GB419053A - Improvements in and relating to processes of purifying liquids and apparatus therefor - Google Patents

Abstract

<PICT:0419053/III/1> <PICT:0419053/III/2> Apparatus for purifying oil used in electrical apparatus, such as transformers or switches or in oilfilled cables, comprises electric-heating apparatus, a vessel in which the oil is dehydrated in films under high vacuum and a sectionalized rotating disc filter. These parts together with gear pumps for circulating the oil, a pump for producing a vacuum and the necessary pipe connections may be mounted on a wheeled base which can be brought up to the transformer or other apparatus containing the oil to be purified. With the apparatus as shown diagrammatically in Fig. 4, oil is drawn from a transformer 2 through strainer 8, electrical-heater 26 and pipe 42 by a gear-pump 44 which delivers it through a pipe 48 into the top of the dehydrating-chamber 52. The de-hydrated oil is withdrawn from the bottom of the chamber 52 by two gear pumps 448, arranged in series, and delivered through a pipe 142 and a differential pressure device 144 to the filter chamber 146. The filtered liquid passes through a pipe 334 to a three-way valve 384 which can be set to direct the oil back through a meter 538 to the transformer 2 or to the inlet pipe 24 of the heater 26 for recirculation through the purifying system. Heating by electricity.--The heating apparatus may comprise a casing 28, Fig. 22 divided by vertical and horizontal partitions 38 into compartments 30 which are in communication through staggered apertures 40 so that the oil passes successively through the compartments. Each compartment has its own heater 32 which is screwed into position through one end of the casing, this end being provided with a cap 36. The switch controlling the heaters is arranged so that as many heaters only are brought into operation as are necessary to raise the oil to the desired temperature. <PICT:0419053/III/3> Film evaporators.--The oil from the pipe 48 is delivered within the chamber 58, Fig. 17, through a spout 110 on to the centre of the uppermost of a series of discs 112, fixed to a shaft 100, rotated by bevel gearing 126 from the shaft 130 of the gear pumps 448, 44 and 484, the shaft 130 being driven by an electric motor 132. Each disc 112 spreads the liquid outwardly against a baffle 114 having a cylindrical wall with an inclined lower section 116 which directs the liquid to the centre of the disc below. In order to maintain a high vacuum within the chamber 58 it is connected through a liquid seal under a glass dome 80 in an outer casing 76, and by a pipe 94 to a vacuum pump driven by a belt from a pulley 516 on the shaft 130. <PICT:0419053/III/4> <PICT:0419053/III/5> Filters.--Each filter element, Figs. 5 and 6, is built up of two discs formed by winding thin metal tape spirally and spaced apart by a web with flanged spokes 198, which divides the space between the discs into sector-shaped sections. These sections are in communication at the centre with longitudinal passages 180 in the shaft 178, each longitudinal passage thus serving to discharge the filtrate from corresponding sections in the several elements. The elements are spaced apart on the shaft and on tie rods 228 which connect end plates 170, 176. The shaft and elements are rotated by means of teeth on the plate 170 which are engaged by a pinion driven by worm and belt gearing from the shaft 130 of the gear pumps. A distributing valve 270 at the end of the shaft 178 has apertures which, for any position of the elements, place all save one of the passages 180 in communication with the chamber 258 from which the filtrate flows away through the pipe 334. The remaining passage 180 registers temporarily with a passage 276 in the valve, which communicates through a bellows connection 264 with a chamber 256 to which oil is supplied by a gear-pump 484, Fig. 17, under the requisite pressure to pass outwardly through the filter sections communicating with the chamber 256 and with impurities therefrom. The impurities are collected in a pan 148 below the filter. Communication from the gear-pump 484 to the chamber 256 is made through the differential pressure device 144, which ensures that the pressure of the oil used for backwash shall be greater than that of the oil delivered for filtration. There is a connection from the device 144 to a channel 366 in the bearing of the shaft 178 through which oil is supplied to the channel 366 at a pressure higher than that of the oil to be filtered. Oil leaking from the channel 366 towards the filter chamber prevents grit entering the bearing from the chamber. For filtering oils used in switches the filter elements may be given a pre-coat of filter aid. The filter aid is supplied to the filter chamber through an opening 520 and mixed with oil in a compartment 152 by an agitator 154. This oil is then passed through the filtering elements, the valve 270 having previously been drawn outwards, by means of a handle connected to a cam working on a lever 300, so that the back-wash connections are broken and all the channels 180 communicate with the chambers 258. During this operation the valve 384 is so placed that the oil passing through the filter is recirculated through the heater. When the filter elements are sufficiently coated the valve 384 is turned so that the filtered oil is discharged.