API 687 - Chapter 0: Normative References and Definitions

The last post summarized the structure for Chapter 0. As I previously shared, I think it would have been best named “Introduction”.

Chapter 0 is full of references and hidden gems that open a whole other world of work and aspects of rotating equipment that don’t have to do with actual repairs.

For instance, Chapter 0, Section 2: Normative References.

This is a long list of standards and other publications that according to the author/s are “indispensable for the application of this document.”

I listed a handful of these API documents, the ones I would duct-tape to my ankle.

Besides those, there are documents from:

• AGMA: American Gear Manufacturers Association Another trade association, accredited by ANSI to write standards on gears.
  

• ANSI: American National Standards Institute A private nonprofit organization that oversees or sets the standards for writing more standards or voluntary consensus.

• ASME: American Society of Mechanical Engineers A professional association that promotes the arts, science, and practice of engineering and writes industrial and manufacturing standards.
  

• ASTM: American Society for Testing and Materials An international standards organization that published voluntary-consensus technical standards with a mission to improve safety and quality in the use of materials in the industry.
  

• ISO: International Organization for Standardization A non-governmental organization, made up of member countries, that develops and publishes standards on pretty much everything.
  

• MSS: Manufacturers Standardization Society of the Valve and Fittings Industry A non-profit technical association dedicated to developing and enhancing codes and standards for the valve and fittings industry.

• SAE: Society of Automotive Engineers A professional association that currently not only focuses on the automotive industry but includes aerospace and anything transportation.
  

• SSPC: The Society for Protective Coatings A professional organization concerned about the use of coatings in industrial- and transportation-related applications.

There are a total of 51 normative references, and, if you were to acquire them all, be prepared to spend approximately USD $9,044.

(I say approximately because ISO standards are sold in Swiss Francs)

Full list of normative references and links to official web stores.

These organizations play a crucial role in setting benchmarks and guidelines that help maintain safety, quality, and consistency across disciplines and industries worldwide.

(Like a bunch of rabbit-holes to geek out on and  acquire tons of knowledge.)

An interesting term I learned from this research is the process of “voluntary consensus”.  This process is characterized by the following key aspects:

1. Participation: It is open to all interested parties who wish to contribute, ensuring a diverse range of viewpoints and expertise.
   

2. Agreement: Decisions and standards are reached through consensus, meaning that substantial agreement is sought; although not necessarily unanimity. This ensures that the standards are acceptable to the majority of participants.
   

3. Voluntary Nature: The adoption and implementation of the resulting standards are voluntary. Organizations and industries choose to comply with these standards to achieve benefits such as improved quality, safety, and interoperability.
   

4. Transparency: The process is transparent, with documentation and deliberations made accessible to all stakeholders. This helps build trust and credibility in the developed standards.
   

5. Iterative Process: Standards developed through voluntary consensus are regularly reviewed and updated to reflect technological advancements, new research, and changing industry needs.

Immediately following this list of normative references, Chapter 0 dives into:

• Terms

• Definitions

• Acronyms

• Abbreviations
  

Finally! Something technical we can start diving into!

I appreciate the reader’s perseverance in following me up to this point. I have spent much time setting things up and introducing background.

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The Terms: From Accuracy to Witnessed Inspection

In total there are 41 terms defined in the API 687. I will not cover all of them, since most are well explained. I will only showcase my favorites, or the ones I think need to be explained in context or simply highlighted.

Accuracy

API 687 provides the definition of accuracy but not the definition for precision, and, in the context of “observational errors” and metrology (the science of measurements), I never think of one without the other.

Accuracy refers to how close a measured value is to the true or accepted value. It indicates the correctness of a measurement.

In practical terms, accuracy is about the validity of the measurement and whether it is free from systematic errors.

Precision, on the other hand, describes the repeatability or consistency of measurements. It indicates how closely multiple measurements of the same quantity agree with each other.

High precision means that the measurements are very consistent and have a low variance.

 If you google “accuracy and precision” and search for images, you will find tons of images like the one I have drawn below. What makes my images different is that I used an official Olympic archery target for the illustration. Enjoy.

Something important to remember: Accuracy applies to a single value; how close that measured value is to the actual value.

Precision, on the other hand, is a characteristic of multiple values; how close they are relative to each other.

Some dictionaries will define precision in terms of accuracy and “exactness”, which can quickly spiral us off into a circular reference. Time travel movies and Microsoft Excel have both warned us that circular references can disrupt the time continuum and create paradoxes.

Another interesting fact is that the instruments we use (calipers, micrometers, gauges, etc.…) are all called “precision measurement tools”.

To clear up this paradox, there is another term “measurement device graduation” that we will discuss in a later installment.

Let’s apply the concepts of accuracy and precision to the dimensional measurement of a part.

When we inspect or reverse-engineer equipment, we need both accuracy and precision, summarized best in the phrase “measure twice, cut once.”

There are many factors that can affect a measurement:

• The skill of the person performing the measurement Does the inspector understand how to use the tool, so it produces the desired degree of accuracy and precision?
  

• The condition of the measurement tool Is the tool in good working order and calibrated for the working range?
  

• The condition of the part being measured Is the part in good condition? How clean is the part?
  

• Environmental factors When taking multiple measurements or small measurements, are the parts at a stable temperature?

Since these factors can affect the quality of a measurement and therefore the quality of the work produced based on those measurements, so in our companies, whether we are an OEM, end user, or service provider, one would expect all these factors to be addressed in procedures, guidelines, and work instructions, as part of our quality systems.