Guidelines for Providing Process Conditions for RBI - Part 2: CUI and How it Relates to Risk Based Inspection

, Be the first to comment

Tags: Data Collection Risk Based Inspection


In this second of our eight part series covering various guidelines for providing process conditions for RBI, one of our senior consultants discusses Corrosion Under Insulation (CUI) and how it relates to Risk Based Inspection. This article identifies several factors to consider during data collection as well as points out some guidelines for selecting potential inspection locations.

Guidelines for Providing Process Conditions for RBI - Part 2: CUI

In Part 2 of our series on guidelines for providing process conditions for RBI, we move on to discuss Corrosion Under Insulation (CUI) and how it relates to Risk Based Inspection. CUI is essentially a type of corrosion that can occur when there is moisture present on the surface of insulated equipment. In addition to being very difficult to predict, CUI can be even more challenging to locate without removing insulation. This article provides some tips on predicting and locating CUI from a Risk Based Inspection perspective.

Corrosion Under Insulation is a concern at many facilities and one that costs the process industry millions of dollars a year to manage. Risk Based Inspection (RBI) is a tool that is currently being used to help understand the consequence of a failure from CUI and to develop inspection and maintenance plans to find potential CUI failures before they become a problem. Collecting data and information related to potential CUI failures, and using the data and information to determine a risk ranking and associated inspection and maintenance plan will go a long way to helping ensure a safer and more reliable facility.

Data Collection:

During the data collection phase of your RBI implementation, a helpful guideline is to take the following into account when considering damage mechanisms for a particular piece of equipment.

  • Most RBI CUI risk calculators use an operating temperature range of 0 to 350 °F to calculate an expected external corrosion rate for insulated carbon steel assets. Based on industry experience, the highest probability for CUI occurs between 170 and 230 °F. Due to the random nature of this damage mechanism, it makes sense to stay on the conservative side for CUI. If a vessel operates in a range of temperature and sometimes that range is between 0 and 350 °F (especially 170 °F to 230 °F), assign the operating temperature to fit in the CUI temperature range.
  • Area Humidity is a key factor depending on the geographical location of the facility. The higher the humidity, the more likelihood of CUI. Many RBI software tools require the user to assign a humidity factor of Low, Medium or High depending on geographic location. High typically makes sense along the Gulf Coast, Low for many parts of Canada.
  • Insulation jacketing condition, insulation type and coating factor can all play an additional role in determining probability of failure for CUI.
  • Based on industry experience, CUI may also be found in the temperature transition section of towers or other fixed assets where the temperature increases or decreases from within the CUI temperature range to something above or below that temperature.
  • Another potential physical factor to take into consideration is whether the insulated carbon steel assets undergo external wetting on a regular basis due to proximity to cooling water towers or condensation dripping down from above.

Potential Inspection Locations

Once the risk priority for CUI has been determined, inspecting for CUI will be enhanced by using the following guidelines:

  • Areas to focus CUI inspection activity for fixed assets include:
    • Barrier penetrations larger than 10" diameter and smaller penetrations that aren't properly sealed, termination of insulation, damaged insulation and insulation support rings.
  • Piping components may experience accelerated CUI near the following locations:
    • Bottom of vertical runs, low points of horizontal runs as well as Barrier penetrations larger than 10" diameter and smaller penetrations that aren't properly sealed, termination of insulation, damaged insulation
    • A Circuit Complexity factor taking into account the number of insulation penetrations and terminations, number of vertical runs, and total piping circuit length can also aid in prioritizing piping CUI inspection activity

Remember, the point is that you want to get as accurate as you can when gathering/providing process information as it might significantly impact the risk. Keep in mind that all RBI team members need to work closely to ensure a good understanding of when and where to look for CUI and the level of risk that it may present. Using the aforementioned guidelines for CUI can help ensure that it is considered when appropriate.

Stay tuned for the next entry in this eight-part series covering guidelines on assigning process conditions for RBI efforts:

  1. Guidelines for Providing Process Conditions for Risk Based Inspection (RBI) Implementation and Revalidation (Introduction)
  2. Corrosion Under Insulation (CUI) and How it Relates to Risk Based Inspection (this article)
  3. Process Fluids and Consequence Models
  4. High Temperature Damage Mechanisms
  5. Low Temperature Damage Mechanisms
  6. High Temperature Hydrogen Attack
  7. Environmental Cracking Damage Mechanisms
  8. Concluding Remarks

Be the first to comment

Comments

There are no comments for this article.

Add your comment

Related Services

Risk Based Inspection (RBI) Implementation and Planning

AOC has delivered thousands of sustainable Risk Based Inspection (RBI) programs earning the trust of owner operators.

Damage Mechanism Review / Corrosion Study

One of the most important steps in an RBI project is the corrosion study or damage mechanism review.

End-of-Life, Remaining-Life, and Fitness-for-Service Assessments

When evaluation of inspection results suggest that an asset is near its end of useful life, Fitness for Service evaluations can determine if the asset us suitable for continued operation.

Corrosion Control Planning

Achieving zero corrosion-related loss of primary containment in the refining industry.

Reliability Based Asset Management - AIM for all asset families

Asset Integrity Management for all asset families - Rotating, Electrical, Instrumentation, and Fixed Assets

Related Training

RBI/MI Overview

What is Risk Based Inspection?

API 580 RBI Overview

What impact does Risk Based Inspection (RBI) have on my organization?

API 580 Training

Is your Risk Based Inspection (RBI) program aligned with the API 580 Recommended Practice? Are you ready for certification?

API 581 Overview

What's actually going on inside all of that fancy software? An introduction to the API 581 methodology.

Risk Based Inspection (RBI) - A Mechanical Integrity Best Practice

What are your goals for RBI? How will you measure your success? How will you sustain that success?

Reliability Revolution - Measuring the Value of an RBI Program

How does one of the largest chemical manufacturers measure the value of their RBI program?

Value Proposition

Developing the value proposition and business case for an RBI program

Related Knowledge

Steam System Risk Mitigation Using Risk Based Inspection

The benefits of utilizing risk-based methodologies for the inspection programs of often overlooked utilities systems

Risk Based Inspection Yields Big Savings for Gulf Coast Plant

A 26-Year-Old Gulf Coast Chemical Plant Saves over $15 Million in Related Inspection Activities.

RBMI Implementation Saves Refinery $63 Million

130,000 BPD Refinery Implements RBMI Program and projects a $63 Million savings over 10 years.

Corrosion Under Insulation (CUI) in Plant Equipment and Piping

Implementation of a managed CUI program yields prioritized inspection plans and identifies imminent failures.

Safe Operation of Aging Hydrogen Generation Plants

Integrating DMR, RBI, and IOWs to manage aging plant reliability

Risk Based Inspection: What To Expect

Significant findings, even after ten years.

Storage Tank RBI

How many RBI studies have been completed on above ground storage tanks (ASTs)? We have completed hundreds.

Time to Value - Asset Integrity Management

Delivering knowledge based asset files from the true sources of data - confidently, accurately, electronically, and in half the time.

Implementing RBI in Remote Locations

The importance of understanding risk and the significant value attainable through the implementation of risk based inspection (RBI)

An Update on Risk Based Inspection (RBI) (RMC-12-46)

Using RISK as a basis for maintenance planning

Risk Based Asset Management - Delivering and Sustaining Value

The business case developed for an RBI program - realized benefits and how the on-going value of the program is measured

5 Things to Consider When Choosing Your API Training Provider

Not all vendors are created equal. Some up-front research can go a long way toward a high-quality learning experience.

Goal: 100% API 580 Certified

A long-standing vision of AOC, we are well on our way to meeting the goal of having 100% of our RBI staff certified to API 580.

Guidelines for Providing Process Conditions for RBI

Incorrectly assigning process conditions for a particular piece of equipment can result in overlooking a variety of applicable damage mechanisms and a skewed calculation of risk.

Risk Based Inspection Seen Through the Eyes of the Experts

Our experts consider why organizations implement RBI, common challenges, and strengths of an RBI champion.

Qualitative RBI of a Commercial Refrigeration System

Refrigeration system owner/users who are maintaining their assets as prescribed may be unaware of the damage mechanisms that could affect the reliability of their assets and safety of their personnel.

Dynamic Risk - Mechanical Integrity

Things are always changing. Including your risk profile.

Risk Management for Kids

One of our consultants brings Risk Based Inspection into the grade school classroom for Career Day.