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Tag: Corrosion

Corrosion and Damage Mechanisms – How do I Learn More? “An example”

Posted by on in Asset Integrity, Inspection, Process Safety Management, ReliabilityLeave a comment

As we discussed in last month’s blog, Loss of Primary Containment (LOPC) or simply leaks in our process facilities is an all too common event. Sometimes we get lucky and it is a minor event but relying on luck is not any way to keep our plant’s safe and reliable. However, other times the leak leads to a serious event and we make the local or national news or worse yet; someone gets injured or loses their life! Today’s blog will be focus on a simple example of using API-571 “Damage Mechanisms affecting Fixed Equipment in the Refining Industry” to improve your corrosion and damage mechanism knowledge.

In today’s example, I will assume that I am the area inspector or engineer working in my refineries Crude unit. Therefore, the first thing I do is review the Process Flow Diagram for the Crude Unit/Vacuum in Figure 5-65. (See example in blog photo) For this example, I’m interested in the atmospheric tower side draw piping. So what damage mechanism do I need to worry about for this area of the Crude unit?

DM#1 Sulfidation
DM#6 Naphthenic Acid Corrosion

So, I need to understand more about damage mechanism DM #1 -Sulfidation—Looking at the DM table of contents, we see that Sulfidation is covered in Section 4.4.2 on pg 4-159. Moving to page 4-159 you will find six pages of information related to sulfidation, including pictures, graphs and other details including: High Level Description of Sulfidation, Affected Material, Critical Factors, Affected Units & Equipment, Appearance of Sulfidation, Prevention/Mitigation, Inspection & Monitoring, and Related Damage Mechanisms. Sulfidation (also known as sulfidic corrosion) is the corrosion of carbon steel and other alloys resulting from their reaction with sulfur compounds in high temperature environments. (>500F) There are eight Critical Factors related to Sulfidation discussed with one of them being the alloy composition (determined by the alloys ability to form protective sulfide scales), temperature (increased corrosion as temperatures increase) and concentration of corrosive sulfur compounds.

Section 4.4.2.7 gives you information about the how to Inspect and Monitor for Sulfidation Corrosion:

  • Evidence of thinning can be detected using external ultrasonic thickness measurements and profile radiography.
  • Process conditions should be monitored for increasing temperatures and/or changing sulfur levels. See API 584-Integrity Operating Window (IOW) for more information on issues that may assist in the development of an IOW program.
  • Proactive and retroactive PMI programs are used for alloy verification and to check for alloy mix-ups in services where sulfidation is anticipated. Note: Inadvertent mixing of Alloy material in a piping circuit has led to several major incidents in the Oil and Gas industry.

The remainder of the section contains additional information related to Sulfidation including graphs giving you information on corrosion based on the affects of temperature, Sulfur content and Alloys in your system.

Now, follow the same review of 571 for DM#6- Naphthenic Acid Corrosion and you will have a good understanding of what you need to look for and how to find it for the Crude Atmospheric Tower Side Draw Piping.

API-571 is an excellent resource to use for improving your corrosion knowledge and that of your work force. I hope this very simple example will encourage you to review API-571 for your area of responsibility or area of corrosion knowledge that you would like to learn more. Additionally, API has an API-571 Certification Program available for anyone with a keen interested in corrosion and potentially becoming a technical resource for your facility. See http://www.api.org for additional information.

Actions to Take:

  1. Complete a quick review of API-571.
  2. Review the damage mechanism PFD for your unit or unit you would like to learn more about.
  3. Have one of your employees present an overview of one damage mechanism for their area during a weekly meeting. The employee and those present will all learn from this type of exercise.

Please contact BoilerRock if you need assistance with any of your Reliability or Asset Integrity issues.

Reference: “API Recommended Practice 571, Second Edition. Washington DC: API Publishing, 2011”