Fuel Sampling & Testing

Hydrocarbon based fuels such as Diesels, Gas Oil and Kerosene are subject to degradation through exposure to light, heat and absorption of water from the moisture in the atmosphere. Moisture in particular is a major problem for fuel, as it collects as free water in the bottom of tanks and also remains suspended within the fuel itself. The water reacts with naturally occurring bacteria within the fuel forming a black sludge like material which forms the bulk of contamination problems for fuel usage.

This issue has been exacerbated due to the Renewable Transport Fuel Obligation (RTFO), which forces fuel refiners to ensure that 5% of all fuel used in vehicles is from a sustainable source, mainly plant derived oils. Whilst these elements behave well as a basic fuel, they are far less stable than the mineral equivalents, but also far more hygroscopic, drawing any available moisture from the surrounding atmosphere. Both these properties make long term storage of Gas Oil (Red Diesel) potentially problematic. In some cases, additional contaminants can be found such as sulphur (from older fuels) and other chemicals such as chlorine have been found which can be hazardous to health

54% of Craggs Environmental customers who
had their fuel sampled had fuel which was
outside of specification.

This issue has been exacerbated due to the Renewable Transport Fuel Obligation (RTFO), which forces fuel refiners to ensure that 5% of all fuel used in vehicles is from a sustainable source, mainly plant derived oils. Whilst these elements behave well as a basic fuel, they are far less stable than the mineral equivalents, but also far more hygroscopic, drawing any available moisture from the surrounding atmosphere. Both these properties make long term storage of Gas Oil (Red Diesel) potentially problematic. In some cases, additional contaminants can be found such as sulphur (from older fuels) and other chemicals such as chlorine have been found which can be hazardous to health

Craggs Environmental has carried out fuel sampling
for over 300 customers who store fuel for critical
applications UK Wide

Craggs Environmental has designed a methodology to categorise fuels into 5 standard grades, based upon a range of factors which can be tested. This simple, but very effective approach helps customers to make sensible decisions as to what quality of fuel is acceptable for the various applications each site might require.

Craggs Environmental Stored Fuel Categorisation

Quality Characteristics Appearance
Grade 1 Quality: Grade 1
  • Refinery quality fuel
  • Fully specified ISO and British Standard quality
  • Cherry Red in colour
  • Water below 100 ppm
  • No visible particulate
  • Cetane Level 45
  • Starts to degrade almost immediately fuel is stored in tank
  • Maximum shelf life of around 6 months at this grade
  • Can be used for any Gas Oil requirement
Grade 2 Quality: Grade 2
  • Stored fuel (more than 6 months)
  • Slight darkening in colour from particulate contamination
  • Still within ISO and BS quality
  • Water levels below 200ppm
  • Maximum shelf life of 18 months at this grade, assuming additive
  • Can be used for any Gas Oil requirement
Grade 3 Quality: Grade 3
  • Stored Fuel (more than 18 months)
  • May fall outside of Gas Oil standards
  • Water levels may be above 200ppm
  • Fuel darker red from higher particulate content
  • Possible small quantities of visible particle contamination or free water at bottom of sample
  • Not recommended for any use in critical environment or in combustion engine (Generator etc)
  • Flash point levels likely to be reduced, hence higher chance of “dirty burning” carbon build up
  • Still generally usable for boiler / heating applications
  • Fuel polishing can bring the fuel back to Grade 2 and within ISO standards
Grade 4 Quality: Grade 4
  • Long term stored fuel
  • Much darker colouring of fuel from particle contamination
  • Likely to see levels of both fungal contamination and free water at bottom of sample
  • Sample likely to be slightly cloudy, due to water particles suspended in fuel
  • Will cause significant damage and likely failure in critical applications
  • Likely to cause filter clogging issues for heating or boiler applications
  • Fuel polishing may be able to bring fuel to Grade 2 (depending on levels of degradation)
Grade 5 Quality: Grade 5
  • Very long term stored fuel
  • High visible contamination
  • More “grey” than “red” in colour
  • Should be consigned as waste
  • Unlikely suitable for fuel polishing
  • Often found at very bottom of tanks with cleaner fuel above
  • Should never be used as Gas Oil, will damage boiler and cause failure