Abstract:
A device and method for detecting bearing overheating in oil-lubricated turbine pumps comprising and temperature transmitting collar and infrared sensor. The temperature transmitting collar is mounted on the pump line shaft immediately adjacent to the stretch bearing, which is the top bearing in the pump system. The infrared sensor is positioned within sensing distance of the temperature transmitting collar and control circuitry is provided to warn of abnormal temperatures and to turn the pump off if temperatures continue to rise to an alarm condition.

Description:
This Non-Provisional Application claims the benefit of U.S. Provisional Application Ser. No. 60/124,598 filed on Mar. 16, 1999. The present invention relates to a device and method for detecting bearing overheating in oil-lubricated turbine pumps, such as the pump systems used to pump water and oil. The device and method of the present invention may also be applied to pumps generally referred to in the industry as centrifical pumps. 
    
    
     BACKGROUND 
     A serious problem associated with turbine pumps and their rotating parts is the overheating of the bearings in which the parts rotate. Bearing overheating can result from the interruption of the flow of lubricating oil due to particle contamination of the needle valve or ambient temperature change. 
     In a typical pump system, the lubricating oil is gravity fed from an oil container drum and regulated through a sight gauge by an adjustable needle valve to provide a flow of approximately 6 to 8 drops per minute for each 100 feet of pump length. It is delivered to the stretch bearing at the top of the well though a ¼″ copper tube and then through grooves cut in the line shaft bearings, which are spaced at five foot intervals, all the way down to the bottom of the well where the pump bowl is located. The needle valve regulator is sensitive to moisture, dust and various foreign particles, all of which are present in the atmosphere in certain environments, and all of which cause clogging in the needle valve. Oil flow interruption can also be caused by a drop in ambient temperature. As the ambient temperature declines, the viscosity of the lubricating oil flowing from the oil container drums increases. The colder the temperature becomes, the thicker the oil becomes, and the slower the oil flows through the needle valve. When the ambient temperature has declined sufficiently, the oil becomes so thick that it cannot pass through the needle valve and onto the pump line shaft and bearings. Oil flow to the line shaft and bearings can also be terminated by the pump operator&#39;s failure to keep a supply of oil in the oil reservoir. The consequent loss of oil flow causes increased friction which, in turn, permits the pump shaft and bearings to overheat. 
     After the lubricant flow interruption, temperatures in the line shaft may exceed the flash point of the oil used to lubricate the line shaft and bearings, causing residual oil in the shaft to vaporize. If the pump continues operation thereafter without lubrication, the bearing temperature will continue to rise, causing the bearings to experience massive wear very quickly and to flake off into the oil tube and onto the bearings below. Flaking of a bearing plugs up the oil transport groove in the bearing immediately below the flaking bearing, and, thereby, permanently stops oil flow to the bearings further down the line shaft, which results in pump shaft failure. 
     Pump shaft failure involves expensive repairs and loss of service while the well is down. In agriculture, crucial periods in crop growth require a constant supply of irrigation water; consequently, any significant loss of water supply at such times results in partial or complete crop failure. 
     Prior art patents offer some suggestions for dealing with the problem of bearing failure resulting from excessive temperature. Heckert (U.S. Pat. No. 2,089,369) described an overheated bearing and journal detection and identification system associated with wheel axles of railway cars. Heckert&#39;s heat detection system relied on the melting point of a fusible closure disk immediately associated with a journal box and bearing. 
     Others have resorted to the use of various temperature sensing means imbedded in the bearing itself, or, alternatively, in the bearing housing support to detect and monitor bearing temperatures (Waseleski et al., U.S. Pat. Nos. 3,824,579; Bergman et al. 4,074,574; Gustafson 3,052,123; Reumund 2,964,875). However, because bearings associated with turbine pumps are located within oil tube line shaft encasements surrounded by flowing fluid, such as water or oil, temperature sensors embedded in such bearings may be inaccurate and their temperature readings unreliable. Even the flow of fluid below the bearing affects the temperature perceived by a sensor embedded in the bearing. Sometimes a packing heats up instead of a bearing, but a sensor imbedded in the bearing is not sensitive to the packing temperature, and it is not practical to embed a sensor in the packing. 
     Devices and methods for detecting bearing overheating using infrared sensors have also been considered. Gallagher (U.S. Pat. No. 5,448,072) teaches a means of determining hot bearings and hot wheels of a train by monitoring the end caps of train wheels with an infrared scanner. Gallagher determined that the temperature of the end caps gives an accurate indication of the bearing temperature. Duhrkoop (U.S. Pat. No. 5,478,151) teaches a device for detecting overheated bearings in rail cars and other moving objects using an infrared beam detector and multiple lenses, each one of which is aimed at a different measuring point, and a scanning device which periodically picks up the measuring beams and focuses the beams onto the detector. The patents discussed above are directed toward overheating of bearings in railroad cars. 
     Because the bearings in a pump system are located either within the pump casing or within the oil tube, which descends deep into the ground, determining overheating in pump bearings presents unique problems. However, it has been discovered that the stretch bearing, which is located in the pump head and positioned on the pump line shaft above the level of fluid flow through the pump column and discharge head, overheats and fails first. 
     Senior, Jr. et al (U.S. Pat. No. 5,145,322) teaches a device and method for detecting overheating in deep well water pump bearings by placing a temperature probe in a bore drilled in the stretch bearing and opening into an air space communicating between the oil inlet chamber below the dust seal packing and the oil tube space. Although Senior teaches an effective means of detecting bearing overheating, it requires retrofitting an existing pump to accommodate the device. Retrofitting an existing pump requires partially disassembling the pump, which further requires machinery and man power. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to overcome the problems of the prior art and provide an inexpensive, accurate method of early detection and system shutdown in the presence of abnormal temperatures before bearing damage or pump failure occurs, saving costly repair bills and preventing loss due to water supply interruption. 
     The device of this invention may be retrofitted to an existing pump or incorporated into original equipment manufacture; 
     The device of this invention may be adapted to remote audio or visual warning; 
     Other objects and features of this invention will become apparent hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevation view of a turbine pump, partially broken away to show interior details. 
     FIG. 2 is a perspective view of the stretch plate and stretch bearing showing the temperature transmitting collar and infrared sensor mounted thereon. 
     FIG. 3 is a circuit diagram of a control circuit used with the detection device of FIGS. 1 and 2. 
     FIG. 4 is a sectional view showing the pump bowl assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, a typical turbine pump system  10  includes pump column  20 , pump head  5 , oil tube  30 , line shaft  40 , and line shaft bearings  50 . Pump column  20  carries fluid from the water or fluid supply. The fluid is then discharged from the pump system through discharge head  21 , which is mounted on pump column  20 . Fluid-tight oil tube  30  is centered within column  20  and pump line shaft  40  is centered within oil tube  30 . Line shaft  40  turns within line shaft bearings  50 , which are conventionally located at five foot intervals along line shaft  40  to the bottom of the well where the pump bowl  100  is located. Stretch assembly  63  is positioned on the top of oil tube  30  in pump head  5 . Stretch assembly  63  includes stretch plate  60  and stretch bearing  61 . Stretch bearing  61  is positioned on stretch plate  60  such that wider head portion  61 A of stretch bearing  61  rests on top of stretch plate  60  while cylindrical body portion  61 B of stretch bearing  61  extends downward through a central opening in stretch plate  60 . Body portion  61 B is threadedly engaged with oil tube  30  such that oil tube  30  is pulled taunt as stretch bearing  61  is turned into engagement with the oil tube. Line shaft  40  extends from the bowl assembly, through stretch plate  60  and stretch bearing  61 , and into the pump motor  72 . 
     A lubricating oil is gravity fed from an oil delivery reservoir  71  serving the well vertical turbine pump system  10 , and regulated through a sight gage  74  by an adjustable needle valve oil regulator  73  providing an oil flow measured in drops per minute, oil is delivered through tube  75  passing through stretch bearing  61  of the pump line shaft  40 . The oil then seeps through grooves cut in line shaft bearings  50 , which are conventionally spaced at five foot intervals along the pump line shaft  40 , to the bottom of the well where the pump bowl is located. 
     Because stretch bearing  61  is positioned on line shaft  40  above the level of fluid flow through pump column  20  and discharge head  21 , it is not cooled by the flowing fluid. Consequently, when oil delivery is interrupted, stretch bearing  61  overheats first, and, therefore, fails first. It has been discovered that a temperature sensing means placed on line shaft  40  directly above stretch bearing  61  can be used to monitor the temperature of bearing  61  and thereby detect imminent failure due to overheating of bearing  61  which precedes failure of the remaining line shaft bearings  50 . 
     As shown best in FIG. 2, the temperature sensing means of the present invention includes temperature transmitting collar  81  and infrared sensor  82 . Collar  81  comprises two releasably joined parts. Because of its two part construction, collar  81  may be easily mounted to the line shaft of an existing pump system. In the preferred embodiment, collar  81  is made of carbon steel with a baked black oxide finish. The top portion  81 A of collar  81  is thicker than the bottom portion  81 B of the collar. Thicker portion  81 A facilitates attachment of the two halves of the collar by means such as allen screws and is preferably made to approximately ½ inch thickness. Thinner portion  81 B, which is preferably about 125 thousandths of an inch thick, facilitates the communication of heat from line shaft  40  through collar  81  and to sensor  82 . 
     Collar  81  is mounted on line shaft  40  immediately adjacent to stretch bearing  61  such that a space of approximately 20 thousandths of an inch is left between stretch bearing  61  and collar  81 . Collar  81  should be mounted to line shaft  40  prior to lateral adjustment of the line shaft and its connected bowl assembly  100 , shown best in FIG.  4 . Lateral adjustment of the line shaft and bowl assembly is necessary to keep impellers  101  of bowl assembly  100  from dragging and rubbing against the pump column  20  at points  22 . The space between collar  81  and stretch bearing  61  should be about 20 thousandths of an inch before lateral adjustment of the line shaft. After lateral adjustment of the line shaft, the space between collar  81  and stretch bearing  61  should be no more than 1 inch. Collar  81  should never touch stretch bearing  61 . 
     In an alternative embodiment of the invention, a temperature transmitting coating is applied directly to shaft  40  at about 20 thousandths of an inch above stretch bearing  61 . When a temperature transmitting coating is applied, it is preferred that a black oxide coating be used. 
     Sensor  82  is held in place by bracket  90 . As shown in FIG. 2, cap screws  65  are located about the circumference of stretch plate  60 . Bracket  90  is held in place on stretch plate  90  by one of cap screws  65 . Bracket  90  functions to hold sensor  82  at the height of thinner portion  81 B of collar  81 . In order to accurately sense the temperature being transmitted by collar  81 , sensor  82  should be no further than ½ of an inch away from thinner portion  81 B of collar  81 . 
     FIG. 3 is a schematic circuit diagram of the control circuitry which is operated in conjunction with the sensor  82  of FIGS. 1 and 2. As indicated in FIG. 3, alternating current power source  120 , which may be of any conventional type, supplies operating power to the pump motor  72  and other components of the system. Prior to operation of the system, a momentary push-button reset switch  128  typically is depressed to close three sets of normally open contacts  128 A,  128 B, and  128 D and to open one set of normally closed contacts  128 C. Closure of the contact  128 A,  128 B, and  128 D supplies operating power from the source  120  through three indicator light bulbs  122 ,  124 , and  126  to operate those bulbs. Operation of the switch  128  is made prior to turning on the pump to ensure that the bulbs  122 ,  124 , and  126  are operable. If operation of switch  128  does not cause illumination of one or more of the bulbs  122 ,  124 , or  126 , replacement is made. 
     Following a successful test of the operation of the indicator bulbs  122 ,  124  and  126 , the push-button switch  128  is released; and the switch contact pairs  128 A,  128 B, and  128 D and  128 C assume the positions shown in the drawing. The system then is ready for normal operation. 
     To initiate operation by turning on the pump motor  72 , an on/off switch  130  is closed. This applies operating power across the switch  130  and the normally closed contact  140 A of a relay operated switch to the pump motor  72 , which commences operation in its normal fashion. At the same time, it can be seen that the indicator light  122  is illuminated, showing that the pump is in operation. Under normal conditions of operation, the status of the circuit and the various switches which are shown is as shown in FIG. 3, with the exception of the pump operating switch  130 , which is closed, as described above. The pump motor  72  then rotates the shaft  40  in the manner described previously, and the infrared sensor  82  supplies a continuous indication of the temperature of the shaft  40  to a temperature processor  134 . As long as the shaft temperature remains in a normal range, nothing more happens to change the status of the circuit shown in FIG.  3 . 
     If the temperature of the shaft  40 , as indicated by the infrared sensor  82 , increases to a level which is considered an early warning temperature of a possible malfunction, the signal from the sensor  82  is processed by the temperature processor  134  to cause closure of a switch  136 , as indicated by the connections from the switch  136  to the processor  134 . The manner in which the switch  136  is actually operated may be any one of a number of conventional operations, including electromechanical or fully electronic operation. The dot-dash line from the switch  136  to the processor  134 , however, indicates the operating connection from the processor  134  to the switch  136 . When the switch  136  is closed, the “high temperature” indicator  124  is illuminated. This places the operator of the system observing this light on notice that a malfunction may be about to occur. Corrective steps can be taken to ensure the oil flow and other operating conditions are corrected, if there is some problem with the oil supply. Once the situation is corrected, the infrared sensor  82  provides a lower temperature indication to the processor  134 , which then effects opening of the switch  136 . This then causes the light  124  to be turned off or extinguished, since the push-button contact pair  128 B also is open during normal operation of the system. 
     In the event, however, that the temperature sensed by sensor  82  continues to rise to an alarm condition, the processor  134  additionally operates another normally open switch  138  to close that switch. As can be seen from the circuit of FIG. 3, this applies operating power through an alternating current relay, diagrammatically depicted as a coil  140 , to energize the relay  140 . This causes operation of switches  140 B,  140 B, and  140 C. As shown in FIG. 3, the normally closed switch  140 A is opened when the relay coil  140  is activated. This immediately breaks the operating circuit for the pump motor  72 , turning off the pump. This also extinguishes the “power on” light  122 . At the same time, closure of the normally open contact  140 B causes a holding current to be applied through the relay coil  140  by way of the normally closed reset switch pair  128  and the now-closed contact  140 B. As a result, the relay  140  remains operated until the reset push-button  128  once again is momentarily operated. When the relay coil  140  is energized, it also closes a normally open switch  140 C to illuminate the alarm temperature light  126 . When the system is in this condition of operation, both the high temperature light  124  and the alarm temperature light  126  are illuminated. Consequently, a clear indication is provided to an operator observing a control panel, on which the lights  122 ,  124  and  126  are placed, that remedial action needs to be taken. 
     After appropriate remedial action has been taken, momentary closure of the reset push-button switch  128  causes an opening of the holding circuit contacts  128 C to break the power supply to the relay coil  140 . When this occurs, the contacts  140 A.  140 B and  140 C return to the position shown in FIG. 3, and the alarm system has been reset. Release of the push-button switch  128  then causes all of the contacts to assume the position shown in FIG.  3 , and the system is ready for normal operation in accordance with the procedure described above. 
     The temperature transmitting collar, infrared sensor and control circuitry described above can also be used to detect bearing overheating in product lubricated pump systems. In product lubricated pump systems, over-tightening of the packing glands in the stuffing box or mechanical seal can create too much compression about the line shaft, which causes excessive heat to be generated as the line shaft turns. Heat created by this excessive friction melts the lubricant in the stuffing box or the O-rings of the mechanical seal, resulting in failure of the stuffing box or mechanical seal. In product lubricated pump systems, the temperature transmitting collar is positioned between the stuffing box or mechanical seal and the pump motor. The temperature transmitting collar should be mounted on the line shaft immediately adjacent to the stuffing box or mechanical seal. Alternatively, a temperature transmitting coating such as black oxide can be applied directly to the line shaft immediately adjacent to the stuffing box or mechanical seal. As described above, an infrared sensor is then positioned within sensing range of the collar or coating.