Diesel fuel is classified by a variety of parameters that determine the quality and properties of fuel. A very important parameter is the limiting filterability temperature for diesel fuel and diesel fuel analogues. It determines the properties of fuel at low temperatures and affects the classification by seasonality: summer, winter, and arctic.
What does the limit temperature of filterability characterize? It determines the lower temperature limit at which the diesel fuel loses the ability to percolate into the filter holes, or 20 cu. cm of fuel are filtered over 1 min. Cooling to this temperature, the fuel becomes so viscous that it clogs the filter holes.
Diesel fuel by the filterability limit is divided into grades according to the European standard EN 590. Its Russian analogue is GOST R 52638, which sets the values of CFPP for temperate zones:
- Grade А – +5°С
- Grade B – 0°С
- Grade C – -5°С
- Grade D – -10°С
- Grade E – -15°С
- Grade F – -20°С
For cold climate zones, summer fuel is not used, so low-temperature properties are determined only for winter and arctic diesel. For the winter limit values are -32 ° C and -38 ° C, for the Arctic – -44 ° C, -48 ° C and -52 ° C. The limiting temperature of filterability of diesel fuel for cold areas is regulated by GOST R 55475.
How is the temperature limit of the filterability of the fuel determined?
The limiting temperature of filterability is an obligatory characteristic when determining the properties of fuel, it is indicated in the quality passport of diesel fuel and diesel fuel analogues. Tests of oil products take place under vacuum conditions, while the fuel mixture is systematically cooled and passed through a filter. Assessment of the patency of the fuel is performed at each degree of cooling until the moment when the fuel is filtered for more than 1 minute.
It is interesting that the temperature of the filtering limit is greater than the full freezing point, but less than the cloud point. The limiting filterability temperature can be decreased by dewaxing the fuel. For this, special additives are used, which reduce the amount of paraffin crystals, changing their structure.
To automate the measurement process and for high accuracy of the results, a device is used to determine the limiting filterability temperature. This device is convenient in use and does not require special preparation for work anywhere. It automatically determines the limiting filterability temperature while cooling the fuel and measuring the temperature. As soon as the passability through the filter stops or is critically slowed down, the device fixes the limiting filterability temperature.
How to apply knowledge about the limiting filterability temperature in practice
The main problems with the limiting filterability temperature are associated with different filter capacities. A standard wire screen filter, used in laboratory tests, has a nominal cell size of 45 μm. And automobile fuel filters for diesel engines have a cell size of 15-20 μm, and sometimes 5 μm.
That is, the same fuel, cooling, will rather clog the car filter than the laboratory one, and the filterability temperature with other equal variables will depend on the fineness of the filter’s screening.
Conclusion: pay attention to the value of the limiting filterability temperature in the quality passport and do not allow the engine to operate at a temperature lowered to this value. For example, do not allow the summer diesel, which has a filterability temperature of -5 ° C, to be used at a value below 0 ° C.