US3633341A - Oil mist eliminator for a fluid drive - Google Patents

Abstract

A fluid drive wherein the runner and impeller assemblies are disposed within a nominally closed tank which defines an oil sump. A fan-filter unit assembly is provided for drawing oil mist from the tank interior through the filter unit, whereby a partial vacuum is established within the tank interior which prevents the mist from leaking into the surrounding atmosphere through small joints in the housing and protruding shafts. The fan-filter unit comprises an oil coalescing device in an upstream portion of the fan-filter unit and a fine mesh filter for trapping fine oil mist droplets which pass through the coalescing device without undergoing coalescence. The coalescing device and fine mesh filter are interconnected by a conduit which has a drain line for draining the coalesced oil droplets into an oil sump.

Description

United States Patent [72] Inventor Henry J. Langlois Detroit, Mich. [21] Appl. No. 42,966 [22] Filed June 3, 1970 [45] Patented Jan. 11, 1972 [73] Assignee American Standard Inc.

New York, N.Y.

[54] OIL MIST ELIMINATOR FOR A FLUID DRIVE 9 Claims, 3 Drawing Figs.

[52] U.S. Cl 55/186, 55/350, 55/423, 55/467, 55/482, 55/505, 55/DIG. 19,55/25, 60/54, 2l0/DIG. 5 [51] Int. Cl ..B01d19/00 [50] Field of Search 55/DIG 25, 350, 482, 259, 423, 186, 467, 505, 521, DIG. 19; 60/54; 210/DIG. 5

[56] References Cited UNITED STATES PATENTS 2,521,785 9/1950 Goodloe 55/482 Primary Examiner-S. Leon Bashore Assistant Examiner-Saul R. Friedman Attorneys-John E. McRae, Tennes l. Erstad and Robert G.

Crooks ABSTRACT: A fluid drive wherein the runner and impeller assemblies are disposed within a nominally closed tank which defines an oil sump. A fan-filter unit assembly is provided for drawing oil mist from the tank interior through the filter unit, whereby a partial vacuum is established within the tank interior which prevents the mist from leaking into the surrounding atmosphere through small joints in the housing and protruding shafts. The fan-filter unit comprises an oil coalescing device in an upstream portion of the fan-filter unit and a fine mesh filter for trapping fine oil mist droplets which pass through the coalescing device without undergoing coalescence. The

. coalescing device and fine mesh filter are interconnected by a conduit which has a drain line for draining the coalesced oil droplets into an oil sump.

OIL MIST ELIMINATOR FOR A FLUID DRIVE THE DRAWINGS FIG. 1 is a semischematic sectional view taken through a conventional fluid drive adapted to utilize the present invention.

FIG. 2 is a right end view of the FIG. 1 fluid drive.

FIG. 3 is an enlarged sectional view of a novel fan-filter unit utilized on the FIG. 1 fluid drive.

THE DRAWINGS IN DETAIL FIG. 1 illustrates a conventional fluid drive of the type commonly used in power stations, boilers, liquid pump stations, etc. to transmit a rotary drive from a power source, usually an electric motor, to a driven load such as a large fan, liquid pump, etc. The general operation of this type equipment is described for example in US. Pat. No. 3,200,594 issued in the name of E. R. Braun.

As shown in FIG. 1, the fluid drive includes a large tank formed by a lower tank sump secton 7 and an upper tank cover section 9. Section 7 comprises a bottom wall 10, two end walls 12 and 14, two sidewalls l6 and 18 (FIG. 2). Cover section 9 includes an arcuate top wall 20 and semicircular end walls 22 and 24 aligned with the end walls 12 and 14. The various walls on cover section 9 and tank section 7 are flanged, as at 26 and 28 (FIG. 2), so that suitable bolts (not shown) can be extended through holes in the flanges to connect the two tank sections together; a gasket 30 (FIG. 3) may be interposed between the mating flanges to better seal the flange joints.

Disposed within the tank are confronting vaned impeller and runner shells 32 and 34 carried on an impeller shaft 36 and runner shaft 38. As will be appreciated, shaft 36 extends through one end wall of the tank for connection to the power source, such as an electric motor, and shaft 38 extends through the other end wall of the tank for connection with a load device such as a large fan or pump.

Shaft 36 is supported and mounted in a baring cage 40 suitably secured to a stationary platform 42. Cage structure 40 comprises an annular liquid housing 42 which mounts a radial bearing 43; a second radial bearing 44 is carried in the main part of bearing cage 40. Axial thrust loads are carried by thrust bearings 45 and 46 engaged with the enlarged shaft flange 39. Shaft 38 is supported in generally the same manner as shaft 36, and corresponding numerals are therefore used where applicable.

During operation oil from the bearings and the tank atmosphere tends to collect on the shaft surfaces 36 and 38, and to escape into the atmosphere surrounding the tank. Conventional shaft seals 35 and 37 (O-ring, labyrinth, screw type, etc.) may be provided to minimize such oil escapage.

OIL CIRCULATION In the illustrated arrangement oil is supplied to the impellerrunner work chamber 47 through an oil supply line 48. The oil is fed from line 48 into the immovable annular chamber 50, and ultimately through ports 52 in the impeller 32 for admission to the work chamber 47. Impeller 3.2 carries a scoop chamber casing 54 which defines a scoop chamber 56. During operation oil continually escapes from the work chamber 47 into the scoop chamber 56 through the space 58 between the impeller and runner elements; the radial thickness of the liquid ring in the scoop chamber 56 determines the quantity of liquid in chamber 47 and hence the power transmitted from shaft 36 to shaft 38.

Control of the liquid ring thickness in chamber 56 is conventionally achieved by means of a scoop tube 59, shown mounted on a plate 60. In practice plate 60 is affixed to a control rod, not shown, that extends through one of walls 16 and 18. Horizontal movement of the control rod by an automatic controller responsive to some parameter such as flow, pressure, temperature, etc., effects movement of the scoop tube 59 horizontally, i.e. normal to the plane of the paper. The controller thereby causes the scoop tube to control the radial thickness of the liquid ring in chamber 56, as by scooping variable liquid quantities from the inner skin of the liquid ring; the scooped liquid is discharged into the subjacent sump 62.

Disposed within sump 62 is a liquid pump housing 64 attached to a rigid tube 66 that depends from the stationary structure 42 or 40; and rotary shaft extends vertically within tube 66. Impeller shaft 36 may be provided with a helical gear 67 that meshes with a similar gear 68 carried on the rotary shaft 70. The lower end of shaft 70 carries the pumping element (meshed gears or vaned rotor) disposed within pump housing 64. The pumping element is thus gear-driven by the impeller shaft 36 at a constant speed, or at whatever speed the shaft is operating. Pump 64 pumps oil from sump 62 through an external cooler 72 and back to a supply pipe 73 that extends through the wall of the tank. Pipe 73 distributes part of the oil to a pipe 75 which leads to the bearings for shaft 38. A second pipe 76 delivers oil to the aforementioned pipe 48 and another pipe 78; pipe 78 delivers lubricant to the bearings for shaft 36 in a somewhat similar fashion to pipe 75.

A typical fluid drive of about 4,000 hp. would require about 500 gallons of oil. Pump 64 would be pumping perhaps 300 gallons per minute, sufiicient to keep the oil from overheating due to the heat generated in work chamber 47. Usually the oil temperature should be kept below about F. The pump is therefore chosen on the basis of temperature and the cooling capacity of cooler 72(air or water-cooled). During operation the sump 62 oil level may vary between a high level designated by numeral 80, and a lower level designated by numeral 82. Some of the system oil is within work chamber 47 and scoop chamber 56, and some of the system oil is flowing through cooler 72. Pump 64 operates on a continuous basis.

FLUID DRIVE OPERATION The power transmitted from shaft 36 to shaft 38 is dependent on the quantity of oil in work chamber 48, and that quantity is determined by the radial thickness of the liquid ring in scoop chamber. Conventional scoop tube 59 is movable radially within the scoop chamber to control the liquid ring thickness and consequently the scoop chamber fill. Adjustment of the scoop tube therefore varies the power transmission and hence the speed of output shaft 38 from zero up to approximately the input shaft speed (less about 3 or 4 percent slip at maximum work chamber filling).

Full acceleration or deceleration of the output shaft (between zero and maximum speed) usually takes something on the order of 15 seconds because the pump is supplying oil to line 48 at nearly the same rate as oil is being removed by the scoop tube. Partial speed change is accomplished in a shorter time span, but for every speed change required there is some time interval between initial movement of the scoop tube and attainment of the desired speed. During this time interval the mass oil flow through scoop tube 59 varies according as it is moving into or out of the liquid ring. During deceleration periods the scoop tube is discharging increased oil quantities into the sump, thereby tending to raise the sump level; during acceleration periods the scoop tube is discharging lesser oil quantities into the sump, thereby tending to lower the sump level. In a typical fluid drive the combined liquid capacity of work chamber 47 and scoop chamber 56 might be about l30 gallons. Full speed change (between zero runner speed and maximum runner speed) might vary the sump 62 level 4 or more inches (depending on the capacity of chambers 47 and 56).

The exterior surfaces on impeller 32 and scoop chamber housing 54 are not perfectly smooth. For example, these members may have projecting bolt heads, ribs, etc. that interrupt the surface contours. Such surface interruptions tend to act as small fan blades and to produce a beating action of the tank air on the sump liquid. The result is a certain amount of foaming on the sump oil surface and the formation of a fine oil mist in the space above the oil surface. The extreme oil turbulence in chambers 47 and 56, together with high oil temperatures,

also cause some oil mist that escapes through the eye 57 of housing 54. Further mist apparently forms due to the splashing of liquid from scoop tube 59 into the sump liquid, and the escape of oil past the shaft bearings. The mist is objectionable in that it can under certain conditions escape through the shaft seals 35 and 37 or through other joints so as to pollute the surrounding atmosphere and form slippery unsafe films on walkways, etc. The sump foam is objectionable in that it interferes with proper mass flow through the oil system, and is not satisfactory for power transmission from the impeller to the runner.

Escape of oil mist from the tank is promoted by the fact that variation in sump 62 level tends to produce a breathing action of the tank with respect to the surrounding atmosphere. Thus, when the sump 62 level is rising the air-oil vapor atmosphere above the sump liquid tends to be exhausted or vented through any cracks or joints in the housing; when the sump 62 level is falling the various joints tend to draw ambient air into the tank. The sump oil tends to act as a giant piston for alternately exhausting oil mist and taking in fresh air, thus producing a net outflow of objectionable oil mist and an increased foaming on the sump oil surface.

The principle joints or escape paths occur between the two shafts 36 and 38 and their respective shaft seals 37 and 39. These shaft seals can be of any construction, as for example ring seals, labyrinth seals, or screw seals, or screw seals, but with known seal constructions there is usually some possibility of oil mist leakage from the tank interior to the ambient atmosphere. It is believed that oil mist can also penetrate the gasket 30 (FIG. 3) between the upper and lower tank sections; pressure differential between the atmosphere within and without the tank can promote a migration of minute oil droplets through the gasket to the surrounding ambient. At least some of the droplets are very minute, on the order of 1 micron or less.

THE INVENTlON The invention comprises a fan-filter unit connected to the tank for drawing oil mist from the tank interior and passing the mist through two filtering devices. These filtering devices remove the oil particles from the air being drawn out of the tank interior, and thus tend to reduce the quantity of oil mist in the upper portion of the tank. The fan-induced fiow also tends to set up a partial vacuum within the tank interior which opposes the outward breathing action that would otherwise take place; thus the slight negative pressure in the tank interior prevents the vapor from escaping through the shaft seals 35 and 37 so as to pollute the surrounding atmosphere and/or form slippery surfaces in surrounding areas. Such oil films have been found to contaminate nearby machinery such as the windings of electrical motors and have created nuisances making them slippery under foot and a fire hazard. By using the present invention it is believed that escape of oil mists from the fluid drive tank will be minimized or eliminated.

As shown in FIG. 2, the invention embodies an oil-filtering and coalescing device 84 within the tank, a fine mesh filter unit 86 outside the tank, and an interconnecting conduit 88 extending through the tank wall 18. Positioned above the filter device 86 is a small electric motor 90 which powers the bladed rotor wheel of a centrifugal fan 92. The fan action draws vapor from the tank interior through the coalescing 'device 84, conduit 88, fine mesh filter device 86 and conduit 138. Very fine oil particles are trapped in filter device 86; larger oil particles drain back into the sump 62 through a small drain line 89.

FILTER-COALESCER 84 FIG. 3 illustrates in somewhat greater detail the construction shown in outline in FIG. 2. As shown in FIG. 3, the combination filter-coalescing device 84 comprises a small housing having a bottom wall 93, a top wall 94, and an intervening porous cylinder or tube 95; a strap 91 is welded to wall 93 for reception of a hold-down bolt 87. Surrounding the cylinder 95 is a mass of porous material 96. This material may be formed of porous sintered metal as described for example in U.S. Pat. N0. 3,460,612 issued in the name of E. I. Valyi or U.S. Pat. NO. 3,439,739 issued in the name of U. R. .lacqer. Alternately the porous media can be formed by a strip of porous wire cloth or screen spirally wound on tube 95, as shown for example in U.S. Pat. No. 1,729,135 issued in the name of H. Slauson. The material can additionally take the form of steelwool or crinkled wire as described for example in U.S. Pat. No. 1,896,640 issued in the name of T. G. Moulding.

Preferably the porous media 96 has a pore size somewhat in excess of 1 micron. Small oil droplets are thereby enabled to pass through the media into the central space 97 within tube 95. During their passage through media 95 the small particles strike the cell walls thereby tending to decelerate. The nextfollowing oil particles impinge against the decelerating particles so that particles coalesce or agglomerate into oil films on the cell wall surfaces. Eventually some of the large droplets of oil tear away from the films and pass into the central space 97; some droplets pass back into the sump through drain holes 85.

CONDUIT 88 Entraining air and oil droplets flow downwardly through pipe section 98 into a horizontal pipe section 99, at which point some of the entrained oil droplets separate out of the stream by inertia separator action. Such separated droplets collect on the upper interior surface 100 of a plug 102, which threads into a pipe coupling 101. Eventually the droplets gravitate downwardly through a drain line 89 and into the subjacent sump 62, as better shown in FIG. 2. A second plug 103 may be provided to removably position the drain line in place, and to permit disassembly for cleaning.

Pipe section 99 is welded to a mounting plate 104 that is in turn welded to the tank wall 18. Plate 104 thus supports the pipe 99, pipe 98, and filter-coalescing device 84. Plate 104 releasably mounts an attachment plate 108 for a conduit 106 which is fixedly connected to the bottom wall 108 of a boxlike housing section 1 l0.

FILTER DEVICE 86 Housing section 110 includes a horizontal flat picture frame 1 12 having a diffuser plate 114 welded to its under face. Housing section 110 forms a plenum chamber 1 16 that reduces the linear velocity of the air-mist mixture that emerges from conduit 106. Diffuser plate 114 exerts a resistance on the individual streams flowing through the diffuser plate openings and thereby tends to equalize the vapor fiow from the plenum chamber into the sinuous filter media designated by numeral 118. The purpose in thus equalizing the flow is to allow the various surface areas of the media to each perform a filtering action without early plug-up of some media areas and without possible reentrainment of collected particles due to high localized supply pressures.

Filter media 1 18 is preferably a conventional filter material obtainable from American Air Filter Company of Louisville, Ky. under the trade name Astrocell. One suitable material is believed to be fine mesh woven fiber glass or gauze having a pore size less than 1 micron. The filter media is preferably disposed in a rectangular frame comprised of four vertical sidewalls120, constructed as shown for example in U.S. Pat.

No. 2,415,579 issued to V. Dahlman or U.S. Pat. No.

2,907,407 issued to P. Engle or U.S. Pat. No. 3,183,286 issued to J. Harms.

Frame 120 is removably disposed within a vertical housing 122 having four flat vertical sidewalls suitably welded together to form a vertical tube of rectangular cross section. The lower edges of the housing walls are welded to a horizontal frame 124 that mates with aforementioned frame 112 of housing suitable bolts 126 may be extended through the mating frame walls to secure housing 110 and 122 together. Filter frame is provided with gaskets 128 at its lower and upper edges for engagement with housing wall 112 and upper ledge wall 130. Thus, the gaskets 128 from bypassing filter media 118.

During passage through media 118 fine oil mist particles are captured by the media, while the cleaned air is drawn into an upper chamber 132 having an imperforate top wall 134 which mount conventional hub means, and is arranged within a scroll-shaped fan housing 92 so as to draw air from the U-tube 138. As shown in the drawing, the U-tube may be attached to the housing 122 through conventional bolt-flange mounting devices. Preferably the fan housing is provided with a removable face plate 140 on its inlet face to seal the fan housing and thus insure that the fan draws air only from chamber 132, not the surrounding atmosphere. The fan discharge is not shown in the drawing, but the direction of discharge is indicated by numeral 142. Fan housing 92 can be mounted in any suitable fashion; in the illustrated arrangement the left sidewall of housing 122 is extended vertically upwardly to form a mounting surface for the fan housing. The assembly comprising housing 120, motor 90, fan 92, and tube 138, may be supported by a bracket 139 welded to tank wall 18.

prevent the upflowing vapor GENERAL FILTER OPERATION Fan rotor 136 draws air from the fluid drive tank via a passage system that includes coalescing device 84, U-tube 88, and filter media 118. This action produces a slight negative pressure in the tank which prevents the tank vapor from being forced past the shaft seals 35 and 37 or other joints. The negative pressure also helps reduce oil foaming in the sump.

Device 84 functions to filter out very large solid particles and liquid droplets. Additionally the pores of device 84 act as fluid drag surfaces for changing the finer oil mist particles into oil films; oil droplets tear off these films but as relatively large size droplets which eventually drain into line 89.

Any fine droplets that escape the coalescing action in device 84 are trapped by media 118.

REMOVAL OF COALESCED DROPLETS Conduit sections 98 and 106 have appreciably smaller flow areas than the flow area through filtdr device 84 or filter device 118. The vapor stream therefore has a relatively slow velocity while passing through devices 84 and 118, and a relatively high velocity while passing through the U-shaped conduit 88. The high velocity in conduit 88 preferably provides sufficient turbulence to achieve some additional coalescing effect by impingement of droplets against one another.

Coalesced droplets produced in device 84 and/or the U- shaped conduit tend to impact against the walls of conduit sections 98, 99 and 106, especially at points where the stream changes direction. Such directional changes occur principally at the juncture between conduit sections 98 and 99, and the juncture between the horizontal portion of conduit section 106 and the upflow portion 106a. During each of these directional changes the relatively heavy oil droplets tend to maintain their original directions and to thus separate out of the turning air stream by inertial separator action. The upflow section 106a also tends to achieve some further droplet separation due to gravity effects.

Drain line 89 connects with the U-shaped conduit 88 at its lowest point. Therefore oil droplets impacting onto the conduit surfaces can gravitate into drain 89 and thence into sump 62. Preferably drain line 89 is a fairly small diameter line, as for example inch. With a small diameter line the stagnant liquid film lining the inner surface of the drain tube tends to exert surface tension on the central tube liquid in a manner resisting upward lift of liquid by the suction action of fan 92. The small diameter line also has a small volume of vapor therein so that the line does not contribute any appreciable numbers achieve l-year service life between each chan e of media 1 l8. REPLACEMENT 0F FILTER 56 The assembly comprising plenum housing and vapor supply conduit 106 is removably disposed between filter housing 122 and mount plate 104. The assembly can be removed by removing the various bolts 107 and 126. Thereafter the filter cartridge can be removed from housing 122 by lowering same through the housing lower end. A new filter cartridge can be installed by the reverse process.

1 claim:

1. In a fluid drive comprising a closed tank defining an oil sump; an impeller-runner assembly comprising confronting vaned impeller and runner shells disposed within the tank, an impeller shaft extending through one wall of the tank, and a runner shaft extending through another wall of the tank: the improvement comprising means for preventing oil mist from escaping from the tank into the surrounding space; said escape-prevention means comprising a filter unit connected to the tank, and fan means for moving oil mist from the tank interior through the filter unit; said filter unit comprising an oil coalescing device in the upstream portion of the unit, means for draining coalesced oil droplets into the oil sump, and a fine mesh filter device for trapping such fine mist droplets that pass through the coalescing device without undergoing coalescence.

2. The arrangement of claim 1 wherein the oil coalescing device and drain means are disposed within the tank, and the fine mesh filter device is disposed outside the tank.

3. The arrangement of claim 1 wherein the fine mesh filter device is an upflow unit whereby oil droplets can gravitate back toward the drain means without tending to plug the filter device.

4. The arrangement of claim 1 wherein the coalescing device and fine mesh filter device are interconnected by a conduit that has an appreciably smaller flow area than the flow area of either device, whereby the mist experiences increased turbulence while flowing through the conduit.

5. The arrangement of claim 4 wherein the interconnecting conduit includes a downflow section coming from the coalescing device and an upflow section leading to the fine mesh filter device.

6. The arrangement of claim 5 wherein the drain means comprises a drain line connected with the interconnecting conduit at a point between the downflow section and upflow section, whereby the drain line can receive oil droplets from both conduit sections.

7. The arrangement of claim 1 wherein the coalescing device and filter device are interconnected by a flow conduit having sufficient flow area to permit the fan to produce a partial vacuum within the closed tank; said drain means comprising a drain line extending downwardly from the conduit into the sump liquid, said drain line having a sufficiently small flow area that the fan is unable to produce any appreciable liquid lift action on the drain line liquid.

8. The arrangement of claim 1 wherein the fine mesh filter device comprises an upflow housing having an upper mediacontainment section, and a lower plenum-forming section; said lower housing section being detachable from the upper housing section to permit removal and replacement of the filter media.

9. The arrangement of claim 8 and further comprising a diffuser means arranged in the lower housing section to equalize vapor flow from the plenum chamber to different sections of the filter media.

Claims (9)

1. In a fluid drive comprising a closed tank defining an oil sump; an impeller-runner assembly comprising confronting vaned impeller and runner shells disposed within the tank, an impeller shaft extending through one wall of the tank, and a runner shaft extending through another wall of the tank: the improvement comprising means for preventing oil mist from escaping from the tank into the surrounding space; said escape-prevention means comprising a filter unit connected to the tank, and fan means for moving oil mist from the tank interior through the filter unit; said filter unit comprising an oil coalescing device in the upstream portion of the unit, means for draining coalesced oil droplets into the oil sump, and a fine mesh filter device for trapping such fine mist droplets that pass through the coalescing device without undergoing coalescence.

2. The arrangement of claim 1 wherein the oil coalescing device and drain means are disposed within the tank, and the fine mesh filter device is disposed outside the tank.

3. The arrangement of claim 1 wherein the fine mesh filter device is an upflow unit whereby oil droplets can gravitate back toward the drain means without tending to plug the filter device.

4. The arrangement of claim 1 wherein the coalescing device and fine mesh filter device are interconnected by a conduit that has an appreciably smaller flow area than the flow area of either device, whereby the mist experiences increased turbulence while flowing through the conduit.

5. The arrangement of claim 4 wherein the interconnecting conduit includes a downflow section coming from the coalescing device and an upflow section leading to the fine mesh filter device.

6. The arrangement Of claim 5 wherein the drain means comprises a drain line connected with the interconnecting conduit at a point between the downflow section and upflow section, whereby the drain line can receive oil droplets from both conduit sections.

7. The arrangement of claim 1 wherein the coalescing device and filter device are interconnected by a flow conduit having sufficient flow area to permit the fan to produce a partial vacuum within the closed tank; said drain means comprising a drain line extending downwardly from the conduit into the sump liquid, said drain line having a sufficiently small flow area that the fan is unable to produce any appreciable liquid lift action on the drain line liquid.

8. The arrangement of claim 1 wherein the fine mesh filter device comprises an upflow housing having an upper media-containment section, and a lower plenum-forming section; said lower housing section being detachable from the upper housing section to permit removal and replacement of the filter media.

9. The arrangement of claim 8 and further comprising a diffuser means arranged in the lower housing section to equalize vapor flow from the plenum chamber to different sections of the filter media.

Images