Winning With Wear Protection

After decades of experience working with fans in different applications, TLT-Turbo has observed a plethora of examples of damaged rotors or casings caused by wear.

Sometimes wear occurs uniformly and will only reduce the thickness of the fan blades themselves. If the wear-induced material loss is uneven however, it will lead to vibration which will grow in magnitude over time until it reaches the vibration limit causing a plant stoppage. In the worst case, even wear would not be identified due to the lack of vibration and will eventually cause fan failure and a prolonged plant shutdown.

There are instances where wear plates work very effectively and protect the surface of the blades themselves, but despite this wear-induced material loss still occurs in the unprotected region next to the wear plates. Figure 2 shows an example of material loss on the cover disc right next to the wear plates.

Apart from the impeller itself, the fan casing can also suffer material loss due to wear. This leads to additional repair work during the plant stoppages.

In the cement industry, fans like those used in the clinker cooler are prime examples of industrial fans that are exposed to wear. This article takes a closer look at wear in cement applications and the measures available to reduce or prevent it.

General factors that influence wear

There are multiple factors that cause fans to suffer damage from wear, however, this article will focus on the primary factors that dictate the severity of the wear.

The most significant factor that influences the damage caused by wear is the velocity of the dust particles hitting the surface of the fan or fan blades. TLT-Turbo describes the correlation between wear and the velocity of the particles with the following equation: ER = C • v_pⁿ. It shows the dependence of the erosion rate (ER) on the material factor (C) and the velocity of the particles (v_p). For velocities below 200 m/s, n = 2 – 3, above that value, n > 3.

As a secondary factor, the shape of the particles also plays an important role. To investigate that influence, TLT-Turbo tested the erosion rates for glass granules and glass beads with comparable particle masses (Figure 4). Unsurprisingly, the bead-like shapes showed the smallest erosion rates. However, Figure 5 shows an unexpected harm potential at flat angles for glass granules. In contrast to the bead-like shapes, this harm potential is reduced for more frontal impact angles.

Another major finding of TLT-Turbo’s investigation was that the combined influence of the material properties and the angle of impact on the erosion rates. It turned out that hard and brittle materials have their maximal material loss at vertical impact angles whilst ductile materials have their maximum at flat angles.

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Read the article online at: https://www.worldcement.com/special-reports/15022023/winning-with-wear-protection/