FR2790613A1 - Sealed enclosing case for submersible electric motor, comprises cylindrical container for motor and ancillaries, filled with cooling oil circulating externally in heat exchanger - Google Patents

Abstract

The motor (9) typically drives an agitator (8) acting on mud or other liquid in which it is immersed. The motor shaft (11) is connected, through reduction gearing (10,12) within the cylindrical outer case (1), to the agitator shaft (13), which passes through the case bottom in a sealed sleeve (51) excluding the mud, etc. The agitator operates within a cylindrical shroud (44) mounted on stand-off brackets under the case. A screw-type pump (19), extending through the case into the shroud, allows fluid samples to be drawn off via a top connection, and is driven by a separate motor, in the case. Both motors are cooled by insulating oil (30) circulated by a third pump, driven off the main gearing (10,12), through an external circuit including the interior of the double-skinned (45) shroud; circulation within the main motor is aided by stator frame perforations (34) and the omission of the usual shaft seal (35). An air space (29) above the oil surface (30) permits pressurization via another conduit (31). The top plate also receives the supply cable (38), auxiliary connections for a manometer and other sensors, and a conduit for diluting water. Subject to constraints on diameter, cooling fins (52) are opt. added to the case.

Description

ELECTRIC MOTOR ARRANGEMENT ENCLOSED IN A TIER BOX

WATERPROOF EXTERIOR

DESCRIPTION

  The invention described here relates to an arrangement of an electric motor enclosed in a housing

waterproof exterior.

  This box must be distinguished from the ordinary box, encountered on any motor, and which is used to isolate its active parts, brushes, windings, rotor, etc. from the outside to avoid both the damage they could suffer from fouling or

  shocks, than those they could produce themselves

  same by electrical contact or rotational movement. The outer casing in question here surrounds the entire engine, including its protective casing, and protects it from the surrounding external environment. Such an arrangement with an external casing can be encountered in fluid agitators, where the motor drives a propeller or an equivalent stirring member and must be immersed like it in the fluid: the external casing prohibits the fluid

reach the engine.

  The heat produced by the work of the engine must find a way to escape and be absorbed by the fluid; however, it can be seen that the heat transfer from the engine to the external housing, through the mounting parts, is quite low, which traditionally leads to limiting the production of heat: to produce a determined power, we therefore tend to choose a high output torque. but a low speed, that is to say a rather bulky engine working at a moderate speed, since the heating is primarily a function of the speed of rotation. In certain applications, the choice of a bulky engine must however be rejected; or else one wishes to have certain additional devices on the agitator, in the external box, and since the constraints of space do not necessarily allow the volume of the box to be increased, these devices tend to encroach on the volume previously reserved for engine: these new layout constraints lead to choosing a smaller engine and working at a higher speed, but

  the heating produced would then become inadmissible.

  A new arrangement of electric motor enclosed in a waterproof outer case has therefore been designed and forms the subject of this invention; it is remarkable by the way in which the heat produced by the engine is evacuated towards the outside: contrary to the known art, the external case is filled with a liquid in which the engine bathes and which allows to easily accomplish the transfer desired heat. It will have been noted that this measure seems to make the external housing unnecessary, the sealing of which has the effect of preventing contact between the engine and the surrounding fluid, generally liquid, to be agitated; however, this is not the case since the liquid chosen here is a dielectric oil which does not disturb the operation of the engine, while lubricating its bearings and causing no corrosion. Tests have shown that the heating of the device remains moderate and allows long-term operations, provided that an oil is selected

  relatively high degradation temperature.

  The oil is so little damaging to the functioning of the engine that it is even recommended to facilitate its passage inside it: suitable measures then consist in piercing the protective casing of the engine or in removing the seal traditionally arranged around the output shaft

  of the motor, thereby producing openings.

  It is preferred that the outer casing be as full as possible, but it is however possible to leave a free volume which remains occupied by a gas; a pressurized gas injection device, connected to the external housing at the location of this gaseous sky, then makes it possible to adjust the pressure prevailing in the housing. In order to improve the heat transfer, one may want to increase the cooling of the oil: an important improvement of the invention meeting this objective consists in adding an oil circulation loop which is connected to the external casing by two opposite ends. and which extends out of the outer casing, providing significant contact, through an extended area, with a portion of the surrounding fluid which is a little further from the outer casing and therefore tends to remain cooler; a pump is arranged in the outer casing to force an oil circulation through the loop. Of course, it is advantageous for the ends of the loop to open in opposite regions of the housing, for example near its top and its bottom. In the case of a propeller agitator, it is particularly useful that the loop encircles the agitator device, because it then helps to channel the surrounding fluid entrained by the propeller while seeing constantly renewing in front of it the fresh fluid: the organs of agitation and cooling somehow become associated since they help improve the

performance of each other.

  The housing can accommodate, in addition to the motor driving the mobile agitating the fluid, other equipment, for example at least part of a means for pumping or taking samples of the fluid; the motor of this pumping or withdrawal means is then protected by the housing in the same way as the

drive motor.

  A more complete description of a

  particular embodiment of the invention will now be made with reference to the following figures: * Figures 1 and 2 are two views in longitudinal section of the housing in two perpendicular planes, * Figure 3 is a detail view of the top of the housing, * Figure 4 is a top view of the housing, * and Figures 5 and 6 are two cross-sectional views of the housing illustrating the top and bottom

of its content.

  The description will be given above all to

  using Figures 1 and 2, which are general.

  The apparatus considered is a stirrer for sludge or other fluids such as resins and concentrates, and it is included in an outer cylindrical casing 1, arranged vertically and which has a crown face 2 with central tab 3 to which is attached a lifter 4 suspended from cables 5 (shown in Figure 3). The cables 5 depend on a lifting device or a not shown unwinder which makes it possible to plunge the device more deeply or to bring it out of the sludge. Any other device to support and move the device would be suitable. The outer casing 1 also has a bottom face 6, opposite the previous one, from which protrudes the fluid stirring mobile, constituted by a propeller 8 or any other means

equivalent agitation.

  An electric motor 9 drives the stirring mobile; it is disposed in the outer housing 1, vertically, the pinion 10 of its output shaft 11 forming a single gear with a toothed wheel 12 secured to a shaft 13 which drives the propeller 8. The blades of the propeller 8 are inclined so that they produce a movement towards the external box 1. This direction is preferable when it is provided that there is, as here, a pump 19 in the external box 1 in order to suck up the mud which has just been agitated or from

collect sample.

  The pump 19 may be a screw pump, the stator 20 of which is arranged under the bottom face 6, next to the shaft 13 of the agitator mobile and the rotary screw 21 responsible for the suction of the sludge depends on a drive shaft 22 housed in the outer housing 1 and driven by a pump motor 23, also housed in the outer housing 1, by a gear train 24. The stator 20 extends into a conduit 25 in the outer housing 1, which surrounds the drive shaft 22 and to which is connected a discharge duct 26 which passes through the crown face 2 of the outer casing 1 and extends to means for taking up (or means for storing the transferred products) not shown and indifferent to the invention. The conduit has a tight seal 27 between the discharge conduit 26 and the gear train 24, so as to close it and prevent sludge rising towards the discharge conduit 26 from entering the rest of the outer casing 1. Finally, there is a plug 28, placed at the bottom of the conduit 25 and just below the bottom face 6, for draining the pump 19 when the device has been raised above the surface of the sludge. The invention consists in filling the housing 1 with a dielectric oil whose essential effect is to dissipate the heat produced by the motors 9 and 23, and the secondary effect is to lubricate the bearings of the rotary axes. The oil will be chosen so that its degradation temperature is not reached under the service conditions provided for the engines, while overheating of up to several tens of degrees will still be achieved. Many classes of oils seem adequate, including certain bearing oils and oils based on polyalphaolefins. The motors 9 and 23 are essentially or totally submerged, as are the gear trains and their bearings, but a gaseous sky 29 may remain above an oil level 30 near the top face 2; a pressurized gas pipe 31, originating from an external gas source which forms with it an injection device, crosses the crown face 2 and makes it possible to inject gas to bring the oil to the desired pressure; a pressure gauge 32 can measure this pressure, and a non-return valve not shown can also be added to the crown face 2 to allow evacuation of excess gas and avoid any accident. Openings are made through the protective housing 33 of the engine 9, which normally serves to isolate its contents from the outside, but not here, where on the contrary it is sought to favor the entry of oil into the engine for the cool: these openings consist of holes 34 through the wall of this housing 33, and an annular opening around the output shaft 11, at the place where this protrudes from the housing 33 and where is

  normally a gasket, which is omitted here.

  Similar arrangements can be made for the pump motor 23. In addition, there is no disadvantage in doing without a protective box for connection terminals 36, usually provided on electric motors but which is therefore omitted. also and shown only in dotted lines, and to expose the

  electrical connection terminals 37 of motor 9 (or 23).

  An electrical cable 38 coming from the outside crosses the crown face 2 and is divided into wires 39 connected to the terminals 37. Another cable 40 parallel to the previous one can be added to accommodate the wires leading to the sensors of the device, such as the pressure gauge 32, a current measurement sensor 41 placed under the face of

  bottom 6 and rotating shaft speed sensors.

  The top face 2 is finally crossed by a dilution water conduit 42 intended to make the sludge more loose and which winds within the outer casing 1 to open out of it through the bottom face 6, at a exit 43 located in front of the agitation mobile. An oil circulation loop has the general reference 44, and most of it consists of a volute 45 arranged around the stirring mobile and with contiguous and very flattened turns, which gives it an overall shape in a cylindrical envelope. thin and substantially continuous. The loop 44 also comprises two end conduits 46 and 47, the first of which is an outlet conduit from the external housing 1, connected to the latter near the bottom face 6 and the second is a return conduit to the housing outside 1, opening not far from the top face 2, just below the oil level 30, after having crossed the bottom face 6 and almost the entire height

of the outer housing 1.

  A pump 48, which can be a gear pump driven by a pinion 49 meshing with the toothed wheel 12, sucks oil from the housing 1 and forces it to circulate through the loop 44; this oil evacuates the calories in the colder surrounding sludge by the large heat exchange surface of the volute 45 and therefore undergoes refrigeration which supplements that which is statically obtained through the walls of the housing 1. The volute 45 surrounds the mobile d agitation and helps channel the flow of

sludge produced by the latter.

  The scroll 45 is connected to the bottom face 6 by ribs 54; a sleeve 50 projecting from the bottom face 6 surrounds and protects the shaft 13 of the stirring mobile; sealing devices 51 are provided between the sleeve 50 and the shaft 13 to prevent sludge from thereby entering the housing 1; finally, a system of mounting flanges 53 makes it possible to mount in stable positions the motors 9 and 23 and all

  other equipment inside the housing 1.

  The housing 1 could be furnished with external fins 52 to promote the exchange of heat with the surrounding fluid, if we accept the increase in size which would result therefrom. These fins could extend in the axis of the housing 1

  cylindrical and radiate outwards.

  The invention can be used for dangerous, corrosive or other fluids encountered

  especially in the nuclear industries.

Claims (10)

  1. Arrangement of electric motor (9, 23) enclosed in a sealed outer casing (1), characterized in that the outer casing (1) is essentially or even completely filled with oil   dielectric in which the motor is immersed.   2. An electric motor arrangement according to claim 1, characterized in that the motor comprises a motor housing (33) provided with openings (34, 35) for passing the oil.   3. An electric motor arrangement according to claim 2, characterized in that one of the openings (35) extends around an output shaft (11) of the motor, at the location of a seal. omitted here.   4. Electric motor arrangement according to   any one of claims 1 to 3, characterized   in that it includes a gas injection device   under pressure (31) connected to the external housing.   5. Electric motor arrangement according to   any one of claims 1 to 4, characterized   in that it comprises an oil circulation loop (44) connected to the outer casing by two opposite ends (46, 47) and extending out of the outer casing, and a pump (48) in the outer casing (1 ), arranged to force a circulation of oil through the loop.   6. An electric motor arrangement according to claim 5, characterized in that the opposite ends of the circulation loop are respectively at the top and bottom zones of the outer casing.   7. Electric motor arrangement according to   any one of claims 5 or 6, intended for   agitate a fluid surrounding the outer casing, characterized in that the loop (44) encircles an agitator device (8) exiting the outer casing   (1) and driven by the motor (9).   8. Electric motor arrangement according to   any one of claims 1 to 7, characterized   in that the electrical connection terminals (37) of the motor are exposed in the external housing (1), in the absence of any protective element (36) covering these terminals.   9. Electric motor arrangement according to   any one of claims 1 to 8, characterized   in that the outer casing (1) is furnished with fins   external (52) cooling.   10. Electric motor arrangement according to   any one of claims 1 to 9, characterized   in that the housing (1) contains at least a part (22, 23, 25, 26) of a pumping device or of   taking samples of a surrounding fluid.