Ⅰ. Brief Introduction
    In petrochemical enterprise, during the process of feeding, polyolefin powder may produce a lot of static and will result in sparkle discharge of high energy when there is metal projection around materials. Ordinary annunciators of high materials position such as tuning fork style and capacitance style are the most dangerous discharge elctrode of powder bunker, and annunciator of high materials position at home and abroad causes a lot of powder explosion. Current discharge igniting as chart1. The danger of annunciator discharge of high materials position is related to structure and dimension of sensor: extending part is too long and lies in high pressure and strong electric field, capacitance of static is small and bring into bieing metal projection which is easy to induce sparkle discharge. Experiment shows that electricity of powder in pipeline 1~5μC/kg, and electric potential of materials which is 20~30cm far from the tank shin is as high as 40~60kv (see chart 2 experiment data), and may brig discharge of several decade milli-joule when the annunciator of high materials position discharge electricity. As a general rule, the minimum igniting energy of polyolefin powder is between 15mj to 30mj, and the igniting rate of discharge is much high.

Chart3 Profile of sensor

Chart4 Quadratic instrument