Hydrocarbon Based Grease for Cryogenics

Cryogenic chamber manufacturers normally refers to operation at temperatures below 123 K, or -150 °C and in a number of branches of science and medicine it is essential to execute experiments and run equipment at cryogenic temperatures, down to as low as a few degrees Kelvin. At these temperatures, specialist materials are required in order to provide sealing and thermal conductance, as standard heat sink compounds and sealing formulations may craze or crack, which in turn reduces thermal conductivity and reduces sealing efficiency.

There are several types of grease on the market presently available, such as PFPE based products that quote operating temperatures much below 0 °C, however almost all these products have a quoted operating temperature range limit of -80 °C. Typical heatsink compounds are only quoted as working down to -50 °C. The one exception is hydrocarbon based grease, with proprietary additives which can work all the way down to -269 °C, the temperature at which liquid helium boils.

For temperature sensors it is vital that good thermal contact is maintained to provide accurate measurements. The thermowell acts to guard the delicate temperature sensors from damage and also allows the placement of the temperature probe into the area of interest, for instance into the middle of a pipeline. One challenge to using a thermowell is that good thermal contact will have to be made between the temperature sensor and the outer wall. Thermowells are usually used where it is necessary to directly measure the temperature of helium or liquid nitrogen plant nitrogen.