Don’t Settle When It Comes to Vibration: Part 1
Sep. 21, 2017
by Doug Fast
High-temperature, industrial insulations operate in hostile environments that would melt, shatter, or otherwise destroy other types of insulating materials such as plastics, fiberglass, or foam rubber. These environments not only reach extreme temperatures, but they can also be rigorously demanding as a result of heavy vibration caused by the proximity and concentration of motors, valves, and high pressure steam. In these kinds of environments, higher than normal levels of vibration are part of the design equation that engineers or specifiers must consider.
Most high-temperature insulations are molded from minerals or mineral fibers. In a typical industrial application, many of these products can last for decades, when properly installed and maintained. However, when the application includes high levels of vibration, the stress on the insulation increases substantially, limiting the insulating materials that would be suitable for the application and potentially shortening the lifespan of the insulation itself.
As a result, insulation used in high-vibration applications can often be limited to mineral wool, calcium silicate, or thin blanket insulations. Each of these insulations has unique features that make them applicable for applications with excessive vibration.
Mineral wool, for example, has excellent acoustical performance. This property can help protect employees’ hearing by lowering what would otherwise be considered dangerous noise levels (as deemed by OSHA standards), making it a very popular choice to insulate pipes and equipment that vibrate. This can be critical in applications where facility workers are working around the pipes or vessels. However, mineral wool’s insulating performance hinges on the insulation’s binder remaining intact. This can become problematic when temperatures reach or exceed 600°F, as the binder will begin to oxidize and burn off, jeopardizing the structural integrity of the insulation. In applications where vibration is likely, this can cause the material to shift, compress, or sag, compromising the performance characteristics of the mineral wool.
The popular alternative, calcium silicate, is usually specified in high-vibration applications because of its high compressive strength and its ability to maintain its shape. The strength of calcium silicate enables it to withstand extremely demanding environments with little to no impact on the thermal performance. However, calcium silicate may not be suitable for every application because of its weight and rigidity.
The third option, thin blanket insulations, can be ideal for applications where operating temperatures exceed 600°F and weight or rigidity can be counterproductive toward the end goal of the application. For the purpose of this blog, we will discuss InsulThin™ HT, Johns Manville’s thin, blanket insulation, as it does not experience thermal shift like the competing silica aerogel blanket insulations, and it has a lower corrosive potential than most other insulations in the industrial market.
While InsulThin HT does not offer the same NRC values as mineral wool, it does offer higher compressive strength, and there is no risk of binder burnout. Additionally, this microporous blanket provides better thermal performance at elevated temperatures than many other traditional high-temperature industrial insulations (including mineral wool, calcium silicate, and high-temperature silica aerogel industrial insulations).
In the case of InsulThin HT, the microporous blanket is made of small, fumed silica particles intertwined with long glass reinforcement fibers to form a composite material. The structure of this material makes it resistant to sagging, settling, and deformation, even in environments where the vibration is substantial. As a result, when temperatures reach and exceed 600°F, we can expect consistent shape and thermal performance from InsulThin HT.
Each material, mineral wool, calcium silicate, and InsulThin HT, has different benefits that come in to play for varying applications, and each one can offer thermal performance in environments where vibration would otherwise damage the insulation. When specifying insulation systems, however, it’s important to keep in mind that only two of the three insulations, calcium silicate and InsulThin HT, will be able to retain their shape and thickness at temperatures beyond 600°F.
In Part 2 of this blog series, we will address recent vibration testing specifically targeting InsulThin HT, confirming its resistance to settling, sagging, and compression in environments and applications with vibration.