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Clogged Diesel Fuel Filters

Posted by: Erik Bjornstad

Clogged diesel fuel filters is one of those canary-in-the-coal-mine problems.  On a simple level, it means filterable particulates passing through the filter are higher than they should be. This implies that there may be something going on in the fuel that’s causing this to happen.  What are the most likely culprits when diesel fuel filters clog at an abnormally high rate?

Excess Sludge and Particulate

minnesotra_biodiesel_filter_plug-1Today’s ultra low sulfur diesel fuels produce sludge and particulates at a markedly faster rate than the high sulfur diesel fuels of the past. Use of cracked feedstocks at the refinery and susceptibility to microbial activity (and its effects on fuel quality) are contributing factors to this.

Microbial Contamination

Speaking of microbial activity, ULSD has much less resistance to microbial activity than diesel fuels of the past. Part of this is due to a change of the fuel’s composition (less sulfur and lower aromatic components), some due to ULSD’s affinity for water.  Microbial activity not only causes diesel fuel to become unstable and produce sludge and varnish at an accelerated rate, they also produce biomass secretions that plug filters.

What Kind of Filters Are We Talking About?

When we mention clogged diesel fuel filters, what kind of filters are we speaking of?  In a general sense we could be applying these principles to any kind of filter used in the diesel storage, distribution and combustion system.  These causes can apply to all of these. But we also acknowledge that not all filters are affected equally by all things.

In the fuel distribution system, you’ve got filters for diesel fuel storage tanks and filters for diesel dispensing units.  Both of these are vital fuel filtration systems for taking out contaminants that may otherwise cause problems for the end user. This also means that abnormal change intervals can be a red flag that there may be something abnormal going on in the storage tank itself, the most likely place for stored fuel deterioration to take place.

Diesel fuel filters on engines are vital to protecting the engine from contamination. These filters are more sensitive than in years past because of the need to protect high tech diesel engines from damaging particulates.  Indeed, today’s filtration system to protect fuel pumps and injectors can take out 1000x more/smaller particles than previous versions, because particulates as small as 4 microns can damage these vital high-tech systems.

Fixing The Problem

If you’re an end user and you have a clogged diesel fuel filter, obviously you have to replace it.  If you’re in the supply chain and you (or your customers) are having these problems, you need to look at the factors in the stored fuel that are causing them.  The things we mentioned earlier – sludge, particulate, microbial presence. A good fuel preventive maintenance program (including preventive applications of biocide and fuel stabilizer) can go a long way towards making sure you and your customers never reach the point of having to deal with these problems. Because it’s always more expensive and problematic to deal with the aftermath of these problems than it is to prevent them.

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This post was published on July 11, 2018 and was updated on July 12, 2018.

Topics: Fuel Storage, Fuel and Tank Services