Instrumentation tubing optimised for high reliability in harsh environments

The design of fluid instrumentation systems for use in harsh and corrosive environments has been boosted by an optimised new grade of 6Mo tubing. The mechanical characteristics of the new ‘Parker Grade’ 6Mo tubing have been optimised to ensure integrity of connections made using instrumentation compression type fittings from the Instrumentation Products Division of Parker Hannifin – the global leader in motion and control technologies.

Parker’s long history in special-purpose alloy tube fittings has enabled it to build up a wealth of expertise and knowledge about corrosion resistant materials such as 6Mo. The company has played a formative role in the industry take-up of the alloy, which is now the material of choice for many instrumentation tubing systems on new and refurbished North Sea oil and gas production platforms.

Containing at least 6 percent molybdenum, 6Mo alloy is a super-austenitic stainless steel. The material is more resistant to chloride-induced pitting, crevice attack and stress corrosion cracking than standard 300 series or duplex stainless steel, making it ideal for offshore applications demanding durability and reliability in a hostile environment. Parker produces 6Mo versions of various types of instrumentation tube fittings, together with a series of 6Mo tubing clamps, and can also machine instrument valves and manifolds in the material.

Many instrumentation system designers specify two ferrule compression fittings for the assembly of small-bore tubing, with the 6Mo version of Parker’s A-LOK design proving a popular choice for today’s offshore projects. As with all two ferrule fittings, the rear ferrule needs to be harder than the tube it is gripping so that it ‘bites’ into the tube material during assembly helping to create a reliable, pressure-tight seal. Parker hardens the rear ferrule of 6Mo A-LOK fittings using its unique Suparcase process, which provides market-leading corrosion resistance.

However, when ordering instrumentation tubing, customers often simply specify an ASTM standard to their supplier. These standards do not always guarantee an optimum material property for a high integrity tube and fitting combination. The result can be tubing that is harder than necessary, for example, and therefore less than ideal for use with twin ferrule compression fittings.

As part of its ongoing commitment to helping users improve the integrity and corrosion resistance of instrumentation systems, Parker ensures that all tubing stocked by the company and its distributors is fully compatible with its range of fittings. After exhaustive testing and analysis of 6Mo tubing, Parker has defined a stringent specification and tolerances for its manufacture that allows the material’s properties to be controlled very precisely. By collaborating with its supplier and auditing the company to verify compliance, Parker is able to provide the new Parker Grade 6Mo tubing with mechanical characteristics that are optimally matched to the capability of its 6Mo instrumentation fittings.

According to Paul Shaddick, Product Manager for Parker Hannifin's Instrumentation Products Division, “Extending the reach of our quality control standards to encompass the manufacturing processes used by our supplier of 6Mo alloy tubing is a major step forward in our product development strategy. Our customers can now obtain all the 6Mo instrumentation connection technology they need for an offshore project from a single source, secure in the knowledge that the components are compatible. This simplifies component procurement and distribution, helps speed installation, and eliminates potential leak paths in 6Mo compression fittings.”

Parker Grade 6Mo instrumentation tubing is available in a wide range of imperial and metric sizes up to 1 inch/25 mm OD, and its 6Mo A-LOK two ferrule compression fittings are suitable for the majority of topside applications involving pressures up to 413 bar/6,000 PSI.