The invention relates to a method and a device for lubricating the cylinders of a roll stand, in particular for roll nip lubrication in a roll stand for a roll band. A mixture of water and oil is produced by means of a mixing and spraying device. The device is supplied with water by a first supply line and is supplied with oil by a second supply line. The mixture is sprayed onto the strip being rolled and/or into the roll nip and/or onto at least one of the cylinders of the roll stand.
It is known that for the production of rolling stock, its surface quality can be improved if the friction coefficient between the cylinders and the rolling stock is reduced. By introducing a lubricant during the production of a roll band, for example, not only is the energy to be expended for the rolling process reduced, but the service life of the cylinders of a roll stand is also increased. Usually oil and water are mixed into an emulsion in a mixer. By means of connecting lines, which may be one or more meters in length, this emulsion is supplied to an arrangement of nozzles which spray the emulsion onto the strip being rolled and/or into the roll nip and/or onto the cylinders.
After a certain operating time, however, the effect of the roll nip lubrication decreases as saponification occurs both in the mixing unit and in the nozzles and also in the connecting lines. That deposit reduces the active flow area. If a saponification particle detaches from the internal wall of a pipe or of the mixer and is washed into the outlets of a nozzle, the nozzle may become blocked. In this area, the roll nip lubrication then fails completely.
To solve the problem of saponification and the associated reduction in the effect of the lubrication, maintenance work for the roll nip lubrication is necessary. In such maintenance, the mixer, the pipes between the mixer and nozzle, and the nozzles themselves are flushed with hot water, if necessary with the addition of one or more chemical cleaning agents, or are blasted to clear them.
Such roll nip lubrication is known, for example, from EP 2 040 860 B 1. Hot water is added to the oil or water supply line, or to the mixing unit itself, by means of a third supply line. During maintenance of roll nip lubrication, the rolling process is interrupted. The heated water is kept ready in a thermally insulated hot water tank. The provision of the hot water, as well as the supply by means of a third thermally insulated line, is associated with corresponding technical effort.
It is an object of the present invention to provide a method and a device for lubricating the cylinders of a roll stand. The constructed as simply as possible and its maintenance affects the availability of a rolling mill as little as possible.
This object is achieved for a method and for a device with the features of the invention.
According to a fundamental idea of the invention, the hot water used for cleaning purposes is produced by a heating device, which heats the water flowing into the water supply line, heating it virtually in line. This heating device is permanently installed but is only active for a time interval which is predetermined by a control device. As a result, a third supply line which supplies hot water to the mixing unit or to connecting lines between the mixing unit and nozzle is unnecessary. The constant provision of hot water is likewise unnecessary. The expense of a thermally insulated container for the provision of warm or hot water is spared as a result. This has several advantages. On the one hand, a system for roll nip lubrication can be easily constructed. On the other hand, cleaning of the roll nip lubrication system can be performed more easily. During a short maintenance downtime, the hot water for flushing the mixing unit and nozzles is also available very quickly and its temperature can be adjusted to requirements very easily. This also enables cleaning during short production downtimes so that saponification can be countered at an early stage. Energy can be supplied to the heating device in various ways, for example electrically or using another fuel, e.g. gas or oil.
In a preferred embodiment, the heating device can be operated electrically, e.g. as an instantaneous water heater. An instantaneous water heater has several advantages. On the one hand, the necessary construction volume for a rolling mill compared with a hot water cylinder is much smaller. The water temperature necessary for cleaning can be very precisely predetermined and adjusted by means of electronic control of the energy supply to the individual resistance heating elements. As a result, the energy requirements can be adjusted to the level of the contamination of the lubrication equipment.
It may be favorable if the control unit for determining the time interval in which cleaning takes place uses a process variable from cylinder lubrication, for example a measurement signal in the water supply, which indicates the level of contamination of the mixing and spraying device. Such a measurement signal may, for example, be obtained by means of a sensor which is arranged in the water supply. The sensor may be a pressure sensor or a flow sensor.
For efficient cleaning, it may be advantageous if the control unit controls the heating device in such a way that the water flowing to the mixing and spraying device is heated to a predetermined temperature of more than 60° C. and is adjusted to this temperature.
Saponification of the emulsion can be reduced by means of a permanent water treatment plant installed in the water supply, e.g. an ion exchanger or osmosis plant. In addition, soft water is favorable for an instantaneous electric water heater as there is less calcification on the heating elements.
In a particularly preferred embodiment provision can be made for the mixing and spraying device to be comprised of a number of nozzle-mixer-units, wherein each nozzle-mixer-unit is supplied with both water and oil separately. In contrast to the prior art, where a mixing device supplies several nozzles, in the present embodiment of the invention, a separate mixing unit is assigned to each nozzle. The design of each nozzle-mixer-unit is structurally compact as a unit and includes both the mixing function and the spraying function. As a result, there are virtually no connecting lines between the mixer and the nozzle in which saponification could occur. The dwell time of the emulsion/dispersion in the unit is very short, resulting in reduced saponification. As a result, the rolling process need not be interrupted as often as with prior art for the purposes of cleaning the roll nip lubrication.
Maintenance work can be made easier if each of these nozzle-mixer-units can be released from its fixture device by means of a quick release fastener e.g. a bayonet fastening. By this means contaminated units can be changed very quickly during maintenance downtime.
For further explanation of the invention, in the following section of the description reference will be made to drawings from which additional advantageous embodiments, details and developments of the invention based on a non-restrictive exemplary embodiment can be taken. These drawings show:
In the exemplary arrangement of
A heating device 6 is permanently installed in the first supply line 3 (the water supply), by means of which the water flowing from a source not identified in more detail to the mixing and spraying device 10 can be heated for the purposes of cleaning. This heating device 6 is for example an instantaneous water heater which has several heating elements in the form of electric resistance heating elements. The method of construction and installation of an instantaneous water heater can be assumed to be known here. As indicated by the dashed line in
The second supply line 2 (supply) supplies the mixing and spraying device 10 with oil. It is likewise split into an upper supply branch 4 and a lower supply branch 5. A respective dosing pump 7 is connected in each of these branches 4, 5. Each of these dosing pumps 7 is controlled by the control unit 9 in such a way that the amount of the oil feed can be predetermined separately in the upper branch 4 and in the lower branch 5.
As aforementioned, the mixing and spraying device 10 comprises several nozzle-mixer-units 1. These nozzle-mixer-units 1 are each a structural unit. In other words, seen in the direction of flow, a respective mixer and spraying unit are locally arranged, with one directly behind the other. By mixing oil and water in an integrated structural unit, the dwell time for the emulsion/dispersion in this structural unit is very short. The cleaning process is comparatively simple as less saponification takes place.
The time at which a cleaning phase starts, as well as the duration of a rinsing procedure, is predetermined by the control unit 9. The control unit 9 takes into account the measurement signal of a sensor 13 in the water supply line 3 for this purpose. The measurement signal supplied by the sensor 13 reflects the level of contamination of the mixing and spraying device 10. In the present example, the sensor 13 is a pressure sensor.
During the cleaning phase, the instantaneous water heater 6 heats the circulating water to a temperature of more than 60° Celsius. In a manner known per se, the energy supply to the heating elements of the instantaneous water heater 6 is predetermined in such a way that a predetermined water temperature can be maintained.
During a cleaning phase the dosing pumps 7 are inactive, resulting in the oil supply to the nozzle-mixer-units 1 being interrupted. The hot water flowing to the individual nozzle-mixer-units 1 cleans these and removes any existing saponification and deposition. The hot water necessary for cleaning is generated virtually online in the water supply line and does not originate from a reservoir.
In
In contrast to the prior art, where a mixer supplies a number of spray nozzles and the distance between the mixer and the spray nozzles usually involves a length of pipe of more than one meter, the dwell time of the emulsion in the device according to the invention is far shorter. The extent of saponification is less with the mixing procedure and the spraying procedure taking place in one structural unit. If deposits are formed in the mixer or nozzle nevertheless, these can be removed with greater ease and the surface on which deposits may form is comparatively small as a result of the integrated construction. This leads to shorter maintenance intervals and consequently enables the availability of a rolling mill to be increased.
Schematic diagram
A major advantage of the device according to the invention is firstly the simpler opportunity for cleaning which is possible without chemical cleaning agents and acids, obviating the need for cleaning agents and acids as consumables.
Although the invention was illustrated and described in greater detail by the preferred exemplary embodiment, the invention is not restricted by the disclosed examples and the person skilled in the art can derive other versions therefrom without departing from the scope of protection of the invention. Thus, it is conceivable that instead of the aforementioned individual instantaneous water heater, a number of instantaneous water heaters are used. It is further conceivable that each nozzle-mixer-unit is assigned its own instantaneous water heater with a lower connected load.
Number | Date | Country | Kind |
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12155480.2 | Feb 2012 | EP | regional |
The present application is a 35 U.S.C. §§371 national phase conversion of PCT/EP2013/052359, filed Feb. 7, 2013, which claims priority of European Patent Application No. 12155480.2, filed Feb. 15, 2012, the contents of which are incorporated by reference herein. The PCT International Application was published in the German language.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2013/052359 | 2/7/2013 | WO | 00 |