Written by Rickdatech

When biodiesel gets cold, sometimes stuff will fall out that can clog filters. This is different from gelling in that most of the biodiesel stays liquid while a white flaky or greasy substance precipitates. On the UK forum they call it HMPE for High Melting Point Esters. This stuff has a high melting point and does not melt back into the biodiesel at normal temperatures. It does melt back in with enough heat.

The ASTM test for this precipitant is ‘The Standard Test Method for Determination of Fuel Filter Blocking Potential of Biodiesel (B100) Blend Stock by Cold Soak Filtration Test (CSFT)’  (ASTM D7501).

In the test, biodiesel is chilled to 40F for 16 hours, then warmed back up to room temperature without stirring or heating the sample. It is then passed through a filter under vacuum. To pass, the full 300ml sample must flow through the filter in under 360 seconds. The term Cold Soak comes from how we chill the biodiesel to 40F for 16 hours.

Related Links:

www.dexterbiodiesel.com - Test explained quickly and in simple terms.

Cold Soak Filtration Training Video  -- NBB

Homebrew cold filter setup - infopop thread

High Melting Point Esters - Biopowered WIKI