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Specification Update for Small-Bore Tube Fittings

IOGP Small-Bore Tubing and Fittings Specification

How the Latest IOGP Small-Bore Tubing and Fittings Specification Enhances Safety for Oil and Gas Producers

Enhanced tube fitting safetySafety is the top priority for many oil and gas producers around the world—so when the industry makes a significant move toward safer fluid system operation, everyone should take notice.

In March 2021, the International Association of Oil & Gas Producers (IOGP) published the latest version of its S-716 “Specification for Small Bore Tubing and Fittings”, which defines a set of standardized requirements for small-bore tubing, tube fittings, piping, and system components that are used in petroleum and natural gas industry applications. The requirements focus on the design, material selection, installation, testing, inspection, and marking of these fluid system components.

Swagelok tube fittingsThis new specification sought input from various industry stakeholders to determine key parameters that would help improve the general safety of oil and gas fluid systems while also reducing total cost of ownership. For oil and gas professionals, there a few notable areas to consider:

Comparing Types of Tube Fittings for Leak-Tight Performance

First, S-716 specifies the use of compression tube fittings, defined as flareless, double-ferrule fittings. In order to meet the specification, single-ferrule designs cannot be used.

Because single-ferrule fittings are more prone to leaking in applications subject to vibrations and other operational stresses, this parameter helps oil and gas producers maintain leak-tight connections throughout their systems.Checkmark

The best fitting choice for most applications will provide hinging colleting action that securely grips the tube and provides both direct and axial support.

The differences between single-ferrule and double-ferrule designs are key:

  • Single-ferrule fittings, also known as bite-type fittings, grip the tubing at a single point of contact—the front nose of the ferrule—around the tubing’s circumference. This lone point of contact is thereby prone to working loose when subjected to continued pulsation, shock, vibration, or other conditions that are inherent to fluid system operation.
  • Double-ferrule fittings, or compression fittings, provide an additional point of contact and grip on the tube, making them a better choice for leak-tight performance.

However, not all compression tube fittings are created equal. The best choice for most applications will provide hinging colleting action that securely grips the tube and provides both direct and axial support. This design helps mitigate the effects of vibration and maintain a leak-tight tube grip.

Product Intermix Prohibited

Next, the updated specification additionally calls for the use of a single tube fitting brand and prohibits the intermixing of fittings from different manufacturers. S-716 joins other notable specifications in doing so, helping to promote more universal practices for fittings across industries.Intermixing components results in unpredictable performance

Mixing components from different manufacturers can often result in unpredictable performance.

Why? Because even when manufacturers use the same materials for a component, the materials’ compositions may differ, yielding slightly different resistances to corrosion or temperature. Additionally, the components themselves may be made to different tolerance and design specifications, as no commercial design standard exists for tube fittings. For these reasons, mixing components from different manufacturers can often result in unpredictable performance in the field, including leaks and potential related safety problems.

New Material Requirements and Cost-Effective Material Combinations

S-716 further recognizes the two industry-accepted 6 moly (6Mo) material grades, UNS N08637 (6HN), and UNS S31254 (alloy 254). 6HN is a more robust grade of 6Mo that provides enhanced resistance to chloride-induced stress cracking. Its inclusion gives system operators the opportunity to improve system performance and safety. New tube hardness requirements are also included to ensure tube and fitting compatibility.

While traditional thinking of higher-grade alloys is using the same alloy for the fitting and tubing, this is sometimes unnecessary and expensive. Recognizing this, the S-716 now enables the use of engineered combinations—the use of different tubing and fitting materials—to achieve the highest levels of performance and cost-effectiveness.

When taking this approach, it is important to be sure such combinations have been approved for service by the fitting manufacturer. This is important because the material combination’s ratings are influenced by not only material compatibility, but also the tube thickness, operating pressures and temperatures, and other factors. A reliable manufacturer should be able to help guide you toward the right combinations for your needs.

Tube fitting installation best practices

Installation Best Practices

Finally, the specification provides new guidelines for hands-on assembly training, noting “the tubing system shall be installed by personnel who have been certified by the fittings manufacturer’s approved product training program or an equivalent.” Training like this can help installers create leak-tight connections required in applications where high pressures, vibration, and temperature changes are regular parts of ongoing operations.

We believe this specification update will contribute to safer and more reliable oil and gas fluid system operations around the world. Selecting the right tubing and tube fittings, material choice, training, and other factors are important, and their further standardization will help make for a stronger industry. If you are interested in further discussions about the new S-716 specification or its implications, our specialists are happy to help with any questions you may have.

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