronic computer.

CLOSED-CIRCUIT TELEVISION

Three closed television circuits are used at the slabbing mill. One of them exhibits the rolling programme to the men in the operational pulpits, another assists the operator in controlling the slab on the outgoing side of the mill, and a third enables the crane operator at the soaking pit to see inside the pit. At the strip mill twelve television cameras, carefully placed at key positions between the slab reheating furnace and the coilers, enable the various operators in their control cabins to get a better and closer view of the strip as it travels down the rolling line.