Dry sump lubrication system for centrifugal pumps
A lubrication system is provided for a centrifugal pump of the type having a bearing housing for maintaining the lubrication of a plurality of pump shaft rolling element bearings. The system includes a lubricant reservoir forming a volume, and having at least one supply port for supplying lubricant to the bearing housing, and at least one return port for returning lubricant to the lubricant reservoir. A lubricant recirculation pump has at least one supply stage and at least one suction stage. A connector is provided between the supply port of the reservoir and the suction stage of the lubricant recirculation pump for the supply of lubricant to the suction stage of the recirculation pump. A connector is also provided for interconnecting the supply stage of the lubricant recirculation pump to the bearing housing for the delivery of lubricant to the bearing housing. Lastly, a connector is provided for interconnecting the bearing housing and the at least one suction stage of the lubricant recirculation pump for the return of lubricant to the lubricant recirculation pump.
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The present invention relates to lubrication systems for centrifugal pumps, and particularly, to a pump-mounted dry sump lubrication system for centrifugal pumps.
BACKGROUND OF THE INVENTIONCentrifugal pumps, as the name implies, employ centrifugal force to lift liquids from a lower to a higher level or to produce a pressure. This type of pump, in its simplest form, comprises an impeller consisting of a connecting hub with a number of vanes and shrouds, rotating in a volute collector or casing. Liquid drawn into the center, or eye, of the impeller is picked up by the vanes and accelerated to a high velocity by rotation of the impeller. It is then discharged by centrifugal force into the casing and out the discharge branch of the casing. When liquid is forced away from the center of the impeller, a vacuum is created and more liquid flows into the center of the impeller. Consequently there is a flow through the pump. There are many forms of centrifugal pumps, including the type used to pass solid and liquid mixtures. These are known as slurry pumps.
Slurry pumps, like other centrifugal pumps, are driven by a shaft that is supported on rolling element bearings that are contained within a housing. Lubrication to the bearings is supplied from oil in a reservoir that is commonly integral to the bearing housing. For proper pump operation, the oil level in the reservoir should be maintained so that the rolling elements continuously run in an oil bath and carry lubricant/oil throughout the bearing surfaces.
Most pumps, including centrifugal slurry pumps are designed to operate on flat, level mounting pads or foundations. In some applications, however, the slurry pump may not be level and there may not be a convenient manner of keeping the pump level, such as might be the case on a marine vessel. As a result, sufficient lubrication of the bearings is not guaranteed. Prior art solutions to this lubrication problem have employed “pillow block” bearing housings which segregated the bearings into smaller distinct sections, each with an individual oil reservoir and bearing seals. This resulted, however, in smaller oil volumes, higher operating temperatures, and reduced oil life.
SUMMARY OF THE INVENTIONThe present invention is directed to a circulating lubrication system for centrifugal pumps of the type having a bearing housing, for maintaining the lubrication of a plurality of pump shaft rolling element bearings and that addresses the problems described above. More particularly, the lubrication system is designed to operate as a “dry” bearing housing sump. This means that substantially all of the lubricant is circulated continuously through the bearing housing so that at any point in time while the pump and system are operating, only a minimal volume of lubricant is in the bearing housing. As will be appreciated by those skilled in the art, removing excess oil volume from contact with the rolling element bearings has the effect of reducing parasitic losses, thus lowering bearing operating temperatures, while increasing operating efficiency of the pump.
Accordingly, one aspect of the present invention is directed to a circulating lubrication system that includes an external lubricant reservoir that is configured for mounting atop the bearing housing of the centrifugal pump. In that embodiment, the capacity of the external reservoir is sized such that the required maintenance change interval for the lubricant is increased by a factor of 10 or more. As will be appreciated by those skilled in the art, increased oil volume has the effect of reducing pump bearing assembly operating temperatures.
The external lubricant reservoir is used in combination with a multiple stage circulating pump, a supply manifold, lubricant return lines, and related controls. The multiple stage pump has a supply stage and two suction stages. The supply stage of the pump delivers clean, cooled, and filtered lubricant from a suction port on the external reservoir to the supply manifold. An internal baffle is provided within the external reservoir to separate the volume of the reservoir into lubricant return and lubricant supply compartments.
The supply manifold interconnects, through the bearing housing casing, to delivery ports proximate each of the pump shaft bearings, typically two or more. At least one return, or scavenge, line interconnects the bearing housing to the suction stage of the multiple stage circulating pump. Each of the return lines is dimensioned to return 100 percent of the required return flow back to the suction stage of the pump. Since, as described above, slurry pumps in particular are not always mounted or moved on a level surface, the bearing housing may be tilted along its primary axis such that a single return line might not be sufficient to remove all or even any of the lubricant flow from the bearing housing. Accordingly, in addition to each line being dimensioned to return 100 percent of the required flow, the return lines are spaced a sufficient distance apart to accommodate up to a 10 degree tilt along the primary axis of the pump shaft bearing housing, the lubrication system will continue to function fully.
During system operation of the pump and the dry sump lubricating system, a pressure balancing vent valve mounted atop the external lubricant reservoir creates an air flow from the air volume in the reservoir to the bearing housing. This balances the lubricant and air circulation through the system. Further, the external reservoir is so dimensioned that during normal system operation, a specified volume and level of lubricant are maintained relatively constant in the external reservoir. Should the system fail, for example by failure of the multiple stage lubricant pump, a check valve mounted interior to the external lubricant reservoir is positioned so that a failsafe gravity feed of about one gallon of lubricant per minute for about five minutes will drain from the reservoir and into the bearing housing. Thus necessary lubrication is ensured to the pump shaft rolling element bearings at all times that the centrifugal pump is running.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiments when considered in conjunction with the drawings. It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed.
The present invention is directed to a circulating lubrication (oil) system for centrifugal pumps that addresses the problems described above. More particularly, and with reference to
The pump shaft bearing housing 140 shown in
Referring now to
The external lubricant reservoir 140 of the exemplary embodiment of
As shown in
As shown in
As will be explained in greater detail below, and as shown in
Further, with respect to the reservoir 120, an oil level monitor 125 is mounted on the side of the external reservoir 120 proximate the scavenge hoses (described below) so that the oil level can be easily viewed from a safe distance. Further, the design and placement of the oil level monitor is such that it shows whether the oil level is correct during normal equipment operation as well as during shutdown. The location of the oil level monitor 125 reduces the problem of debris obscuring visibility so that an operator can obtain an accurate reading. The location of the monitor 125 also reduces the possibility of damage to the monitor from tools used in the routine maintenance of the bearing assembly 140.
Turning again to
The lubrication system 100 of the present invention includes the multiple-stage recirculation pump 150. The multiple-stage pump 150 comprises two suction stages 150a, 150b and one discharge, or supply, stage 150c. One suitable multiple-stage pump 150 is available from Viking Pumps of Cedar Falls, Iowa as Model No. GPV-0782-47. This model pump is double suction, single discharge gear pump.
Referring again to the Figures in general, and to the schematic of
Clean and cooled lubricant is drawn from the reservoir 120 via a supply port 157 through a hose 157a to the supply stage 150c of the pump 150. As shown in
The supply manifold 161 comprises three branches 161a, 161b, and 161c interconnected to the ports 141a, 142a, and 143a for the bearings 141, 142, and 143. To ensure an even distribution of lubricant to each of the bearings 141, 142, 143, an orifice (not shown) is provided at the terminal ends of each of the ports 141a, 142a, and 143a internal to the bearing housing 140. Each of the orifices has a diameter sized to provide the required individual flow rate to each of the respective bearings 141, 142, and 143. Simultaneously therewith, the pressure balance vent valve 123 directs a specified flow rate of air through line 123a to the bearing housing 140 via port 144c.
In one exemplary embodiment of the present invention, at the initial startup of the centrifugal pump 110, approximately five gallons of lubricant are held in the bearing housing 140. With startup of the pump 110 and of the multiple-stage recirculation pump 150, the two suction stages 150a, 150b of the recirculation pump 150 take oil from the scavenge ports 144a, 144b. As best seen in
Clean and cooled lubricant is drawn from the reservoir 120 via a supply port 157 through a hose 157a to the supply stage 150c of the pump 150. During normal operation, the suction rate to the suction stage 150c is about 8.0 gallons (30.3 liters) per minute. As shown in
The supply manifold 161 comprises three branches 161a, 161b, and 161c interconnected to the ports 141a, 142a, and 143a for the bearings 141, 142, and 143. To ensure an even distribution of lubricant to each of the bearings 141, 142, 143, an orifice (not shown) is provided at the terminal ends of each of the ports 141a, 142a, and 143a internal to the bearing housing 140. Each of the orifices has a diameter sized to provide the required individual flow rate to each of the respective bearings 141, 142, and 143. The flow rate to the three bearings 141, 142, 143 is approximately a combined 7.5 gallons (28.4 liters) per minute. Simultaneously therewith, the pressure balance vent valve 123 directs approximately 8.5 gallons (32.2 liters) per minute of air through line 123a to the bearing housing 140 via port 144c.
The foregoing describes the normal operational process and flow paths of the system 100 of the present invention. The following describes an operation of the system 100 during faulted or failed conditions is necessary. With reference to
This line 161 is sized such that the gravity feed to the bearing housing 140 is approximately one gallon (3.8 liters) per minute for a period of five minutes for a total of about five gallons (18.9 liters) of lubricant. The resulting volume of lubricant, in this embodiment, is sufficient to create a lubricant level in the bearing housing 140 such that the bearings 141, 142, 143 would receive sufficient “splash” lubrication to the running centrifugal pump. This failsafe provision will also activate during normal shutdown in order to provide a level of oil to the bearings for the next startup.
Further to the lubricant system 100 described herein, certain electric/electronic control and protection devices have been incorporated therein. For example, the oil filter 147 contains a switch contact (not shown) which activates in the event that the filter element becomes plugged and the flow is diverted through the bypass, thus triggering an alarm to notify the pump operator of the problem. This condition would cause the passive gravity feed provision to deliver flow to the bearing housing 140.
Although the present invention has been described with a preferred embodiment, it is to be understood that modifications and variations may be utilized without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims and their equivalents.
Claims
1. A lubrication system for a centrifugal pump of the type having a bearing housing for maintaining the lubrication of a plurality of pump shaft rolling element bearings, comprising:
- (a) a lubricant reservoir forming a volume, and having at least one supply port for supplying lubricant to the bearing housing, and at least one return port for returning lubricant to the lubricant reservoir;
- (b) a lubricant recirculation pump having at least one supply stage and at least one suction stage;
- (c) a connector between the supply port of the reservoir and the suction stage of the lubricant recirculation pump for the supply of lubricant to the suction stage of the recirculation pump;
- (d) a connector for interconnecting the supply stage of the lubricant recirculation pump to the bearing housing for the delivery of lubricant to the bearing housing; and
- (e) a connector for interconnecting the bearing housing and the at least one suction stage of the lubricant recirculation pump for the return of lubricant to the lubricant recirculation pump.
2. The lubrication system of claim 1 wherein the lubricant reservoir is configured for mounting above the bearing housing.
3. The lubrication system of claim 1 wherein the lubricant reservoir further comprises at least one internal baffle, the internal baffle separating the volume of the reservoir into lubricant supply and lubricant return portions.
4. The lubrication system of claim 1 wherein the external lubricant reservoir further comprises an auxiliary lubrication mechanism, the mechanism comprising:
- (a) a check valve mounted at a predetermined height within the reservoir;
- (b) a discharge port proximate the bottom of the reservoir; and
- (c) wherein the check valve is configured to permit a predetermined quantity of lubricate to flow through the discharge port to the bearing housing.
5. The lubrication system of claim 1 wherein the external lubricant reservoir further comprises a pressure balancing air vent valve proximate the top of the reservoir, the pressure balancing air vent valve configured for interconnection with the bearing housing.
6. The lubrication system of claim 1 further comprising a supply manifold through which the supply stage of the lubricant recirculation pump delivers lubricant to the bearing housing.
7. The lubrication system of claim 6 wherein the supply manifold comprises a plurality of discharge branches configured for interconnection with bearing housing proximate each of the plurality of pump shaft rolling element bearings.
8. The lubrication system of claim 1 further comprising a lubricant filter positioned upstream of the return port of the reservoir.
9. The lubrication system of claim 1 wherein:
- (a) the multiple stage pump comprises at least two suction stages; and
- (b) wherein a return line is configured to interconnect each of the at least two suction stages to the bearing housing for the return of lubricant from the bearing housing to the at least two suction stages.
10. The lubrication system of claim 9 wherein each of the return lines further interconnect to a scavenge hose, each scavenge hose configured to scavenge lubricant at spaced points within the bearing housing.
11. A centrifugal pump, comprising:
- (a) a pump shaft rotatably supported by a plurality of rolling element bearings;
- (b) a bearing housing for maintaining the lubrication of the plurality of pump shaft rolling element bearings;:
- (c) a lubrication system, comprising: (i) a lubricant reservoir forming a volume, at least one supply port for supplying lubricant to the bearing housing, and at least one return port for returning lubricant to the lubricant reservoir; (ii) a lubricant recirculation pump having at least one supply stage and at least one suction stage; (iii) a connection between the supply port of the reservoir and the suction stage of the lubricant recirculation pump for the supply of lubricant to the suction stage of the recirculation pump; (iv) a connection between the supply stage of the lubricant recirculation pump and the bearing housing for the delivery of lubricant to the bearing housing; and (v) a connection between the bearing housing and the at least one suction stage of the lubricant recirculation pump for the return of lubricant to the lubricant recirculation pump.
12. The lubrication system of claim 11 wherein the lubricant reservoir is configured for mounting above the bearing housing.
13. The pump of claim 12 wherein the lubricant reservoir further comprises at least one internal baffle, the internal baffle separating the volume of the reservoir into lubricant supply and lubricant return portions.
14. The pump of claim 12 wherein the external lubricant reservoir further comprises an auxiliary lubrication mechanism, the mechanism comprising:
- (a) a check valve mounted at a predetermined height within the reservoir;
- (b) a discharge port proximate the bottom of the reservoir; and
- (c) wherein the check valve is configured to permit a predetermined quantity of lubricate to flow through the discharge port to the bearing housing.
15. The pump of claim 12 wherein the external lubricant reservoir further comprises a pressure balancing air vent valve proximate the top of the reservoir, the pressure balancing air vent valve interconnected to the bearing housing.
16. The pump of claim 12 further comprising a supply manifold through which the supply stage of the lubricant recirculation pump delivers lubricant to the bearing housing.
17. The pump of claim 16 wherein the supply manifold comprises a plurality of discharge branches interconnected to the bearing housing proximate each of the plurality of pump shaft rolling element bearings.
18. The pump of claim 12 further comprising a lubricant filter positioned upstream of the return port of the reservoir.
19. The pump of claim 12 wherein:
- (a) the multiple stage pump comprises at least two suction stages; and
- (b) wherein a return line interconnects each of the at least two suction stages to the bearing housing for the return of lubricant from the bearing housing to the at least two suction stages.
20. The pump of claim 19 wherein each of the return lines further interconnect to a scavenge hose, each scavenge hose configured to scavenge lubricant at spaced points within the bearing housing.
Type: Application
Filed: Aug 16, 2006
Publication Date: Feb 21, 2008
Applicant:
Inventors: Robert J. Visintainer (Augusta, GA), Robert A. Courtwright (Evans, GA)
Application Number: 11/504,836
International Classification: F01M 5/00 (20060101);