Cold Filter Plugging Point Process

Norms and standards • DIN EN 116 (former DIN 51428) • EN 116 / BS 6188 (former IP 309) • ASTM D 6371 Application When paraffinic hydrocarbons, which may form part of distillate fuels, are cooled, n-paraffines come out of solution by forming wax crystals due to limited solubility of the fluid. The highest temperature at which the fuel, when cooled under defined conditions, will not flow through a filter of a defined wire mesh within a certain time, is called cold filter plugging point (CFPP). It indicates the low temperature operability of fuels with / without flow improver additives when cooled below the cloud point (CP) temperature. Blending of middle distillate fuels with flow improver additives changes the crystalline structure and the coalescence (size) of the n-paraffines. This effect cannot be measured by determining the CP (extinction in a light path resulting from the amount of crystallized paraffines). The CFPP is a measurement more directed to “end use” applications (filter clogging), than to measure the pour point as a characteristic of the low temperature behavior of fuel oils. CFPP – between CP and solidification point (pour point) – is not a directly measurable physical quality / performance characteristic. The method is based on reference values obtained from a defined identical test procedure. The CFPP measurement is often combined with the determination of the CP, giving a better control of the base blend. Knowledge of CP temperature permits a reduction of the measurement cycle time by starting the measurement at temperatures that are a few degree above CP. Special features visible function cycles by using a measuring cell made of plexiglass / glass no paraffin – adhesions on test sieve by flushing with preheated sample no correlative measurement, but exact reconstruction of cycles as described in DIN EN 116 identical test sieve as used in laboratory method Procedure The sample is filled into a standard measuring cell, where it is cooled to a pre-set temperature. By means of a vacuum, the sample is then sucked through a filter of defined dimensions and filter mesh. It has to reach a light barrier within 60 seconds. If the sample has reached the light barrier, the measurement cycle ends. The sample then flows back to the measurement cell where it is cooled further by 1 °C before the next cycle starts. After each signal generated by the light barrier, it is checked whether the entire sample volume flows back to the cell or not. In case not, the paraffin crystals have already started to block the sieve. At this stage the temperature in the cell is measured. This temperature is defined as CFPP. The explosion protected mechanical cooler (two-stages) reaches temperatures as low as – 67°C. Reproducibility and repeatability are equal to or better than the limits indicated in the standards. The complete analysis procedure is controlled, monitored and visualized by the PACS (Process Analyzer Control System) software. It offers a user interface for local analyzer operation. At the end of the analysis cycle, in addition to the standard analog 4 - 20 mA CFPP signal, a digital output signal can be generated (programmable). During the analysis, an optional, galvanically separated 4 - 20 mA signal can also be used. As an alternative, a MODBUS interface is available as an option, which also allows a direct control of the anlalyzer from the DCS. In case remote access to the CFPP analyzer is demanded, it can be equipped with a remote access interface (e.g. Modem, ISDN) for service and maintenance purposes.

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