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The stakes are high when it comes to material compatibility. We’ve seen components get damaged by crystalized fluids, valve polymers become brittle, and seals swelling until they leak – all failures that jeopardize safety, performance, and the longevity of your system.
In this article, we’ll uncover five often-overlooked aspects of material compatibility and share practical strategies engineers can use to design safer, more reliable systems.
Have you ever noticed how a bridge expands on hot summer days and contracts in the winter? Materials in your system behave similarly, but they may not change at the same rate. This mismatch in properties is known as the coefficient of thermal expansion (CTE). Systems may perform flawlessly in the lab, but experience warping, cracking, or material fatigue in the field under extreme or fluctuating temperatures.
To mitigate these risks, it is essential to select materials that can endure the expected temperature range of your application, including ambient conditions, the operating temperature of the fluid, and any potential temperature spikes or thermal cycling that may occur. Additionally, fluid properties like viscosity, density, and specific gravity can change significantly with temperature variations in both the operating fluid and the surrounding environment. Since liquids and gases possess distinct characteristics that influence flow rate, leakage, and the movement of internal components, these variations must also be considered to ensure the system performs reliably under all operating conditions.
Key Takeaways:
The biggest driver of material selection is fluid compatibility. Materials that come into contact with fluids – like fuels, lubricants, or cleaning agents – must be chemically compatible.
Think about your car’s engine, which relies on oil to keep its parts moving smoothly. Rubber seals help prevent oil and coolant from leaking out, while also blocking dirt and air from getting inside the engine. If these seals aren’t chemically compatible with the fluids used, they can swell or crack. This kind of damage can lead to leaks, which may reduce engine performance, cause mechanical issues, or even result in engine failure over time.
Incompatible fluids can degrade materials, alter fluid characteristics, impair system performance, and shorten operating life. Metals may corrode, polymers can embrittle, and elastomers might swell or lose strength, leading to leaks, chemical attacks, contamination, system failure, or other safety hazards.
Certain fluids pose unique risks that require additional material design considerations. For instance, systems handling blood or chemicals require inert materials to avoid contamination, while those transporting flammable gases must avoid metals that could spark. Some fluids can also damage seals: crystallizing fluids may form solids that compromise sealing surfaces, while surfactants, which lower surface tension, can slip past seals entirely.
To ensure chemical compatibility, engineers should consult compatibility charts and databases that match materials with specific fluids. However, because real-world conditions can vary, it’s also important to test material samples with the actual fluids used in your application. Many component manufacturers offer sample materials for soak testing and can provide guidance based on their experience with similar systems, materials, and fluids.
Key Takeaways:
Combining materials that respond very differently to stress can create weak spots where a structure might fail. That’s why engineers need to carefully consider mechanical properties like tensile strength, ductility, and hardness. These properties often influence each other – so improving one might mean sacrificing another. As an engineer, you might have to make smart trade-offs to find the right balance for your design.
Take smartphones, for example. The screen is made of tough glass that resists scratches, but it’s also brittle. The frame, on the other hand, is usually made of metal or plastic, which can bend a little. If you drop your phone, the flexible frame might absorb some of the impact, but the stiff glass can crack because it doesn’t flex the same way.
Mechanical properties can also change depending on the specific demands and use cases of your application. For instance, metals exposed to hydrogen may suffer from hydrogen embrittlement, which reduces ductility and makes them more prone to cracking. This kind of degradation isn’t always obvious at first, but it can seriously affect long-term performance. That’s why it’s important to consider not just current performance, but how mechanical properties are likely to change over time.
To ensure materials work harmoniously in a system, designers should evaluate how each will behave under expected mechanical loads. This includes aligning mechanical properties like strength, stiffness, and fatigue resistance with the specific demands of the application. Simulation tools such as Finite Element Analysis (FEA) can model these interactions, helping to identify weak points early in the design process and optimize material selection accordingly.
Key Takeaways:
Picking the right material for a system is a bit like choosing the right tires for a car – racing tires might be great on a smooth track but wear out fast on rough roads. In the same way, some materials work well in perfect conditions but don’t hold up under pressure, heat, or constant use.
Material performance is influenced by the operating conditions of your application or system. A material that performs well initially may degrade over time depending on how often the system is used and the general environment in which it operates.
Conditions such as operating pressure, cycle life, thermal stress, vibration, shock, chemical exposure, and radiation are just a few of the many factors that can impact material performance. Wear and tear from continuous use can cause elastomers to weaken or leak. Other materials may be suitable for one environment but fail in another. For instance, an application operating 10,000 cycles per day will likely require more frequent preventative maintenance compared to one operating only ten times per week.
Environmental factors can also accelerate degradation in some materials more than others. Long-term exposure to certain elements may even alter material properties due to oxidation, creep, or fatigue.
When selecting materials for your system, it’s essential to consider the full range of environmental conditions it will encounter – from the environment where it will be stored to where the system will operate most frequently (and any other places it may travel in between). Equally important is understanding the application’s cycle life and the maintenance your system will require over time. Choosing materials with proven durability, planning for regular inspection or replacement intervals, and designing for easy maintenance can extend system life and reduce downtime.
Key Takeaways:
Manufacturer data often reflects ideal lab conditions, not the unpredictable realities of actual use – like designing an aircraft for optimal performance at cruising altitude, only to find its systems falter under the stress of repeated takeoffs, landings, and extreme weather. Relying solely on data sheets can lead to performance discrepancies, unexpected failures, and costly redesigns.
To mitigate these risks, it’s essential to collaborate with suppliers who go beyond the data sheet. Look for partners who can provide detailed material compatibility testing data or supply materials for your own field testing. Suppliers with deep expertise in materials science can guide you in selecting the most appropriate materials and components tailored to your specific application needs. Additionally, those who offer expert engineering support throughout the lifecycle of your system and have a proven track record in the industry can be invaluable allies in ensuring long-term performance and reliability.
Key Takeaways:
At The Lee Company, we understand that material compatibility is critical to system performance – and often more nuanced than it appears. We’ve earned the trust of customers across multiple by solving their most complex fluid control challenges, backed by an engineering heritage over 75 years in the making.
We provide that give you the freedom to innovate without compromise. Our COTS components can be tailored to meet specific application demands — including materials, envelopes, pressure ratings, temperatures, fluid types, and more.
Lee engineers specialize in working with customers on an engineer-to-engineer level to navigate design and material complexities with confidence. Our global presence allows us to provide local and accessible technical support to our customers, streamlining product development and innovation. Lee components are made in the U.S. and are 100% functionally tested to guarantee performance throughout the life of the systems they are installed in. The Lee Quality Management system is recognized as a benchmark to independent auditors and our stringent product development and revalidation testing requirements allow engineers to focus on system level challenges instead of component level problems.
If you are looking for more information on material compatibility best practices, explore our Engineering Tools reference materials, or contact a Lee Sales Engineer today.
Always verify flow calculations by experiment.
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