Exploring the Latest Revisions to API 6D: Enhancing Valve Standards for the Oil and Gas Industry

The American Petroleum Institute's API 6D is one of the most widely used API standards currently. In the United States, numerous government agencies reference this standard, including the Bureau of Safety and Environmental Enforcement (BSEE) in the Code of Federal Regulations (CFR), the Pipeline and Hazardous Materials Safety Administration (PHMSA), and state regulatory agencies. Additionally, this standard is widely referenced by government regulatory agencies worldwide.

In response to market demand, the American Petroleum Institute released the 25th edition of API 6D in November 2021, which became effective in November 2022. As the third most referenced API standard among all API standards, the new content introduced in this edition was carefully crafted based on suggestions and information provided by manufacturers, operators, and representatives of the International Association of Oil & Gas Producers (IOGP). Some notable changes in this edition include:

Changing the name of valve standards

• Mandating the reference to API 6DX for consistency, also known as "normative reference"
• Introducing new requirements for bolts
• Adding a new informative Appendix F on design validation
• Defining and supplementing requirements for "acceptable purchaser deviations" in new informative Appendices K and L
• Updating requirements for "Quality Specification Levels (QSL)"
• Optimizing guidance on non-standard valves and application of intermediate pressure-temperature ratings
• Adding Appendix A on valve repair and modification, replacing API 6DR
• This article will focus on certain items of the aforementioned changes, elucidating their impacts on manufacturers, engineering contractors, and operators.

Evolution of API 6D Development

The first version of API 6D was API No.5-G-1, published in September 1936. It consisted of 20 pages and was priced at $0.35. The initial version covered gate valves, plug valves, and check valves for trunk pipelines. Until the 23rd edition, the scope and name were consistently about valves for trunk pipelines. Responding to new industry needs, the 24th edition, published in August 2014, expanded the scope and name to include valves for non-trunk pipelines. Similarly, the 25th edition saw changes in scope and name, with the new name simply being "Valve Specification." This change indicates that both the API committee and industry working groups believe that API 6D valves are applicable not only to pipelines but also to various aspects of the entire oil and gas industry and other industries.

Latest Changes

One change that may have an immediate impact is the requirements for actuators and gearboxes. The 25th edition requires actuators to meet all the requirements of API 6DX. In contrast, the 24th edition only required compliance with the section of API 6DX concerning actuator sizing. This means that for actuated valves to comply with the 25th edition of API 6D, their actuators must first comply with API 6DX. Another change in the 25th edition is that the safety factor for manual gearboxes sizing calculation has been changed to 1.5. This change was prompted by a request from the International Association of Oil & Gas Producers (IOGP) representatives of operators. The 24th edition did not specify a safety factor for gearbox sizing, leaving it to the manufacturers to implement according to their own standards. Furthermore, the new version makes a clear distinction between pressure boundary bolts and non-pressure boundary bolts for scenarios such as bolted gearbox installations. Importantly, the new version requires pressure boundary bolts to be procured from suppliers certified to comply with API 20E (carbon steel bolts) and API 20F (corrosion-resistant bolts). Although bolt manufacturers are not required to hold these certifications, it can be assumed that most sources will come from suppliers meeting these requirements. Indeed, API 20E and API 20F have been incorporated into API 6A and API 6DSS, and more recently into API 6D. These trends are likely to encourage suppliers to obtain certifications, thereby improving the supply of bolts.

The new edition standard gives a new definition for pressure boundary bolts, with specific requirements for marking, quality assurance, and material, which differ from the requirements for pressure vessel components and are therefore not classified together. A significant change in API 6D is the introduction of a new appendix on design validation. Many API 6D valve manufacturers also manufacture valves according to the API 6A standard, which is well known in the valve industry for its "PR2 Performance Verification Test." The 25th edition adopts a format similar to API 6A Appendix F and incorporates many of its requirements, while also drafting an appendix on design validation. Table 1 lists the specific contents of this appendix.

Similar to API 6A, the appendix also specifies rating rules for valve types, pressure ratings, and nominal sizes

The 24th edition of API 6D mentioned "unless otherwise specified" 11 times and "by agreement" 12 times. These statements allow for a certain degree of flexibility in adopting specific requirements from the standard. However, this can also lead to a reduction in the potential for standardization of products. Ultimately, if certain content not found in the standards is accepted, the possible combinations in valve design options may be countless. Therefore, the API committee requires the standard writing workgroup to reduce the occurrence of the above statements. Consequently, the 25th edition only includes "unless otherwise specified" twice and "by agreement" three times.

The latest technical standards certainly do not completely eliminate the flexibility favored by users. Most of the related content has actually been moved to the reference (non-mandatory) Appendix K. The name of Appendix K is "Specific Conditions Determined by the Purchaser - Permitted Deviations from Design and Manufacturing Requirements." As the title suggests, Appendix K allows the purchaser to specify proprietary design standards, such as custom pressure-temperature ratings or apertures different from those in relevant provisions in the main body of the standard. These customized contents, or variations relative to the relevant provisions in the main body of the standard, do not affect API 6D product certification.

Conclusion:

The evolution of API 6D reflects the dynamic nature of the oil and gas industry, with each revision addressing emerging needs and advancing technological standards. The latest edition, API 6D 25th edition, demonstrates a commitment to excellence by incorporating feedback from manufacturers, operators, and industry associations. With changes ranging from updated valve specifications to new requirements for actuators and bolts, this standard continues to set the benchmark for valve technology in the global market. As stakeholders adapt to these revisions, they pave the way for safer, more efficient operations and contribute to the ongoing progress of the industry as a whole.