Material innovations help combat oil and gas challenges

While Formula 1 might push the limits of physical properties it is for a relatively short amount of time. Yet many oil and gas platforms are still in operation 25 years after initially being built.

However the two are not mutually exclusive and there is more transfer of both engineering technology and material science between the likes of motorsport and the offshore industry than you may first think.

Zircotec, based just outside of Oxford, developed a ceramic plasma spraying technology specifically for the motorsport industry to cope with the extremely high temperatures being generated. However, it has since been able to take the inherent attractive heat properties of ceramic and spin them out in to other industries.

One of the methods that makes its application of ceramic so adaptable, is a flexible heatshield material known as Zircoflex. It sprays platelets that are closely packed together to provide comprehensive heat protection. This structure allows the foil to be bent and manipulated to suit different shapes.

This flexibility has meant it has been able to recently be used on an oil platform in the Caspian Sea. The oil platform was having issues protecting its HVAC (heating, ventilation, and air conditioning) system from its flare stack.
The ability to quickly retrofit a heat shield in the harsh and isolated environment without having to force a costly shutdown led to engineers specifying ZircoFlex flexible ceramic heat shield. The close proximity of the HVAC air handling unit to a flare stack had led to surface temperatures of up to 80°C, risking crucial reliability issues for the production facility.

The unique flexibility offered by the 0.8mm thick ZircoFlex III heat shield enabled engineers to cut, form and apply ZircoFlex to large external areas of the HVAC during routine maintenance. Despite difficult to reach areas, the self-adhesive backing allowed the material to be cut, trimmed and fitted in situ.

The whole of the HVAC was covered, including its 4m2 side panels and 8m of 500mm diameter ducting, all during a period of outage for routine maintenance. The high temperature adhesive used allows the material to operate at temperatures of up to 500°C. Each adjacent sheet was overlapped and then painted making the whole structure watertight, though ZircoFlex and the adhesive used is itself resistant to water.

"The rig operators needed a proven solution that could be implemented quickly, preferably without having to disassemble parts or fit heavy purpose-made heatshields," says Peter Whyman, Zircotec's sales manager. "ZircoFlex is highly efficient but is also light and compact. Our ability to send ZircoFlex sheets in a flat-packed crate helped tremendously in this instance, minimising shipping issues and allowing easy movement of the material to the engineers on the platform."

The rig's engineers were also keen that any heat shielding could be painted over so as not to interfere with routine anti-corrosion treatments. This requirement eliminated many products that just rely on their reflective capability or those that could not be painted such as wadding. It also eliminated those materials where water ingress would cause damage or reduce effectiveness.

"Our heat shield can be painted and this will not affect the ceramic thermal barrier performance," says Whyman. "Coupled with the ability to supply the heat shield either flat-packed or in rolls, we have a transportable, robust and effective product for harsh and isolated environments."

As well as managing heat, the other factor that must be controlled is corrosion. With so many metal components on board, it is vital they are engineered in the first instant to stand up to the corrosive challenges.

Standing up to corrosion
Parker Hannifin recently developed its new snap-together tubing clamp, constructed almost entirely from 6Mo austenitic stainless steel. The new 'Snap-Trap' was in response to the challenges being faced by energy companies as they strive to recover and process oil and gas from more remote and environmentally hostile areas. In such environments instrumentation can often be exposed to corrosive chemicals such as sulphur, chlorine or salt, and even some standard alloys can corrode quickly in such environments - posing a safety risk.

Based on the same innovative design as Parker's field-proven 316 stainless steel Snap-Trap tubing clamps, the 6Mo has an even higher resistance to corrosion. The corrosion resistant alloy is particularly suitable for applications in high chloride environments such as offshore oil and gas production platforms, and desalination plants. The clamp provides a durable means of securing small bore instrumentation tubing and it can be installed quickly and reused.

The clamp fully complies with NORSOK standard Z-CR-101, which demands that tubing clamps should be made of non-corrosive material, must avoid galvanic corrosion between the tubing and its support system, and must not allow water or seawater to accumulate between the clamp and the tubing, which could cause crevice corrosion.

For maximum corrosion resistance, Parker's latest Snap-Trap tubing clamps are fabricated almost entirely from 6Mo. Containing at least 6% molybdenum, this super austenitic stainless steel has a much greater resistance to chloride-induced pitting, crevice attack or stress corrosion cracking than standard 300 series or standard duplex stainless steels. These products are key drivers behind the industry's adoption of the alloy as a standard for use wherever corrosion has previously proved a problem.

Design for function
Parker's Snap-Trap clamps are compact square components with a U-shaped body and a hinged tube clamp arm. Both the body and the arm feature small tube contact points to minimise opportunities for crevice corrosion, and the entire assembly is free-draining. As the clamp arm closes, it progressively tightens its grip on the tubing, until the end of the arm springs - or 'snaps' - against retaining lugs on the clamp's body, locking it in position. Once closed, the geometry of the clamp ensures that it maintains a very secure hold on the tube. There are no nuts or bolts to tighten, and the flexibility of the clamp arm mechanism enables each Snap-Trap to accommodate two sizes of tube.

Invisible protection
While the corrosion on the snap-trap is excellent, there has been recent research to show that further improvement is possible. A coating so thin it's invisible to the human eye has been shown to make copper nearly 100 times more resistant to corrosion, creating tremendous potential for metal protection even in harsh, offshore, environments.

In a paper published in the September issue of Carbon, researchers from Monash University and Rice University in the USA say their findings could mean paradigm changes in the development of anti-corrosion coatings using extremely thin Graphene films.

Graphene is a microscopically thin layer of carbon atoms. It is already in use in such things as smartphone screens, and is attracting research attention for its possibilities as a means of increasing metal's resistance to corrosion.

"We have obtained one of the best improvements that have been reported so far," says study co-author Dr Mainak Majumder. "At this point we are almost 100 times better than untreated copper. Other people are maybe five or six times better, so it's a pretty big jump."

The polymer coatings that are often used on metals can be scratched, compromising their protective ability, but the invisible layer of Graphene – although it changes neither the feel nor the appearance of the metal – is much harder to damage.

The researchers applied the Graphene to copper at temperatures between 800 and 900°C, using a technique known as chemical vapour deposition, and tested it in saline water.

Initial experiments were confined to copper, but Dr Banerjee said research was already under way on using the same technique with other metals. This would open up uses for a huge range of applications, from ocean-going vessels to electronics: anywhere that metal is used and at risk of corrosion. Such a dramatic extension of metal's useful life could mean tremendous cost savings for many industries.

The process is still in the laboratory-testing stage, but Dr Majumder said the group was not only looking at different metals, but also investigating ways of applying the coating at lower temperatures, which would simplify production and enhance market potential.

Super absorbent sponge detects oil
The international team includes scientists from the United States, Spain, Belgium and Japan have created solid, spongy blocks of carbon nanotubes that have an astounding ability to absorb oil, separating it from seawater. The new material, which could be used to clean up oil spills in oceans, also has other novel applications related to electronics, materials science, and medicine. The new material is formed using carbon and a dash of boron.

Carbon nanotubes are tiny tubes with diameters ranging from 1-50nm - much narrower than the width of a human hair. They are also 100times stronger than steel and about one sixth the weight.

"Our goal was to find a way to make three-dimensional networks of these carbon nanotubes that would form a macroscale fabric - a spongy block of nanotubes that would be big and thick enough to be used to clean up oil spills and to perform other tasks," says researcher Mauricio Terrones. "We realised that the trick was adding boron which is a chemical element that is next to carbon on the periodic table because boron helps to trigger the interconnections of the material. To add the boron, we used very high temperatures and we then 'knitted' the substance into the nanotube fabric."

The boron puts kinks and elbows into the nanotubes and promotes the formation of covalent bonds, which give the sponges its robust qualities. The boron helps to tangle the sponges into a complex network. In the past, people have made nanotube solids via post-growth processing but without proper covalent connections. The advantage with this method is that the material is created directly and comes out as a cross-linked porous network.

First author Daniel Hashim, a graduate student at Rice University, explains that the spongy carbon-nanotube blocks are special for two reasons. "First, they are superhydrophobic, which means that they hate water, so they float really well. Second, they are oleophilic, which means that they love, and thus absorb, oil. In fact, they can absorb 123 times their weight in oil."

A nanotube sponge dropped into a dish of water with used motor oil floating on top soaked up the oil. The oil can then be burned off and the sponge returns to the water to absorb more. A carbon-nanotube sponge remained elastic even after 11,000 uses in the lab.

"This material can be used repeatedly and stands up to abuse," Hashim adds. "Another interesting feature of these nanotube sponges, which are 99% air is that they also conduct electricity and can easily be manipulated with magnets."

The research team will continue working on how to make even larger sheets of the carbon-nanotube blocks. For oil spills, it would have to make large-enough sheets or find a way to weld smaller sheets together. The team members are also looking into ways to exploit the three-dimensional structure of the nanotube sponges for use in other applications.

"Oil-spill remediation and environmental clean-up are just the beginning of how useful these new nanotube materials could be," Terrones says. "For example, we could make use these materials to make more-efficient and lighter batteries. We could use them as scaffolds for bone-tissue regeneration. We even could impregnate the nanotube sponge with polymers in order to fabricate robust and light composites for the automobile and plane industries."

Author
Justin Cunningham

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