VALVE SEAT SELF-CLEANING DEVICE FOR ALUMINA PRODUCTION PLANTS

Abstract: This valve is applied to the conveying of bauxite through pipes and is intended to perform its self-cleaning with the association of a locking element which makes the actuation crown integral with the valve stem, whereby the rotation of said crown is transmitted to the valve stem which, when rotatin in friction contact with the seats of the valve body in order to remove the depositions.

Description: OBJECT OF THE INVENTION The present invention relates to a device applicable to valves in alumina obtaining installations with the object of providing self-cleaning of bauxite depositions inside the valve body, by rotation and scraping of seats inside the valve body. BACKGROUND OF THE INVENTION As is known, aluminium is obtained by electrolysis from bauxite, with the bauxite passing through several phases or process stages before alumina, and afterwards aluminium, may be obtained. At installations where this type of processes are carried out, over time bauxite adheres to valve seats, and although occasionally this problem may result in that the bauxite acts as a sealant between the valve disc or ring and the seat, it generally results in that the disc cannot rest properly on the valve seat. These depositions inside the valve must be removed manually. This type of valves comprise a rod or shaft with a disc or seal solidarily joined to it which is housed inside the valve body, so that these elements make up the valve itself. The valve is driven by means of an input shaft which, through a bevel gear, drives a crown provided with recesses in which fit battlement-shaped projections provided in the spindle nut, so that the rotation of the crown is transmitted to the spindle nut, which in turn causes the valve shaft to ascend or descend, and therefore the coupling or decoupling of the valve disc or ring on the valve body seats. DESCRIPTION OF THE INVENTION The valve for alumina obtaining installations disclosed has been conceived to solve the above exposed problem, by incorporating a device which allows internal self-cleaning of the same, and more specifically elimination of bauxite depositions on the seats, in order to ensure a perfect contact between the disc and packing rings of the valve body. To this end, a device is provided which causes rotation of the ring or disc about its shaft, so that said rotation causes scraping of the ring on the seats inside the valve body, and thus this friction to remove the adhered depositions. The device consists of a locking cap which is coupled to the top end of the valve shaft by means of an inner toothing, and is additionally inserted by means of flaps in recesses of the crown which drives the spindle nut, thus relating the valve shaft to the crown so that they will both move simultaneously. Thus, rotation of the input shaft will cause, through the bevel gear, a rotation of the crown, and in turn the latter will carry in its motion the spindle nut and the locking cap. The locking cap will carry the valve shaft in its motion, causing a rotation of the valve disc or ring inside the valve body, and with it scraping of the seats. In order to resume normal operation of the alumina valve, the locking cap is withdrawn, decoupling motion of the crown and the shaft so that rotation of the input or driving shaft in either direction causes rotation of the crown and therefore the spindle nut, and the rising or lowering of the valve shaft. DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the present invention will more fully appear from the accompanying set of drawings where, for the purpose of illustration only and not intended as a definition of the limits of the invention, the following is shown: Figure 1 is a plan view of the top of the valve shaft or rod and an elevation view of section A-A, all of this in normal operation, when the locking cap is not attached. Figure 2 is a similar representation to the above figure but with the locking cap attached in order to perform self-cleaning of the valve unit. Figure 3 is a top plan view and a sectional view of the locking cap. PREFERRED EMBODIMENT OF THE INVENTION Figures 1 and 2 show the valve unit partially, showing only the valve shaft (4) inside the top part of the valve body. Said shaft (4) acts as a spindle as it is inside spindle nut (3), which rotates due to the action of drive shaft (1) which transmits its motion to nut (3) through bevel gear (2) and crown (11), making said valve shaft (1) ascend or descend. For this, the spindle nut is provided with upper projections in the shape of battlements (12) which couple to corresponding recesses made in crown (11) so that, in its rotation, the crown carries spindle nut (3). The top end of valve shaft (4) is accessible from the top and is provided in its side wall with a toothing (7) which is visible in figure 1. The device employed to perform self-cleaning of the valve consists of a locking cap (5) which allows to engage crown (11) and valve shaft (4) so that shaft, crown and spindle nut rotate simultaneously. The locking cap, shown in figure 3, comprises a cylindrical body with different internal diameters provided with perimetral flaps (8), and internally in its top segment with an inner toothing (6) complementary to toothing (7) of valve shaft (4). Said locking cap (5) can be easily handled by its handle (10), which is screwed to cap (5) on its top area. Thus, when self-cleaning of the seat is desired, locking cap (5) is coupled as shown in figure 2, so that perimetral flaps (8) match and are inserted in recesses or key slots (9) provided for this purpose in crown (11). The upper end of the valve shaft is coupled inside locking cap (5), with internal toothing (6) engaging toothing (7), so that rotation of shaft (4) inside locking cap (5) is prevented. Due to this coupling crown (11) and valve shaft (4) can only turn in the same direction, so that the action of drive shaft (1) makes the rotation of crown (11), through locking cap (5), carry valve shaft (4) with the entire unit rotating and therefore causing scraping of the ring in the valve seats in order to remove any depositions.

Claims: Device for self-cleaning of valve seats in alumina obtaining installations, with the purpose of removing bauxite depositions in the valve seat of a valve, said valve further containing a crown (11), a valve shaft (4) and a valve ring connected to the valve shaft (4), said device comprising a locking cap (5) which is provided with a toothing (6) along its entire internal perimeter of its top segment and with perimetral flaps (8), whereby said locking cap (5) can be coupled between the crown (11) and the valve shaft (4) of the valve such that its toothing (6) engages in a complementary toothing (7) provided in the top part of the valve shaft (4) and that at the same time its perimetral flaps (8) are housed in key slots (9) made in the crown (11), thus relating the motion of the valve shaft (4) and the crown (11) so that the rotation of the crown (11) is transmitted to the valve shaft (4), rotation of which causes friction of the valve ring with the valve seat, thus removing the depositions. Device for self-cleaning of valve seats in alumina obtaining installations according to claim 1, characterised in that the locking cap (5) is further provided at its top with a handle (10) which simplifies handling in coupling and decoupling to the valve.

Inventors: GONI USABIAGA JUAN JOSE, GONI USABIAGA, JUAN JOSE, GONI USABIAGA, Juan José
Applicants: AMPO S COOP, AMPO, S. COOP.
Application year: 1998
Main classification: F16K31
IPC codes: F16K29, F16K31