Abstract:
A lubricating oil change system for the roll wheel bearings of a coal pulverizer in which old lubricating oil is withdrawn from the bearings by a suction pump and new lubricating oil is introduced to the bearings by a second pump during continuous operation of the coal pulverizer. Alternatively, the lubricating oil may be withdrawn from the bearings and passed through a filter and then returned to the bearings.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to lubricant change systems and more particularly to a lubricant change system for the bearings of the mill roll wheels in a coal pulverizer.  
       BACKGROUND OF THE INVENTION  
       [0002]     Industrial coal pulverizers of the roll-and-race type typically have roll wheels which bear on a rotating track to grind and pulverize coal for use in the boilers of an electric power plant.  
         [0003]     However, the lubricant (oil) in the roll wheel bearings needs to be changed from time to time, usually at least once in every 3000-5000 hours of operation. At the present time, it is necessary to shut down the entire coal pulverizer to change the oil. The average down time for an oil change is 8-12 hours. Shutting down the pulverizer is very costly because there is a loss of approximately 50-100 megawatts of power for each hour that the pulverizer is down.  
       SUMMARY OF THE INVENTION  
       [0004]     In accordance with the present invention, it is not necessary to shut down the pulverizer for a change of lubricating oil. The lubricating oil in the wheel bearings can be changed while the pulverizer is running. To accomplish this, two conduits or pipes, preferably one within the other, are connected to the lubricating oil reservoir for the bearings of each roll wheel. When it is time for a change of lubricating oil, the used lubricating oil is withdrawn from the bearings through one pipe and, when most of the used lubricating oil has been withdrawn, fresh lubricating oil is introduced into the bearing through the other pipe. The pulverizer may continue to operate normally throughout the complete oil change.  
         [0005]     Alternatively, the used lubricating oil withdrawn through one pipe may be delivered to a filter where impurities are removed to restore the lubricating oil for reuse, and the restored lubricating oil is returned to the bearings through the other pipe. The filtration may continue through several cycles, continuously withdrawing the lubricating oil for filtering and routing the filtered lubricating oil back to the bearings. This alternative method can also be carried out while the pulverizer is running, requiring no shut down whatsoever.  
         [0006]     One object of this invention is to provide a lubricant change system for a coal pulverizer having the foregoing features and capabilities.  
         [0007]     Another object is to provide a lubricant change system which is rugged and durable in use, is composed of a relatively few simple parts, and is easy to operate and inexpensive to manufacture and install.  
         [0008]     Other objects, features and advantages will become apparent as the following description proceeds, especially when considered with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a sectional view of a coal pulverizer constructed in accordance with the invention.  
         [0010]      FIG. 2  is an enlarged sectional view with parts in section showing one of the mill roll wheels seen in  FIG. 1 ;  
         [0011]      FIG. 3  is a perspective view showing apparatus for use with the coal pulverizer of  FIG. 1  to change the lubricating oil in the bearings of the roll wheels;  
         [0012]      FIG. 4  is a perspective view similar to  FIG. 3  but showing an oil change apparatus of modified construction; 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     Referring now more particularly to the drawings and especially to  FIGS. 1-3 , a coal pulverizer  10  is shown, comprising a housing  12  forming a chamber  14  in which coal is pulverized for use in the boiler of an electric power plant. The housing has a burner line bonnet  16  at the top. A vertical coal downspout  18  extends through the top plate  20  of the bonnet. Raw coal admitted through the open upper end of the downspout is discharged onto a dome-shaped cover cone  22  of a yoke  24 .  
         [0014]     The yoke  24  has a lower extension  26  which extends down through a central opening  28  in the bottom of the housing  12  and is supported for rotation on a vertical axis coinciding with the vertical centerline of the housing. The yoke  24  is supported for rotation by bearings  30 .  
         [0015]     The yoke is rotated by a motor  32 . More specifically, the motor  32  has an output shaft extending into a gear box  34  and is geared to a vertical shaft. The shaft is secured to a plate  37  which is secured to the bottom of the yoke by fasteners  38 .  
         [0016]     The yoke has an annular ring  40  surrounding the cover cone  22 . Free turning roll wheels  42  engage the concave top surface  44  of the ring  40  to pulverize coal that has been dropped on the cover cone and diverted radially outwardly onto the ring  40 . The roll wheels are mounted for free rotation in journal housings  52  that are installed beneath a pressure frame  54 . The pressure frame  54  is mounted for vertical sliding movement by frame supports  56  secured to the housing and are pressed downwardly by compression springs  58  carried by a spring frame  60  suitably secured within the housing.  
         [0017]     Hot air enters the housing through an air inlet  62  and rises upwardly, following the path of the arrows. The rising air passes through the cone classifier  64  and out through burner lines  66  leading to a boiler burner deck. The flow of air carries with it the fine coal pulverized by the roll wheels. A seal air header  70  in the coal pulverizer housing directs seal air to the journal housings of the roll wheels.  
         [0018]     All of the roll wheels  42  are of the same construction shown in  FIG. 2 . As they are shown, the roll wheel  42  is mounted on a shaft  72  carried by one of the journal housings  52 . The roll wheel  42  is mounted on the shaft  72  for rotation by a bearing assembly  73  including two roller bearings  74  which encircle the shaft and are spaced apart by a spacer  76 . The bearing assembly  73  is axially positioned between a retainer plate  78  secured on the shaft  72  by fasteners  79  at one end of the bearing assembly, and a retainer ring  80  secured to the shaft  72  at the opposite end of the bearing assembly. A cap  82  is secured to the end of the shaft  72 . The cap  82  and ring  80  provide a closed reservoir  84  for lubricating oil which keeps the bearings lubricated.  
         [0019]     Extending through the shaft  72  and through the plate  78  is a relatively large diameter, tubular oil fill pipe  88  for introducing lubricating oil into the oil reservoir  84 . Extending lengthwise within the oil fill pipe  88  is a relatively small diameter, tubular oil suction pipe  90  for withdrawing lubricating oil from the oil reservoir  84 . The two pipes have pipe extensions  92  and  94  which extend outside the housing  12 . The pipe extension  92  has a shut-off valve  96  and a coupling  98 . The pipe extension  94  has a shut-off valve  100  and a coupling  102 . The pipes and pipe extensions form part of an oil change system which will now be described.  
         [0020]     Referring to  FIG. 3 , the oil change system comprises oil pumping apparatus including an oil pressure pump  104  and an oil suction pump  106 , both mounted on a wheeled cart  108 . A pipe  110  extends from the pressure pump  104  and is adapted to be attached to the pipe extension  92  by the coupling  98 . A pipe  112  extends from the suction pump  106  and is adapted to be attached to the pipe extension  94  by the coupling  102 . The pressure pump  104  draws lubricating oil from an oil can  114  through a conduit  116 . The suction pump  106  is connected to an oil collector  118  by a conduit  120 .  
         [0021]     In use, and when it is time for an oil change, the cart  108  is moved to a position adjacent to one of the roll wheels, the pipe  110  from the pressure pump  104  is attached to the pipe extension  92  by the coupling  98  and the pipe  112  from the suction pump  106  is attached to the pipe extension  94  by the coupling  102 . The shut-off valve  100  is opened. The suction pump  106  is then operated to withdraw old lubricating oil from the oil reservoir  84  through the pipe  90 , the pipe extension  94  and the pipe  112 , and discharge it into the oil collector  118 . After a portion of the old oil is withdrawn from the oil reservoir  84 , the shut-off valve  96  is opened. The pressure pump  104  is operated to withdraw new lubricating oil from the oil container  114  and deliver it to the oil reservoir  84  through the pipe  110 , the pipe extension  92  and the pipe  88 . At the same time the remaining old oil is withdrawn and an equal amount of new oil is added. After the oil reservoir  84  of one of the roll wheels is filled with new oil, the oil change is completed. The shut-off valves  96  and  100  are closed and the pipes  110  and  112  from the pumps are uncoupled from the pipe extensions  92  and  94 . The cart may then be moved to a position adjacent to another of the roll wheels where the oil change procedure can be repeated. The oil change is made quickly and with no shut down whatever of the coal pulverizer being required.  
         [0022]     Referring to  FIG. 4 , an oil change system of modified construction is shown. The oil change system in  FIG. 4  includes an oil pump  120  mounted on a wheeled cart  124 . A pipe  126  extends to the suction side pump  120  and is adapted to be attached to the pipe extension  94  by the coupling  102 . An oil filter  128  is mounted on the cart to filter and recondition used or old oil and make it like new. The oil filter  128  is connected to the pressure side of pump  120  by a conduit  130  providing an inlet connection to the filter. The filter  128  is connected to a pipe  132  which provides an outlet connection from the filter that is adapted to be connected to the pipe extension  92  by the coupling  98 .  
         [0023]     In use, and when it is time for an oil change, the cart  124  is moved to a position adjacent to one of the roll wheels, the pipe  126  to the pump  120  is attached to the pipe extension  94  by the coupling  102  and the pipe  132  from the oil filter  128  is attached to the pipe extension  92  by the coupling  98 . Both shut-off valves  96  and  100  are opened. The pump  120  is then operated. Old lubricating oil is withdrawn from the oil reservoir  84  through the pipe  90 , the pipe extension  94  and the pipe  126 , and pumped into the filter  128  by the pump  120 . Filtered lubricating oil is then passed through the filter  128  and delivered back to the oil reservoir  84  through the pipe  132 , the pipe extension  92  and the pipe  88 . The withdrawal of the old oil, filtering of the old oil and then returning it in a filtered condition to the oil reservoir  84  continues until it is determined that all of the old oil has been sufficiently filtered to remove impurities and restore it to a condition suitable for continued use. The withdrawing of the lubricating oil through the pipe  90 , the pipe extension  94  and the pipe  96  continues simultaneously with the returning of the filtered lubricating oil through the pipe  132 , the pipe extension  92  and the pipe  88 . Upon completion of the filtering process for one of the roll wheels, the shut-off valves  96  and  100  are closed, and the pipes  126  and  132  are uncoupled from the pipe extensions  92  and  94 . The cart may be moved to a position adjacent to another of the roll wheels where the oil filtering procedure can be repeated. The filtering of the oil is carried out quickly and requires no shut down of the coal pulverizer.