Some patents for FRP manufacturing go back to the 1940’s and 1950’s. FRP has been used in industrial service for tanks and piping for over 45 years. That’s a long time, and in services from seawater to chlorine dioxide to sulfuric acid. Having success in a variety of industries, such as chemical process, pulp & paper and power utilities all over the world. Yet, with all this success, confidence and expectations for FRP are still low with some engineers and plant end-users. Why is this?
FRP is not a traditional material of construction, such as steel or concrete, so engineers are less familiar with FRP. It’s also a flexible material comparably. It’s plastic, so it’s easy. Therefore anybody can do it, engineer it, make it, weld it. WRONG!!!
FRP is a refined material of construction and requires unique training and skill and a significant attention to detail to do it well. To do a good job with engineering, which frequently means pipe stress analysis, one needs to understand the materials behavior, not just obtain material properties. There are proven and definable design techniques that can go a long way to ensuring a reliable FRP design. Similarly the absence or inconsistent application of these approaches can leave an FRP system unpredictable and at risk. Not many A/E firms that have been trained in the design of FRP piping. Similarly, there is limited opportunity for regular exposure and experience.
It’s easy to say, “We’ll just work through it.” Sometimes the complexity of FRP is underestimated. FRP is not harder to design than metals, but it does take a different knowledge of materials, construction benefits as well as limitations. It’s not just a different set of material properties.
FRP has many benefits. It has fantastic corrosion resistance in a broad range of service and pH. FRP is a flexible material and can be very forgiving in construction. FRP is an economically attractive material of construction as opposed to some expensive metal alloy alternatives.
Like all materials, FRP is not without its limitations and unique attributes. FRP has a thermal expansion and contraction rate of about 2 to 3 times that of carbon steel. This is a significant consideration for design of FRP piping. Piping systems operating at 140 F and above should be analyzed with a formal pipe stress analysis program, such as Caesar II.
The challenge and expertise of designing FRP piping and equipment comes into play in designing to allowable stress levels, which are 1/6 that of steel. To design a reliable system the design engineer must have a sound understanding of the material and how the codes should be applied. With that, FRP will exceed most expectations.
“There is no substitute for proper training and expertise through experience.”
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