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Success stories

Carbolite’s Moving Wall Coke Oven enables Thermal Technologies Centre Sponsored Process Innovations in Biomass Torrefaction

A recently installed Carbolite 350kg Moving Wall Coke Oven is making a real difference to investigations taking place at the Thermal Technologies Centre at Redcar, UK. The Carbolite oven is designed to test the forces produced during carbonisation of a 350kg sample of coking coal as a measure of the forces generated within a full-scale industrial coke oven and thus enabling the optimal processing of coking coals of varying grades and origins. In addition to its conventional application the Thermal Technologies Centre plans to use the Carbolite oven as a large scale batch pyrolysis oven to test the torrefaction of biomass materials. In a process similar to coke manufacture, torrefaction involves baking wood and other biomass materials to increase their energy density. By driving off moisture and low energy volatile materials, a product is left behind which is much easier and more economical to transport and handle and can be more easily co-fired in existing coal plants.

Carbolite’s Moving Wall Coking Ovens are normally used for testing suitably granulated and graded coals under accurately controlled conditions. They are used to optimise the coke manufacturing process by enabling operators to avoid excessive coking pressure during operation, something that is known to affect the longevity and integrity of production scale coke ovens. As the contents of the test oven are heated, pressure is exerted against a fixed wall on one side and a moving wall on the other. A load transducer, activated by the moving wall, measures the extent of the pressure. All instrumentation is housed in a separate control cabinet to reduce any risk of damage. A variety of oven widths is available from Carbolite meaning there is one to fit any line, and accessories such as charge hoppers, discharge rams and wet or dry quench carts allow customers the flexibility to fit the ovens into their operations.

The Thermal Technologies Centre is a collaboration between Tata Steel and the Centre for Process Innovation (CPI). The Centre for Process Innovation is a member of the High Value Manufacturing Catapult, one of a network of seven ‘Catapult’ centres established and overseen by the Technology Strategy Board in partnership with major public sector industrial partners and Universities. The batch pyrolysis oven is co-located with a large scale continuous flow gasification test rig. The objective of the Catapult centres is to bring together state of the art resources, innovation and research in order to improve the UK's commercial exploitation of current and future advanced technologies and drive forward economic growth.

Accuracy of Carbolite ovens proves invaluable to testing at the James Walker Technology Centre

Carbolite ovens are making a real difference to work being conducted at the James Walker Technology Centre in Cockermouth, UK. The centre has been equipped with twelve 120-litre capacity, 300°C, Peak ovens for high-temperature product testing. James Walker provides fluid sealing products and associated knowledge-based services to a broad range of industries, from pharmaceuticals to oil and gas. Control and quality are high on their list of priorities, and this is reflected in the selection of Carbolite equipment.

Following extensive flooding in 2009, James Walker took the opportunity to update and upgrade equipment. The James Walker Technology Centre team selected the Carbolite ovens which are now used as part of the research, design and quality control processes. Samples are aged in the oven for up to several weeks at temperatures ranging from 70°C to 250°C to monitor any changes in the materials. Due to the precise nature of the work, it is vital that all equipment used at the centre delivers consistent results and has excellent control uniformity, allowing the required standards to be met.

“Carbolite ovens and furnaces are extremely accurate and we can rely on them to hit and maintain the correct temperatures. They are robust and easily serviceable, but if we ever do have any queries they are dealt with quickly and efficiently,” said Andrew Douglas, Lab Manager of the James Walker Technology Centre. “We already used several Carbolite large factory ovens on site, and knew that they could provide us with high-quality equipment that met our needs completely. Having reliable products which meet both British and International standards is vital for us and our customers, and the Carbolite ovens help us hugely in achieving this.”

Carbolite oven accelerates Formula 1 aerofoil development

An increasingly important aspect of many Formula 1 racing teams’ engineering operations are sister companies focused on commercialising and developing Formula 1 spin off technologies and IP into the wider automotive and aerospace engineering sectors, as well as other advanced high performance engineering applications.

Carbolite has many Formula 1 teams amongst its customers so when the company was approached by one the most successful Formula 1 teams on the grid to help ‘give their car wings’ it was taken as read that Carbolite would have a product to solve the racing team’s requirements.

Excellence in engineering is required to stay ahead in Formula 1 and demands that the Milton Keynes based company is continually designing, developing and refining prototype components and sub assemblies which need to be built, assembled, tested and then re-engineered to meet specific high performance requirements. As part of this challenging development cycle Carbolite has supplied them with a customised LGP3-1500 high specification large general purpose oven to implement post curing drying of composite moulds and moisture extraction for adhesives used for a variety of component parts such as carbon fibre composite body parts and aerofoils.

The customised oven ensures reproducibility in the curing cycles by incorporating a controller option which enables five different programmable temperature profiles to be stored and recalled and also includes RS232 communications. The operator can easily select the correct ramp rate and heating duration for the job at hand. The valuable loads and oven are protected by the addition of an independent over temperature protection thermostat and a further option in the form of a top mounted moisture/fume extraction fan was also installed, enabling process fumes to be ducted away from the work area. Based on Carbolite’s standard design the 1500 litre capacity, large general purpose oven has an operating temperature range from 50°C to 300°C with a uniformity of ±5°C and control accuracy of ±5°C.

An additional requirement was customisation of the standard design so that the control panel was side mounted rather than in the conventional front mounted position. Relocation of the control panel module required the oven’s air circulation fans and baffle assembly to be mounted into the oven base rather than into the side or rear.

Carbolite constructs a furnace for the thermal treatment of foamed ceramics

The Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden is using a Carbolite furnace to research debinding and sintering of ceramics as part of in-depth investigations into the application benefits of foamed ceramics.

The research at Fraunhofer IKTS required a custom-built 35 litre capacity 1400°C furnace with silicon carbide heating elements. Additionally, Fraunhofer IKTS required the furnace to provide improved management of the toxic cyanide, isocyanate and nitrogen dioxide fumes which were produced from their previous, conventional furnace, as the polyurethane foam matrix and organic binders were burned-off. This was achieved this by mounting a secondary catalytic after-burner on top of the primary chamber furnace.

The after-burner derives from a modified variant of a Carbolite ‘G-range’ tube furnace incorporating a central core comprising a catalytic labyrinth to ensure the toxic fumes are fully combusted. Samples containing up to 150g of polyurethane can now be tested with the processed fumes from the furnace now being fed into the Fraunhofer's extractor system which operates at 150 to 250 litres/minute.

The overall solution is designed and constructed to automatically run through variations on a two step temperature cycle. For debinding purposes the furnace runs at 600°C, but the furnace also needs to run at 1290°C for sintering of the ceramic foam once the binder has burned off. To protect the afterburner, a damper system is fitted, which is designed to close automatically when the main furnace temperature exceeds 600°C.

The furnace is specially constructed to ensure the exhaust fumes are introduced to the catalyst at the optimum effective temperature for catalytic performance, without damaging the catalyst. To achieve optimal catalytic conditions the furnace system is equipped with a sophisticated control system. The main furnace chamber and the sample being studied are protected by a variable temperature and over-temperature protection thermostat in addition to the main programmable controller.

Additional control equipment includes an afterburner controller pre-set at 550°C plus a flip-flop over-temperature device set at 750°C in order to protect the afterburner.

Carbolite raises the roof on an advanced ceramic materials production process

Facing the introduction of a new manufacturing process to its Gloucester production facility, the abrasives division of a major multinational manufacturer of advanced ceramic materials needed to rapidly replace some large raised hearth furnaces which had reached the end of their useful lifespan.

Carbolite was asked to meet the challenge and quickly realised that rapid implementation of a well trusted design was crucial for the abrasives manufacturer to ensure the new manufacturing operation had the best chance of starting on schedule.

The requirement called for a rapid cycling batch furnace capable of de-binding and sintering 100kg of graphite matrix with a ceramic powder inclusion at up to 1000°C, under a reducing atmosphere of nitrogen and hydrogen. The design is well tested, having been previously built for several export customers.

Unlike previous occasions this application did not require an afterburner, but it was vital that a 600 x 1200mm Inconel 601 retort was used to contain the nitrogen/hydrogen atmosphere. Inconel-coated catch trays were also added to the retort to capture any process material that might fall from the load. As the nitrogen/hydrogen reducing gas was pre-mixed and below the explosive limits for hydrogen, it was not necessary to provide the gas safety system which Carbolite would normally provide when working with higher concentrations of hydrogen.

Uniform heating of the load was critical so a 3-zone control system compatible with the aerospace standards NADCAP Class 2 / AMS 2750D was installed, which offered optimum control uniformity. Each of the three zones was equipped with its own independent over-temperature protection device and at the heart of the control system a sophisticated multiple segment programmer system was fitted that was able to recall multiple separate, process specific, temperature profiles.

To enable fast turn-around times between process batches, a wheeled load handling device featuring a jacking lift mechanism was included in the specification. Faster cooling of the retort at the end of the process was achieved using an electrical lifting device which progressively raises the highly efficient, low thermal mass, insulated roof of the furnace to allow heat to escape more quickly.

Custom oven solution divides to conquer aerospace manufacturer’s increased capacity challenge

When a large blue chip aerospace manufacturer’s paint and coatings plant based at Filton in Bristol in the UK faced the need to expand capacity to handle increasing demand, the organisation soon realised that the Carbolite ovens it was using were no longer large enough to satisfy the new production output requirement.

The need to expand capacity at the aerospace manufacturer’s combustion and castings operation called for a new much larger paint stoving and curing oven that would meet the need for a strict internal performance specification or ‘Statement of Requirement’ (SOR) as well as conform to the specifications of the aerospace heat treatment regime of NADCAP / AMS 2750D Class 2.

An initial assessment of the challenge suggested that one of the heavy duty industrial ovens from Carbolite’s LGP (large general purpose) range looked to be the ideal solution to the increased capacity constraints. Carbolite’s LGP 6/2700 provides a durable stainless steel interior with 2,700 litre capacity and a maximum operating temperature of 600°C. The system’s powerful horizontal airflow offers excellent uniformity.

On further review of the requirements it quickly became clear there was a key compelling obstacle to installing a standard oven. Put simply, the size of the oven required would not fit through the aerospace manufacturer’s workshop doors. However, as all Carbolite ovens are designed and built to order in Carbolite’s UK factory, design modifications can be made simply and precisely.

Carbolite simply cut the oven design in half. Once built, the two modules were re-assembled in order to enable the customer to view, test and approve the oven’s performance at Carbolite’s factory. On approval, the oven was again split into separate halves for delivery and installation. At the Filton site, Carbolite’s engineering team then reunited the two halves in their final working location.

Carbolite also supplied a range of custom options including a twelve channel chart recorder, independent over temperature protection, a tower light to signal the process cycle and over temperature status, explosion relief panels, forced cooling and exhaust dampers as well as a reinforced base for additional load carrying. An internal panic switch was also fitted to prevent entrapment. Once activated the switch shuts down the oven and sounds an alarm.


Customised tube furnaces offer thermoelectric material researchers a versatile processing solution Carbolite has supplied the Fraunhofer Institute for Physical Measurement Techniques (Fraunhofer IPM) in Freiburg, Germany with a test rig that comprises two specially customised wire wound horizontal three-zone tube furnaces. The customised furnaces, based on a system that was developed by the Fraunhofer IPM in 1981, will provide the Institute’s research teams with a versatile processing system for studying and improving the thermo-electrical properties of advanced thermoelectric materials and systems.

The Institute will use the two separately controlled, rail-mounted three-zone tube furnaces to play a key role in optimising compound semiconductors. The systems are designed to maximise operational flexibility by combining the two furnaces to form a single large multi-zone furnace, or separating them to give two differently heated regions with a gradient of 200°C between the two. The three-zone tube furnaces feature a specially developed desk and rail system that provides vibration-free movement of the furnaces and is constructed to support a very long fixed quartz tube through both furnaces.

Fraunhofer IPM is engaged in research on new materials, particularly nanocomposites and the Institute's scope of activity includes materials research, development of thermoelectric modules, thermoelectric simulation, measuring technology and systems. Thermoelectrical energy harvesting will increasingly provide a significant contribution to more efficient use of energy in the future and will be featured in a wide range of power plants, industrial processes or automobiles.

Fraunhofer IPM has extensive experience in the entire range of thermoelectric technologies which include studying and developing processes for production of nanoscale thin layer systems using different coating and epitaxial processes; production and processing of solid materials; assembly and packaging technologies as well as thermoelectric measuring technology.

A double horizontal tube furnace was supplied by Carbolite to maximise the temperature gradient capabilities of the system. The two three-zone furnaces have different sizes. The larger has a heated length of 600mm, the smaller 400mm each with an integral recrystalised alumina work tube. The three zone design of the furnaces uses three controllers to apply separate control to the central zone and each of the end zones in each furnace. These end zone controllers, with their own thermocouples, compensate for the tendency for tube furnace ends to be cooler and ensure that the furnaces have a longer uniform zone than can be achieved with only one control loop.

Each of the two furnaces is equipped to accept an accessory tube with a maximum outer diameter of 65mm. The customised system also includes smaller end insulation discs between both furnaces to enable a more linear temperature gradient from the one end of the furnace to the other. Power to the furnace’s end zones is automatically adjusted to compensate for heat loss.

To provide a more user-friendly, ergonomic working environment the furnace systems feature separate controller boxes which are specially positioned under the worktable. The furnaces are specified to operate at a maximum temperature of 1200°C, but by using modified control algorithms they are able to operate between 150°C and 600°C. Before deliver to Fraunhofer IPM, test measurements between were taken beween 500°C and 700°C to ensure good uniformity in each middle zone, a sharp linear gradient in the middle of both furnaces and a small thermal wall of 15°C in both outer end zones.

Carbolite furnaces play key role in sample preparation at Diamond Light Synchotron

Diamond Light Source, the UK’s national synchrotron facility in Oxfordshire, has taken delivery of seven Carbolite electric furnaces designed to provide researchers with a broad spectrum of high-quality thermal equipment for sample preparation and processing.

Diamond, the largest UK scientific investment for 40 years, is a third-generation light source with an electron beam energy of 3 Giga electron volts (three thousand million volts). At its heart is a circular vacuum chamber, half a kilometre in circumference, through which electrons travel at just below the speed of light. Passing the electrons through specially designed magnet arrays produces infra-red, ultra-violet and X-ray beams of exceptional quality and brightness, which enable researchers to study the basic structure of many materials, down to the scale of molecules and atoms.

Within the doughnut-shaped building 14 experimental stations are currently located (known as beamlines) with eight more due for completion by 2012. The beamlines are supported by laboratories that provide researchers with comprehensive in-house facilities for performing cutting-edge experiments into a very wide range of fields, including health research, engineering, environmental science, sustainable energy, cultural heritage and fundamental physics. Plans for a further ten beamlines are currently under review.

Carbolite furnaces have been previously supplied for sample preparation and related activities at the Synchrotron Radiation Source (SRS) at Daresbury, Cheshire. The equipment supplied by the company to Diamond Light Source includes a specially

designed high-vacuum tube furnace, four conventional tube furnaces and two chamber furnaces. Maximum operating temperatures are between 1200°C and 1500°C. These furnaces are mainly used for heat treatments commonly used for inducing structural and phase changes, which is essential for material, engineering and environmental science. The tube furnaces allow additional species to be introduced or intercalated into the structure of materials, which can then be examined using X-ray diffraction.

The vacuum tube furnace has silicon carbide heating elements which provide a maximum operating temperature of 1500°C, with control provided by a Carbolite 301 PID instrument that allows temperature ramp rates and dwell periods to be pre-set for different procedures. Samples are held in a 50mm diameter 450mm long work tube. Reliable vacuum performance is achieved by means of a rotary vane roughing pump combined with a high-vacuum oil diffusion pump. Models with a turbo-molecular high-vacuum pump and fully oil-free roughing pump are also available from Carbolite.

The four tube furnaces provide heating capabilities up to 1500°C in air or inert atmosphere and include two models with three-zone control which allow temperature gradients to be applied or very accurate control of long heated lengths to be achieved. The two chamber furnaces have operating temperatures up to 1300°C and 1500°C, the higher-temperature model having a rapid-heating capability.

Special furnaces simulate aero-engine conditions

Five specially designed Carbolite furnaces are enabling Vibro-Meter UK to perform long-term thermal test programmes that simulate conditions experienced by thermocouples in gas turbine aero-engines. Vibro-Meter UK is part of Meggitt plc and one of the leading manufacturers of sensors for the aerospace sector.

The furnaces were bought to enable the company to carry out research into the stability and accuracy of thermocouples as a result of long-term exposure to temperatures up to 1100°C in aero-engines. An important aspect of the equipment is the ability to simulate working conditions by cycling the thermocouples for long periods between typical operating temperatures and ambient temperatures.

In order to achieve this, the Carbolite furnaces have an automatic actuator mechanism that pushes and pulls bundles of thermocouples in and out of the heating zone of a horizontal tube furnace. The five furnaces have a maximum temperature of 1200°C and three heated zones in order to ensure precise temperature control at the centre of the 38mm diameter tube where the thermocouples are heated.

Each thermocouple is typically 2mm in diameter and usually 15 are tested at a time.

Test programmes typically involve holding the samples in the furnace for 30 minutes at a temperature between 700°C and 1050°C, extracting them and exposing them to ambient air for five minutes and then re-inserting them into the furnace again for 30 minutes. This sequence is generally repeated 4000 times before the samples are analysed and calibrated to determine the effects.

The furnace design allows entire cyclic programmes lasting over 2000 hours to be carried out automatically once the temperature and time data has been input into the control system. The five furnaces allow Vibro-Meter to carry out several programmes in parallel at the same time.

The equipment is compact and convenient to use in a laboratory situation, with double skin construction helping to keep the outer case cool and high-quality insulation optimising thermal efficiency. A high-precision PID temperature controller, timer and associated power control equipment are housed within an integral control box.

High temperature oven ensures ultra clean glassware

Purifying glassware in a high-temperature Carbolite oven has enabled ELGA LabWater to stop using chromic acid for the preparation of samples in the R and D laboratory where new high-purity water systems are designed.

Minimal total organic carbon (TOC) levels, which are used as an indicator of overall organic purity, are a key requirement for users of pure water in laboratories. ELGA’s PURELAB Ultra system achieves TOC levels as low as 1 μg/litre.

In order to stop water samples being contaminated by organic compounds on the glassware, ELGA used to soak it in chromic acid, which is both toxic and corrosive. Now, following the recommendations in Preparation and Testing of Reagent Water

in the Clinical Laboratory (CLSI 4th edition, 2006), sample bottles are rinsed in ultra-pure water and then heated to 450°C for two hours in the high-temperature Carbolite oven. Tests have shown that any organic contamination present after this procedure is not detectable, according to Dr Paul Whitehead, R&D laboratory manager.

The equipment has a maximum temperature of 500°C and a 60-litre capacity stainless steel chamber. A PID controller is fitted to ensure temperature stability, and fan-assisted air circulation gives temperature uniformity better than ±5°C, as well as fast heat-up and recovery times.

Carbolite manufactures high-temperature LHT ovens, in three sizes – 30, 60 and 120 litres, each with a choice of 400°C, 500°C and 600°C maximum temperatures.

Furnaces expand Daresbury laboratory facilities

‘The Daresbury Laboratory is a world-class facility that is used by researchers at the cutting edge of materials science, so our equipment and services have to be of the highest quality’, said Ray Jones, the Materials Science Laboratory manager.

‘Access to use of the Synchrotron Radiation Source is usually very limited, so sample preparation and other associated activities have to be exceptionally reliable to ensure the experimental time is successful. Temperature accuracy, temperature uniformity and repeatability between sample batches are extremely important’.

Off-line preparation, analysis and support services for users of the Synchrotron Radiation Source (SRS) at the Daresbury Laboratory in Cheshire have been expanded and upgraded with the installation of two Carbolite chamber furnaces.

The Daresbury SRS is a world-class facility that delivers radiation with wavelengths from the infrared to hard X-rays and is used by over 1300 scientists a year from some 25 countries for multiple simultaneous experiments. The SRS is supported by a Materials Science Laboratory which has a broad spectrum of sample preparation and analytical equipment, including a dedicated furnace room for calcination, sintering and other procedures.

The two chamber furnaces supplied by Carbolite have maximum temperatures of 1300°C and 1700°C and temperature uniformity within ±5°C. The CWF1300 unit has a chamber capacity of 5 litres and is heated by free-radiating coiled wire elements within moulded alumina-based carriers on either side the chamber. Elements are graded to compensate for heat loss and to optimise uniformity. The HTF1700 furnace, which has a 10-litre chamber, is heated by U-shaped molybdenum disilicide elements, which are extremely durable at high temperatures but can also be easily replaced when required.

The HTF1700 has an eight-segment programmer, while the CWF model has a PID controller. Both units have over-temperature protection and are linked to PCs to allow pre-programmed processing cycles to be run automatically without staff supervision.

Carbolite furnaces expand Siemens laboractory facilities

Seven chamber furnaces from Carbolite have expanded laboratory facilities for evaluating nickel-based superalloys and associated coating materials at the Siemens Industrial Turbomachinery factory at Lincoln, UK.

The furnaces are used for long-term thermal and atmospheric exposure of the alloy substrates and coatings used for components in hot-end sections of industrial gas turbines. They work alongside a custom-built thermal rig with a maximum operating temperature of 1500°C, also manufactured by Carbolite, which is used to subject coating materials to heating and cooling cycles.

The chamber furnaces are used to hold samples at specific temperatures

between 700°C and 1100°C for thousands of hours, with sections being removed periodically for analysis. They have five-litre capacity chambers and a maximum temperature of 1200°C, provided by heating modules on either side of each chamber. The modules consist of alumina-based carriers housing coiled wire elements which are graded to compensate for heat loss and optimise temperature uniformity. Hard-wearing refractory brick is used around the entrance and in the base of the chamber, and secondary insulation reduces power consumption.

The equipment has replaced a number of existing Carbolite furnaces which had been in use at the factory for nearly 20 years.

High specification ovens boost production capacity and quality

Two high-specification Carbolite ovens have been installed by specialist sealing solution provider Greene, Tweed and Co Ltd to increase the capacity and consistency of the raw material sintering operation at its UK manufacturing facility.

Greene, Tweed is a world leader in the supply of polymer-based engineered solutions to market leaders in industries such as defence, aerospace, chemical processing, medical equipment and oil and gas production and has been experiencing a growing demand for its products. The company uses a wide variety of proprietary PTFE formulations for its products, which are moulded in both tube and bar form in the facility, before being sintered and then machined to custom designs required by customers.

The two new ovens, which join two existing units that have been in the factory for over ten years, have a maximum volumetric capacity of 1.73m³ and have a maximum operating temperature of 425°C. Temperature uniformity is guaranteed to be better than ±5°C and is typically as good as ±3°C.

The tube and bar that are being processed stand on rotating tables, ensuring that heat is applied very evenly to all the material. The tables, which are perforated to improve air circulation throughout the chamber, rotate approximately once every two minutes. Heating is provided by Incoloy-sheathed, mineral-insulated rod elements located behind side duct sheets. Air is circulated by heavy-duty fan impellers on either side of the chambers.

Furnace tests hydrogen storage materials

A Carbolite tube furnace is playing a key role in a research programme at the Risø National Laboratory in Denmark to investigate the potential of metal hydrides for hydrogen storage.

While the advantages of hydrogen as a fuel are well recognised, suitable ways of storing it, particularly for mobile applications such as cars, have yet to be developed. The Institute has installed a special experimental rig to test the capacity, kinetics, thermodynamics and stability of hydrides that could be used for this purpose.

In order to prevent samples being exposed to air, they are tested in a sealed reactor that is loaded and unloaded in a glove

box with an inert atmosphere and then heated in the Carbolite furnace at temperatures up to 500°C. The MTF model used is particularly compact and is mounted on rails on the work-bench so that it can be moved from side to side to give access to the reactor.

The maximum operating temperature of the furnace is 1200°C, has a 250mm long heated zone and is used with a 25mm diameter work tube. Low thermal mass insulation ensures rapid heat-up, and a microprocessor-based digital controller delivers precise, repeatable temperatures.

Carbolite furnaces speed high-quality drill production

Dormer Tools is one of the world’s largest producers of high-speed-steel cutting tools, with five major manufacturing centres in the UK, Sweden, Italy and Brazil. Since buying the company in 1993, the Sandvik Group has maintained a policy of product development and investment in advanced manufacturing facilities which has secured its reputation for quality and service.

One of the most recent investments in production equipment is at the UK factory at Worksop, Nottinghamshire, which specialises in the manufacture of high-quality twist drills for production engineering and maintenance applications. A new Carbolite furnace line has been installed to carry out double-tempering of hardened HSS cut pieces, in a continuous process

without intermediate handling, in volumes up to 7000 per hour. The tempering furnace joins an existing Carbolite furnace used for hardening drill blanks at temperatures up to 1250°C.

The Worksop factory produces 6500 different types and sizes of twist drill at a rate of around 600,000 finished products a week. The raw material arrives in the form of annealed bar, with diameters ranging from 3mm to 25mm, before being cut to length. At this point, the cut pieces are hardened using one of three procedures currently used in the factory – a Carbolite electric rotating hearth furnace, several electric vacuum furnaces and salt baths.

Salt baths have been used for heat treatment for many years by Dormer and are widely used by other tool manufacturers. They are simple and robust, but expensive to run due to their high power consumption. They also have a number of other environmental disadvantages, including the need to store and dispose of the barium chloride salts used.

The vacuum furnaces are sophisticated and flexible – they can be used for hardening only or tempering only or hardening and tempering in a single continuous process. However, productivity is relatively low, and the 1200°C required for hardening the cut pieces damages the furnace linings, which frequently need to be repaired and replaced. A complete hardening and double-tempering cycle takes approximately 11 hours.

For some years, most of the hardening has been performed in a Carbolite rotary hearth furnace. This equipment has a much higher throughput than a vacuum furnace without any reduction in quality and provides far better working conditions than the salt baths, according to Eddie Dabill, Technical Manager.

To complement the Carbolite hardening furnace, Dormer recently invested in a tempering unit from the same company in order to further increase the productivity of the heat treatment processes in the factory. The two units, which Dormer is planning to link together to form a continuous production line, are used for processing the material used for the main product sizes – from 5mm to 13mm diameter and 86mm to 150mm in length. Dormer also intends to install more Carbolite hardening and tempering furnaces in the future, which will allow the salt baths to be removed completely.

The Carbolite hardening furnace has a rotating hearth with three heating zones operating up to 1250°C, and provision for a nitrogen atmosphere to prevent oxidation of the material. Each of the heating zones has four temperature controllers and two over-temperature instruments to optimise temperature uniformity, which is guaranteed to be no more than ±10°C.

After hardening and fully cooling, the drill blanks are placed manually in hoppers above the mesh conveyor belt that carries them through the new Carbolite tempering furnace. This is 13.5 metres long and includes two three-metre-long heating sections and two cooling sections for the double tempering required for these products.

The heating and cooling parameters have been tailored by Dormer Tools to significantly reduce the overall tempering time, thus achieving significant savings in reduced inventory and lead-time. The line has a nominal throughput capacity of over 150 kg/hr, and a typical tempering cycle from loading to unloading takes approximately 40 minutes. The processing speed can be adjusted to match the output from the hardening furnace.

Furnaces provide accurate heat treatment of turbine components

The Rolls Wood Group, one of the world’s leading companies specialising in the servicing of gas turbines for industrial applications, has increased its heat-treatment capabilities with the addition of two specially designed electric furnaces from Carbolite.

The company is a joint venture between a well-known aerospace company and the Wood Group, employing about 400 people in Scotland, Canada and the USA and specialising in the repair and overhaul of aero-derived engines such as the RB211, Avon, Olympus and 501 used in the oil, gas and power-generation industries. The furnaces were ordered in order to meet a growing need for accurately controlled diffusion and solution heat treatment of turbine blades and nozzle guide vanes at the Aberdeen headquarters.

Both the Carbolite furnaces are top-loading units with inconel alloy retorts, 600mm diameter x 1000mm high internally, which allow the use of gas atmospheres. One unit has a maximum nominal temperature of 1200°C and is designed for use with argon, while the other heats to 1250°C and can be used with argon and hydrogen if a surface cleaning effect is required. Temperature uniformity on both furnaces meets RPS953 inside the retorts at 50°C below maximum.

Components to be processed are placed in a ‘cake stand’ style jig before being loaded into the retort from above. After fitting a gas-tight water-cooled sealing flange, the retort is lifted from its cradle by a crane and lowered into the furnace chamber. The operator can then start one of a number of pre-set programmes held in the digital control system or set a new programme to suit the material to be processed. Both furnaces are rated to heat a 50kg load to 50°C below their maximum temperatures in three hours.

At the end of the heating cycle, the retorts are lifted on to a separate frame to cool.

Temperature accuracy and uniformity throughout the heating chamber are achieved by the use of a cascade control system with a master multi-segment programmer linked to two end-zone controllers which inter-communicate with each other. Over-temperature instruments are also fitted, and an eight-channel chart recorder provides a hard-copy record of each cycle.

A sophisticated gas control system is included on the furnace with argon and hydrogen gas facilities, to ensure that hydrogen can only enter the retort when the temperature is above 800°C. The retort is also automatically purged with argon before and after hydrogen is admitted.

Thermal rig puts brake systems to the test

AP Braking, a division of AP Hydraulics Ltd, has expanded and upgraded its R & D facilities with the installation of a specially modified Carbolite thermal chamber suitable for long-term test programmes involving flammable liquids.

The new equipment is an upgraded version of an existing chamber used by the company for several years and is designed to accept rigs for thermal stroking tests on components such as brake cylinders and calipers. These components can incorporate a number of different metals and plastics, as well as various fluids and greases.

Thermal stroking tests are carried out by attaching components to jigs fixed inside the chambers, with hydraulic pipework

passing through the oven walls to external actuators. Up to four components can be tested at a time. A typical SAE (Society of Automotive Engineers) test requires brake cylinders to be subjected to 1000 strokes per hour for 70 hours at a temperature of 120°C to simulate conditions in an engine compartment.

The chamber has a maximum temperature of 200°C and can be programmed to provide temperature cycling if required. It is integrated with the test rigs, so it automatically switches off if a fault develops, and an explosion relief panel is also fitted.

Should a component fail, surfaces that could come into contact with flammable liquids are below their auto-ignition temperature, and elements are positioned away from flammable vapours. The chambers are also sealed to prevent liquid escaping. Internal lighting has been fitted so that staff can see clearly when setting up equipment.

Thermal chambers test Airbus hydraulic systems

FR-HiTEMP, one of the UK’s leading aerospace component manufacturers, has installed two special Carbolite thermal cycling chambers for testing hydraulic systems on the Airbus A380 ‘super-jumbo’.

The company, which specialises in fuel, ducting, actuation and control systems for aero engines, missiles and military vehicles, supplies most of the world’s aircraft manufacturers and also supports airlines & air forces in the field. Current contracts on the A380 include supplying hydraulic system components, which operate at pressures up to 5000psi (345 bar).

On the A380 some of the hydraulic pipe-work and associated components are positioned around the massive Rolls-Royce Trent engines, while other sections are in the wings, involving a range of temperatures from -55°C to +90°C. The thermal chambers are used to replicate these service temperatures while components are subjected to pressure impulse testing up to 6000psi (400 bar), sometimes for several days at a specific temperature.

The chambers are 1000mm wide x 1000mm deep x 1000mm high internally and have a thermal range from -70°C to +150°C. Heating is by means of mineral-insulated metal-sheathed elements with a low surface watt loading to prolong service life. The chambers are cooled by directly injecting liquid nitrogen, and the equipment includes pressure relief valves & exhaust vents. Temperature stability & uniformity are better than ±5°C. A digital indicating microprocessor-based three-term time/temperature programme controller is fitted, which allows thermal cycles lasting up to 99 days to be programmed. A cut-out operates if pre-set temperatures are exceeded.

Furnaces support efficient chemical analysis

One of the world's leading independent laboratories uses Carbolite furnaces for a wide variety of analytical procedures and applications.

Alfred H Knight International, one of the world's leading independent laboratories specialising in metals and minerals analysis for the mining and refining industry, uses Carbolite furnaces for a wide variety of analytical procedures and applications within its ISO/IEC 17025 accredited laboratory.

The laboratory at the company's St Helens head office provides a comprehensive analytical service for minerals and ferrous and non-ferrous metals. Some 100 scientists, chemists and laboratory technicians employ a combination of traditional chemical techniques and the most modern instrumental procedures to produce accurate results quickly and efficiently for commercial transactions in the metal commodity market. For the classical fire assay analysis of precious metals the laboratory uses six Carbolite cupellation furnaces, regarded as one of the leading furnace designs for this application.

More recently eight ashing furnaces were supplied for loss-on-ignition analysis of precious metal bearing catalyst commodities and routine analytical calcination procedures. These furnaces have calibration ports in the front door mechanism to supplement temperature calibration for optimum temperature quality control, as required for British UKAS accredited laboratories.

The AAF furnaces are designed for a wide variety of uses in a laboratory environment and are successfully used for ashing food, animal fats & natural fibres, as well as materials such as plastics, coal & other hydrocarbons which generate aggressive fumes requiring extraction. Models are available in three sizes, all with a maximum temperature of 1100°C. The air passing through an AAF furnace is pre-heated to ensure optimum temperature uniformity throughout the chamber. High regulated airflows help to remove fumes effectively, with large furnace chambers allowing many samples to be processed at a time.

The GSM model, which has a fused quartz chamber, has been developed for procedures where a dust-free environment is particularly important. The design of this model also protects the elements from harmful vapours and minimises leakage if gases are used.

Furnace provides precise economical heating

Hindustan Aeronautics Ltd, one of India’s leading aerospace component manufacturers, has upgraded its production facilities with a specially designed Carbolite furnace for heating titanium and stainless steel parts before forging.

The equipment has been designed to a high specification to meet Rolls-Royce forging specifications and EU machinery directives in a compact unit that is easy to operate and requires little maintenance. Maximum operating temperature is 1150°C, and temperature uniformity is ±8°C, which is better than Rolls-Royce Technical Specification RPS953. Provision has been made for inert atmospheres, and an oxygen probe is included to monitor the atmosphere in the chamber at temperatures above 750°C.

The furnace consists of a 1200mm OD rotating hearth inside a gas-tight square cabinet with a single door that is raised and lowered pneumatically. The hearth, which is ceramic, rotates through a sand seal and is driven by a mechanism that can be disconnected to allow the hearth to be turned by hand for maintenance. Hearth speed is adjustable between 3 and 20 minutes per rotation.

The door is controlled by a pair of foot pedals – one for opening it and the other for closing it -- and has a fail-safe mechanism so that it only moves when one of the pedals is pressed.

Carbolite equipment for thermal coatings research

A specially designed thermal cycling rig (TCR) and seven chamber furnaces have been supplied by Carbolite to the Siemens Industrial Turbomachinery factory at Lincoln to expand facilities for research and development work on thermal barrier coatings.

The Lincoln factory manufactures small industrial gas turbines for power generation and mechanical drive applications with outputs from 3mW to 13mW. The Carbolite equipment is being used to evaluate coating materials such as yttria-stabilised zirconia (YSZ) bonded to cast and wrought nickel-based super-alloys used in the production of hot gas path components.

While the chamber furnaces provide isothermal exposure for this work, enabling samples to be heated to a temperature, held and then cooled, the TCR allows samples to be subjected to long cycles of heating and cooling that accurately simulate thermal conditions within a turbine. The equipment has a maximum operating temperature of 1500°C, but the maximum temperatures used by Siemens are generally between 1000°C and 1300°C. In future the company may also use the equipment for thermal fatigue testing.

The TCR consists of a heating zone above a loading and quench zone, with an actuator that raises and lowers samples between the two. In a typical long-term test a sample is lifted into the heating zone, heated to a pre-set temperature, held at that temperature and then lowered into the quench area where it is air-cooled before being raised again into the heating zone for another cycle.

Time and temperature are controlled through a cascade system, with over-temperature protection provided for the heating chamber. A probe thermocouple in the centre of the lifting rod provides temperature readings for the control system and is also linked to a six-channel digital-display chart recorder. The heating elements used have been designed to increase resistance to oxidisation and to provide easy replacement when required.

Rather than the silicon carbide elements usually used for this type of application, Carbolite has installed wire wound elements, which are less expensive and last longer. The elements are mounted horizontally above the hearth and controlled in three zones by three-term digital instruments with over-temperature protection. As the elements remain on when the furnace door is opened, an internal guard has been fitted so they cannot be touched by operators loading and unloading. Low thermal mass insulation enables the furnace to heat up quickly when it is switched on.

Components are protected from oxidation by a controlled flow of nitrogen gas that passes into the chamber to maintain an inert atmosphere. The nitrogen also flows through holes above and below the door to create a gas curtain that reduces air-flow into the chamber when the door is open.

The furnace controls are located in a separate free-standing cabinet, which also houses a chart recorder.

Furnaces ensure high quality ceramic sheet production

GE Infrastructure Sensing, a leading manufacturer of thermisters, has increased its production facilities with the addition of a fourth Carbolite top-hat furnace for processing ceramic sheet at temperatures up to 1300°C.

The thermal sensors manufactured by the company, which are widely used in the automotive industry and in heating, ventilation and refrigeration equipment, incorporate several types of ceramics to suit different applications. The materials are produced from metal oxides mixed with binders, which are formed into thin sheets and then fired in the Carbolite furnaces.

Heating the sheets to 400°C over four hours burns off the polymer binders, after which the material is sintered at between 1200°C and 1300°C to form the new crystal structure. Sintering can last up to 20 hours, depending on the formulation and the performance characteristics required. After cooling, the sheets are cut with a diamond saw to the size required for the finished assembly.

The hearth, which can hold many sheets at a time, runs on a track and is driven by an electric motor, so it can be moved in and out of the furnace. The heating elements are in a ‘top hat’ structure, which is lowered over the hearth when a charge is being processed and raised at the end of a cycle.

The success of the sintering process depends on heating the material to very accurate and uniform temperatures, so the furnaces have been designed to provide a working area within the chamber 200mm wide x 600mm long x 350mm high where temperature uniformity is ±2°C at 1200°C. Access ports allow thermocouples to monitor load temperatures in the chamber.

Multi-strand heat treatment furnace gives high throughput strip processing

Azmüsebat, one of Turkey’s biggest razor blade producers, has increased throughput at its factory in Istanbul with the installation of a second specialised heat-treatment furnace from UK manufacturer Carbolite.

The furnace, which is designed to harden and temper four strands of thin stainless steel strip simultaneously in a continuous process, joins an existing unit with similar specifications built by Carbolite three years ago. Processing four strands of strip simultaneously has been found to bring considerable cost/throughput benefits compared with single-strand equipment. When strip 22.5mm wide x 0.1mm thick is processed at 12.5 metres per minute, typical throughput is 50kg/hour.

The equipment is designed to produce sufficient hardness in the strip for it to retain a sharp edge without being brittle and hard to work. The material also has to remain flat at the end of the process, despite the potential for distortion. The 6000mm long hardening section has a maximum temperature of 1150°C and is divided into six independently controlled zones, allowing a temperature profile to be created, generally between 750°C and 1100°C. Temperature uniformity at 1000°C is guaranteed to be better than ±10°C. The power rating allows a fast heat-up to operating temperature from cold.

Each strand runs in a rectangular stainless steel tube, which is designed to minimise friction and is also tensioned to ensure it remains straight when hot. The strip and tubes are protected from corrosion and discolouration by injecting a nitrogen and hydrogen gas mixture into the tubes. After passing through a quench unit, the four strands are tempered in a 1000mm-long section with a maximum operating temperature of 500°C. This section incorporates four special heat transfer plates, designed to give rapid heating and to maintain product flatness and straightness. It also has two heating zones to give accurate control of temperature. After tempering, the four strands are cooled again and coiled.

The furnace has separate control and over-temperature instruments operating off independent thermocouples fitted to each heating zone. The controller is a microprocessor-based PID unit with dual display of set-point and measured value.

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