Key Differences Between API and ISO Standards

Valves are used for a wide variety of applications throughout the industrial, commercial, and residential communities. Valve manufacturers are required to meet certain standards of quality to manufacture, operate and provide products that are certified to the customer specific operating conditions for their applications.

Due to this wide range of uses and user requirements, there are several major regulatory organizations for Standards Publishing like API, ISO, ASTM, BSI, CEN, MSS, ASME, DIN, JIS, NACE and many more which provide general standard requirements and guidance to ensure proper valve functionality, compatibility, and safety for users.

Without precise guidelines in place, any number of problems can arise. Over time, business practices and other factors change, and as a result, the standards developed by various publishing organizations govern the path to develop a standardized product in the market. This article will focus specifically on key major differences between API and ISO.

Equivalents & Comparisons

The American Petroleum Institute (API) and the International Standards Organization (ISO) are two major regulatory organizations intended to establish guidelines for both manufacturers and end users in the valve selection, manufacture, design, lab (type) testing & certification, quality and to drive standardization among the largely competitive oil and gas market to operate continuously at the best possible efficiency.

API is solely dedicated to the petroleum and energy industries while ISO rarely publishes industry-specific standards. In the past, there has been cooperation between ISO and U.S. valve standards makers, however due to local governing regulations, requirements, and inability to reach agreements regarding intellectual property rights, there has been a shift in design and testing standard requirements. Using API and ISO Certified valves helps to not only improve production and revenue, but more importantly safety and quality.

There are many equivalent designs, testing and quality standards between API and ISO, here are some examples that pertain to the valve market that standout

  • API 6A & ISO 10423
  • API 6D & ISO 14313
  • API 600 & ISO 10434
  • API 602 & ISO 15761
  • API 608 & ISO 17292
  • API 598 & ISO 5208
  • API 624, API 641 & ISO 15848-1
  • API 6FA, API 6FB, API 6FD (“API 6F Series”), API 607 & ISO 10497
  • API Q1 & ISO 9001 and many more.


While API necessitates companies to implement standards for licensing and certification, ISO remains a certification body where participation is predominantly voluntary.

For leading manufactures, implementing both sets of quality standards is part of the cost for doing business.

Both organizations establish a minimum set of design parameters with which the manufacturer must comply to claim design conformity, but the actual quality of product and its safety for intended use is displayed through the valve testing and certification process. Qualification/certifications ensure the product meets certain design standards and desired functionality expectations.

Top ISO & API Certifications to Consider in the Valve Market

  1. Fugitive Emission Testing:

With an increasing number of consent decrees set forth by the Environmental Protection Agency (EPA) to abide by the Clean Air Act to reduce greenhouse gas emissions, valve fugitive emission control has been a hot topic in the US market. It is also a growing concern in the refinery and chemical process industries and lot of work is put in place to set acceptable limits and criteria.

API has since developed the standard API 622: type testing of process valve packing for fugitive emissions. This standard is to guide the packing manufacturers to set limits for the packing, in order to meet the EPA consent decree requirements. The latest developments in the standard include addition of High temperature testing of graphite packing.

Alongside, API has also developed type testing standards of valves for fugitive emissions:

  • API 624: Rising stem Valves
  • API 641: Quarter turn valves.
  • Both the valve type testing standards require the graphite seals to be incompliance to API 622.

An equivalent ISO standard for fugitive emission valve type testing is ISO 15848, which has been classified into 2 parts:

  • Part 1: Type test
  • Part 2: Production Valve testing.

The type testing requirement in ISO 15848, Part 1 is more complicated and stringent compared to API test requirement. It allows different levels of test parameters such as fugitive emission levels, number of mechanical cycles, stem seal adjustments, temperature ranges, choice of test media, and endurance classes.

The tests performed between API and ISO cannot be compared as the methodology used and governing factors are very different. Ultimately, the decision lies with the user to specify the minimum acceptance criteria to meet their specific operating conditions.

The testing and certifications for ISO are not mandated by their design standards and allows the manufacturer to determine if the market necessitates the need for testing and certifying the valve. The API standards, on the other hand have embedded these fugitive testing standard requirements into the valve design standards to enforce the American Clean Air act right from the design phase of the valve.

  1. Fire Safe Testing:

Fire safe testing is another critical part in the valve design; it is solely intended to keep personnel, process, facilities, and equipment safe from fire hazards when the valves are subjected to dangers of fire accidents and explosion.

The “API 6F Series” is for evaluating the valves designed under API 6A and API 6D. These standards are maintained under the API wing of Valves and Wellhead equipment, an upstream oil and gas segment. The downstream oil and gas refinery segment has developed standard API 607 for evaluating the fire testing  capabilities of quarter turn valves and other valves equipped with non-metallic seating.  The scope of this standard is currently under revision to include fire testing capability of metallic seats for quarter turn valves to avoid any misinterpretation.

While API fire testing standards are written considering both the upstream (Well Head) and downstream (refinery) segments differently, ISO originally adopted API 6FA, an upstream segment fire testing standard to create ISO 10497. With recent updates, the most current edition of ISO 10497 is more equivalent to API-607 (refining segment) and is different than API 6FA testing requirements.

Valve manufacturers often choose to dual certify their valve testing when the testing requirements overlap or are in close proximities. Until 2004, API 6FA and ISO 10497 were considered equivalent standards so the tests could have been dual certified to meet both. Now, the API 607 and ISO 10497 current standard editions are mirror like, so valve testing can be dual certified to meet both test standards.

  1. Quality Certification:

Valve manufacturers receive their Quality management certifications by successfully demonstrating their ability to meet safe manufacturing practices and other supporting processes in their quality management system for doing business.

A certification shows that the product adheres to the expectations and qualifications of the latest standards set in the industry and the manufacturing organization is keeping up with the latest industry standards and regulations. . Quality certification is both crucial and necessary for valve manufacturers to demonstrate their product worthiness and differentiate themselves in this fast paced and competitive market.

Quality and safety are two terms that go hand in hand – a product that meets the set quality standard requirements is safer to use than the product for which none exists.

ISO informs and guides several industry leaders around the world for manufacturing processes, safety requirements, quality assurance, and more. ISO 9001 is a singular measure within the body of the ISO 9000 standards that specifies requirements for a quality management system when an organization needs to demonstrate its ability to consistently provide products/services that meet customer and applicable statutory and regulatory requirements. 

ISO 9001:2015 is the current version of ISO quality management system and has several updates from its previous version with main focal points on measuring and properly assessing the input and output processes, risk-based thinking to solve potential problems, leadership, and commitment from all levels of the organization. Quality Certifications to ISO 9001 are very common in valve industry and serve as one of the basic requirements to differentiate between product and process quality. All requirements are generic and are intended to apply to any organization regardless of the product type.

On the other hand, API qualifications are specifically developed for natural gas and oil businesses. Historically API Quality management requirements are in line with ISO 9001-2008 but later in 2011 it parted ways to elaborate and exceed the Quality management requirements to make API Q1, 9th edition. The latest version of these guidelines was issued in 2013, with a large focus on risk management and risk assessment, a new addendum added in 2018 for supply chain requirements and an Errata addressed in 2019 for Product Quality plans.

Following are some key differences between the two systems that should be noted:

  • Formal approach to the training of employees and personnel competency
  • Emphasis of risk management and risk assessment (Potential problem accessing).
  • Contingency planning (Potential problem prevention plan)
  • Control within the supply chain
  • Design Validation
  • Preventive maintenance
  • Management of change

The Future for API & ISO

With the supply disruptions and increasing global economy conflicts, the need for design compatibility with multiple material sources in best interests of product availability plays a key role in present times.  One such example, is introduction to a partial re-test for new material sources meeting certain stated requirements to improve the valve production scope.

In addition, API fugitive emission standard development group, together with the support of several valve and packing manufacturers, testing laboratories, performed high temperature tests to define a new scope for valves used in high temperature services. This may pave the way for more standard developments in the future for valves in severe service conditions.

In recent years ISO has recognized the importance of valve packing type test API 622 and is working to create ISO 15848-3, an equivalent version to API by adopting the standard API 622 limitations.

API is also currently underway creating the 10th edition for API Q1 with significant changes from the 9th edition and anticipates publishing the document on third quarter of 2022. Following are some significant changes proposed in the latest ballot:

  • Alignment with the requirements of ISO 9001:2015
  • Document Scope Change to include “Organizations providing products for Petroleum and Natural Gas Industry”
  • Revised requirements for supplier evaluations
  • Removal of preventive actions
  • Addition and revisions of definitions
  • Examples of organizations that provide the product/service.

Having two different sets of guidelines for natural gas and oil companies to adhere gets confusing at times. With API Q1 adopting and aligning requirements of ISO 9001, it shows that the two systems work together to ensure a more productive outcome. Both API Spec Q1 and ISO 9001 ensure that the proper documentation has been developed and is in place in the event of certain proceedings.

Meeting ISO 9001 would generate a certificate for the business organization while API Q1 is a monogram program, and its compliance would have the product monogrammed as well.


Ultimately, the end results for both API & ISO governing standards are the same: to provide a higher quality of service and ensure that businesses carry out the safest and most efficient way possible.

In the end, the user must decide the correct approach to meet either ISO or API based on their desired need and requirements set forth by the operating parameters and business necessity.

About the Author: Mani P. Pilla, P.E.


Mani P Pilla, Mechanical Engineer at Smith Valves has over 10 years’ experience in the valve design and testing for the Chemical and Refining Industries. He graduated with master’s in mechanical engineering from University of Houston and brings a unique perspective of product design cycle management and application engineering.  His focus for the years in the Valve Industry has been in improving the valve designs and optimization, troubleshooting problems, valve testing and certification.