GB1151456A - Method of and Apparatus for Reducing Electrostatic Charges in an Electrically Charged Liquid - Google Patents

Abstract

1,151,456. Reducing electrostatic charges in liquids flowing through pipes. STANDARD OIL CO. 12 May, 1967 [18 May, 1966], No. 22058/67. Heading F2P. Apparatus for reducing electrostatic charges in an electrically charged liquid, e.g. military jet fuel which has a relatively low electric conductivity, comprises a capacitor, consisting of a tubular metallic grounded outer cylinder 10, a dielectric 12 of thick, non-conductive, material 12, e.g. polyethylene, polystyrene, of high resistivity and low dielectric constant fixed within said outer cylinder 10, the dielectric having a hollow core the surface of which acts as the other plate of the capacitor, and a plurality of sharply pointed grounded electrodes 14 which are spaced apart axially and have points which slightly protrude into said hollow core, so that liquid having an electrical charge flowing through the hollow core, will contact the points. It is stated that positioning a sharp grounded point in the liquid in a region of high voltage causes an intense electric voltage gradient to be set up in the vicinity of the point to ionize liquid molecules which are of opposite sign to the charged liquid to neutralize the latter. Successive neutralization points reduce the charge of the liquid to a point where it no longer presents a hazard. The internal diameter of the dielectric 12 should match that of the piping in which it is installed so that smooth surfaces are provided at the junctions. As the internal diameter of the dielectric is increased so should its thickness be increased in order to decrease the capacity as the size of the capacitor increases, the small capacity being essential for a short starting transient time before the device becomes effective as liquid commences to flow through the capacitor. The electrodes are arranged in axially-spaced circumferential rows, the electrodes of one row preferably being offset from an adjacent row by 60 degrees and the rows being spaced by an amount which allows mixing of the charge in the liquid and the injected charge before the additional charge is injected. The number of rows is from about 3 to 5. As shown, each electrode comprises a bolt 18 which is threaded into an adaptor ring 24 welded to the cylinder 10 and which carries a pointed electrode 16 which is formed of a hard, non-corroding precious metal, e.g. osmium, the point having a radius of 2-3 mils. A continuous spiral groove in the back of the dielectric 12 forms a keying surface for an epoxy cement used to fix the dielectric 12 to the cylinder 10.