Asset Integrity Management

MPY

MPY: The Silent Threat in Oil & Gas – Understanding Corrosion Rates

In the harsh and demanding world of oil and gas, corrosion is a constant threat, silently chipping away at infrastructure and potentially leading to costly downtime, environmental damage, and even safety hazards. To quantify this invisible enemy, the industry relies on a metric known as MPYmills per year.

What is MPY?

MPY stands for mills per year and represents the rate at which metal is corroded away. One mill is equal to 0.001 inches, making MPY a measurement of corrosion thickness loss per year.

How is MPY Determined?

MPY is determined through various methods, often utilizing techniques like:

  • Weight Loss Tests: This involves measuring the weight of a metal sample before and after exposure to a corrosive environment over a specific time.
  • Coupon Tests: Metal coupons are exposed to the corrosive environment and their thickness loss is measured after a set period.
  • Electrochemical Techniques: These methods use electrical measurements to estimate the corrosion rate.

Why is MPY Important in Oil & Gas?

MPY is crucial for several reasons:

  • Predicting Equipment Lifespan: By understanding the corrosion rate, engineers can estimate the lifespan of critical equipment like pipelines, storage tanks, and processing units. This allows for preventative maintenance and timely replacements.
  • Design Considerations: MPY data helps engineers choose materials and designs that can withstand the specific corrosive environments they will encounter.
  • Safety & Environmental Concerns: Uncontrolled corrosion can lead to leaks and spills, posing safety hazards and environmental risks. Knowing the MPY allows for proper mitigation measures.

Factors Influencing MPY:

  • Environment: The type and concentration of corrosive agents (e.g., seawater, acids, sulfides) significantly influence MPY.
  • Material: Different metals have varying corrosion resistance.
  • Temperature and Pressure: Elevated temperatures and pressures can accelerate corrosion rates.
  • Stress and Strain: Mechanical stresses can create areas of higher corrosion susceptibility.

Mitigating Corrosion:

  • Corrosion Inhibitors: Chemicals are added to prevent or slow down corrosion.
  • Protective Coatings: Coatings like paint or metal cladding create a barrier against corrosive environments.
  • Cathodic Protection: This technique uses electrical currents to prevent metal from corroding.

Conclusion:

MPY is a critical parameter for understanding and managing corrosion in the oil and gas industry. By accurately measuring and analyzing MPY, engineers and operators can take proactive steps to mitigate corrosion, ensuring the safety, reliability, and longevity of critical infrastructure. As the industry strives for greater efficiency and environmental sustainability, understanding MPY plays a crucial role in achieving these goals.


Test Your Knowledge

Quiz: MPY - The Silent Threat in Oil & Gas

Instructions: Choose the best answer for each question.

1. What does MPY stand for?

a) Meters per year b) Mills per year c) Millimeters per year d) Miles per year

Answer

b) Mills per year

2. How is MPY typically determined?

a) Measuring the weight of a metal sample before and after exposure to a corrosive environment b) Examining the surface of the metal for visual signs of corrosion c) Estimating the corrosion rate based on the type of metal used d) Using a special device that measures the rate of metal deterioration

Answer

a) Measuring the weight of a metal sample before and after exposure to a corrosive environment

3. Which of these factors does NOT influence MPY?

a) Temperature b) Material type c) Presence of oxygen d) Color of the metal

Answer

d) Color of the metal

4. Why is MPY important in the oil & gas industry?

a) To determine the price of oil and gas b) To predict equipment lifespan and plan maintenance c) To measure the efficiency of oil and gas production d) To identify the best location for drilling wells

Answer

b) To predict equipment lifespan and plan maintenance

5. What is one method used to mitigate corrosion in oil & gas infrastructure?

a) Using only highly resistant metals b) Applying protective coatings c) Increasing the temperature of the environment d) Adding more corrosive agents to the environment

Answer

b) Applying protective coatings

Exercise: MPY Calculation

Scenario:

A steel pipeline in a saltwater environment has a corrosion rate of 5 MPY.

Task:

Calculate the amount of metal thickness lost due to corrosion over a period of 10 years.

Instructions:

  • Remember that 1 MPY is equal to 0.001 inches of metal loss per year.
  • Use the formula: Thickness Loss = MPY x Time (in years)

Exercise Correction

Here's how to calculate the thickness loss:

Thickness Loss = 5 MPY x 10 years

Thickness Loss = 50 mills

Since 1 mill is 0.001 inches, the total thickness loss is:

50 mills x 0.001 inches/mill = **0.05 inches**

Therefore, the steel pipeline would lose 0.05 inches of thickness due to corrosion over 10 years.


Books

  • Corrosion Engineering by Dennis R. Croft and J. T. S. Roberts (This book provides a comprehensive overview of corrosion and its control, including sections dedicated to MPY and corrosion rates).
  • Corrosion and its Control by H. H. Uhlig (This classic text offers a detailed explanation of corrosion principles and discusses MPY in the context of various corrosion phenomena).
  • Corrosion in the Oil and Gas Industry by R. E. Smith (This book specifically focuses on corrosion challenges in the oil and gas sector, featuring insights on MPY and its implications).

Articles

  • "Corrosion Rate Measurement" by NACE International (This article provides a detailed explanation of various corrosion rate measurement techniques, including MPY determination methods).
  • "The Importance of Corrosion Rate Measurement in Oil and Gas Production" by J. M. Jones (This article highlights the significance of MPY measurements in ensuring the safety and reliability of oil and gas facilities).
  • "Corrosion Control in Oil and Gas Production: A Review" by M. J. Thompson (This review article discusses various corrosion mitigation strategies and the role of MPY in evaluating their effectiveness).

Online Resources

  • NACE International: NACE (National Association of Corrosion Engineers) is a leading organization dedicated to corrosion control. Their website offers a wealth of resources, including articles, standards, and training programs on MPY and corrosion management. (https://www.nace.org/)
  • Corrosion Doctors: This website provides information on various aspects of corrosion, including MPY, corrosion mechanisms, and mitigation techniques. (https://www.corrosiondoctors.org/)
  • ASM International: ASM International is a global materials science and engineering society. Their website offers a wide range of technical resources related to corrosion, including MPY calculations and material selection guidelines. (https://www.asminternational.org/)

Search Tips

  • Use specific keywords like "MPY corrosion," "corrosion rate measurement," "oil and gas corrosion," and "corrosion control."
  • Combine keywords with specific terms like "pipeline corrosion," "tank corrosion," or "sour gas corrosion" to focus your search on relevant applications.
  • Include the term "NACE" in your search to identify articles and standards published by the National Association of Corrosion Engineers.
  • Utilize advanced search operators like "site:nace.org" to limit your search to the NACE website.
  • Explore related keywords like "corrosion prevention," "corrosion inhibitors," "cathodic protection," and "protective coatings."

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