JPS60199515A - Method for controlling operation of fluid pump for hot rolling - Google Patents

Abstract

PURPOSE:To save power consumption by providing a variable-speed control device so as to regulate the rotational speed of a pump to set lower limit of speed at the time of no-load running and to a set upper limit of speed different for each material to be rolled at the time of normal load running in controlling the operation of pump. CONSTITUTION:When the front tip of a material to be rolled, delivered from a roughing mill 1, is detected by a pump-accelerating metal detector 7, a process computor 11 sets the upper speed-limit of a pump 14 at the time of normal load running in accordance with the kind of steel and size, etc. of material. Next, a variable-speed control device 12 drives a motor 13 of pump 14 at an instructed upper speed limit. Further, when the run-out of the tail end of material is detected by a load cell 91 of the 1st finishing mill 4, the device 12 drives the motor 13 at a set lower speed-limit (about 30% of rating) at the time of no- load running, and closes a solenoid on-off valve 17 for spraying. In this way, the power consumption is remarkably saved in both cases of normal and no-load runnings.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fluid pump such as a descaling pump and a roll cooling water pump in hot rolling of hot-rolled steel strips, thick plates, billets, sections, etc. The present invention relates to a method for controlling the rotation speed of a motor using a computer and a variable speed control device.

[Prior art] Conventionally, pumps for descaling and roll cooling water pumps used in hot rolling of hot strip thick plates, billets, sections, etc., have been driven at a constant speed, and the rated speed is constant both during no-load and under-load conditions. The power loss was large because it was operated at Energy-saving control for this purpose involves closing the spray valve during no-load conditions (no injection) and reducing the load by allowing water to flow through the bypass piping, but this method only achieves an energy-saving effect for a small amount of power. The problem was that it couldn't be done. This is shown in Figure 3a. In Figure 3a, the area marked by diagonal lines (D) is the amount of power saved by flowing water to the bypass piping.

Furthermore, Japanese Patent Publication No. 58-27009 discloses a technology that prevents descaling water from being sent from the high-pressure water pump to the spray header when the injection valve is closed, while at the same time continuing to supply water to the spray header through other pipes. However, the main purpose of this is not to reduce pump power consumption, but to reduce the load during no-load and prevent water hammer phenomenon, so it is not effective in reducing power consumption. There was a problem.

In hot rolling such as hot strip rolling, descaling pumps and roll cooling water pumps need to supply high-pressure water, so the electricity used accounts for a large proportion of the electricity consumption of the entire mill. Furthermore, the amount of water used is enormous. Therefore, the power consumption of the fluid pump is large, and it is desired to further reduce the power consumption.

OBJECTS OF THE INVENTION The present invention aims to further reduce the power consumption of fluid pumps.

[Summary of the invention] In the present invention, low pressure,
In addition to lowering the rotation speed of the pump drive motor to the minimum required rotation speed during no-load conditions, which can reduce water flow, even during load conditions, upper limit speeds are set for each target depending on the steel pipe to be rolled, rolling size, etc. The rotational speed of the pump drive motor (hereinafter referred to as the rotational speed of the desk pump) is controlled to a set value using a variable speed control device. According to this, the required fluid pressure can be obtained, and significant [1] power and resource savings can be achieved.

Hereinafter, an example of application of a hot strip mill to a finish descaling pump will be described in detail with reference to FIG.

In Fig. 1, l is a rough rolling mill, 2 is a crop shear,
3 is a descaling device installed in the front of the finishing rolling mill, 4 is the Magic 1 finishing rolling mill, 5 is the Nα2 finishing rolling mill, 6 is the final stage finishing rolling mill, and 7 is the desuke pump acceleration metal installed above the line. It is a detector. Reference numeral 8 denotes a metal detector for opening the spray electromagnetic on-off valve, which is provided above the line in front of the descaling device 3.

The installation interval between the metal detector 7 for accelerating the Desuke pump and the metal detector 8 for opening the spray electromagnetic valve is as follows: Desuke pump 15
This is determined by the time it takes for the acceleration to be completed and the time it takes for the tip of the rolled material to reach the descaling device 3. 91 to 93 are load cells, and 10 is a business computer. 1] is a process computer which instructs the speed of the desuke pump 15.

12 is a variable speed control device including a DC amplifier, a V/F converter or a phase shift circuit, etc., 13 is a motor for driving the deske pump, 14 is a deske pump that supplies water to the descaling device 3, and 15 stores water (accumulates pressure). accumulator,
16 is an electromagnetic on-off valve for the accumulator, and 17 is an electromagnetic on-off valve for spray.

This electromagnetic opening/closing button t17 is opened when the metal detector 8 detects the tip of the material to be rolled, and is closed when the load cell 91 of the N011 finishing mill 4 detects ash removal from the tail end of the material to be rolled.

18 is a header of the descaling device 3, and 19 is a bypass path for spray water. A pressure sensor 20 detects the output pressure of the desk pump 14 and detects acceleration (end) and deceleration of the desk pump 14.

When the pressure sensor 20 detects acceleration of the desk pump 14, the accumulator electromagnetic on-off valve 16 is opened.

When deceleration is detected, the accumulator electromagnetic on-off valve 1G is closed.

〔motion〕

When the tip of the rolled material that has been rolled in the rough rolling mill 1 is detected by the metal detector 7 for accelerating the desque pump, a detection signal is inputted to the process computer 11 .

The process computer 11 receives the steel type from the business computer 10 according to the rolling schedule.

Information such as rolling size and self-destruction is input. Based on this information, the computer 11 sets the upper limit speed of the desuke pump 14 under load, and the set upper limit speed is instructed to the variable speed control device 12.

The setting value for the upper limit speed under load is determined by the steel type and rolling size.

The speed is between 70% and 100% of the rated speed depending on the speed and other factors.

For example, for tinplate materials that have strict surface quality requirements, the upper speed limit is set to the rated speed (100%); for tinplate materials that have less stringent surface quality requirements, such as pipe materials, the upper speed limit is set to the rated speed. It is assumed that the speed is between 70% and 100% of the speed. If the speed is less than 70% of the rated speed, descaling unevenness tends to occur, so the lower limit of the upper speed limit set during load is set to 70% of the rated speed.

The variable speed control device 12 energizes the motor to set the motor speed to the instructed upper limit speed. The motor 13 is accelerated to the specified upper limit speed by this motor tie force. When the designated upper limit speed is reached, the output pressure of the pump 13 goes from increasing to becoming stable. At this time, the pressure sensor 20 detects motor acceleration (completion) and opens the accumulator electromagnetic on-off valve 16.

When the tip of the material to be rolled is detected by the metal detector 8, the spray electromagnetic on-off valve 17 is opened, and water is injected from the header 18 at a constant pressure determined by the rotational speed of the desuke pump 14 to perform descaling. It will be done. During descaling, the motor 13 that drives the desuke pump 14 is energized to a set upper limit speed.

When the tail end dropout of the rolled material is detected by the load cell 91 of the No. 1 finishing rolling mill 4, this is detected by the process computer 1.
1 will be notified. On the condition that the metal detector 7 does not detect the rolled material, the process computer 11 instructs the variable speed control device 12 to the lower limit speed (30% of the rating) set for no-load operation, and The on-off valve 17 is closed.

In response to this, the variable speed control device 12 starts energizing control to set the motor 13 to the lower limit speed during no-load.

When the motor 13 starts decelerating and the output pressure of the pump 14 starts to decrease, the pressure sensor 20 detects this and closes the accumulator electromagnetic on-off valve 16.

This prevents the pressure in the accumulator 15 from decreasing.

The lower limit speed of the Desuke pump 14 at no load is the rated speed (1
00%) is set to 30%. This lower limit speed value is
Torque ripple frequency generated by variable speed control device 12;
Torsional resonance point of pump drive mechanical system.

Motor life, pump lubrication, acceleration/deceleration time (rise time,
20~
It was concluded that a range of 50% is appropriate, with 30% being the most efficient.

When the next material to be rolled arrives, the motor 13 is energized and controlled at the upper limit speed corresponding to this material to be rolled in the same manner as described above.

During the waiting period (idle time) between the arrival of the rolled material or during a short rest, the motor 13 is energized and controlled in the above-mentioned no-load operation (30%). At this time, the output water amount of the pump 14 is quite small. This water flows through bypass 19 to header 18 . This bypass water flow makes it possible to drive the pump with an extremely low load (this is referred to as no load), that is, to drive the pump on standby. If there were no bypass flow path, the pump output pressure would gradually rise, the pump load would increase, and the motor would become overloaded and stop. When restarting the motor from a stopped state, the increase in pump output pressure will be slow and it will not be possible to cope with the intermittent arrival of the rolled material. The rise of the motor rotational speed when the material arrives is fast, and the rise sufficiently corresponds to each of the rolling materials that arrive one after another at a short pitch.

〔Example〕

Medium carbon type (C=0.
15% or more) to a finished plate thickness of 8.0111+11 or more, the rotational speed of the scaling pump at no load (idle time 2 lower limit speed) is rated speed (pressure: 155 Kg/cm", electric power 3050 to V) (pressure: 16 to g/cm" r power: 68 to V), and when loaded (during descaling injection), 90% of the rated speed (pressure to 120 Kg/cm", power to 2,220 Kv). ) to perform operation control.

At that time, the acceleration time from 30% (no load: lower limit speed) to 90% (load: upper limit speed) is 5.0 seconds, and 90%
The deceleration time from to 30% was 5.3 seconds. As a result, there is no problem in controlling the operation of the descaling pump 14 in response to the arrival of the material to be rolled one after another, and even if the descaling water is used at a low pressure and flow rate (70 to 100%), the material to be rolled is Surface descaling properties equivalent to those of the conventional method were obtained.

[Other fields of use]

In the above explanation, an example was shown in which the present invention was applied to a finish descaling device for a hot strip mill.
Needless to say, the present invention can be applied not only to finishing rolling mills but also to descaling devices of rough rolling mills.

Further, the present invention is not limited to fluid pumps for descaling, but can be similarly applied to, for example, fluid pumps for high-pressure water for cooling rolls in finishing rolling mill rows. Regarding pressure and flow rate control during threading, in addition to the steel type, rolling size, application, etc., which are taken into consideration in the case of descaling, the cumulative ratio of threading time to rolling pitch (threading time and idle time), etc. It is possible to achieve energy savings by changing the roll cooling water pressure during sheet threading by controlling the rotation speed so that the amount of roll expansion is predicted from the table and the amount of roll expansion is corrected according to the target plate crown of the rolled plate. I can do it. The equipment configuration is such that a booster pump for roll cooling water is provided in place of the first desk pump 13, and spray headers for roll cooling are placed on the exit side of each of the upper and lower work rolls in the finishing rolling mill row, and the cooling water flow to these is provided. The passage is opened and closed by an electromagnetic on-off valve 17. Solenoid on-off valve 17
The closing signal can be generated by using the output from the load cell 91 of the final stage rolling mill 6.

Furthermore, the present invention can be implemented in hot rolling other than hot strip rolling, such as rolling of thick plates, strips, and sections.

〔Effect of the invention〕

The Desuke pump is set to 30% of the rated speed when there is no negative idle time, and the upper limit speed when loaded with descaling injection is set to 7% of the rated speed depending on the steel type, rolling size, etc.
By setting the speed in the range of 0 to 100% and controlling the operation using a variable speed control device, power consumption can be significantly reduced as shown in FIG. 3b.

The hatching (■) in FIG. 3b shows the range in which the power consumption is even lower than in the conventional case when the speed is set to 30% by controlling the rotation speed of the desk pump during idle time. Further, the hatching (■) indicates a smaller range of electric power than the conventional one when the desuke pump speed control (70% to 100%) corresponding to the steel type is performed during desuke injection.

By implementing the present invention, power consumption can be reduced by 40% for hunting (2) alone, and by 60% when both hunting (2) and (2) are combined. In addition, the amount of water used is 50% of the conventional amount when both hatchings and (2) are combined, which is a significant reduction in water usage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a device implementing one embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of the device i! It is a time chart showing motor energization control timing, descaling injection control timing, etc. in the configuration. FIG. 3d is a graph showing the power consumption of the pump drive motor in conventional descaling pump control. FIG. 3b is a graph showing the power consumption of the pump drive motor when the present invention is implemented. Rough rolling mill 2: Crop shear 3: Descale link group @ 'I: No, 1 Finishing mill 5
: No, 2 finishing rolling mill 6: Final stage finishing rolling mill 7:
Metal detector 8: Metal detectors 91 to 93: Port-1 cell 10: Business computer 11: Process computer 12: Variable speed control device 13: Pump drive motor 14
: Pump (fluid pump) 15: Accumulator 16: Solenoid on-off valve 17: Solenoid on-off valve 18: Herada 19: Bypass path 20: 20: Pressure sensor

Claims (1)

[Claims] In a method for controlling the operation of a fluid pump used in hot rolling, the rotational speed of the pump is set to a lower limit speed when no load is applied,
A method for controlling the operation of a fluid pump for hot rolling, characterized in that during load, the operation is controlled using a computer and a variable speed control device so that the target setting upper limit speed differs for each material to be rolled.