Many industrial processes and the preparation of samples for scientific analysis require the use of highly corrosive materials at elevated temperatures
The design of thermal systems and the materials being used in their construction need to account for and compensate for such effects.
Applications can be very diverse ranging from bead preparation for X-ray fluorescence analysis, where the samples are dissolved into a homogeneous mix of lithium metaborate, to de-wax and burnout of ceramic moulds for metal casting applications.
Alf Roberts, managing director of Elite, explained: "Corrosive agents can be produced as a by-product of a thermal process in the form of gases or liquids.
"In addition, the testing of components and materials used inside turbines, jet engines or nuclear reactor heat exchangers in aggressive environments is becoming more common as designers seek to determine material characteristics under real application conditions.
"Applications vary from the use of a simple corrosive material to others that call for corrosive and aqueous environments".
Elite has found that the performance of consumable components in a typical atmosphere heat-treating furnace will directly affect the operating cost of that furnace. Also, that the design and choice of material will have a direct bearing on the service life, cost and thermal efficiency.
For these reasons the company says it is always looking at new materials and methods to improve the life of their consumable components.
The corrosion resistance of metals, alloys and ceramics differ depending on the temperatures at which the equipment is operating.
Elite says it is constantly looking at new alloy formulations and materials that can improve the performance and safety of the systems it designs.
The fabric of the system has to withstand both the thermal stresses and the corrosive action of the material being processed.
And any corrosive gases have to be contained and not leak into the atmosphere.
Elite has worked with a number of top universities and research establishments to produce special corrosion resistant thermal systems needed for their research.
Commenting on the research sector, Roberts said: "We specialise in dealing with the requirements of leading edge scientific research.
"It requires innovative and creative thought to present a solution, which are our key abilities.
"We have also designed a number of interesting industrial applications that required special corrosive protection.
"One such application was for a leading international photographic manufacturer who required a special 450C oven for the production of barium bromide.
"The challenge presented to Elite was to produce a system that was capable of withstanding the corrosive properties of the product and by-products of the process while maintaining safe working conditions for personnel".
An oven, designed with innovative features to provide a solution to the problem, is now installed and working at production capacity.
The oven is capable of processing up to 30kg of barium bromide per day.
The highly corrosive properties of the product and evolved vapours demanded special design characteristics and the use of a work chamber manufactured from a special corrosion and heat-resistant material.
The access door was also fitted with specially designed gas-tight thermal seals.
Multiple gas inlets were provided together with exhaust and drain points for the safe collection of evolved condensates, with the heating elements being isolated from the process atmosphere.
Full temperature programming with digital communications for integration into a production supervisory system was also provided.
Underlining Elite's abilities, technical manager Howard Thorpe explained how the company overcame the corrosion challenge at Hydro Polymers: "Hydro Polymers required a system that would allow them to determine that products meet BS 6425 and CEI IEC 754-2. "The process produced enveloped gases from burnt material that were corrosive so the design needed to incorporate a way of naturalising them".
The solution provided by Elite comprised a specially designed 1200C single zone tube furnace with a heated zone of 610mm, a quartz combustion tube, three wash bottles, combustion boats, sample carrier, load monitoring thermocouple and temperature indicator, all necessary connecting glass tubing and leak-tight rubber stoppers.
In addition, Elite designed the system with a number of innovative features that make it ideal for this work.
These include graded low thermal mass insulation, which provides rapid response times and optimum thermal efficiency and an outer mesh case cover to promote natural air-cooling that ensures operator safety and comfort.
The process starts with a weight sample being loaded into a combustion boat, which is inserted into the combustion tube and then into the hot zone of the furnace via a non-contact sample carrier system to maintain the integrity of the sample environment.
Dry, filtered air is then introduced, the temperature in the furnace raised to 800C and held for 30 minutes.
Enveloped gases from burnt material are trapped by bubbling through distilled water in the wash bottles and the acidity measured by determining the pH value. Fred Bateman, chief analyst at Hydro Polymers, said, "We needed a system that would determine the amount of acid gas evolved during combustion of PVC compounds, as detailed in BS 6425 and CEI IEC 754-2.
"Hydro considered various suppliers and selected Elite as being able to supply the best solution. "Elite's expertise and knowledge in building full test systems of this nature made them our first choice".
Elite produces a range a standard ovens and furnaces up to 2000C, which are suitable for many applications.
Where specific thermal process characteristics are required, the company will design a custom solution to meet the needs of the system.
