CA1038358A - Protective device for a roller type pulverizer - Google Patents
Protective device for a roller type pulverizerInfo
- Publication number
- CA1038358A CA1038358A CA206,852A CA206852A CA1038358A CA 1038358 A CA1038358 A CA 1038358A CA 206852 A CA206852 A CA 206852A CA 1038358 A CA1038358 A CA 1038358A
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- Canada
- Prior art keywords
- oil
- mill
- temperature
- level
- roller
- Prior art date
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Abstract
PROTECTIVE DEVICE FOR A ROLLER TYPE PULVERIZER
Abstract An arrangement for detecting changes in the opera-tion of individual crushing rollers in a pulverizing mill.
Changes in the lubricating oil temperature and level in each roller are indicated for comparison purposes so that the operator can stop and restart the pulverizing mill motor to thereby eject obstructions in the path of the rollers.
Abstract An arrangement for detecting changes in the opera-tion of individual crushing rollers in a pulverizing mill.
Changes in the lubricating oil temperature and level in each roller are indicated for comparison purposes so that the operator can stop and restart the pulverizing mill motor to thereby eject obstructions in the path of the rollers.
Description
Case 4018 BACKGROUND OF THE INVENTION
The invention pertains to a method and apparatus for protecting a mill consisting of a horizontally revolving pul-verizing bowl and stationary crushing rollers that are posi-tioned for rolling upon a race on the bowl, in which the crush-ing rollers are attached each to a shaft through an oil lub-ricated bearing, said rollers thus transferring the crushing pressure to the pulverizing race.
In this type of mill, sometimes a single lump of es-pecially hard consistency or of foreign material is not rolledover and crushed to pieces, but acts like a drag shoe to block the crushing roller. The blocked roller, instead of grinding, pushes the softer grinding material to the sides in a snow-plow fashion and slides over the bare race. There is no noticeable change in power consumption. This may last until the lump wears off by attrition, or until the foreign material falls ;~ aside. During that time a flat spot is worn on the circumfer-ence of the roller due to sliding, which further favors the blocking of the roller at the same position. This leads to enlargement of the flat spot. The larger the flat spot the greater is the danger that the crushing roller will block at the same position due to minor causes, such as a change in hardness of the feed material, reduction in grinding pressure or damage to the bearing. This has the disadvantage that a continuation of the operation reduces the grinding yield and leads, through the rapid wear, to the failure of the mill which results in costly outages and expensive repair work.
It is customary to monitor bearings during operation in order to detect early any irregularities in the pressure of the lubricating oil, or in the oil level and oil temperature in immersion lubrication. A drop in oil level means a loss of Case L~018 oil and an excessive rise in the oil temperature is an indica-tion of lubrication deficiency. An increase in the temperature of the bearing is a warning of an eminent bearing failure.
Methods for remote monitoring and control of the tem-perature and of the liquid level of liquids are well known.
However, the continuous surveillance of the oil temperature and/or oil level during operation in the bearings of crushing rollers as in the previously described mill has not been known.
SUMMARY OF THE INVENTION
The purpose of this invention is to substantially elimi-nate the generation of flat spots on the circumference of the crushing rollers. A solution to this problem is, according to this invention, that during the normal operation of the mill the oil temperature and oil level in the immersion lubricated bearings of the crushing rollers are monitored by remote in-dicators. The mill is stopped and re-started when, during the mill operation, the oil temperature in one of the bearings drops a certain amount and/or the oil level increases by a cer-tain amount.
The normal start-up and shut-down switch is used to accomplish the proposed protection method. In addition, a number of electro-sensors are used that are shrouded in metal sheaths. Also a number of electronic transmitters and remote indicators are used, which react to temperature differences of the sensors or to change of electrical capacitance in them.
These devices can eventually be connected to alarm devices.
According to a feature of the invention, apertures are formed or drilled in each of the roller shafts, in which are located temperature sensors connected to a remote indicator, so that the sensors reac~ into the oil sump of the bearing.
The metal sheath of the temperature sensor is electrically Case 4018 ~ ~038358 lnsulated from the walls of the aperture and together with them provides two opposing surfaces of a condenser with an annular space between them, into which the oil from the sump enters r from the bottom up to the oil level. The metal sheath is con-nected to a remote indicator which is sensitive to changes in electrical capacitance.
The temperature sensor responds, through heat transfer, to the temperature of the oil and through an electronic remote transmission may be made visible on an electronic instrument.
The capacitance of the condenser formed by the metal sheath and the surface of the aperture of opening changes depending on the oil level in the annulus of the condenser, because of the effect of the dielectric coefficient of the oil itself.
The dielectric coefficient of the lubricating oil nearly doubles the capacitance of such a condenser. The change in oil level thus causes a change in capacitance. The level of the oil is then made visible on an electronic instrument through the re-mote transmission of the change in the capacitance.
Through the unique arrangement of the sensors in the openings or apertures of the roller sha~ts, a way is provided in the mill to remotely monitor simultaneously both the tem-perature and the oil level in the sump of the immersion bear-ing of each crushing roller.
In operating immersion bearings, in which there is an oil film between the gliding and rolling surfaces, the oil temperature always ad~usts itself to a point above the tem-perature of the surroundings, because of fluid friction. When a bearing stops operating due to a blocked roller, the oil friction also stops, and the oil temperature in the sump of the splash bearing drops in a short time due to heat exchange.
The temperature drop indicates that the roller is blocked.
During the start-up of the mill a part of the oil is Case 401~
removed from the sump to lubricate the bearing~ so the oil level drops. When a roller is blocked the entire oil collects in the sump and the oil level rises.
If during the normal operation of the mill there is a temperature drop and/or an oil level increase in the sump of a bearing of a crushing roller, this provides a warning for the operator that the crushing roll is blocked and that the mill should be stopped and re-started before a larger flat spot will be ground on the circumference of the tire.
At the instant of stopping, the tire rolls back a bit on the race from the especially hard lump or from the foreign material. This results in the grinding bowl being slightly turned back, so that the lump becomes free and during the sub-sequent start-up is shoved away or is popped off the raceway by the roller. As a precaution to insure that a previously blocked roller actually became free, or if not, to be ready to shut-down the mill again and re-start, the operator should preferably observe the behaviour of the oil levels, because they react during start-up much faster than the oil temperatures.
When it ls observed that the oil level in one of the oil sumps does not drop~ this means that the corresponding crushing rol-ler is blocked and that the mill should be stopped again and re-started to remove the danger.
In order to recognize more easily a temperature drop of the oil in any of the crushing rollers it is advantageous to compare continuously the oil temperatures o~ the three bearings. The measured oil temperature o~ a blocked roller indicates its actual oil temperature and the other oil tem-peratures indicate how high the oil temperature of the blocked roller would be if it would operate properly. The comparison permits an easy recognition of the temperature drop.
The advantages achieved by the invention are that - Case 4018 1038358 ~
through continuous monitoring of the oil levels and of the oil temperatures, an early warning of imminent damage to bearings is obtained. Further, it permits a considerable reduction in the grinding of flat spots on the circumference of the tires, through which an improvement in mill availability is achieved, because of avoidance of excessive wear, costly shut-downs and maintenance work.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a cross section of a part of a crushing roller mill;
Fig. 2 shows a diagram for monitoring the oil levels and the oil temperatures of the crushing roller bearings; and Figs. 3 and 4 show plan and elevation views respectively of a pulverizing mill in which the invention is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Of the three non-orbiting crushing rollers Al, A2, A3 of a pulverizer shown in Figs. 3 and 4 only roller A2 is shown in Fig. 1.
The crushing rollers are stationary relative to the pulverizer housing and roll on a ring shaped grinding race or strip of a hori-zontally rotating bowl or plate 2 which is driven by a motor 3 (shown schematically only) through a gear 4. The switch 5 represents the normal device used for start-up and shut-down of the mill.
The crushing rollers Al and A3 are attached in a similar manner as is crushing roller A2 to a shaft 7 through a combination of roller bearings 6 as shown in Fig. 1. The hub 21 of the roller, together with a bearing cover 22, enclose the roller bearing 6 and the shaft 7 to form a tight enclosure that is filled with a mineral or other lubricating oil to a level B2. The oil collects in the sump D2 of a splash lubrication system in which the bearing rollers repeatedly immerse during the rotation of the crushing _5_ ~ .
Case 4018 1038i~58 rollers. This way a part of the oil is carried out of the sump by the bearing rollers and the oil level drops to a level B2, but rises again to the original level B2 when the rotation stops because no oil is carried out and all the oil collects again in the sump D2.
Furthermore, during the rotation of the crushing roller? heat that is generated by the fluid friction of the lubricating oil is added to the oil fill. T~s heat is trans-ferred to the shaft and to the housing through a temperature gradient. Therefore, the oil temperature may rise above the temperatures of the shaft 7 and housing 23, but drops again ; by a certain amount when the rotation is stopped because the heat generation ceases and the heat transfer to the shaft and housing continues until the temperature of the oil equals that of the shaft end housing 23 When a crushing roller blocks, the rotation of the roller stops and the temperature of the oil drops by a cer-tain amount and also the oil level rises from B~ to the original level B2.
When the crushing roller rotates, but an irregular-ity develops in the bearing, then the oil temperature rises too high and if the lubrication fails or an oil loss occurs, the oil level will fall below B2.
~ A temperature sensor 8 is provided to measure the oil temperature. The sensor is shrouded with a metal sheath 9 and reaches into the sump D2. me temperature sensor 8 is connected through electrical leads with a measuring de-vice 10 and an indicating instrument E2 to indicate the oil temperature. The metal sheath 9 serves to measure the oil level. It is connected by electrical leads with a trans-mitter ll and an indicator F2.
.~.
~ Case 4018 103835~
To perform the remote transmission of the oil level indications B2 or B2 the metal sheath 9 is so arranged in the aperture or opening 12 of the shaft 7, that it is elec-trically insulated and forms, together with the surface of the aperture or drilling, two oppositely located condenser surfaces An annular space 13 is defined between these surfaces, in which the oil contained in the sump D2 pene-trates from the bottom to a height of the oil level B2.
Above the oil level B2 the aperture or drilling 12 is pro-vided with a perpendicularly drilled hole 12' for pressureequalization within the roller bearing space. Oil is con-tained in the section 14 of the space of the condenser an-nulus 13, so that the capacitance of that part of the con-denser is about doubled due to the dielectric coefficient of the mineral oil. When the oil level drops to the B2 height some of the oil flows out of the annulus 13 and the capaci-tance of the condenser changes. This change of the capaci-tance is utilized for the remote transmission of the oil levels B2 or B2. A transmitter ll sensitive to changes of capacitance is used, therefore, for remote indication of the oil level.
Each crushing roller Al, A2 and A3 has a temperature sensor 8 with a metal sheath 9 arranged the same way in rela-~ tion to the apertures or drillings 12 and 12', as shownschematically on Fig. 2. Reslstance thermometers are provided for the measurement of the oil temperature, with the tempera-ture sensor 8 used as part of a Wheatstone bridge 10 and the instruments El~ E2 or E3 measuring the corresponding current in the bridge for each of the rollers Al, A2 and A3; respec-tively.
m e transmitter ll which reacts to changes of capaci-Case 4018 tance consists of a high frequency generator 15 with an oscil-lating circuit composed of an inductance 26 and a capacitance 27, which is excited by a transistor 28 connected across the capacitance. The condenser formed by the metal sheath 9 and the drilling 12 is part of the oscillating circuit. mus the frequency of oscillation is changed wnen the capacitance changes due to variation of the oil level from B2 to B2, or the reverse. m e frequency of the high frequency generator 15 is tuned by a Wien-Robinson bridge circuit 16, consisting of resistors and capacitances which are tuned to the high frequency generator 15, so that with a change in the frequency of oscillation in the bridge a change occurs in the electrical potential. This electrical potential, upon amplification by a transistor 31, controls a direct current circuit wnich de-livers the measurement signal to the indicating instrument F2 The indicating instrument F2 s'nows for example that the oil level has risen from B2 to B2 The continuous supervision of the operation of the bearings is achieved through observation of the indicating instruments El, E2 and E3, which can also be coupled with alarms or other annunciating devices to make sure that the oil temperatures in the sumps Dl, D2 and D3 are not, compara-tively, too hot or too cold Furthermore, attention must be given to the indicating instruments Fl, F2 and F3 to make sure that the oil levels Bl, B2 and B3 do not drop too much due to loss of oil If an observation is made on one of the instruments El, E2 or E3/ for example on the instrument E2, that the oil temperature in sump D2 dropped in comparison to the indica-tions on the instruments El and E3, this does not mean thatthe running conditions of the bearing have impro~ed, but that - Case 4018 the crushing roller A2 is blocked. In that case the indication of the instrument F2 does not mean that the oil in the sump D2 was replenished, but that the rise of the oil level from B2 to B2 indicates also that the crushing roller A2 is blocked.
me roller pushes the unground material from the race 1 (see Fig. 1) and glides on a bare race, so that the race wears off and a flat spot G2 (Fig. 1) starts to appear on the circum-ference of the crushing roller A2. Such occurrence is detri-mental and an increase in the size or num~er of flat spots G2 can be avoided by stopping the mill and starting again.
When, during normal operation of the mill one of the indicating instruments, for example E2, indicates directly or through a warning signal that the oil temperature is dropping and/or if it is determined through a direct reading of the in-strument F2 or through a warning signal that the oil level rises from B~ to B2, then for the safety of the mill it is best to stop the mill by actuating the switch 5 (Fig. 1) and to re-start it a~ain using the switch 5. m rough this action, the especially hard lump or the foreign material that had blocked the crushing roller is shoved aside or pops off the grinding race.
During the re-start care must be taken to ascertain that the indicating instrument F2 shows a drop of the oil -level from B2 to B2 in order to be sure that bearing damage does not prevent the rotation of the crushing roller. The same safety procedure is performed when any of the other crushing rollers Al or A3 are blocked.
While there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of Case 4018 ' ~0383S~
the invention may sometimes be used to advantage without a corresponding use of the other features.
The invention pertains to a method and apparatus for protecting a mill consisting of a horizontally revolving pul-verizing bowl and stationary crushing rollers that are posi-tioned for rolling upon a race on the bowl, in which the crush-ing rollers are attached each to a shaft through an oil lub-ricated bearing, said rollers thus transferring the crushing pressure to the pulverizing race.
In this type of mill, sometimes a single lump of es-pecially hard consistency or of foreign material is not rolledover and crushed to pieces, but acts like a drag shoe to block the crushing roller. The blocked roller, instead of grinding, pushes the softer grinding material to the sides in a snow-plow fashion and slides over the bare race. There is no noticeable change in power consumption. This may last until the lump wears off by attrition, or until the foreign material falls ;~ aside. During that time a flat spot is worn on the circumfer-ence of the roller due to sliding, which further favors the blocking of the roller at the same position. This leads to enlargement of the flat spot. The larger the flat spot the greater is the danger that the crushing roller will block at the same position due to minor causes, such as a change in hardness of the feed material, reduction in grinding pressure or damage to the bearing. This has the disadvantage that a continuation of the operation reduces the grinding yield and leads, through the rapid wear, to the failure of the mill which results in costly outages and expensive repair work.
It is customary to monitor bearings during operation in order to detect early any irregularities in the pressure of the lubricating oil, or in the oil level and oil temperature in immersion lubrication. A drop in oil level means a loss of Case L~018 oil and an excessive rise in the oil temperature is an indica-tion of lubrication deficiency. An increase in the temperature of the bearing is a warning of an eminent bearing failure.
Methods for remote monitoring and control of the tem-perature and of the liquid level of liquids are well known.
However, the continuous surveillance of the oil temperature and/or oil level during operation in the bearings of crushing rollers as in the previously described mill has not been known.
SUMMARY OF THE INVENTION
The purpose of this invention is to substantially elimi-nate the generation of flat spots on the circumference of the crushing rollers. A solution to this problem is, according to this invention, that during the normal operation of the mill the oil temperature and oil level in the immersion lubricated bearings of the crushing rollers are monitored by remote in-dicators. The mill is stopped and re-started when, during the mill operation, the oil temperature in one of the bearings drops a certain amount and/or the oil level increases by a cer-tain amount.
The normal start-up and shut-down switch is used to accomplish the proposed protection method. In addition, a number of electro-sensors are used that are shrouded in metal sheaths. Also a number of electronic transmitters and remote indicators are used, which react to temperature differences of the sensors or to change of electrical capacitance in them.
These devices can eventually be connected to alarm devices.
According to a feature of the invention, apertures are formed or drilled in each of the roller shafts, in which are located temperature sensors connected to a remote indicator, so that the sensors reac~ into the oil sump of the bearing.
The metal sheath of the temperature sensor is electrically Case 4018 ~ ~038358 lnsulated from the walls of the aperture and together with them provides two opposing surfaces of a condenser with an annular space between them, into which the oil from the sump enters r from the bottom up to the oil level. The metal sheath is con-nected to a remote indicator which is sensitive to changes in electrical capacitance.
The temperature sensor responds, through heat transfer, to the temperature of the oil and through an electronic remote transmission may be made visible on an electronic instrument.
The capacitance of the condenser formed by the metal sheath and the surface of the aperture of opening changes depending on the oil level in the annulus of the condenser, because of the effect of the dielectric coefficient of the oil itself.
The dielectric coefficient of the lubricating oil nearly doubles the capacitance of such a condenser. The change in oil level thus causes a change in capacitance. The level of the oil is then made visible on an electronic instrument through the re-mote transmission of the change in the capacitance.
Through the unique arrangement of the sensors in the openings or apertures of the roller sha~ts, a way is provided in the mill to remotely monitor simultaneously both the tem-perature and the oil level in the sump of the immersion bear-ing of each crushing roller.
In operating immersion bearings, in which there is an oil film between the gliding and rolling surfaces, the oil temperature always ad~usts itself to a point above the tem-perature of the surroundings, because of fluid friction. When a bearing stops operating due to a blocked roller, the oil friction also stops, and the oil temperature in the sump of the splash bearing drops in a short time due to heat exchange.
The temperature drop indicates that the roller is blocked.
During the start-up of the mill a part of the oil is Case 401~
removed from the sump to lubricate the bearing~ so the oil level drops. When a roller is blocked the entire oil collects in the sump and the oil level rises.
If during the normal operation of the mill there is a temperature drop and/or an oil level increase in the sump of a bearing of a crushing roller, this provides a warning for the operator that the crushing roll is blocked and that the mill should be stopped and re-started before a larger flat spot will be ground on the circumference of the tire.
At the instant of stopping, the tire rolls back a bit on the race from the especially hard lump or from the foreign material. This results in the grinding bowl being slightly turned back, so that the lump becomes free and during the sub-sequent start-up is shoved away or is popped off the raceway by the roller. As a precaution to insure that a previously blocked roller actually became free, or if not, to be ready to shut-down the mill again and re-start, the operator should preferably observe the behaviour of the oil levels, because they react during start-up much faster than the oil temperatures.
When it ls observed that the oil level in one of the oil sumps does not drop~ this means that the corresponding crushing rol-ler is blocked and that the mill should be stopped again and re-started to remove the danger.
In order to recognize more easily a temperature drop of the oil in any of the crushing rollers it is advantageous to compare continuously the oil temperatures o~ the three bearings. The measured oil temperature o~ a blocked roller indicates its actual oil temperature and the other oil tem-peratures indicate how high the oil temperature of the blocked roller would be if it would operate properly. The comparison permits an easy recognition of the temperature drop.
The advantages achieved by the invention are that - Case 4018 1038358 ~
through continuous monitoring of the oil levels and of the oil temperatures, an early warning of imminent damage to bearings is obtained. Further, it permits a considerable reduction in the grinding of flat spots on the circumference of the tires, through which an improvement in mill availability is achieved, because of avoidance of excessive wear, costly shut-downs and maintenance work.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows a cross section of a part of a crushing roller mill;
Fig. 2 shows a diagram for monitoring the oil levels and the oil temperatures of the crushing roller bearings; and Figs. 3 and 4 show plan and elevation views respectively of a pulverizing mill in which the invention is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Of the three non-orbiting crushing rollers Al, A2, A3 of a pulverizer shown in Figs. 3 and 4 only roller A2 is shown in Fig. 1.
The crushing rollers are stationary relative to the pulverizer housing and roll on a ring shaped grinding race or strip of a hori-zontally rotating bowl or plate 2 which is driven by a motor 3 (shown schematically only) through a gear 4. The switch 5 represents the normal device used for start-up and shut-down of the mill.
The crushing rollers Al and A3 are attached in a similar manner as is crushing roller A2 to a shaft 7 through a combination of roller bearings 6 as shown in Fig. 1. The hub 21 of the roller, together with a bearing cover 22, enclose the roller bearing 6 and the shaft 7 to form a tight enclosure that is filled with a mineral or other lubricating oil to a level B2. The oil collects in the sump D2 of a splash lubrication system in which the bearing rollers repeatedly immerse during the rotation of the crushing _5_ ~ .
Case 4018 1038i~58 rollers. This way a part of the oil is carried out of the sump by the bearing rollers and the oil level drops to a level B2, but rises again to the original level B2 when the rotation stops because no oil is carried out and all the oil collects again in the sump D2.
Furthermore, during the rotation of the crushing roller? heat that is generated by the fluid friction of the lubricating oil is added to the oil fill. T~s heat is trans-ferred to the shaft and to the housing through a temperature gradient. Therefore, the oil temperature may rise above the temperatures of the shaft 7 and housing 23, but drops again ; by a certain amount when the rotation is stopped because the heat generation ceases and the heat transfer to the shaft and housing continues until the temperature of the oil equals that of the shaft end housing 23 When a crushing roller blocks, the rotation of the roller stops and the temperature of the oil drops by a cer-tain amount and also the oil level rises from B~ to the original level B2.
When the crushing roller rotates, but an irregular-ity develops in the bearing, then the oil temperature rises too high and if the lubrication fails or an oil loss occurs, the oil level will fall below B2.
~ A temperature sensor 8 is provided to measure the oil temperature. The sensor is shrouded with a metal sheath 9 and reaches into the sump D2. me temperature sensor 8 is connected through electrical leads with a measuring de-vice 10 and an indicating instrument E2 to indicate the oil temperature. The metal sheath 9 serves to measure the oil level. It is connected by electrical leads with a trans-mitter ll and an indicator F2.
.~.
~ Case 4018 103835~
To perform the remote transmission of the oil level indications B2 or B2 the metal sheath 9 is so arranged in the aperture or opening 12 of the shaft 7, that it is elec-trically insulated and forms, together with the surface of the aperture or drilling, two oppositely located condenser surfaces An annular space 13 is defined between these surfaces, in which the oil contained in the sump D2 pene-trates from the bottom to a height of the oil level B2.
Above the oil level B2 the aperture or drilling 12 is pro-vided with a perpendicularly drilled hole 12' for pressureequalization within the roller bearing space. Oil is con-tained in the section 14 of the space of the condenser an-nulus 13, so that the capacitance of that part of the con-denser is about doubled due to the dielectric coefficient of the mineral oil. When the oil level drops to the B2 height some of the oil flows out of the annulus 13 and the capaci-tance of the condenser changes. This change of the capaci-tance is utilized for the remote transmission of the oil levels B2 or B2. A transmitter ll sensitive to changes of capacitance is used, therefore, for remote indication of the oil level.
Each crushing roller Al, A2 and A3 has a temperature sensor 8 with a metal sheath 9 arranged the same way in rela-~ tion to the apertures or drillings 12 and 12', as shownschematically on Fig. 2. Reslstance thermometers are provided for the measurement of the oil temperature, with the tempera-ture sensor 8 used as part of a Wheatstone bridge 10 and the instruments El~ E2 or E3 measuring the corresponding current in the bridge for each of the rollers Al, A2 and A3; respec-tively.
m e transmitter ll which reacts to changes of capaci-Case 4018 tance consists of a high frequency generator 15 with an oscil-lating circuit composed of an inductance 26 and a capacitance 27, which is excited by a transistor 28 connected across the capacitance. The condenser formed by the metal sheath 9 and the drilling 12 is part of the oscillating circuit. mus the frequency of oscillation is changed wnen the capacitance changes due to variation of the oil level from B2 to B2, or the reverse. m e frequency of the high frequency generator 15 is tuned by a Wien-Robinson bridge circuit 16, consisting of resistors and capacitances which are tuned to the high frequency generator 15, so that with a change in the frequency of oscillation in the bridge a change occurs in the electrical potential. This electrical potential, upon amplification by a transistor 31, controls a direct current circuit wnich de-livers the measurement signal to the indicating instrument F2 The indicating instrument F2 s'nows for example that the oil level has risen from B2 to B2 The continuous supervision of the operation of the bearings is achieved through observation of the indicating instruments El, E2 and E3, which can also be coupled with alarms or other annunciating devices to make sure that the oil temperatures in the sumps Dl, D2 and D3 are not, compara-tively, too hot or too cold Furthermore, attention must be given to the indicating instruments Fl, F2 and F3 to make sure that the oil levels Bl, B2 and B3 do not drop too much due to loss of oil If an observation is made on one of the instruments El, E2 or E3/ for example on the instrument E2, that the oil temperature in sump D2 dropped in comparison to the indica-tions on the instruments El and E3, this does not mean thatthe running conditions of the bearing have impro~ed, but that - Case 4018 the crushing roller A2 is blocked. In that case the indication of the instrument F2 does not mean that the oil in the sump D2 was replenished, but that the rise of the oil level from B2 to B2 indicates also that the crushing roller A2 is blocked.
me roller pushes the unground material from the race 1 (see Fig. 1) and glides on a bare race, so that the race wears off and a flat spot G2 (Fig. 1) starts to appear on the circum-ference of the crushing roller A2. Such occurrence is detri-mental and an increase in the size or num~er of flat spots G2 can be avoided by stopping the mill and starting again.
When, during normal operation of the mill one of the indicating instruments, for example E2, indicates directly or through a warning signal that the oil temperature is dropping and/or if it is determined through a direct reading of the in-strument F2 or through a warning signal that the oil level rises from B~ to B2, then for the safety of the mill it is best to stop the mill by actuating the switch 5 (Fig. 1) and to re-start it a~ain using the switch 5. m rough this action, the especially hard lump or the foreign material that had blocked the crushing roller is shoved aside or pops off the grinding race.
During the re-start care must be taken to ascertain that the indicating instrument F2 shows a drop of the oil -level from B2 to B2 in order to be sure that bearing damage does not prevent the rotation of the crushing roller. The same safety procedure is performed when any of the other crushing rollers Al or A3 are blocked.
While there is illustrated and described herein a specific embodiment of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of Case 4018 ' ~0383S~
the invention may sometimes be used to advantage without a corresponding use of the other features.
Claims (8)
1. In a pulverizing mill including a plurality of crushing rollers bearing upon and circumferentially equally spaced about the center of rotation of a horizontally disposed ring shaped grinding race, electric motor drive means for rotating the ring about the center of rotation including means for starting and stopping the motor, each roller being rotatably mounted on a shaft through bearings lubricated by immersion in a pool of lubricating oil, the improvement comprising means for sensing the temperature of the lubrication oil in the pool of each roller, means for sensing the level of lubricating oil in the pool of each roller, and means for remotely indicating comparable values of oil temperature and oil level for each crushing roller as an operating guide during operation of the pulverizing mill.
2. In a pulverizing mill according to claim 1 wherein an axial bore is provided in the shaft of each roller shaft, a temperature sensor having a shrouding metal sheath is extended through the axial bore with an end portion immersed in the lubri-cating pool, the external surface of the sheath being radially spaced from the inner surface of the axial bore to provide an annular space therebetween with at least some lubricating oil therein.
3. In a pulverizing mill according to claim 2 wherein the temperature sensor is connected to a remote measuring device, and the metal sheath is connected to a remote measuring device reacting to changes in capacitance resulting from changes in the oil level in the annular space.
4. A method for monitoring and controlling the operation of a crushing roller mill of the type including a rotating hori-zontal plate having an annular grinding strip over which roll one or more non-orbiting crushing rollers rotatably mounted to shafts by means of bearings splash lubricated by oil contained in a sump within the crushing roller bearing housing comprising continuously measuring at least one of the temperature and the level of the oil in the sump of at least one of the rollers, generating a signal related to at least one of the aforesaid measurements and stopping the operation of the mill in response to the signal generated.
5. A method as claimed in claim 4 wherein the measure-ment taken of the oil is of its temperature and the operation of the mill is stopped if the measured temperature of the oil changes during operation by a predetermined amount.
6. A method as claimed in claim 4 wherein the measure-ment taken of the oil is of its level in the sump and the operation of the mill is stopped if the measured level of the oil changes during operation by a predetermined amount.
7. A method as claimed in claim 4 wherein the oil temperature and the oil level in the sump are measured and the operation of the mill is stopped if either the temperature or the level of the oil changes, by predetermined amounts, during operation of the mill.
8. A method as claimed in claim 4 comprising measuring at least one of the temperature and the level of the oil in the sump of each of the rollers rolling on the grinding strip of a mill, comparing the same among the foregoing measurements for all of said rollers determining if said compared measurements of one roller differ by a predetermined amount from those of the other rollers, and stopping the operation of the mill in response thereto.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,852A CA1038358A (en) | 1974-08-12 | 1974-08-12 | Protective device for a roller type pulverizer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,852A CA1038358A (en) | 1974-08-12 | 1974-08-12 | Protective device for a roller type pulverizer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038358A true CA1038358A (en) | 1978-09-12 |
Family
ID=4100881
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA206,852A Expired CA1038358A (en) | 1974-08-12 | 1974-08-12 | Protective device for a roller type pulverizer |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1038358A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5050810A (en) * | 1990-01-16 | 1991-09-24 | Parham Robert L | One-piece pulverizing roller |
| WO2012049094A1 (en) * | 2010-10-11 | 2012-04-19 | Flsmidth A/S | Roller mill |
-
1974
- 1974-08-12 CA CA206,852A patent/CA1038358A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5050810A (en) * | 1990-01-16 | 1991-09-24 | Parham Robert L | One-piece pulverizing roller |
| WO2012049094A1 (en) * | 2010-10-11 | 2012-04-19 | Flsmidth A/S | Roller mill |
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