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The high frequency reciprocating rig (HFRR) was developed in the early 1990s as a test method to assess diesel fuel lubricity in order to provide wear protection for fuel injection pumps. This was necessary in response to the many field failures that occurred following the introduction of ultra-low sulphur diesel in Sweden. The prevalent fuel injection equipment (FIE) technology at this time utilised rotary pumps capable of reaching maximum fuel pressures of ∼650 bar in systems for direct injection engines. The continued drive for efficiency led to many changes in FIE technologies, materials and pressures. Modern high pressure common rail pumps reach significantly higher pressures, with 2200 bar available today and pressures up to 3000 bar discussed in the industry.

The introduction of fatty acid methyl ester (FAME) into the diesel pool has led to an increase in the incidence of diesel fuel filter blocking. In contrast to conventional diesel, filter blocking events can occur above a fuel's Cloud Point (CP). It has been shown that this phenomenon is due to trace levels of impurities carried over from the original oil source into the final fuel. The two species identified as being the main cause of the filtration problems are saturated monoglycerides (sMG) and sterol glucosides (SG). Reported in this paper is an extensive study completed to understand the impact that these impurities have on the filterability of FAME and FAME containing fuels. This has been investigated using laboratory based filterability tests that incorporate a specific cold soak and the critical contaminant levels causing failure have been determined.