The role of diesel coarse filter: 
1. Filter out harmful impurities and moisture in the fuel system, protect the normal operation of the engine, reduce wear, avoid clogging, and improve engine life. The filter element of the diesel filter mostly uses filter paper, and some also use felt or polymer materials. The filters are the same, with replaceable and spin-on types;
2. The original filter efficiency characteristics, the filter of the diesel generator set plays a role of filtering, and it must be able to filter out a certain size and number of impurity particles during use. The filtration efficiency of the new filter element is determined, which is called the original filtration efficiency. Diesel generator sets pass the oil containing a certain number of particles of a certain size through the filter at a certain flow rate at a time, and analyze the impurity content in the filtered oil to calculate the original filtration efficiency. If you use multiple specifications of particles to test, you can get different efficiency data;
3. Flow resistance characteristics, the pressure difference generated before and after the filter of the diesel generator set at a certain flow rate. This pressure difference is the resistance of the filter and the pressure loss value. Its value should be as small as possible. It is generally required that the original resistance of the full-flow filter when passing the rated flow should not be greater than 0.5 kg cm2 or 30 of the opening pressure of the bypass valve. The flow resistance characteristics of the diesel generator set filter can be measured on the test bench.