Thermal management company Zircotec employs technologies originally developed within the UK nuclear industry, to provide resistance to heat and wear for a range of metals and even composites. Already proven in harsh environments, the technology is seeing new growth in a range of industries.
Novel surface coatings were one of many technologies developed by the UK’s Atomic Energy Authority to solve performance and reliability issues in the nuclear reactor and associated plant. Zircotec, formally part of the government-owned UK AEA, saw an opportunity to commercialise the technology beyond the power generation industry, leading to a number of other applications. The firm has expanded into the automotive sector and now looks to solve challenges found in the oil extraction and refining industries.
The application process
Zircotec employs a plasma spraying process to apply its range of coatings and heat shield products. During plasma spraying, powder particles are injected into nitrogen or argon plasma with a flame temperature operating at around 12 000°C. The process provides a very short residence time for the particle in the flame and by using its knowledge, the firm has the ability to adjust the parameters to ensure that the range of substrate materials that can be coated is maximised. The experience derived from coating often intricate components for nuclear installations, means the firm can ensure an even coating is built up in thin layers helping to reduce stress in the final coating, minimising failure in the field that inevitably leads to the unwanted downtime and disruption that can cripple oil extraction. “The coating is designed to be robust and is highly resistant to vibration and mechanical damage during its operational life,” says Terry Graham, Zircotec’s managing director. “To survive the conditions experienced in oil extraction environments, careful control of process parameters and a proprietary bond coat is used to make sure the coating is extremely well adhered to the underlying substrate.”
According to Graham, any attempt to coat directly onto a part without such pre-treating would result in very low bond strength. Further proprietary physical and chemical methods are used to prevent damage to the substrate during the application process. “We deal with many delicate components from F1 cars and the process has to be gentle yet durable in service.”
Figure 1. ZircoFlex® is a flexible ceramic that can be used in a variety of applications to manage heat at temperatures of up to 500 °C.
A lighter future
With the oil industry venturing into more hostile environments and deeper locations to recover oil, the ability to improve performance and reliability through the use of ‘fit and forget’ coatings is an attractive option. These operating environments involve extremes of temperature and pressure in what are often highly corrosive environments where space and packaging can be a real issue. In testing on exhaust gas manifolds, Zirconia-based coatings have been proven to reduce metal surface temperatures by over 170 °C (from an original condition of 600 °C. For composite applications such as on structures, pipes or venting systems, the reductions are equally impressive; testing has shown carbon fibre surface temperature lowered by over 125 °C, crucially providing the ability for these light materials to be used in temperatures above their delamination point. “The highly corrosive environment of oil extraction means that composites are an attractive solution for offshore users,” says Graham. “Composites are known to be stronger, and around six times lighter than copper nickel equivalents,” adds Graham. “If they are subjected to high temperature environments, they were often ignored for fear of damage. We can now offer a solution.”
Graham believes that there is future potential for more use of carbon composites offshore in salt laden environments. Research suggests reducing pipe weight on the decks of a tension leg platform would improve buoyancy, leading to reduction in the amount of steel required and therefore cost. Like for like composites are known to be stronger and around six times lighter than copper nickel equivalents.
Zircotec is able to apply a metal coating to a composite offering a lightweight structural component that has excellent wear characteristics. Like the ceramic coating, a proprietary bond coat is applied to the composite before applying a top layer of molybdenum, aluminium, stainless steel or tungsten. These coatings are also being used on composite substrates to enable their use in environments where previously they would have failed or required higher levels of maintenance. Formula One is an area where such coatings are increasingly popular to prevent both heat and wear related failures. In the 2013 Formula One motor racing season, ten of the eleven teams relied upon a Zircotec coating to protect against such failures. Recent automotive OEM work with Aston Martin enabled engineers working on the One-77 supercar to specify composite components where previously it would not have been possible due to delamination from exposure to high temperatures, that could not meet OEM requirements for longevity.
Further refinement can also allow engineers the opportunity to ‘engineer’ a coating to suit a particular need. Zircotec’s engineers can adjust the coating properties both through thickness and across the surface of a component to cope with ‘hot spots’ and differing forms of heat transfer such as radiant, conductive or convective heating. “Unlike some processes or coating, we only coat areas that need treatment,” suggests Graham. “This is more cost effective and further minimises weight. We also have the ability to build in a conductive sub-layer that will help to dissipate heat away from any concentrated high temperature areas, and can also help deal with transient heating situations. This means we apply just the right amount of coating to deliver the necessary protection whilst minimising the weight impact of the coating” (As low as 0.03 g/cm²).
Simple solutions
The growing work the firm has done in the automotive sector has led to the development of a flexible ceramic supplied on an aluminium foil. Believed to be the first of its kind, ZircoFlex® enables users to solve heat issues without having to send components for spraying. Conveniently supplied in sheets from A5 size or ‘from the roll’ that can shipped directly to end users, it can be cut, folded and bent to fit any shape and offers surface temperature reductions of 64% in single layer form and, up to 85% when used in its three layer variant. “Very lightweight and flexible, it is an easy solution than can be applied in the field,” adds Graham. The firm has made installation easier in difficult to access plant equipment locations by also introducing a self-adhesive option and pre-prepared two and three layer derivatives. Good for applications in environments subjected to temperatures up to 500 °C, its usage in oil field applications is likely to be extensive. The first example of this was to protect an HVAC unit from a flare stack on an oil platform located in the Caspian Sea, where the ability to retro-fit a heat shield in the field during a routine maintenance period avoided costly downtime.
Adapted by David Bizley