ASTM D4539 Low Temperature Flow Test (LTFT) is generally recognized as a better predictor of diesel fuel filter plugging temperature than the more commonly used ASTM D6371 Cold Filter Plugging Point (CFPP). Please review ASTM D975-08a Appendix X5.1.3 for more Historical Background. Lawler’s automated units remove the tedium of the test and need for operators to run tests at inconvenient times.

Lawler automated models are liquid baths with a semicircular arrangement of sample beakers such that filter distance to the receiving beaker of each sample is exactly the same. This is to insure that all dimensions of the apparatus are identical to the specifications of ASTM D4539. A common receiver beaker is used for all samples and is automatically drained in preparation for the next test.

The test starts with the operator installing 1 to 6 sample beakers into the bath. After inserting the filter holders and making the connections for the vacuum, the computer program is started. No further operator attention is needed until all samples have been tested.

When the sample cools to the pre-selected temperature, the vacuum is automatically applied and the time recorded when the vacuum breaks (i.e. all the sample has been filtered). The pass temperature is when the filtration time is less than 60 seconds. Cooling continues at 1°C/hour and the next sample is filtered as before.

The full process is controlled by software running on a Windows based PC computer or laptop. The software allows the operator flexibility to configure the test parameters. All results are stored in XML format on the computer allowing future review, statistical analysis, printing in the software or import into a spreadsheet such as MS-Excel®.

Refrigeration is provided by two hermetically sealed compressors in a cascade configuration using ozone friendly refrigerants. Temperature control is provided by a digital temperature controller that communicates with the software.

AVAILABLE MODELS:

Model 362 is a liquid bath with 6 sample capacity. It is a research model with a laser detection of the filtered volume and plots the volume in the receiver with time. The pass temperature is determined by loss of vacuum (i.e., all the sample has filtered). Model 362 comes fully equipped, complete with an electronic vacuum regulator, vacuum pump, PC or laptop, and all needed accessories (glassware, filter assemblies, etc.)

Model 289 is similar to Model 362 also with 6 sample capacity, but does NOT include the receiver level detection feature. It is a pass/fail model where the pass temperature is determined by loss of vacuum (i.e., all the sample has filtered). Like Model 362, Model 289 comes fully equipped with accessories.