When designing piping systems for corrosive environments, engineers must balance numerous competing factors—from understanding the complete chemical exposure profile to considering long-term lifecycle costs. Kevin Campbell, applications engineer at Corzan® Material and Piping Solutions, shares critical insights into common pitfalls that compromise system performance and reliability. His expertise highlights why a holistic approach to material selection, encompassing both internal process conditions and external environmental factors, is essential for achieving durable, cost-effective corrosion-resistant piping systems that maintain operational integrity throughout their service life.
Q: What are the most common pitfalls that plants face when choosing piping materials for corrosive environments?
A: There’s an “inside” and an “outside” answer. One of the most overlooked things when selecting a piping material is a comprehensive understanding of all the media that will come into contact with the system. It makes sense to choose a material based on the primary process fluid, slurry or gas that will run through it and sometimes easy to overlook the secondary chemicals, cleaning compounds, or byproducts in the system. Even trace concentrations of certain chemicals can degrade materials over time, can compromise system integrity or can contaminate the overall product quality. A thorough chemical compatibility assessment of everything that might run through a piping material is critical to long-term performance.
Corrosive external conditions can also be overlooked and underestimated and end up shortening a piping system’s service life. For example, coastal environments are often very humid and saline, both of which can significantly contribute to corrosion. Prolonged exposure to ultraviolet light or chemical vapors, such as the acidic mist in a galvanizing plant, can speed up piping material degradation–not to mention the toll from extreme outdoor temperatures and radiant heat from nearby equipment or structures or the expansion and contraction of freezing and thawing. It’s very important to understand both what’s going through the pipe and the external environment in which the pipe will be operating to make sure it can perform reliably under both internal and external stress. This can help reduce unplanned maintenance and downtime and keep the system operational for longer.
Q: How should engineers balance upfront cost vs. life cycle performance when evaluating piping systems?
A: Focusing on upfront cost is short-term thinking, and engineers specifying materials for industrial plants need to think in terms of decades or dozens of years. Some materials may have a larger initial cost than others, but they may also have a substantially longer service life, making them cheaper in the long run than a lower-cost option.
Rather than fixating on price tags, specifiers should instead seek a piping material with a longer and better life cycle performance. One of the most important questions to ask is, “Is this piping material robust enough and chemically resistant enough to handle changes in the process or concentration of media?” Material commonality and availability are also worth considering. A specialty non-metallic material, such as PVDF, may have great performance characteristics but may come with significant lead times that can make planning installation and service complicated. A highly resilient but more common material like CPVC may not have this issue.
Q: What are some key warning signs that existing piping may be mismatched to process conditions?
A: The warning signs of a mismatch are usually pretty obvious once they’ve advanced enough, because the material will often start to deteriorate or allow for scale buildup. Signs that your pipes have fouling or buildup can include decreased flow and/or sudden pressure changes. If you notice leaks at the pipe joints, there are likely pinhole leaks, which are often caused by pitting corrosion or flow-accelerated corrosion. Other evidence of corrosion will depend on the material: On your typical carbon steel, it’s rust. Even stainless steel starts to pit or scale eventually. A plastic like PVC may begin to swell or flake, whereas tough, more high-resiliency plastics like CPVC avoid fouling for longer under harsher conditions.
It's essential to ensure compatibility between piping materials and process conditions before installation and to never switch what’s running through pipes before completely confirming compatibility. If purity is important, extra care must be taken to avoid contamination when switching pipe contents.
Q: What decision-making tools or guidelines can engineers use to compare different materials fairly?
A: I’d give three pieces of advice. The first is related to what I said before, about not focusing only on initial cost. Looking at just the price tag could miss some heavy expenses that come right after purchase, during construction or during maintenance. Where pipes end up in a facility may make it difficult or impossible to do hot work (versus a material that could be solvent-welded). The same is true for weight and ease/difficulty of installation in general: final pipe placement may be in tight spaces that could necessitate operation shutdowns if the piping material is heavy enough to require special lifting equipment.
Second is to view systems holistically, rather than as individual parts. Thinking about medium, temperature and pressure throughout the whole system, and not just one element of it, lets you really calculate whether a material is overkill or if a single-material system maybe is the right choice for a long-life, cost-effective system.
Third, look for and use chemical resistance and compatibility data whenever you can. There’s a lot to be said for a piping material that tests itself against chemicals and compounds and makes that data public.
Q: What role does piping material selection play in minimizing unplanned downtime and ensuring process reliability?
A: Material selection plays a very important role, but it’s just one factor. It all comes back around to that point about holistic thinking. This includes ensuring chemical compatibility between the pipe material and the medium that will run through it. It also includes insisting on quality from start to finish.
Use proper joining techniques. Whether you’re using solvent cement, mechanical couplings, welding or brazing, all joining methods need properly trained workers to perform the work. Poor installation will always create the weakest, most maintenance-prone parts of any system. In a similar vein, purchasing high-quality materials rather than choosing a cheaper option can get you those intangibles like traceability, excellent product support and confidence that you can really trust that the material can keep its promises. Nothing can ever eliminate risk, but material selection choices can help minimize risks.
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