Pumps for synthetic heat-transfer liquids


Courtesy of ALLWEILER GmbH

As soon as the temperature in a heat-transfer system becomes too high for water, a plant operator must choose between petroleum-based or synthetic oils as the heat-transfer liquid. When modern petroleum oils are used, systems with feed temperatures up to about 300 °C can stay in service for their entire service life with one filling and with virtually no maintenance. Once feed temperatures rise above 300 °C, only high-quality synthetic oils will be appropriate. Under these conditions, even minor temperature increases will have a decisive effect on the service life of the oils. An additional 10 °C commonly doubles the product's specific rate of decomposition. When compared to petroleum-based heat-transfer oils, the amount of maintenance associated with synthetic oils is significantly lower.

Influence on pump performance
The quality of the oil also directly influences pump performance. If a large number of low-boiling compounds form, pockets of gas and flow breakaways will be the result. This puts greater stress on the pumps and reduces their capacity. Low-boiling compounds reduce pump capacity, which elevates the film temperature in the heater, accelerating decomposition of the heat-transfer fluid, and ultimately forming more low boilers. Irrespective of this, synthetic heattransfer oils place special demands on pumps. Compared to petroleum-based oils, their lubricity is lower.

That is why Colfax Fluid Handling’s Allweiler brand has developed thermal-oil pumps that are specifically adapted to the properties of synthetic oils. Two factors are critical: lower lubricity and, in many cases, lower viscosity. Traditional pump designs are not suitable for handing these conditions. Just starting the pumps is difficult. Normal operation is accompanied by high wear and consequently higher maintenance costs as well.

Thermal oil heaters manufactured by INTEC Engineering GmbH of southern Germany provide a good example of how these pumps are used. This company’s thermal oil heaters supply process heat to industrial plants around the world. INTEC focuses on the requirements of the wood, textile, palm oil, chemical, shipbuilding, and food industries. Standard heaters cover an output range of 100 to 20,000 kW; custom designs can deliver even higher output.

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