The decision to build Trostre Works on this site was, in the main, for sociological reasons. A number of the old type of hand mills had or were about to close, leading to prospective unemployment for around 12,000 local people. For a long time, Llanelli and the surrounding districts had been an important centre of tinplate manufacture. As a result, a large section of the local population bad acquired the skills and knowledge of the trade which would have otherwise been wasted. The building of Trostre helped to obviate this.

Building started in August 1947 on what was formerly marshland. Production started gradually, beginning in 1951 but soon grew to an annual output of 400,000 tonnes a year. Today, through continued investment in modern production equipment, the anticipated annual output for Trostre is 500,000 tonnes a year.

Over this time, Trostre Works has remained a leading supplier of high quality light gauge steels supplying over 50 countries worldwide. Substantial investment in new plant and technology, people, training and research and development, keeps Trostre at the forefront of European tinplate production.

The feedstock material for the production of tinplate and tin free steel is hot rolled coil which is produced by the Corus Strip businesses in South Wales (mainly at Port Talbot) and the Netherlands. The coils arrive via the railway in specially designed rail trucks and are stored in the purpose built external facility at the entry end of the Pickle Line.

The first stage of converting hot rolled coil to tinplate or ECCS (chromium plated steel) is the removal of high temperature surface oxides formed during the hot rolling coil process. To achieve this the steel is passed through a series of tanks containing sulphuric acid. The acid is contained in five acid tanks and the strip passes through each one before being rinsed, dried and side trimmed. The top and bottom surfaces of the coils are electro-statically oiled to aid rolling at the 5 stand and to protect from surface rust.

A continuous operation is achieved by automatically welding the leading end of the new coil to the trailing end of the previous one. The line is over 226 metres long and has the ability to process a 23 tonne coil in under 8 minutes.

At the exit end the coils are recoiled, banded and identified before being stored in racks ahead of the 5 Stand.

After pickling, the coils are then reduced in gauge by the 5 Stand Tandem Mill which consists of 5 sets of back-up and work rolls, loaded using hydraulically powered capsules and apply loads of between 700 and 1,200 tons per stand. Work rolls are changed frequently to maintain quality standards with around five pairs changed per shift on average. Back-up rolls are changed less frequently at around three weekly intervals.

The coils are reduced from a typical 2mm down to any thickness ranging between 0.61mm and 0.16mm.

The gauge reduction is achieved by a combination of roll pressure and strip tension, using the very latest world-class technology. This incorporates computerised speed and hydraulic control systems for ultimate process control and accuracy together with gauge and shape control systems – essential for creating the steel flatness required by our customers. The line can process up to 920 tonnes per shift at typical rolling speeds of 1,500 m/min.

The cold reduction process leaves the steel stiff and brittle which is unsuitable for container production. This is rectified by the strip passing through the next production unit – annealing,

Annealing is a controlled process of heating and cooling which gives the steel its required hardness. Two different annealing processes are used at Trostre: continuous annealing and batch annealing depending on the end application.

Before annealing can begin the strip is meticulously cleaned to remove any trace of roiling residue. To achieve this the strip is passed through an alkaline electrolytic cleaning section and subsequently scrubbed, hot rinsed and dried. Cleaning before the batch annealing process is carried out separately at the electrolytic cleaning line but is incorporated into the continuous annealing line processes.

BA is generally used for products which need to be softer and more ductile for deep drawn applications. Four coils are stacked on to an annealing base and separated by convector plates to ensure even heat distribution. A cover is placed over the stack, which is then filled with an inert hydrogen/nitrogen gas mixture to prevent oxidation of the strip surface. A furnace hood is then lowered on to the whole arrangement before the heating and cooling process begins, usually for around 48 hours.

In 2002, work began on the development of four new hydrogen annealing bases, transferred from the Corus plant at Shotton, to bring additional BA capacity to the Works. These were scheduled to be completed and operational during 2003.

Continuously annealed products are generally harder than those produced through batch annealing. They are ideally suited to a number of applications including can ends and bodies. The physical strength of continuously annealed products allows ‘down gauging’ whilst maintaining premium performance.

Continuous operation is achieved by automatically welding the leading end of a new coil to the trailing end of the previous one. Strands of steel strip pass through the cleaning, rinsing, heating and cooling sections. As with batch annealing, the heating process is carried out in an inert atmosphere but is quicker and more intense. The strip is heated up to 700°C, with any one pant of the strip taking about 3 minutes to pass through the complete heating and cooling cycles.

Trostre has two CA lines, the CAL and the CAPL. The CAPL is the most modem, commissioned in 1988 at a cost of £60 million, plus additional line improvements over the years to enhance performance. As the name suggests, the operation is continuous, a process achieved through the use of two entry and exit reels. At any one time there will be 3,000 metres (3 kilometres) of strip running through the line. The furnace section of the line heats the strip to a selected temperature within a 650°C to 690°C range. This temperature is maintained through the mid section and the strip is gradually cooled in the final furnace. Further cooling is achieved by the strip passing through cooling chambers and a quench tank. Finally the strip is recoiled for further downstream processing.

CA coils can be processed in 15 to 20 minutes while the BA cycle can take anything up to 6 days. Annealed coils are banded and protected from handling damage by plastic edge and core protectors before passing on to the secondary rolling process either at the Temper Mill or the Double Reduction Mill.

After annealing the steel strip undergoes a second. rolling process in a two-stand Temper Mill. This mill is a 2-stand tandem mill consisting of two sets of back-up and work rolls.

This operation gives the steel the final mechanical properties and flatness as well as the customer’s required surface finish. The elongation of the strip (typically 1½%) is tightly, and accurately controlled to achieve the properties required in today’s demanding container formation processes.

The second set of rolls gives the steel its surface finish which suits the particular end use of the product. Precise control of roll forces, roll camber and surface roughness ensures the highest level of accuracy for the critical shape demands of the customer. Three principle finishes are currently rolled at Trostre, Stone, Bright and Matte (though there are variations of each finish).

Canmakers are constantly striving to reduce the amount of material required for packaging without compromising on strength or integrity. One method with a proven record of success for a diverse range of applications is ‘double reduction’. This process takes annealed material and further reduces its gauge by up to 40%.

The Double Reduction mill has 3 sets of rolls through which the steel strip is cold reduced to produce thinner material. The mill consists of 3 stands of back up and work rolls. Reduction is achieved in the same way as the 5 stand mill, through a combination of roll pressures and increasing tensions.

On-line micro-electronic control systems ensure tight tolerances on gauge and shape. The process gives enhanced strength at thinner gauges and makes the material ideal for welded food can bodies and the draw-re-draw technique for two-piece cans.

After tempering or double reduction, coils; are once again banded and protected against damage before being transported by tractor to the Coil Protection or the Coating Lines.

If required, coils can be trimmed and inspected prior to the coating process. One of the two remaining lines is used as a coil inspection line for finished products with the objective of ensuring that no defects reach the customer. However the majority of work today is trimmed as well as coated on the coating lines themselves.

Before tinning, the steel is cleaned and pickled to produce a perfect surface. The tinning process involves the coils passing through. tanks, holding an electrolte solution, at speeds of up to 450 metres a minute. An electric current is applied resulting in a precise deposition of tin on each side of the strip. For bright finishes the strip is also passed through a heated section which ‘flow melts’ to produce a shiny surface.

The next stage is chemical ‘passivation’ which stabilises the surface before electrostatic oiling for further protection.

Electrolytic tinning incorporates modem ‘tension levelling’ technology which produces excellent flatness. In addition to automatic monitoring the strip is also given a critical, visual examination before recoiling. All information is fed into a data logging computer which provides a quality summaty for each coil. Trostre has two Electrolytic Tinning Lines – ETL5 which was built in the 1990s to meet the demands of the DWI (wide) route; and ETL6 which was transferred from Ebbw Vale in 2003. These two lines enable the production of material up to 1,200mm wide and within all the required gauge parameters.

Increasingly acknowledged as an alternative to tin coated steel for a variety of applications. ECCS is produced by a similar electrolytic using the same steel substrate as tinplate but is coated with a combination of chromium and chromium oxides.

As with other coating lines, the latest ‘seam’ welding machines produce a fully integral join between coils with no loose edges and and minimun strip overlap. This not only eliminates the possibility of damage to customer’s equipment but also improves yield and efficiency by maximising the coil size.

Ferrolite is an advanced multi-layered material developed, specifically for the packaging industry, combining the advantages of steel with sophisticated poltmer coated technology: Excellent performance and formability are the main attributes of this product which is available in a variety of film coatings for a wide range of end uses.I

The production process involves the application of polymer films to the steel strip, normally using ECCS as the base. The steel substrate is induction heated before the film is applied. The coated steel is then post heated to form a strong bond between the film and substrate before being water quenched. The sophisticated instrument system together with advanced temperature control and visual inspection, ensures a final product with consistent adhesion, appearance and structure.

Coil inspection facilities allow the selective inspection of coils from the coating lines and is a clear demonstration commitment to the highest quality standards. Inspection lines are fitted with gauge and pinhole monitoring equipment as well as illuminated morror systems for visual inspection.

As well as coiled products, there is considerable customer demand for material cut into flat sheet . Coated coil is subjected to automatic quality checks for flatness, gauge and any holes before being cut into sheets of the required length by Hallden Shears, and finally a visual inspection before being stacked for packing and despatch.

The final process is the thorough and careful packaging of the finished products prior to storage and subsequent transportation. Both coil and flat sheet are meticulously packed in custom-designed and specially treated material to give utmost protection during storage and transportation. This ensures that the same amount of care is taken over the protection of the material and its correct documentation during transit as is applied during production.

The Roll shop is where the rolls used in the various mills are recovered by grinding the steel barrels to remove any bruising or damage and to restore the require surface finish and barrel profile. All mill rolls are serviced the Roll shop in this way. Some are sent for a hard chrome finish after surface .preparation which for some mill rolls includes shot blasting the surface for certain applications.

The bearings and their carrier boxes (or chocks) for all mill rolls are also serviced in the the roll shop to ensure that the mills are furnished with high quality equipment to enable the achievement of exacting demands in terms of gauge, shape and surface finish.

The stores department in Trostre runs 52 weeks and 365 days a year. More than 80,000 items (with a value exceeding £25m) are stored there andover 200 items pass through the department every day

New state of the art storage equipment has recently been transferred from Ebbw Vale in the form of a carousel and 3 shuttle lifts. The new equipment is 12 metres high and is designed to maxmise space and efficiency for the storage of spares, creating an effective storage area of 671 square metres with a load capacity of over 130 tonnes and storing them securely and cleanly in a fire-protected area. The equipment also allows pick times (the time it takes to retrieve an item from its holding position) to be vastly reduced.

Trostre works is a complex manufacturing facility containing closely linked processing units. The value of a works of this type is approximately £1 billion at today’s prices. In order to be profitable the units are required to operate 24 hours hours a day, 7 days a week. A failure on one unit can very quickly bring the whole plant to a stop. Failure on one unit will very shortly stop the lines that are fed by the failed unit [down stream], as they, will run out of material to process, also the lines feeding the failed unit (upstream) will in time be forced to a stop.

Reliability, safe operation and efficient running of the units meaning operating at a good rate of output and minimum defect level, is paramount. Effective maintenance and servicing is a vital pre-requisite to securing a reliable, safe and efficient operation.

It is not only the equipment on the lines that needs to be cared for, trostre works is like a small Town. It has an infrastructure, buildings, roads,:sewers, electricity, water, steam, waste treatment, all of which need to be cared for as a malfunction of these facilities will also bring the plant to a standstill. Additionally, environmental requirements mean that our facilities need to operate efficiently and without risk of damage to the natural surroundings.

Trostre offers a full range of mechanical properties to a variety of surface finishes and dimensions. At any one time there may be in excess of 600 different specifications being processed. This complex operation is efficiently managed by computer tracking of every item and by statistical process control at the operating units. This ensures that each item is manufactured precisely to the customer’s specification and end application.

A key aspect of high quality achievement is the ability to demonstrate recognised independent standards. Independent certification through Lloyds Register Quality Assurance approval has been achieved which means that the quality management system has been examined in detail and meets the requirements laid down by the British Standard BS5750 (Part 2) 1994, as well as the International Standard ISO 9002.

The main units are fitted with automatic surface vision recognition systems. These systems inspect the material automatically to sub-millimetre detail, whilst the strip is moving at 500 mph. Each system comprises 27 Pentium processors to analyse the data.

The logistics department is split into two principle sections – Production, Planning and Control (PP&C) and the Customer Service Group. PP&C is responsible for managing the Trostre order book by optimising production at the plant in order to meet customer requirements. The Customer Service Group provides the essential link between the Works and the central Commercial team at our Head Office in the Netherlands. This group also liaises with customers to synchronise order shipments.

At the commencement of operations in 1952 all our processes were manually controlled and our communications paper based. In 2002 all Trostre’s manufacturing units are now managed by automated process control computers, which enable the production of a consistent world-class product. All our data storage and processing information is held on a mainframe computer and our personal communications assisted by using over 400 networked PC’s.

The works was one of the first large manufacturing sites in the UK to attain ISO 14001 accreditation – the European Standard for Environmental Management.

Photographs © Andy Taylor 2003

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