Thermal transfer compound : Good or not?

Thermal transfer compound is sometimes used with mica band heaters and cartridges.

Let’s be clear (drum roll): Volton does not recommend using thermal transfer compound.

Surprising? Not really! First, the maximum temperature written on the compound’s bottle label is the maximum temperature it can reach. Therefore, even if your operating temperature is, let’s say, 450°F, a cartridge heater can reach surface heat of 800°C (1472°F) during normal use. With compound such as our Safekote 60, the cartridge temperature must be limited to 600°F, otherwise the compound will react to the heat and possibly stick to the cartridge or on the wall of the hole, interfering with thermal transfer, even lead to permanent damage to the part to be heated (i.e. the casting).

Therefore, to limit the temperature to 600°F, the cartridge must have power density much lower than generally seen.

The same goes with the band heater. Its heating process being metal to metal conduction, the compound would therefore act as a barrier to the material to be heated, and cause the band heater to work harder to reach or maintain its operating temperature. This can result in overheating, hence cooking the compound. A crust would then form on the cylinder and allow less grip when trying to install a band in that area in the future. Also the band could get internal contamination from this compound.

 

Clearly, thermal transfer compound can cause early breakage of the heating element, since these elements use conduction heating, but also and mainly because not many thermal transfer compounds on the market perform well at 800°C (1472°F).

 

The only time compound is useful, is when your cylinder or hole is damaged in a specific area and not completely round.

To alleviate that defect, the compound will be useful to avoid an air pocket which would cause premature breakage of the element.

Apply only in that area and make sure to use a transfer compound that can minimally withstand up to 1562°F (850°C). Volton can provide it.

 

In short, thinking that a heat transfer compound can lengthen a cartridge or band heater service life, is a myth. On long term, solving the problematic not-so-round-cylinder or hole, will go a long way.