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API RP 687 Chapter 1, Section 10: Phase I Inspections and my first API conference

Updated: May 17



Why inspect? For someone in charge of an asset in a plant the answer may be obvious.

But to understand WHAT we inspect and HOW we do it, it is important to review the reasons why.

 

Part of the answer is contained within the API RP 687 document itself.

Let’s look back at Chapter 0, Section 1.2.1: General recommendations.

This section states that recommendations should produce safe and reliable equipment while:


  • Returning dimensions for parts interchangeability (fits and clearances)

  • Using existing spares

  • Documenting dimensional changes to avoid future errors when manufacturing parts

  • Maintaining capabilities

 


These statements mainly point towards maintaining dimensional control of all the parts to maintain interchangeability between multiple machines or spare parts.

Dimensional control also allows us to fulfill the last point in Chapter 0 which is to maintain capabilities. To be capable means the part must be able to fulfill its design intent. That means that it must be the correct shape and be in the correct form.

 

Now, let’s look now at Chapter 1, Section 4: Purpose.

This statement contains: …properly evaluate the condition of rotors being considered for overhaul.

 


FFS


I like mashing up all these concepts into a term that did not make it into 687, but a term that engineers in the repair industry use, which is “fit for service”.


In engineering, the concept of “fit for service” (or well meaning “FFS”) is the assessment we perform on something that has already been put in service and has potentially experienced degradation to determine if it is still safe and capable or operating as intended.


  • It still performs the intended function reliably.

  • It still meets the specified requirements and complies with any relevant standards.

  • It is still suitable for the operating environment.

  • It still maintains appropriate durability or safety margins.


(There is another term, FFP or Fit For Purpose. We use this more in the context of design, when we are designing a new machine or modifying the design of a part. This is the assessment we perform to ensure parts can meet an intended use or application, regardless of whether it is new or has been in application.)


So, it all comes down to: we inspect rotors to ensure they are fit for service, in a condition that they can safely and reliably perform the work they were designed to perform.


We are inspecting parts that were already designed and manufactured once. Meaning we are inspecting parts that allegedly were already qualified for being fit for purpose.

So we are looking for deviations from a previous condition, mainly a dimensional or material deviation. We are also looking for how individual parts are placed or function within an assembly.


The conclusions from a Phase I rotor inspection will tell if the rotor is fit for service as it is, or if further investigations are required. Further investigations we call a Phase II!

 


Phase I Rotor Inspections


API RP 687 Phase I inspections, focus mainly on assessing the condition and capability of a rotor by following five fundamental procedures:

 

  1. Visual Inspection before cleaning

    1. Record “as received” condition

  2. Cleaning

    1. Wash complete rotor

    2. Blast flow path

    3. Polish shaft ends

  3. Visual Inspection after cleaning

  4. Non-destructive Evaluations

    1. Wet Magnetic Particle

    2. Liquid Penetrant

    3. Ultrasonic Testing

    4. Coating Detection

  5. Dimensional Inspection

    1. Outer Diameters

      1. General Rotor and Component Areas

    2. Journal Inspection

      1. Detailed inspection (3 locations 3 orientations)

      2. Journal weights

    3. Axial Dimensions (stackup)

    4. Clearances (thermal gaps)

    5. Runouts

      1. Axial

      2. Radial

        1. Electrical

        2. Mechanical

    6. Coupling Inspection

      1. Taper

      2. Keyway

  6. Check balance (if possible)

 


Visual: “As Received”


When inspecting things, especially machines that have just been taken out of service, I always make the analogy to being on a Crime Scene Investigation CSI unit.


First, be very careful not to contaminate or disrupt any of the evidence.


Just as important, make sure you wear the correct personal protective equipment (PPE) as many of the fluids that travel through compressors in the petrochemical could be harmful.


Take pictures, lots of pictures. Make sure they are in focus and make sure you can identify the content of the picture. Every detail captured now may explain a condition found later during closer inspections.


Make a note of all the details, even note how parts are packaged or secured during transport.Once you receive a rotor at a shop, you may not know what damage occurred during operation, during the handling of the parts, or even the transport.

 


Cleaning


Step1: Wash

The next step is to clean the rotor so that thorough dimensional inspections and the condition of the rotor can be assessed.


First, wash any heavy deposits from the rotor.DO NOT use water or steam, unless you know for a fact you will be taking the rotor apart immediately after cleaning.

Use mineral spirits or solvents that may help remove the oil or other products that may be on the rotor, impellers, blades.

 

Step 2: Blast

After the wash, prepare the rotor for media blast.Before blasting, protect each shaft end and basically all the areas that do not come in contact with the steam or working fluid.


Protect shaft ends, threads, coupling surfaces, and fit areas if thrust bearings or trim parts have been removed. Protect the journal areas and the probe areas and protect any fit areas if mechanical seals were uninstalled.


You only need to blast whatever has come in contact with the working fluid or may have heavy deposits of foreign material. Based on how heavy the soiling or fouling is, blast the rotor with aluminum oxide or blast bead.


Aluminum oxide is the same stuff that you see stuck on sandpaper. Inside a blast booth, you basically shoot it out of a nozzle at high speed, and it removes dirt and will also erode the part if you are not careful.


For this reason, sometimes when more delicate treatment is required, we blast parts with glass beads. It basically looks like fine white sand. It is tiny glass spheres that will also clean but not as aggressively as the aluminum stuff will.


Afterwards, all the parts that were blasted will look matte or dull gray, almost like the color and look of shark skin.


Finally, if you do this in a humid place like Houston, do not be surprised if your rotor starts to rust within half a day of cleaning.


In API RP 687, there is a note that serves as an interesting warning in terms of blasting. It states that blasting cleaning can peen and/close small open cracks that then may be difficult to detect with liquid penetrant.



Step3: Polish

The shaft end areas that had been protected before blasting the rotor, must now be lightly polished.

This is done so accurate dimensional and runout measurements as well as non destructive tests can be performed on clean and smooth surfaces.


 

Non-Destructive Testing (NDT)

 

I’ve explained the main methods in a past post:


The key is that with these methods we can detect conditions that would not be recognized only by the naked eye.


We are looking for “indications”, meaning anything that can be considered “interesting” or noteworthy. Like a small crack, pits or holes, a wear pattern on an airfoil, a discoloration from heat on a seal area, etc.


In the business of non-destructive testing, do not forget the acronym DIE.


Detect

Interpret

Evaluate


You can remember this by telling yourself. “I don’t want to DIE, I must do a good job performing my inspections.” In other words, if you are a non-destructive inspector, you have to inspect as if your life depended on it.


I also wrote more on this here:

 

Here we are going to take a break and continue with Dimensions and Check Balance in the next post.



++++++++++++++++++++++++++++++++++++++++++


About my experience at the API Conference


I want to make a parenthesis and take the opportunity to mention something I observed last week. Last week I went to San Francisco and attended my first API Conference. I had participated from the 687 workgroup efforts, mostly via online meetings, and had never attended an event in person.


Needless to say, I was blown away. By the scale, by what it meant, and by the commitment of the attendees.


First the scale. This was a meeting attended by at least 1,200 engineers from API member companies. Keep in mind, this is not a trade show or expo. The attendees were there to WORK!


Most arrived and began working on Sunday, the day before the meetings officially began.

The purpose of this conference was to bring together several of the committees and workgroups that are reviewing or developing documents, such as standards or recommended practices.


These work groups and committees are made from volunteers, engineers that have other day jobs, but their passion for engineering, their commitment to safety, reliability, and to being the best engineers drives them to participate, to create, or to review new or existing standards.


I was blown away as I sat in and listened to the API 610; Centrifugal Pumps work group navigate through all the comments and observations made to the working edition of the document.


It did not matter that these engineers were from competing companies or represented end users or manufacturers or service providers.


In that room, those engineers were the most dedicated engineers I have ever observed, working relentlessly to clarify and improve the requi

rements and expectations for how pumps should be designed and manufactured.


I was inspired, and I invite the next generation of engineers to get involved. If you work for a company that is a member of the API, find out who is participating in the committees that are relevant to your area of responsibility or expertise.


The industry needs our voices and perspectives as engineers to keep improving.


Never stop improving.

 
 
 

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