Filter Blockages


What Causes Your Fuel Filter to Get Blocked

There are a number of different causes of filter blockages. These can include suspended water, suspended particulate matter, fungal contamination, or additives. Suspended water appears as a haziness in the fuel and is normally an issue in colder seasons. When diesel fuel cools during storage, dissolved water will be released as small droplets. If the droplets do not drop to the bottom, they will form a haze. Suspended water is generally seen as a greasy emulsion on blocked filters, which disappears when the filter is dried. This problem can be resolved by ensuring that any settled water is drained from the tank.

Suspended particulate matter can occur in the form of dirt, rust, or oxidized fuel. This forms a fine suspension of red or brown particles, causing a greasy black deposit on the fuel filter. Wax can also form, and can be seen as a light yellow suspension in the fuel. When the fuel is cooled below the temperature at which the wax comes out of solution, this is called the cloud point. These particles can then block filters by forming a yellow waxy deposit. These deposits are the result of using the incorrect fuel for the season or region; e.g. using summer grade fuel in winter. This issue can be fixed by waiting for the fuel to warm up and changing the filter, or by lowering the cloud point. To prevent waxing problems, fuel should be changed over to the proper grade at the proper time. Timing can depend on the region, and there is generally a two month lead time in fuel distribution.

Fungal contamination can also block filters, and is a symptom of poor water drainage. It is normally associated with long standing free water, hazy fuel, suspended water, and dirt. Fungi normally occur as a black/brown sludge that will block filters. Lab analysis of the filter and fuel may be required to confirm that active fungal growth is present. Fixing this issue will require changing of filters, frequent and regular draining of water, slime, sediment, and hazy fuel from all storage tanks. Clean Fuels Associates can assist in this process.

Additives can sometimes block filters if they are not mixed correctly with the fuel. The appearance of the filters and contents of the filter bowl will depend on the additives used. Sometimes, the additive will discolor water in the filter bowl so that it looks like fuel. Other times, combustion improvers may impart a waxy appearance. Clean Fuels tests all additives, and will only use additives that will not compromise the integrity of your diesel fuel for mission critical facilities.