Enhancing oil, gas platform operations with the right components

Recognizing the best materials to use for fluid system components is critical to realizing successful outcomes for oil and gas professionals

By Brian Van Valkenburg February 15, 2023
Courtesy: Swagelok

 

Learning Objectives

  • Discover how proper materials science training programs can help oil and gas professionals prevent corrosion from compromising their systems.
  • Learn how training can help operators choose the right component materials to resist pitting and crevice corrosion in offshore oil and gas applications.
  • Understand why materials science training should focus on local and regional regulations or other geographic-specific factors.

Oil and gas components insights

  • Component reliability is an ongoing issue for oil and gas project managers.
  • Selecting training programs for oil and gas professionals is difficult, and selecting a trainer with real-world experience benefits the student.

The oil and gas market has evolved over the past decade to become more focused on safety than ever before. As a result, it is increasingly important for the fluid systems that transport caustic materials at elevated temperatures and pressures to be reliable and leak free. With this renewed safety focus, oil and gas operators who are trying to keep their environment and workers free from harm must build systems with the highest quality components possible.

Figure 1: Preventing fluid system component corrosion begins with choosing the best materials of construction for the end-use application.

Figure 1: Preventing fluid system component corrosion begins with choosing the best materials of construction for the end-use application. Courtesy: Swagelok

The question of how to find reliable components is a challenge for all platform operators. They are seeking to control operational costs and account for labor shortages while still using the best components. In short, they want to find components that do not need to be changed as often and have the potential to last for the lifetime of their platforms.

The desire for long component service lives relates to the increasing complexity of the various fluid systems that support platform operations. Between instrumentation lines, hydraulic power, chemical injection, deluge systems and other components, a single platform might have 50,000 feet of tubing, more than 20,000 fluid system components, no fewer than 10,000 fittings and potentially 8,000 mechanical connections.

Figure 2: Pitting corrosion can easily form on 316/316L stainless steel tubing contaminated by acids, salt water and other deposits.

Figure 2: Pitting corrosion can easily form on 316/316L stainless steel tubing contaminated by acids, salt water and other deposits. Courtesy: Swagelok Co.

Keeping each of these contact points operating at peak performance is no small feat and it starts with choosing the right components for the job. That means selecting fittings and fixtures that resist pitting (see Figure 2) and crevice corrosion (see Figure 3), both of which are common in offshore oil and gas applications.

Figure 3: Localized crevice corrosion (left) is likely to form between tubing and tubing supports (right). Accelerated reactions take place within the confines of the crevice, allowing corrosion to proliferate.

Figure 3: Localized crevice corrosion (left) is likely to form between tubing and tubing supports (right). Accelerated reactions take place within the confines of the crevice, allowing corrosion to proliferate. Courtesy: Swagelok Co.

To avoid these problems, platform operators must maintain an in-depth understanding of metallurgy and materials science. It is vital to have proper training programs to allow oil and gas professionals to keep corrosion from compromising their systems and putting the environment and team at risk.

But how do companies find the appropriate training to ensure their teams have the necessary knowledge? Working with a reliable supplier who offers training programs on how to select and specify the proper components can certainly help.

Which components are needed?

Harsh oceanic conditions can lead to various types of corrosion (see Figure 4), causing components to fail long before the platform. Under difficult operating conditions at sea, replacing these components may be expensive and can be risky. Hence, the desire for long-lasting components.

Figure 4: Corrosion occurs when a metal atom is oxidized by a fluid, which leads to a loss of material in the metal surface. It may appear in the form of general (rust), pitting or crevice corrosion or a variety of other types. Courtesy: Swagelok Co.

Figure 4: Corrosion occurs when a metal atom is oxidized by a fluid, which leads to a loss of material in the metal surface. It may appear in the form of general (rust), pitting or crevice corrosion or a variety of other types. Courtesy: Swagelok Co.

Yet, deciding what materials make the most sense for enabling long-term component use in specific applications is often more complex than it may first appear. In addition, the various factors involved are not always easy to understand.

Historically, 316 stainless steel tubing, which has a passive, chromium-rich oxide layer on its surface in ambient temperatures that protects it from corrosion (see Figure 5), has been the most common material used in oil and gas applications. It usually performs adequately and has a proven track record of affording the proper corrosion resistance for many applications. However, as performance requirements have ratcheted up, 316 stainless steel has become less ideal.

Figure 5: Stainless steels automatically form a passive, chromium-rich oxide layer on the surface in ambient air (top), protecting the material from corrosion. If this outer layer is damaged (middle), it will reform automatically (bottom). Courtesy: Swagelok Co.

Figure 5: Stainless steels automatically form a passive, chromium-rich oxide layer on the surface in ambient air (top), protecting the material from corrosion. If this outer layer is damaged (middle), it will reform automatically (bottom). Courtesy: Swagelok Co.

Fortunately, it is no longer necessary to rely solely on 316 stainless steel because new alloys are available that also resist corrosion well, including duplex stainless steel, 6 moly stainless steel and others. But should oil and gas professionals always specify higher-performing alloys for every situation? Not necessarily.

Choosing the proper materials for individual applications should be informed by a multitude of factors, including environmental conditions, required performance and cost. But choosing a particular material just because it is simple to use may unnecessarily increase expenses in the long run.

For example, 316 stainless steel offers good ductility, which means it is easy to form and weld. At an attractive price point, it may still be the right choice for many applications, particularly if the system in question is not subject to harsh environmental conditions like sun and salt spray exposures. It is important to understand, however, that not all 316 stainless steels are created equal. Those with higher concentrations of nickel and chromium and that exceed the ASTM International minimums can improve corrosion resistance and reliability.

At the same time, if the system is transporting sour gas, even the highest quality 316 stainless steel may not be sufficient to resist sour gas cracking or sulfide stress cracking (see Figure 6). Sulfide stress cracking is a common, severely corrosive combination of hydrogen sulfide and moisture, which weakens the metal in question and makes it more brittle.

Figure 6: Sulfide stress cracking is common in fluid systems containing sour gas, as the metal deteriorates due to contact with hydrogen sulfide and moisture. Courtesy: Swagelok Co.

Figure 6: Sulfide stress cracking is common in fluid systems containing sour gas, as the metal deteriorates due to contact with hydrogen sulfide and moisture. Courtesy: Swagelok Co.

This phenomenon often happens on offshore platforms, particularly now that more sour reservoirs are being developed throughout the world. The brittle metal is more prone to cracking when it is subjected to the combination of tensile stress and corrosion. In these situations, it makes more sense to specify advanced alloys like Alloy 825, Alloy 625 and others. The requirements may be found in the NACE MR0175/ISO 15156 standard.

In between these two extremes are other opportunities to use other alloys that can perform optimally depending on the application. For some oil and gas applications, it may only be the tubing that needs to be an advanced alloy, while the tube fittings can be made of 316 stainless steel. Understanding these subtle differences can be the difference between the success or failure of a system, which is why a thorough understanding of materials science is so crucial. Training oil and gas professionals to have a robust understanding of materials will allow them to optimize their choices and provide the most value to their operations.

How to build a materials science training program

Training oil and gas professionals in the intricacies of materials science is a complex task. Being able to differentiate between effective and ineffective training courses is key. One should start by evaluating whether the instructors have real-world experience and are thoroughly trained themselves so they can provide effective training for your team.

To be effective and successful, training programs cannot be generalized. Instead, they should be specific to the needs and challenges of the facility where the training is taking place. The trainer should have a full understanding of local circumstances, regulations and other geographic-specific factors that can affect particular facilities (see Figure 7). After all, the regulations governing a facility in the Gulf of Mexico will vary significantly from those for a plant operating in the northern United Kingdom. Trainers should be able to adapt their presentations to meet specific operational needs.

Figure 7: Materials science training should focus on local and regional regulations or other geographic-specific factors to ensure it relates to your facility’s operations.

Figure 7: Materials science training should focus on local and regional regulations or other geographic-specific factors to ensure it relates to your facility’s operations. Courtesy: Swagelok Co.

For example, there is a thriving but still emerging oil and gas market in Malaysia, Indonesia, Singapore, Thailand and Vietnam. Suppliers with sufficient local knowledge may recognize that materials science and corrosion training are what these markets need most at this point in their development. Training teams from those suppliers can offer specific metallurgy and materials science training that can improve the knowledge of all industry stakeholders, leading to more effective education and promoting long-term success.

In a different market or different facility, the training needs may be significantly different. Working with reliable suppliers who can adjust their training to meet specific needs is key. The trainers should be able to delve into specific questions about alloys to ensure the right components are specified.

Because no two oil and gas platforms are alike, it is critical to work with trainers who understand how each platform operates. Decisions about how tubing and fittings are installed, how they are cleaned or what kinds of elements they are exposed to will ultimately affect what materials will be best for particular applications. Proper understanding of these subtle differences can make the training even more effective and build trust in the supplier-platform relationship.

Reliable suppliers should always have ongoing conversations with their customers about material science training as well as materials selection and specification. After all, localized service and specific expertise can be the difference between the successful operation of a system and a catastrophic failure.


Author Bio: Brian Van Valkenburg is training and services marketing manager for Swagelok Co.