By Carlos F Molina

Here are my thoughts on the numeral 5.1 of API 571, “Determination of Need for Cathodic Protection”

It starts saying that “The need for cathodic protection shall be determined for all aboveground storage tanks.

Determination of Need for Cathodic Protection

Almost any tank of certain size that is in contact with soil will need a cathodic protection in the bottom, because coatings are not perfect (NACE SP0169), so it will be a moment when corrosion starts to act. With more reason if the surface is not coated. Keep reading

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By Eng. Carlos F Molina
To protect metal from corrosion, there are several things that can be made
  • Coat the surface with paint so there is no contact between the metal and the electrolyte.
  • Coat the surface with a another metal that is sacrificial metal that protects the steel.
  • Pasivation.
  • Anodization.
  • Cathodic protection from sacrificial anodes – no power supplies.
  • Cathodic protection by the use of an impressed current from an electrical source.
A tank bottom can make good use of cathodic protection and coatings. The most effective protection for a tank bottom is a combination of a corrosion resistant coating and a cathodic protection system (says API 571 and NACE RP0193). The provision of an insulating coating to the structure will greatly reduce the current demand for cathodic protection.

Keep reading

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By Eng. Carlos F Molina

The following article is about API RP 652 for the API 653 certification exam. What do you think is the difference between a lining and a coating? Between a coating and a paint?….. Before you continue reading, share your thoughts in the comment section.

As far as I know,  paint is a liquid or paste that, when applied in a substrate, coats a layer over the surface, protects it and then gets to be known as a coating. Any material applied to the internal surfaces of a tank to serve as a barrier to corrosion and/or product , it is known also as a lining. Right now we are going to study linings. If you are preparing to take the API 653 certification exam, do me a favor an read the 652 RP. Keep reading

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By Eng. Carlos F Molina

As any person in a project knows, consumables control is difficult, and critical. And while there are some calculators and guides in the internet and literature for things like control of welding and safety consumables, there is not much for painting consumables. In fact, a google search for “abrasive performance” has little results, and a search for “paint control” yields almost no result. For people in charge of paint control, this can be a nightmare.

I haven´t found any paint control strategy on the web. I am sharing one I have used before with success. It is mainly useful in large surfaces that are going to be painted by the airless spraying method.
I am aware this might not be the only nor the best approach there is to the subject. But maybe it will serve as a catalyst for debate in the subject. I am open to criticism. I know there are many experts in the field already. And finally, this is not my creation only, but the work of others put together as an overall strategy.

NOTE 1: In this article, I use the word paint for a) the liquid in the buckets before applied b) the act of painting, and I use the word coating when referring to the product applied and already dry over the substrate.
NOTE 2: In this article, I use the example of a project where you have to paint the inside of  tank with a single coating and the exterior with a 2-coat arrangement.
NOTE 3: In this article, I assume all paints are 2-part (a resin and a hardener). However, it serves with single component paints.
NOTE 4. In this article, I talk about the possibility of being untrue to specifications of a paint job in very small areas. Take the advice at your own risk. (Remember: any standard is a form of risk reduction, so your professional criteria should always be used.)
NOTE 5. Finally, none of this information can be used to blame me later about anything. This is not a contractual document anyways, but only an strategy. Keep reading

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By Eng. Carlos Molina

To download 52 questions for your own study, based in SOIL and CAUSTIC corrosion in the API 571 RP, click here

Both DM ares listed in the API 571 RP under the “Uniform or Localized Loss of Thickness” Keep reading

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By Eng. Carlos F Molina

Liquid penetrant examination is a NDE technique used many situations. It is an effective means for detecting discontinuities which are open to the surface of nonporous metals and other materials. Typical discontinuities detectable by this method are cracks, seams, laps, cold shuts, laminations, and porosity. In fillet welds of big size (you define big size), it can be used in several stages to make an approximation to a volumetric NDE. It is better used if applied to the root pass of containment welds.

The Body of Knowledge for the API 653 exam (there is a new BOK here) says the following:

body-of-knowledge-article-6 Keep reading

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By Eng. Carlos F Molina

Hi. Following two months and a half of a new job in Panama, I haven´t been so atentive to my website. I am again working for a contractor, meaning I have almost no time at all to update this site. I am usually void of energy because of all of the work that needs to be done.  I hope that changes in the near future. By now, I am trying to retake writing in apiexam.com and to really commit to an schedule. Even when I didn´t write in a long time, the number of people that found value in my content grew (I have 255 suscribers now) in the past 2 and a half months.

Last time, we talked about Ultrasound according to Article 23 Ultrasonic Standards, Section SE–797, only things related to the Body Of Knowledge. This time we will review the use of ultrasound in tanks.

INTRODUCTION

Ultrasonic testing, I think, is going to replace RT as a mean of inspecting welded joints in tanks, because of its many advantages, like reducing hazards and downtime associated with radiography.

Keep reading

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By Carlos F Molina

In the Body Of Knowledge for the API 653 exam, Ultrasonic Testing is one of the smallest parts that needs to be studied. This is what the Body Of Knowledge says you need to get:

E. Article 23, Ultrasonic Standards, Section SE–797 only – Standard practice for measuring thickness by manual ultrasonic pulse-echo contact method:
The inspector should be familiar with and understand;
1. The Scope of Article 23, Section SE-797,
2. The general rules for applying and using the Ultrasonic method
3. The specific procedures for Ultrasonic thickness measurement as contained in paragraph 7.

Keep reading

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By Carlos F Molina

Here I present the resources in my website: the Q&A documents and a simulator.

Please download 47 more Q&a in the Api 653  series.

HOW TO USE THE Q&A LISTS

The questions of the Q&A list were extracted from the standards by me, or remembered by me or other students that took the exam before. The format is a Q&A one, different from the multiple choice question format from other courses I have seen online. I prefer this method because it takes away all the clutter that leads to confusion when treating these standards. I advise you to copy these questions (maybe you will have to actively copy and paste the Q&A sets in word or excel) and paste it in a spaced repetition software like Anki or Supermemo, as the Q&A format allows, and start studying right away.  Please edit the questions yourself looking to the references if you have difficulty remembering any of them. When days pass by, you will see who you remember all of the information with no problem.

Keep reading

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By Carlos F Molina

This is my last article about radiology in tanks for readers who are studying for the API 653 exam. We will see

  • Radiographic Technique
  • Placement of IQIs
  • Radiographic density

Keep reading

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