what vs. why and API 687 Intro

What vs Why Poster

This is a quick disclaimer, so people don’t start to worry.

My intention is not to copy word-for-word or violate any copyrights on API documents.

While API guidelines are comprehensive in detailing what needs to be done, they often don't delve into the reasons behind these practices or the methods of implementation. In this blog, I aim to bridge that gap by explaining why these standards are important and how they can be practically applied.

Disclaimer: API explains what to do, and I will explain why and how.

I will use API 687 as a guide or roadmap to explain the world of turbomachinery repairs in the petrochemical and general industry.

It is important to note that there are other important API documents that influence the world of equipment design and repairs.

If I were stranded alone on a faraway planet, I would want these API publications on a USB stick duct-taped to my ankle, along with the Machinery’s Handbook:

API 612 and 617 specify the minimum requirements for the design and manufacture of Special-Purpose Steam Turbines and Compressors/Expanders (axial and centrifugal).

API 613 covers the minimum requirements for Special-Purpose Gears.

API 614 covers the minimum requirements for Lubrication Systems.

API 670 covers the minimum requirements for Machinery Protection Systems.

API 684, one of my personal favorites, describes practices for Rotordynamics and Stability Analysis.

API 686 describes Machinery Installation.

API 610 specifies requirements for Centrifugal Pumps.

And don’t let the fact that these documents are written for petrochemical applications seem irrelevant for other industries. These documents and guidelines are useful from a general engineering perspective for all applications of rotating equipment.

API RP 687

Like most other APIs I have read, 687 starts with Special Notes and a Foreword.

Special Notes

The spirit of the Special Notes in API publications is one of caution and responsibility.

They emphasize that while API standards provide valuable guidelines for industry practices, they are not a substitute for professional judgment or regulatory compliance. Users are reminded to consider local laws and regulations, use sound engineering and safety practices, and recognize that API does not guarantee the information's accuracy or assume liability for its application. Essentially, these notes encourage informed and prudent use of API standards, underscoring the importance of individual responsibility and due diligence in their implementation.

Foreword

Overall, the foreword underscores the importance of precision, transparency, and accountability in the use and interpretation of API standards.

This section emphasizes clarity, responsibility, and procedural integrity. It clarifies that API standards do not grant patent rights or liability protection and outlines the specific meanings of terms used in the document to ensure accurate understanding.

It also highlights the rigorous process of standard development, including stakeholder participation and regular review, reinforcing the commitment to maintaining high-quality and relevant standards.

The document uses specific verbal forms to express its provisions:

Shall: Indicates a minimum requirement.

Should: Indicates a recommendation, not mandatory.

May: Indicates permissible actions.

Can: Indicates possibilities or capabilities.

Chapter 0?

Chapter 0 did not exist in the 1st Edition of API 687. The original document only focused on recommended practices for rotor repairs. The taskforce introduced the concept of Stationary Components and thus Chapter 0 was born.

One can debate a bunch about starting lists with 0 or 1. It was the taskforce majority to maintain the original order of chapters, reserving Chapter 1 for general information on rotor assemblies. Chapter 0 really serves as a general introduction, and in my opinion should be called Introduction.

Chapter 0 does have a table of contents with 17 sub chapters, 11 Annexes, 24 Figures and 25 Tables.

The condensed Table of Contents reads:

Chapter 0 - Sub Chapters:

1.                  Scope and General Recommendations                     

2.                  Normative References       

3.                  Terms, Definitions, Acronyms, and Abbreviations

4.                  Process for Inspection and Refurbishment                              

5.                  Selection of a Repair Shop 

6.                  Communication    

7.                  Shipment of Equipment or Components to or from Repair Shop    

8.                  Receiving Inspection           

9.                  Disassembly           

10.              Inspections and Cleaning 

11.              Inspection Methods and Testing    

12.              Repair Processes and New Component Manufacture

13.              Assembly

14.              Shipment and Storage Containers

15.              Proposals and Finalized Work Scopes

16.              Repair Shop’s/Vendor's Data (Documentation)

17.              Owner's Data (Documentation)

The set of General Recommendations is probably the single hardest thing to accomplish in the world of repairs.

It basically says:

The primary goal of repair recommendations is to produce safe and reliable components or equipment by:

a) Ensuring dimensions match the latest design fits and clearances for spare parts interchangeability.

b) Maintaining interchangeability with other units.

c) Using existing spare parts.

d) Preventing errors in manufacturing future spare parts due to undocumented dimensional changes.

e) Maintaining the equipment's capabilities.

Note: The latest design fits and clearances may differ from the original equipment manufacturers’ (OEM) design due to possible rerates and/or upgrades.

A lot of debates or 6 beer arguments can be had about how complex these recommendations are. Not because it is the wrong thing to ask, but because it requires having a lot of information that no one has access to or that no one has kept.

Imagine that most pieces of turbomachinery were designed and manufactured 20 to 40+ years ago. Many of the original manufacturers bought by others. A legacy of design history that existed only in paper form that did not survive mergers. And a wealth of repair history that may not be in the hands of only one service provider but many.

Consider that each steam turbine and compressor was designed with a specific set of process conditions, so there is very little interchangeability by design between sites.

And, finally, consider that  during an emergency repair, time does not always allow things/machines to be restored to their original design.