Monitoring vibrations, mechanical seals, and bearings for safety and performance

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Courtesy of ALLWEILER GmbH

With more than 70 years of experience in plastics processing, Switzerland-based Quadrant Group is a leading expert in a wide range of polymer materials and technologies for polymer conversion. In order to maintain a high level of quality in the production process, Quadrant's heat-transfer pumps must work safely and reliably. These pumps are commonly subjected to high loads. At the same time, failure of a pump can have serious consequences, especially if hot oil escapes. The high loads on the pump are the result of high temperatures and large temperature differentials as well as decomposition reactions that may occur when the heat transfer liquid is subjected to excessive thermal loads.

High pump requirements
In order to maintain a high level of quality in the production process, Quadrant's heat-transfer pumps must work safely and reliably. These pumps are commonly subjected to high loads. At the same time, failure of a pump can have serious consequences, especially if hot oil escapes. This makes operators of heattransfer systems very sensitive to leakage. Consequently, engineers walk a fine line when designing shaft seals in heat-transfer pumps. While it is normal for water (mostly in vapor form) to escape through the sealing clearance, any escaping heat transfer oil will be readily visible. Therefore, although leakage must be kept low, it is critical to avoid overloading the seal. The high loads on the pump are the result of high temperatures and large temperature differentials as well as decomposition reactions that may occur when the heat transfer liquid is subjected to excessive thermal loads. In particular, chain-like hydrocarbons decompose over time into 'low boilers' and 'high boilers'. If the proportion of low boilers is too high, the pump may cavitate. High boilers accelerate wear on the pump and appear in many forms, from bitumen-like consistency to extremely hard carbonized products. Both threaten the pumps’ bearings and shaft seals. Using synthetic heat-transfer oils reduces formation of low and high boilers, but the low viscosity and low lubricity of these materials means that they have disadvantages as well. Tribological loads on the gliding components of mechanical seals are particularly high.

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