Technical Article
Figure 3 : Suppliers should provide mechanical properties like the yield strength and tensile strength of component metals to help determine suitability for specific applications .
Figure 4 : Working with a reliable supplier can help inform design engineers in making the right component selection for industrial fluid systems .
Resistance to SCC improves with increasing nickel ( Ni ) content in austenitic stainless steels and Ni-based alloys . In oil and gas environments , multiple stress-assisted corrosion mechanisms can act synergistically . The NACE MR0175 / ISO 15156 standard provides guidance for alloy selection based on the environmental conditions such as acidity ( pH ), chloride ion and H 2
S concentration , and temperature . More aggressive environments lead to the need to use more highly alloyed stainless steels or Ni-based alloys .
Working With Reliable Suppliers
The simplest way to avoid corrosion problems damaging industrial fluid systems is to work with suppliers with stringent quality control measures . Even the bar stock should be inspected , whether visually or using non-destructive testing techniques . In some cases , ensuring corrosion resistance may require specialized testing , which the supplier should provide .
Another way a supplier can help verify the material ’ s suitability is to check for levels of specific elements in the material ’ s composition . Optimizing the composition of the material alloy is important for corrosion resistance , strength , weldability , and ductility . As an example , adding greater quantities of Ni and Cr in 316 stainless steel than are minimally required by the American Society of Testing and Materials ( ASTM International ) standard specifications results in materials with better corrosion resistance . A supplier should always provide the chemical composition of a material and indicate compliance with standards published by the International Standards Organization ( ISO ) and ASTM International ( Figure 2 ).
Maintaining Quality Assurance During Manufacturing
Reputable suppliers inspect components throughout their production . Verifying that the manufacturer follows best practices during the component ’ s construction and then testing them afterward helps ensure no corners were cut . Components coming off a manufacturing line should have no visual defects or imperfections that could lead to premature failure . They should be tested to ensure they are leak tight to keep employees safe and reduce overall production costs .
Choosing Suppliers with Materials Science Expertise
If both the materials and components pass manufacture and design standards , deciding which components to use should be application-specific and requires a full understanding of specific operating conditions . A reliable supplier with materials science expertise can guide designers through the process to ensure they choose the right components .
Seeking Higher-Strength Materials
A component ’ s mechanical properties should be examined before it is chosen for specific applications . Considerations should include tensile strength and ductility . The higher the quality of materials used in the component ’ s construction , the more likely it will perform as expected , particularly when subjected to high pressures ( Figure 3 ).
Ensuring Component Compatibility
In addition to affecting system performance , corrosion can cost significant money to correct . According to NACE International , corrosion costs the oil and gas industry USD $ 1.4 billion per year .
More than pipes
Understanding where corrosion is likely to occur and catching it early can help to lower repair costs over time . If system designers choose the right materials at the outset , then system integrity , component life cycles , consistent performance , and safety all improve .
The following steps reduce the impact of corrosion on applications :
• Identifying types of corrosion – what it looks like , where it occurs , and why it happens ,
• Selecting materials resistant to corrosion ,
• Minimizing locations where corrosion can occur and reducing contact with non-compatible metals , and
• Specifying everything from the supports and clamps to the tubing itself to reduce the potential for corrosion .
The Bottom Line
About the Author
Buddy Damm is Senior Scientist for Swagelok .
When choosing between components for offshore oil and gas platforms , selecting premium materials suited for the application minimizes corrosion . Suppliers should provide ongoing support over the life cycle of the system , although not every supplier has the expertise to advise which components will work best for specific applications .
Suppliers with highly credentialed experts on staff can offer fluid system professionals training in materials science and metallurgical engineering , which may help them make the right component selections . Armed with this knowledge , design engineers will develop industrial fluid systems to withstand even the harshest operational conditions .
Images © 2024 Swagelok Company .
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