Tomofumi Mogami

Experimental study on detection of electrostatic discharges generated by polymer granules inside a metal silo.

To detect electrostatic discharges generated by polymer granules within a metal silo, we developed a novel and simple electrostatic discharge detector that utilizes a photosensor. The novel detector consists of a photosensor module in a metal cylinder, an optical band-pass filter, a quartz glass, a power supply, an amplifier for the photosensor module, and a digital oscilloscope. In this study, we conducted experiments at a real pneumatic powder transport facility that includes a metal silo to evaluate the novel detector using polypropylene granules. To determine the performance of the novel detector, we observed the electrostatic discharge within the metal silo using a conventional image intensifier system. The results obtained from the experiments show that the novel detector worked well in this study. The signals obtained with the novel detector were identical to the electrostatic discharges obtained with the conventional image intensifier system. The greatest advantage of this novel detector is that it is effective even when placed under external lights. In addition, the influence of various optical band-pass filters on the performance of the novel detector was discussed. Our study confirmed that an optical band-pass filter with a center wavelength of λ 330 nm (λ1/2: 315-345 nm) was the best performer among the optical band-pass filters used in this study.

Experimental Study on Safe Performance of Nozzle-Type Electrostatic Neutralizer

The safe performance of a nozzle-type electrostatic neutralizer was examined experimentally in inflammable gas (ethylene)–air mixtures. A 100 MΩ-coupled electrode produced ion pairs safely for reducing static charges from polymer materials, and incendiary discharges were suppressed by the resistor and voltage supplied to the electrode. The performance of the neutralizer (flange-type) driven with an AC (50 Hz) or DC high-voltage power source was also evaluated with a full-size pneumatic powder-transport system. It was confirmed that the nozzle-type neutralizer is markedly effective for reducing electrostatic charges from polymer materials; however, several disadvantages were also noted.