Analysis: Choosing the right elastomers for the oil & gas industry

London - The drive to exploit new energy resources over recent years has seen the oil & gas industry push to Arctic, deep-sea environments, as well as shale and other unconventional fields.

The push to recover hydrocarbons from ever more challenging and extreme environments has raised the bar for engineers involved in the design, specification and supply of rubber materials and components to the sector.

As well as meeting a more exacting array of performance requirements, the reliability of components is becoming increasingly critical, particularly as the applications are often in hard-to access regions of the world.

These trends have, in turn, increased the need to understand the performance and limitations of elastomeric materials used to seal the often critical equipment used on these facilities. Given the increased range of application conditions in terms of resistance to temperature, pressure and chemicals, reliance on ‘default’ or tried & trusted materials can lead to costly and potential disastrous equipment failures.

“The rubber parts used in various applications face challenges like higher temperatures, longer lifetimes, durability, reliability expectations, lower wear and a bucket full of partially secret fluids used for drilling and exploitation,” a Lanxess spokesman commented.

When selecting the material, engineers have to carefully weigh up the advantages of elastomers ranging from statndard materials such as EPDM  and nitrile rubber  to high-end silicone and fluoroelastomers which can far outlast general-purpose elastomers.

Fluoroelastomers, for instance, withstand high heat, as well as low temperatures and aggressive fuels and chemicals, to help seals, coatings, gaskets, O-rings and a wide variety of custom shapes last longer.

And as supplier DuPont explains, these materials often prove their worth by allowing customers to stretch maintenance intervals and budgets, especially in hard-to-get-at down-hole applications.

However as some of the more exotic materials such as perflouroelastomers can cost 100 times higher than standard materials, engineers must be able to justify being specified for any application.

The materials-selection challenge then gets even tougher when modifications to the different rubber types are taken into account.

Lanxess’ NBR slate for example, includes grades such as for pumps stators with improved flowability and resistance to mould-fouling. As a result, the stators for drilling motors /pumps can be filled much easier, while the grades also allow better rubber-to-metal bonding. These polymers are also useful in other applications like blow out preventers, seals, hoses, pipeline cladding, packers or moles, according to the company.

The same company also offers hydrogenated NBRs to meet the challenges of rising pressures and temperatures in the field. These include grades designed with tailor-made low viscosities for ease of processing.

Fully saturated HNBR grades, meanwhile, can be compounded to meet 165°C ageing resistance in air. These compounds can also be highly filled to cope with the requirements of explosive decompression resistance while still offering good processability.

Both NBR and HNBR are also available as carboxylated grades that give parts with further increase in abrasion resistance.

Another important part of the tool-kit is silicone rubber, which is being used, for example, in wet insulation system for HP/HT equipment used in deepwater production and tieback systems.

Trelleborg Offshore UK is applying Dow Corning recently introduced XTI-1003 silicone rubber  for subsea insulation to meet performance specifications for: Fluid temperatures up to 135°C, water depths up to 3,000 m (9,850 ft)

Dow Corning claims the RTV silicone rubber Insulation can achieve a more reliable, cost-efficient and lower-risk subsea wet insulation system for HP/HT equipment used in deepwater production and tieback systems.

Based on a room-temperature-curing (RTV) liquid silicone rubber (LSR) elastomer, the precisely engineered Dow Corning XTI-1003 RTV Silicone Rubber Insulation formulation is easy to mix and apply. It cures to a durable, flexible translucent rubber without potentially harmful by-products.

Uses for Dow Corning XTI-1003 RTV silicone rubber insulation as a core raw material, is used on components such as tapered stress joints, manifolds, pipeline end terminations, pipeline end manifolds and vertical connection systems.

The challenges now faced by those specifying rubber materials for oil & gas application underline the need to facilitate the exchange of information throughout the industry.

As information management specialist Jagdish Patel comments: "The overwhelming majority of our exchanges are done between two parties, any subsequent exchange is now in the hands of two people only! We generally stick to our known sources of information and so the system is rendered static.

"The rubber industry is crying out for a dynamic method of exchanging information that gets the user the information they need in a ready-to-use form

"The foundations of a different way of using information have been laid and it is recognised that involvement from raw materials suppliers, compounders, moulders and OE manufacturers would prove beneficial to all.

"It has potential for all to look at materials, their properties and applications in different ways. It enables the participation of everyone so that ideas from outside the well known ‘top ten’ can be included in different ways of looking at thing that lead to those elusive real ‘game-changing’ breakthrough developments."