阅读说明：本技术 扬水泵的速度控制装置 (Speed control device of lift pump ) 是由 尾坂侑香 于 2019-02-04 设计创作，主要内容包括：本发明的实施方式提供一种扬水泵的速度控制装置,具备：数据收集部,收集对轧制的第1被轧制材设定的,设定向上述第1被轧制材的前端注水的冷却水的流量的第1数据以及设定于上述第1被轧制材的包含上述第1被轧制材的输送速度的模式的第2数据；第1计算部,基于上述第1数据以及上述第2数据,计算向上述第1被轧制材注水的冷却水的预想值即第1预测注水量；以及第2计算部,基于上述第1预测注水量和上述扬水泵的速度相对于上述扬水泵能够汲取的流量的特性数据,计算向驱动上述扬水泵的逆变器装置供给的速度指令值。(An embodiment of the present invention provides a speed control device for a lift pump, including: a data collection unit that collects 1 st data set for a 1 st rolled material to be rolled, the 1 st data setting a flow rate of cooling water to be supplied to a tip of the 1 st rolled material, and 2 nd data set for a mode including a feed speed of the 1 st rolled material for the 1 st rolled material; a 1 st calculation unit that calculates a 1 st predicted water injection amount, which is an expected value of the cooling water to be injected into the 1 st material to be rolled, based on the 1 st data and the 2 nd data; and a 2 nd calculation unit that calculates a speed command value to be supplied to an inverter device that drives the lift pump, based on the 1 st predicted water injection amount and characteristic data of the speed of the lift pump with respect to a flow rate that can be drawn by the lift pump.)

1. A speed control device for a lift pump for controlling the speed of the lift pump for pumping cooling water to a high-level tank provided above a material to be rolled and for discharging the cooling water to the material to be rolled which has passed through a plurality of rolling mills, the speed control device comprising:

A data collection unit that collects 1 st data and 2 nd data set for a 1 st rolled material, the 1 st data setting a flow rate of cooling water to be supplied to a cutting plate which is a material of a unit length of the 1 st rolled material, and the 2 nd data including a pattern of a transport speed of the 1 st rolled material set for the 1 st rolled material;

a 1 st calculation unit that calculates a 1 st predicted water injection amount, which is a predicted value of the cooling water to be injected into the 1 st rolled material, based on the 1 st data and the 2 nd data; and

a 2 nd calculation unit for calculating a speed command value to be supplied to an inverter device for driving the lift pump, based on the 1 st predicted water injection amount and characteristic data of the speed of the lift pump with respect to the discharge flow rate of the lift pump,

the 1 st calculation unit is configured to increase the 1 st predicted injected water amount according to the size of the 2 nd data,

the 2 nd calculation unit sets the speed command value to a large value in accordance with an increase in the 1 st predicted water injection amount.

2. The speed control apparatus of a lift pump of claim 1,

the 1 st calculation unit is configured to increase the 1 st predicted water injection amount before the 1 st material to be rolled is bitten into the last stand of the plurality of rolling mills,

The 2 nd calculation unit is configured to increase the 1 st predicted water injection amount together with the water injection amount.

3. The speed control apparatus of the lift pump of claim 2, wherein,

the 2 nd calculation unit is set to decrease the speed command value after the 1 st rolled material reaches a value corresponding to the maximum speed set in the 2 nd data and the 1 st rolled material is discharged from the last stand.

4. The speed control device of the lift pump according to claim 1, further comprising:

a 1 st monitoring unit that generates a 1 st correction value for correcting the speed command value when the actually used coolant is larger than the 1 st predicted injected water amount; and

and a speed correction unit for generating a new speed command value based on the 1 st correction value.

5. The speed control device of the lift pump according to claim 1, further comprising:

a 2 nd monitoring unit that compares a water level threshold value, which is a water level of the high water level tank and is a water level at which the pressure can be maintained, with an actual water level, and generates a 2 nd correction value that corrects the speed command value when the actual water level is lower than the water level threshold value; and

and a speed correction unit for generating a new speed command value based on the 2 nd correction value.

6. The speed control of the lift pump of claim 5, wherein,

the 2 nd monitoring unit prohibits the speed command value from being decreased until the actual water level reaches the water level threshold again after being lower than the water level threshold.

7. The speed control of the lift pump of claim 3, wherein,

the data collection unit is provided with a data acquisition unit,

setting a 2 nd rolled material to be rolled next to the 1 st rolled material,

collecting the 3 rd data for setting the flow rate of the cooling water to be injected to the tip of the 2 nd rolled material and the 4 th data including the mode of the transport speed set for the 2 nd rolled material,

the 1 st calculation unit described above is such that,

calculating a 2 nd predicted water injection amount which is an expected value of the cooling water to be injected into the 2 nd rolled material based on the 3 rd data and the 4 th data,

the 2 nd calculation unit described above is that,

calculating a 2 nd speed command value for the inverter device based on the 2 nd predicted water injection amount and the characteristic data,

the 2 nd calculation unit described above is that,

and stopping the reduction of the speed command value when the 2 nd rolled material is bitten into the first rolling stand of the plurality of rolling stands before the 1 st rolled material is discharged from the last rolling stand.

8. The speed control of the lift pump of claim 3, wherein,

the data collection unit is provided with a data acquisition unit,

setting a 2 nd rolled material to be rolled next to the 1 st rolled material,

collecting the 3 rd data for setting the flow rate of the cooling water to be injected to the tip of the 2 nd rolled material and the 4 th data including the mode of the transport speed set for the 2 nd rolled material,

the 1 st calculation unit described above is such that,

calculating a 2 nd predicted water injection amount which is an expected value of the cooling water to be injected into the 2 nd rolled material based on the 3 rd data and the 4 th data,

the 2 nd calculation unit described above is that,

calculating a 2 nd speed command value for the inverter device based on the 2 nd predicted water injection amount and the characteristic data,

the 2 nd calculation unit described above is that,

when the 2 nd rolled material is bitten into the first rolling stand among the plurality of rolling stands before the 1 st rolled material is discharged from the last rolling stand and the 1 st speed command value reaches a value corresponding to a preset minimum speed, the reduction of the 1 st speed command value is stopped.

Technical Field

The embodiment of the invention relates to a speed control device of a lift pump for supplying cooling water to a rolling line.

Background

The rolling line has a run-out table. The run-out table is a facility that cools a material to be rolled so as to satisfy desired product quality after rolling the material to a predetermined product thickness. The delivery roll has a high water level trough disposed above the mill pass line. The material to be rolled is cooled by injecting cooling water from the high-level tank. The cooling mode of the rolled material is controlled by appropriately setting the open/close state of a plurality of nozzles for discharging the cooling water supplied from the high-level tank.

The lift pump supplies cooling water to the high water level tank, and therefore, the lift pump draws cooling water from the underground water pit and supplies the cooling water to the high water level tank. When water is drawn in excess of the capacity of the high-level tank, the high-level tank overflows. The overflowing cooling water is sent to the water treatment apparatus together with the water after being used for cooling. The cooling water is cooled by a cooling tower after being subjected to a predetermined purification treatment or the like by a water treatment apparatus, and is collected again in the water cellar.

The flow rate of the cooling water injected into the rolled material affects the quality of the final product of the rolled material. The flow rate of the cooling water to be supplied to the rolled material is calculated using a preset model. The water pressure of the cooling water is generated by the difference between the water level of the cooling water stored in the high water level tank and the setting height of the nozzle. The amount of cooling water injected is set by opening and closing a valve. To achieve the required amount of cooling, the lift pump is set to constantly draw sufficient cooling water to maintain the overflow condition of the high water level tank or close to the overflow water level.

Conventionally, a lift pump is driven by being directly connected to a commercial power supply, and constantly lifts a certain amount of cooling water to a high-level tank. On the other hand, the amount of the material to be rolled injected into the run-out table varies depending on the rolling state and the material type of the material to be rolled. When the lift pump is driven to raise water regardless of whether the rolled material flows on the run-out table or does not flow, the lift flow rate becomes excessive, and the drive power of the lift pump becomes wasteful.

In addition, depending on the material to be rolled, the required amount of injected water may be small. In such a case, when the lift pump is driven to raise the water regardless of the water injection amount, the lift flow rate becomes excessive, and the drive power of the lift pump becomes wasteful.

Disclosure of Invention

Problems to be solved by the invention

Patent document 1 discloses the following technique: the power consumption of the lift pump is suppressed by predicting the usage of the cooling water and controlling the flow rate of the cooling water pumped by the lift pump. However, in the technique of patent document 1, the water level of the high water level tank changes between the upper limit value and the lower limit value during the prediction period in which the usage state of the cooling water is predicted. Therefore, the water level in the high water level tank constantly fluctuates. Therefore, the pressure of the cooling water for cooling the rolled material changes in the prediction period.

An embodiment of the present invention has been made to solve the above-described problems, and an object thereof is to provide a speed control device for a lift pump, which maintains the water level of a high water level tank in an overflow state, and suppresses unnecessary drawing of cooling water to save energy in a rolling line.

Means for solving the problems

According to an embodiment of the present invention, there is provided a speed control device for controlling a speed of a lift pump for pumping cooling water to a high-level tank provided above a material to be rolled, the cooling water being discharged to the material to be rolled that has passed through a plurality of rolling mills. The speed control device is provided with: a data collection unit that collects 1 st data and 2 nd data set for a 1 st rolled material to be rolled, the 1 st data setting a flow rate of cooling water to be supplied to a cutting plate which is a material of a unit length of the 1 st rolled material, and the 2 nd data including a mode of a transport speed of the 1 st rolled material set for the 1 st rolled material; a 1 st calculation unit that calculates a 1 st predicted water injection amount, which is an expected value of the cooling water to be injected into the 1 st material to be rolled, based on the 1 st data and the 2 nd data; and a 2 nd calculation unit that calculates a speed command value to be supplied to an inverter device that drives the lift pump, based on characteristic data of the speed of the lift pump with respect to the 1 st predicted water injection amount and the discharge flow rate of the lift pump. The 1 st calculation unit is configured to increase the 1 st predicted water injection amount according to the size of the 2 nd data. The 2 nd calculation unit sets the speed command value to a large value in accordance with an increase in the 1 st predicted water injection amount.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiment of the present invention, a speed control device of a lift pump is realized, which can maintain the water level of a high water level tank in an overflow state, and can suppress unnecessary cooling water from being drawn, thereby saving energy of a rolling line.

Drawings

Fig. 1 is a schematic configuration diagram illustrating a hot rolling line.

Fig. 2 is a schematic configuration diagram illustrating a circulation system of cooling water of the run-out table.

Fig. 3 is a block diagram illustrating a speed control apparatus of a lift pump according to an embodiment.

Fig. 4 is a graph schematically showing the speed versus flow characteristics of a lift pump.

Fig. 5 is a schematic timing chart for explaining the operation of the speed control device of the lift pump according to the embodiment.

Fig. 6 is a schematic timing chart for explaining the operation of the speed control device of the lift pump according to the embodiment.

Fig. 7 is a schematic timing chart for explaining the operation of the speed control device of the lift pump according to the embodiment.

Fig. 8 is an example of a flowchart for explaining the operation of the speed control device of the lift pump according to the embodiment.

Fig. 9 is a schematic timing chart for explaining an operation in the case where the material to be rolled is continuously fed in the speed control device of the lift pump according to the modified example of the embodiment.

Fig. 10 is a schematic timing chart for explaining an operation in the case where the material to be rolled is continuously fed in the speed control device of the lift pump according to the modified example of the embodiment.

Fig. 11 is a schematic timing chart for explaining an operation in the case where the material to be rolled is continuously fed in the speed control device of the lift pump according to the modified example of the embodiment.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

The drawings are schematic or conceptual, and the relationship between the thickness and width of each portion, the size ratio between portions, and the like are not necessarily the same as in the actual case. Even when the same portions are shown, the dimensions and the ratios thereof may be different from each other in some cases according to the drawings.

In the present specification and the drawings, the same elements as those described in the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

Hereinafter, a case of a hot rolling line will be mainly described, but the embodiment of the present invention is not limited to the hot rolling line, and can be applied to all rolling processes having facilities for cooling a material by directly spraying water thereto, such as a heavy plate rolling line.

< composition of rolling line >

Fig. 1 is a schematic configuration diagram illustrating a hot rolling line.

As shown in FIG. 1, the hot rolling line 100 includes a heating furnace 1, a Scale remover before rough rolling (HSB) 2, a rough rolling mill 3, a Scale remover before finish rolling (FSB) 4, a finish rolling mill 5, a Run Out Table (ROT) 6, and an underground coiler 7. The rolled materials 200a to 200c are sent from the heating furnace 1 to the underground coiler 7. In fig. 1, the rolled materials 200a to 200c are conveyed from left to right. The same applies to fig. 2 described later.

The rolled material 200a drawn out from the heating furnace 1 passes through the HSB 2. The oxide film formed on the surface of the rolled material 200a is removed by the high-pressure water of the HSB 2. The material to be rolled 200a is rolled in a plurality of passes by the roughing mill 3. The material to be rolled 200b rolled by the roughing mill 3 to a certain thickness passes through the FSB 4. The oxide film formed on the surface of the rolled material 200b is removed again by the high-pressure water of the FSB 4.

After that, the rolled material 200b is conveyed to the finishing mill 5. The finishing mill 5 includes a plurality of stages of mill stands 5a to 5g, and the material to be rolled 200b is rolled to a desired product thickness by the respective mill stands 5a to 5 g. In this example, a 7-stage rolling stand is shown, but rolling is similarly performed in a 6-stage rolling stand, for example.

The ROT6 includes a high water level tank 6a, injection valves 6b, 6c, and roller bed rollers 6 d. At least the injection valves 6b, 6c and the roller table roll 6d in the ROT6 are provided between the final-stage mill stand 5g of the finishing mill 5 and the down coiler 7.

The high water level tank 6a is provided at a position higher than the material to be rolled 200c conveyed by the roller bed rollers 6 d. The rolled material 200c rolled to a desired thickness is cooled by cooling water using the ROT6 so as to have a desired product quality. The cooled rolled material 200c is wound by the down coiler 7.

< construction of run-out RoT >

The apparatus configuration of the ROT6 will be explained.

Fig. 2 is a schematic configuration diagram illustrating a circulation system of cooling water of the run-out table.

The high water level tank 6a stores cooling water for cooling the rolled material 200 c. Both the injection valves 6b and 6c are provided below the high water level tank 6 a. The injection valves 6b and 6c discharge the cooling water by a pressure generated by a difference in height from the high water level tank 6a provided above.

A plurality of injection valves 6b and 6c are provided along the conveying direction of the rolled material 200 c. The plurality of injection valves 6b and 6c are provided along a direction (width direction of the rolled material 200 c) orthogonal to the conveying direction of the rolled material 200 c.

The injection valve 6b is provided above the rolled material 200c with its discharge port directed downward. The injection valves 6b spray cooling water onto the upper surface of the rolled material 200 c. The injection valve 6c is provided below the material to be rolled 200c with its discharge port directed upward. The injection valves 6c spray cooling water to the lower surface of the rolled material 200 c.

The plurality of injection valves 6b and 6c are opened and closed by a programmable controller so as to have flow rates set by a winding temperature control device described later.

The roller bed rollers 6d are arranged to form a rolling line which is a conveying surface of the conveyed rolled material 200 c. The rotation axis of the roller bed roller 6d is parallel to a plane including the pass line and extends in a direction substantially perpendicular to the conveying direction of the material to be rolled 200 c. A plurality of roller bed rollers 6d are arranged along the conveying direction such that the respective rotation axes are substantially parallel. The rolled material 200c is conveyed from the exit side of the mill stand 5g toward the underground coiler 7 by the rotation of the roller bed rollers 6 d.

The cooling water is pumped from the water pit 8 to the high water level tank 6a by the lift pump 9. The water pit 8 is provided, for example, underground in a plant in which the hot rolling line 100 is installed. The lift pump 9 is driven by a motor 10. The inverter device described later controls the flow rate of the cooling water pumped by the lift pump 9 by controlling the speed of the lift pump 9 via the electric motor 10. The speed control device of the lift pump according to the present embodiment switches the speed command value to the inverter device that performs speed control of the lift pump 9 and the motor 10, and controls the speed and the flow rate of the lift pump 9.

The cooling water used in the ROT6 is not only mixed with iron powder and the like of the material to be rolled, but also increases in temperature due to contact with the material to be rolled. The high-temperature cooling water is purified by the water treatment device 11, and is returned to the water pit 8 through a cooling process using a cooling tower, not shown. A circulation pump 12 and a motor 13 are used for circulation of the cooling water. The water treatment apparatus 11 is used not only for the cooling water of the ROT6 but also for the circulation of water or the like used for other facilities including the hot rolling line 100, for example, for roll cooling. Therefore, the capacity of the water treatment apparatus 11 is sufficiently large, and sufficient cooling water is always accumulated in the water pit 8.

A plurality of lift pumps 9 may be provided, and in this case, a common pipe is connected to the discharge side of each lift pump 9. When a plurality of lift pumps 9 are provided, for example, redundant operation may be performed to cope with a failure, or parallel operation may be performed to increase the flow rate of the cooling water. In the case of redundant operation, 1 or more of the plurality of lift pumps 9 are set to stand by, and the operation is switched between the stop pump and the operation pump at a constant cycle. When the flow rate of the cooling water is increased or decreased by the speed control of the inverter, the lift pumps 9 that are operated in parallel are controlled at such a speed that the discharge pressures of the respective pumps are all the same.

A pipe 14 for sending cooling water from the lift pump 9 is connected to the high water level tank 6 a. The high water level tank 6a has a structure in which the cooling water overflows when the cooling water is drawn up to a capacity or more thereof. The cooling water overflowing from the high water level tank 6a is recovered to the water treatment apparatus 11 in the same manner as the water used for cooling, and returned to the water pit 8 in the same manner as described above. A water level gauge is provided inside the high water level tank 6a, for example. The water level gauge includes a water level gauge that constantly monitors the water level in the high water level tank, a water level gauge that outputs an alarm when the water level is equal to or lower than a set value, and the like.

< composition of water pump control device >

Fig. 3 is a block diagram illustrating a speed control apparatus of a lift pump according to an embodiment.

Fig. 3 shows, in addition to the speed control device 20, other elements for controlling the speed of the lift pump 9 and the motor 10.

As shown in fig. 3, the speed control device 20 is connected to a Coiling temperature control device (CTC) 30, a finish rolling setting calculation device 40, a Programmable Logic Controller (PLC) 50, and an inverter device 60. The speed control device 20, the CTC30, the finish rolling setting calculation device 40, the PLC50, and the inverter device 60 are connected to a control system network, not shown, for example, and can transmit and receive data to and from each other.

The speed control device 20 receives predetermined data from the CTC30, the finish rolling setting calculation device 40, and the PLC50, generates a speed command value based on the data, and supplies the speed command value to the inverter device 60. The inverter device 60 drives the lift pump 9 and the motor 10 based on the supplied speed command value.

The speed control device 20 includes a data collection unit 21, a calculation unit 22 for predicting the amount of water injected, and a calculation unit 23 for calculating the speed of the lift pump 9.

Data collection unit 21 obtains data a of the initial flow rate setting information from CTC 30. The data collection unit 21 obtains data V of the rolling speed set value from the finish rolling setting calculation device 40. The data collection unit 21 acquires the data b of the actual value of the cooling water use, the data v of the actual value of the rolling speed, and the data c of the actual value of the water level of the high water level tank from the PLC 50. The data collection unit 21 distributes these data to other parts of the speed control device 20.

The data collection unit 21 acquires the data A, V at an appropriate timing before the water injection into the rolled material is started, and supplies the data to the calculation unit 22 that predicts the amount of water injected.

The data collection unit 21 sequentially acquires the data b, v, and c in real time at a fixed cycle set in the control system network, for example. The data b, v, c are used for the water level monitoring function described in detail later.

The predicted water injection amount calculating unit (1 st calculating unit) 22 calculates data E of the amount of water injected into the material to be rolled based on the data A, V. The data a is a set value of the water injection amount of the cooling water for injecting water into the first cut piece of the cut pieces of the rolled material. Here, the cut strip means a material to be rolled per unit length, and 1 strip of the material to be rolled includes a plurality of cut strips. The cut strip is a virtual unit for the manufacturing specification of the material to be rolled, and does not indicate the material actually cut.

The data V includes information of the rolling speed pattern set for each rolled material. Here, the rolling speed pattern is set according to the rolling speed of the material to be rolled on the exit side of the finishing mill 5. The rolling speed pattern includes a leading end strip passing speed, a maximum rolling speed, and a trailing end strip passing speed, and a plurality of acceleration rates may be set between the leading end strip passing speed and the maximum rolling speed.

The calculation unit 22 calculates the data E in proportion to the product of the data A, V so that the amount of water injected into the cutting blade is constant regardless of the feed speed of the rolled material. That is, the calculation unit 22 calculates the amount of water injected in proportion to the speed of the material to be rolled when the data a is a constant value and the data V changes according to the speed pattern of the material to be rolled. In this way, the speed control device 20 predicts the total amount of water injected into the material to be rolled, using the initial flow rate setting information for the first cut piece and the rolling speed.

The lift pump speed calculation unit (2 nd calculation unit) 23 calculates the discharge flow rate Q of the lift pump 9 based on the data E of the water injection amount calculated by the calculation unit 22. The discharge flow rate Q is the flow rate of the cooling water drawn by the lift pump 9. The calculation unit 23 extracts the speed s of the lift pump 9 corresponding to the desired discharge flow rate Q using the speed vs. flow rate characteristics of the lift pump 9. The calculation unit 23 determines a target value Gopr of a speed command value for the inverter device 60 for driving the lift pump 9 and the motor 10, based on the extracted speed s. The determined target value Gopr is directly supplied to the inverter device 60 without being corrected by the monitoring unit 24 described later.

The calculation unit 23 calculates the acceleration time Ta from the minimum value Gmin of the speed command value to the target value Gopr. The calculation unit 23 calculates the deceleration time Td from the target value Gopr of the speed command value to the minimum value Gmin of the speed command value. As described later, the calculation unit 23 uses the equipment length of the ROT6 in addition to the data V of the rolling speed pattern when calculating Ta and Td.

When receiving a signal to start acceleration of the lift pump 9 from the PLC50, for example, the speed control device 20 changes the acceleration time Ta from the minimum value Gmin to the target value Gopr and supplies the speed command value to the inverter device 60. The acceleration rate in the acceleration time Ta is constant.

When the speed control device 20 receives a signal to start deceleration of the lift pump 9 from, for example, the PLC50, it takes the deceleration time Td to change from the target value Gopr to the minimum value, and supplies the speed command value to the inverter device 60. The deceleration rate in the deceleration time Td is constant.

The signal to start acceleration and the signal to start deceleration may be selected as appropriate, and for example, a signal used in a conventional CTC-based pass line may be used. The signal to start acceleration may be generated at a timing sufficiently before the timing at which the leading end of the rolled material enters the ROT 6. For example, the timing can be a timing at which the material to be rolled is bitten into the first mill stand 5 a. The signal to start deceleration may be a signal generated at a timing when the rolled material starts to separate from the ROT 6. For example, the signal may be a signal that the tail end of the rolled material is separated from the final stand 5 g. Signals relating to the load of the roll stand can be received from the PLC 50.

Fig. 4 is a graph schematically showing the speed versus flow characteristics of a lift pump.

Fig. 4 depicts a graph with the speed s of the lift pump 9 on the horizontal axis and the discharge flow Q of the lift pump 9 on the vertical axis.

As shown in fig. 4, the speed s of the lift pump 9 is determined according to the discharge flow Q of the lift pump 9. The discharge flow rate Q represents the flow rate of the cooling water flowing out from the discharge side of the lift pump 9, and is equal to the inflow amount into the high water level tank 6 a. The speed versus flow characteristic of the lift pump 9 is stored in the calculation section 23 as a function of an approximate curve representing the characteristic, for example, in a table format. Alternatively, the speed vs. flow rate characteristic may be stored in a storage unit or a storage device, not shown. The calculation unit 23 extracts a velocity s corresponding to the discharge flow rate Q with reference to the velocity-to-flow rate characteristic every time, and calculates a velocity command value G based on the velocity s.

Since the lift from the cistern 8 to the high level tank 6a is high, the minimum speed smin of the lift pump 9 needs to be such that the discharge pressure of the lift pump 9 must exceed the actual lift. The minimum speed smin is often set to about 60% to 70% of the maximum speed, depending on the pump characteristics and the like. When the lift pump 9 is driven at a speed at which the pump discharge pressure is lower than the actual head, the lift pump 9 cannot pump the cooling water, and the lift pump 9 itself may be damaged due to overheating. Therefore, in the operation described below, the speed command value G for the lift pump 9 and the motor 10 is set to be equal to or greater than the minimum value Gmin of the speed command value corresponding to the minimum speed of the lift pump 9. The maximum speed smax of the lift pump 9 is set according to specifications such as the maximum rated value of the lift pump 9.

The calculation unit 23 calculates the discharge flow rate Q so as to be a value equal to or greater than the data E of the predicted water injection amount. The discharge flow rate Q is calculated by multiplying (1+ α 1) by the data E using the adjustment parameter α 1, which will be described later in detail. By making the discharge flow rate Q exceed the estimated water injection rate, the water storage amount in the high water level tank 6a can be maintained at a predetermined value. The adjustment parameter alpha 1 is more than 0 and less than 1.

The description is continued with reference to fig. 3. The speed control device 20 further includes a monitoring unit 24 and a speed correction unit 25. The monitoring unit 24 monitors the actual value of the cooling water used and the actual value of the water level in the high water level tank 6a so that the data E of the water injection amount predicted by the calculation unit 23 is not lower than the actual water injection amount. The monitoring unit 24 obtains necessary data from the data collection unit 21 and the calculation unit 23, and obtains a correction value of the discharge flow rate Q. The speed correction unit 25 calculates a corrected speed command value G' based on the correction value of the discharge flow rate Q. The calculated speed command value G' is supplied to the inverter device 60.

The monitoring unit 24 includes a cooling water actual value monitoring unit 241 and a high-level tank water level monitoring unit 242. The data b of the actual value of the cooling water usage, the discharge flow rate Q of the lift pump 9, the data V of the actual value of the rolling speed, and the data V of the set value of the rolling speed are inputted to the actual value monitoring unit 241 of the cooling water usage. The coolant-use actual value monitoring unit 241 corrects the discharge flow rate Q based on the data b, Q, V, and supplies the corrected discharge flow rate Q' to the speed correction unit 25. The speed correction unit 25 extracts a speed s 'corresponding to the corrected discharge flow rate Q', and generates a speed command value G 'corresponding to the speed s'.

More specifically, the actual value of the cooling water usage monitoring unit 241 calculates the corrected discharge flow rate Q' when the data b of the actual value of the cooling water usage exceeds the discharge flow rate Q of the lift pump 9. For example, the discharge flow rate Q' is calculated by adding the adjustment parameter α 2 for correction to the adjustment parameter α 1. The adjustment parameter α 2 is set in advance to 0 < α 2 < 1.

The cooling water use actual value monitoring unit 241 corrects the discharge flow rate Q even when the data V of the rolling speed actual value exceeds the data V of the rolling speed set value. The speed correction unit 25 generates a corrected speed command value G' based on the corrected flow rate, and increases the speed of the lift pump 9. Since the flow rate of the cooling water to be used varies depending on the rolling speed, the monitoring target of the actual value monitoring unit 241 for cooling water use may be either the data b or the data v.

The speed correction unit 25 extracts a speed s 'corresponding to the discharge flow rate Q' with reference to the data of the speed-flow rate characteristics of fig. 4. The speed correction unit 25 calculates a corrected speed command value G 'based on the extracted speed s'.

In the actual value monitoring unit 241 for cooling water use, the speed of the lift pump 9 may be reduced to a range equal to or higher than the lower limit value, for example, the speed s before correction, when the data b is lower than the discharge flow rate Q or the data V is lower than the data V.

The high-level tank water level monitoring unit 242 acquires data c of the actual high-level tank water level value, and calculates a corrected discharge flow rate Q' based on the data c. The corrected discharge flow rate Q' is input to the speed correction unit 25.

More specifically, the high-level tank water level monitoring unit 242 is preset with a high-level tank slowdown water level Cth that is the lower limit of the water level of the cooling water stored in the high-level tank 6 a. When the data c is smaller than the high-level tank decelerated water level Cth, the high-level tank water level monitoring unit 242 generates a corrected discharge flow rate Q' so as to increase the original discharge flow rate Q.

The reduction of the water level of the high water level tank 6a may cause a reduction in the pressure of the cooling water, thereby possibly causing a reduction in the quality of the product. Therefore, when the data c is lower than the high-level-tank decelerated water level Cth, the high-level-tank water level monitoring unit 242 may set the maximum discharge flow rate without calculating the discharge flow rate Q, Q' and output the maximum value Gmax of the speed command value.

In addition, when the speed command value G before correction is already set to the maximum value, the speed command value G may be lowered to decelerate the lift pump 9 after detecting that the water level in the high water level tank 6a exceeds the high water level tank decelerated water level Cth again.

< construction of peripheral System of speed control device >

The CTC30 obtains the steel grade, thickness, and required product quality of each rolled material from a host computer system, and determines the amount of water injected into the cooling water per unit length of the rolled material 200c in accordance with these. That is, CTC30 determines the amount of water injected into the cooling water for each cut board. The water injection amount determined by CTC30 for each cutting board is switched to the open/close mode of injection valves 6b and 6c by a PLC (not shown) for injection valve control provided at a lower position of CTC 30.

CTC30 is a device for feeding back the Temperature (FDT) of the rolled material at the exit side of the finishing mill 5 and the Temperature (CT) of the rolled material at the time of Coiling when water injection is started, and controlling the opening/closing pattern of the injection valves 6b and 6c via a PLC (not shown) to change the amount of water injection.

The CTC30 sets data a of the initial flow rate setting information for each rolled material. The data a is the amount of water injected into the first cut plate of the material to be rolled, and is transmitted to the speed controller 20 at an appropriate timing. The data a is set according to facilities and the like, for example, at the time when the final pass of the rough rolling process is finished, and is transmitted to the speed control device 20.

The finish rolling setting calculation device 40 performs calculation for setting various parameters of the material to be rolled 200b in the finish rolling mill 5. The various parameters include a rolling speed pattern including a leading end pass speed V1, a trailing end exit speed V2, a maximum speed Vr at the time of rolling, a primary acceleration rate a1, and a secondary acceleration rate a2 of the rolled material 200 b. The front end pass speed V1, the tail end exit speed V2, the maximum rolling speed Vr, the primary acceleration rate a1, and the secondary acceleration rate a2 are collectively referred to as data V of a rolling speed set value. After the rolled material is pulled out from the heating furnace 1, the setting calculation of the data V is performed a plurality of times according to the rolling condition, and the correction is performed every time. The data V of the corrected rolling speed set value is sent to the speed control device 20.

The CTC30 and the finish rolling setting calculation device 40 are, for example, a server, an engineering workstation, and the like that can be connected to a control system network. The CTC30 and the finish rolling setting calculation device 40 may be implemented by different servers or the like, or may be implemented by programs installed in the same server or the like.

The PLC50 collects various data at a fixed cycle, for example, by sensors and the like disposed in the hot rolling line 100. The various data include data b of an actual value of cooling water use, data v of an actual value of rolling speed, and data c of an actual value of water level of the high water level tank. In addition, data b, v, c may be interfaced to the same PLC or may be interfaced to and collected from different PLCs, respectively.

The PLC50 creates a reference based on the result calculated by the host computer system, and issues commands to the drive device of the finishing mill 5, the actuators of the injection valves 6b and 6c, and the like. The PLC50 receives feedback information such as actual speed and opening/closing setting of the injection valves 6b and 6c from a driving device, an actuator, and the like.

The PLC50 calculates data b based on the opening/closing information of each of the injection valves 6b and 6c and the rated flow rate of each valve. Since the setting of the opening/closing information of the injection valves 6b and 6c changes with time, the data b of the actual values of the cooling water is calculated as the time-series usage flow rate.

The data v of the actual rolling speed is obtained by multiplying the transport speed of the material to be rolled 200c at the ROT6 by the forward slip ratio of the final stand 5g, or the roll table transport speed detected by the roll table rolls 6d provided at the ROT 6. Here, the transport speed of the rolled material 200c at the ROT6 is the rolling speed of the final stand 5 g.

The data c of the actual value of the water level in the high water level tank indicates the water level of the high water level tank 6a at the present time. The data c is supplied as an output signal of a water gauge provided in the high water level tank 6 a. In addition, when the water level gauge is not provided in the high water level tank 6a, the actual value of the water level in the high water level tank may be calculated based on a predetermined calculation formula. This calculation formula is set in consideration of the shape of the high water level tank and the tank capacity based on the inflow amount of the cooling water to the high water level tank 6a, that is, the discharge flow rate Q of the lift pump 9 and the data b of the actual water injection amount.

< actions of speed control device 20 >

The operation of the speed control device 20 of the present embodiment will be described.

Fig. 5 to 7 are schematic timing charts for explaining the operation of the speed control device according to the present embodiment.

Fig. 5 shows an example of a timing chart in the case where the monitoring unit 24 does not operate.

Fig. 6 and 7 show examples of timing charts in the case where the monitoring unit 24 operates.

The graphs of fig. 5 to 7 are all shown about the same axis. The horizontal axis of the graph is a time axis. The vertical axis of the graph is data b of the actual value of the cooling water, data v of the actual value of the rolling speed, a speed command value G of the lift pump, and data c of the actual value of the water level of the high water level tank, and is arbitrarily graduated.

In fig. 5 and 6, the data c of the actual water level value of the high-level tank is always equal to or higher than the decelerated water level Cth of the high-level tank.

Among the data V of the set rolling speed values, the actual measurement data corresponding to the leading end pass speed V1 is denoted by V1, the actual measurement data corresponding to the maximum rolling speed Vr is denoted by Vr, and the actual measurement data corresponding to the trailing end exit speed V2 is denoted by V2.

First, the operation of the monitoring unit 24 in the case where it does not operate will be described.

Data v of the actual rolling speed shown by the broken line in fig. 5 will be described.

As shown in fig. 5, at time t1, the material to be rolled is bitten into the first stand 5a at the leading end passing speed v 1. The rolled material is bitten into the last stand 5g at the front end passing speed v1 at time t 2.

At time t2, the material to be rolled starts acceleration once at a timing when the tip end is bitten into the final-stage stand 5 g. At time t3, the leading end of the rolled material reaches the underground coiler 7, the primary acceleration is completed, and the secondary acceleration is started. At time t5, the rolled material reaches the set maximum pass speed vr and is maintained at that speed.

When the tail end of the rolled material approaches the mill stand 5g of the final stage, deceleration is started. The time at this time is t 6. The speed is reduced to the tail-end exit speed v2 in accordance with the timing at which the tail end of the rolled material is disengaged from the mill stand 5g of the final stage. The time at this time is t 7.

The rolled material is wound by the down coiler 7 at the tail exit speed v2, and the winding is completed at time t 9. After that, the roller bed roller 6d of the ROT6 is decelerated and stopped.

Next, a time change of the data b of the actual value of the cooling water shown by the one-dot chain line will be described.

Since the data b of the actual value of the coolant use is equal to the actual water injection amount feedback-controlled by the CTCT30, the curve of the graph can be regarded as the actual water injection amount. Since there is a time lag between the completion of the opening and closing setting of the injection valves 6b and 6c by the CTC30 and the start of the actual water injection, the water injection into the rolled material 200b is started before the rolled material is bitten into the last mill stand 5 g. The opening and closing settings of the injection valves 6b and 6c are preset in consideration of a time lag from when the PLC50 sends a valve opening and closing command to when water injection is actually started.

In CTC30, since the speed of the material to be rolled increases during the period from time t1 to time t4, the amount of water injection increases by the temperature feedback of the material to be rolled. After time t4, the set maximum water injection amount is maintained until time t 6.

In CTC30, since the speed of the rolled material is reduced, the amount of water injection is reduced by the temperature feedback of the rolled material. From time t6 to time t7, the amount of water injection is reduced in accordance with the reduction in the speed of the rolled material from the maximum pass speed vr to the tail end exit speed v 2.

The time change of the speed command value of the lift pump 9 shown by the solid line will be described.

The speed command value G of the lift pump 9 is set to the minimum value Gmin at time t1, and thereafter increases with the acceleration rate described later. The timing at which the acceleration of the lift pump 9 is started is the timing before the leading end of the rolled material enters the ROT 6. In this example, the time t1 is the timing at which the rolled material is bitten into the first stand 5 a. For example, at this time, the opening/closing commands of the injection valves 6b and 6c are output, and water injection is started. The lift pump 9 is accelerated from time t1 until the acceleration time Ta elapses, and is operated at a constant speed s corresponding to the discharge flow rate Q obtained from the predicted water injection amount, and the speed control device 20 outputs a target value Gopr of the speed command value.

The acceleration time Ta of the lift pump 9 can be calculated using the data V (V1, Vr, V2, a1, a2) of the rolling speed set value and the equipment length d of the run-out table 6. The facility length d of the run-out table 6 can be expressed by the following formula (1).

[ numerical formula 1]

Here, T1 is a period during which the rolled material is accelerated at the primary acceleration rate a 1. This period is referred to as a primary acceleration time. The primary acceleration time T1 is T1 ═ T3-T2. The primary acceleration rate a1 is a constant value.

The primary acceleration time T1 is obtained from equation (1) as shown in equation (2) below.

[ numerical formula 2]

The secondary acceleration time T2 during which the rolled material is secondarily accelerated at the secondary acceleration rate a2 can be obtained as shown in the following equation (3). The secondary acceleration rate a2 is a constant value.

[ numerical formula 3]

As shown in the following expression (4), the acceleration time Ta can be obtained as the sum of the primary acceleration time T1 and the secondary acceleration time T2.

Ta＝T1+T2 (4)

The speed command value G of the lift pump 9 is set to a target value Gopr of the operating speed after the acceleration time Ta has elapsed.

The calculation unit 22 calculates data E of the predicted water injection amount using the data a of the initial flow rate setting information and the data V of the rolling speed setting value. The maximum predicted water injection amount is determined so that the maximum water injection amount becomes a × Vr/V1.

The discharge flow rate Q of the lift pump 9 is set with a margin with respect to the predicted water injection amount. The adjustment parameter α 1 is a coefficient indicating a margin of the discharge flow rate Q drawn by the lift pump 9 with respect to the predicted water injection amount. The discharge flow rate Q is set to (1+ α 1) × E.

The 2 nd calculation unit 23 obtains the speed s of the lift pump 9 when Q is (1+ α 1) × E from the speed vs. flow rate characteristic of the lift pump 9. The speed command value G supplied from the speed controller 20 to the inverter device 60 is set to be equal to the speed s of the lift pump 9. The adjustment parameter α 1 can be set to an appropriate arbitrary value, for example, by estimating a calculation error of the flow rate estimated by the calculation unit 22, an error of the speed of the lift pump with respect to the flow rate characteristic, or the like.

From the viewpoint of ensuring sufficient pumping to the high water level tank 6a, the speed of the pump 9 is preferably set to a timing later than the timing at which the rolling material starts to decelerate. In this case, the timing is later than the timing of reducing the amount of injected water. In this example, the timing at which the lift pump 9 starts to decelerate is time t 8. The time t8 is the timing at which the final stand 5g discharges the tail end of the rolled material.

As shown in the following equation (5), the deceleration time Td of the lift pump 9 may be, for example, a time obtained by dividing the ROT equipment length d by the tail end exit speed V2.

[ numerical formula 4]

In this case, as shown in the following equation (6), the deceleration rate ad is obtained by dividing the difference between the deceleration start speed and the acceleration/deceleration by the deceleration time Td.

[ numerical formula 5]

The timing of the start of deceleration may be set later than the timing of the start of run-out 6 of the rolled material, and the timing of the start of deceleration and the deceleration time Td may be set to any appropriate value such as the tail end pass speed. In this example, the time t10 at which the speed reduction of the lift pump 9 is completed is set by the time t8 and the speed reduction time Td.

t10＝t8+Td

Next, a case where the coolant in the monitoring unit 24 is operated by using the actual value monitoring unit 241 will be described.

In the state shown in fig. 6, the operation from time t1 to time t5 is the same as in the above case, and after the rolling speed and the water injection amount become constant values at time t5, these actual values exceed the set values at time t 18.

As shown in fig. 6, during the period from time t18 to time t19, the data V of the actual rolling speed exceeds the data V of the set rolling speed value supplied from the finish rolling setting calculation device 40 for some reason (not shown). As a result, the temperature (FDT, CT) of the rolled material changes, and the amount of water injected increases in response to the change in the temperature (FDT, CT) of the rolled material at the CTCT 30.

The actual value monitoring unit 241 for cooling water detects that the data V of the actual value of the rolling speed exceeds the data V of the set value of the rolling speed, and that the data b of the actual value of the cooling water (the actual value that is approximately equal to the water injection amount) exceeds the discharge flow rate Q. In this example, the coolant-use actual value monitoring unit 241 calculates a correction value of the discharge flow rate by adding the adjustment parameter α 2 for correction to the adjustment parameter α 1 and multiplying the result by the data E of the predicted water injection amount. That is, the corrected discharge flow rate Q' is expressed by the following formula (7).

Q’＝(1+α1+α2)×E (7)

Here, α 2 is 0 < α 2 < 1, and is set in advance to an appropriate value.

The corrected discharge flow rate Q ' is input to the speed correction unit 25, and the speed correction unit 25 extracts a speed s ' corresponding to the corrected discharge flow rate Q ' with reference to the speed convection flow rate characteristic of the lift pump 9. The speed correction unit 25 generates a corrected speed command value G ' based on the speed s ' and supplies the corrected speed command value G ' to the inverter device 60.

In fig. 6, the speed command value G' of the lift pump 9 is set to a target value Gopr2 that is greater than the previous target value Gopr1 after time t 18.

At time t20, the speed controller 20 detects that the rolled material is discharged from the final stand 5g, and decelerates the lift pump 9 after time t 20. The deceleration period of the lift pump 9 and the like are set in the same manner as described above, and the speed command value G' is set to reach the minimum value Gmin at the time t22 after the time t21 when the rolling of the rolled material is completed.

Next, the operation of the high-level tank water level monitoring unit 242 in the monitoring unit 24 will be described.

In fig. 7, the time change of the actual rolling speed value from time t1 to time t5 is the same as in the above case, but in this example, the actual value of the injected water amount is larger than in the above case. In this way, depending on the material type of the material to be rolled, more cooling water may be injected. Therefore, in this example, the target value Gopr of the speed command value of the lift pump 9 is set to the maximum value G100% of the speed. Therefore, the speed of the lift pump 9 cannot be increased, and the discharge flow rate of the lift pump 9 cannot be further increased.

As shown in fig. 7, the amount of water injected increases significantly from time t3 to time t36, and as a result, data c of the actual value of the water level in the high water level tank becomes lower than the decelerated water level Cth in the high water level tank at time t 37.

Here, the high-level tank water level monitoring unit 242 detects that the data c of the actual high-level tank water level is lower than the high-level tank decelerated water level Cth, and calculates the correction value of the speed command value, but since the current speed is the maximum value G100%, the speed command value cannot be set to exceed the maximum value even if the calculation of the correction value is performed.

The data c of the actual water level value of the high water level tank is changed to rise due to the decrease of the amount of injected water after the time t 38. In the above-described cases of fig. 5 and 6, the speed reduction of the lift pump 9 is started at the time when the rolled material is discharged from the final-stage stand 5g (time t8 in the case of fig. 5 and time t20 in the case of fig. 6). However, in this example, when the speed reduction of the lift pump 9 is started at this time, there is a possibility that the water level in the high water level tank 6a cannot be returned to the high water level tank decelerated water level Cth. When the operation of the ROT6 is continued in a state where the water level of the high water level tank 6a is lower than the high water level tank decelerated water level Cth, the pressure of the discharged cooling water may be insufficient, which may affect the quality of the product.

Therefore, the high-level-trough water level monitoring unit 242 and the speed correction unit 25 stop the start of the deceleration of the lift pump 9 even when receiving a signal indicating that the tail end of the rolled material is separated from the final stand 5 g. The high-level tank water level monitoring unit 242 continues to monitor the data c of the actual high-level tank water level while maintaining the speed of the lift pump 9. The high-level tank water level monitoring unit 242 and the speed correction unit 25 generate a speed command value to decelerate the lift pump 9 after detecting that the data c exceeds the high-level tank decelerated water level Cth at time t 40.

Thereafter, at time t41, the rolling of the rolled material is completed, and at time t42, the speed command value G reaches the minimum value Gmin.

In addition, the high-level tank water level monitoring unit 242 may calculate the discharge flow rate using the adjustment parameter α 2 and set the speed command value G' in the same manner as in the case where the actual value monitoring unit 241 is used for the cooling water when the arrival speed of the lift pump 9 has a margin with respect to the maximum speed.

A series of operations of the speed control device 20 according to the embodiment will be described with reference to a flowchart.

Fig. 8 is an example of a flowchart for explaining the operation of the speed control device of the lift pump according to the embodiment.

As shown in fig. 8, in step S1, the data collection unit 21 collects data a, V, b, V, c of the initial flow rate setting information, the rolling speed setting value, the actual value of the cooling water usage, the actual value of the rolling speed, and the actual value of the water level in the high water level tank. The data collection unit 21 collects these data from the CTC30, the finish rolling setting calculation device 40, and the PLC50 via the control system network.

In step S2, the predicted water injection amount calculation unit 22 calculates the predicted water injection amount data E based on the data a of the initial flow rate setting information and the rolling speed setting value V.

In step S3, the lift pump speed calculation unit 23 calculates the acceleration time Ta and the deceleration time Td using equations (1) to (6).

The calculation unit 23 calculates the discharge flow rate Q of the cooling water pumped by the lift pump 9 using the data E of the predicted water injection amount and the adjustment parameter α 1. The calculation unit 23 extracts a speed s corresponding to the discharge flow rate Q from the speed vs. flow rate characteristics of the lift pump 9 set in advance. The calculation unit 23 sets a target value Gopr of the speed command value corresponding to the speed s.

The calculation unit 23 receives the timing at which the rolled material is gripped by the first stand 5a from the PLC50, and accelerates the speed command value G from the minimum value Gmin. The calculation unit 23 takes the acceleration time Ta to linearly increase to Gopr, and supplies the acceleration time Ta to the inverter device 60.

In step S4, the cooling water use actual value monitoring unit 241 receives the data b of the cooling water use actual value and the discharge flow rate Q as input, and compares the magnitude relationship between them. The actual value monitoring unit 241 for cooling water receives the data V of the actual rolling speed and the data V of the set rolling speed, and compares the magnitude relationship between them.

The cooling water usage actual value monitoring unit 241 shifts the process to step S5 when the actual value data b is larger than the calculated discharge flow rate Q or when the actual value data V is larger than the set value data V. The coolant-use actual value monitoring unit 241 shifts the process to step S6 when the actual value data b is equal to or less than the discharge flow rate Q and the actual value data v is equal to or less than the set value data. In step S5, instead of comparing data V and V, determination may be performed by comparing data b and discharge flow rate Q, or a logical product between the result of comparison of data b and Q and the result of comparison of data V and V may be used.

In step S5, the coolant-use actual value monitoring unit 241 calculates a corrected discharge flow rate Q'. The discharge flow rate Q' is calculated using equation (7). The speed correction unit 25 extracts the speed s ' corresponding to the corrected discharge flow rate Q ' with reference to the speed vs. flow rate characteristic, and generates a new speed command value G '.

In step S6, the high-level tank water level monitoring unit 242 compares the actual value data c with the high-level tank decelerated water level Cth. When the data c of the actual value is lower than the high-level-tank decelerated water level Cth, the high-level-tank water level monitoring unit 242 proceeds to step S7. When the data c is the high-level tank slowdown possible water level Cth or more, the high-level tank water level monitoring unit 242 proceeds to step S8.

In step S7, the high-level tank water level monitoring unit 242 and the speed correction unit 25 calculate the corrected discharge flow rate and speed command value. In this example, the corrected discharge flow rate and speed command value are set to maximum values. The high-level tank water level monitoring unit 242 and the speed correction unit 25 maintain the discharge flow rate and the speed command value at the maximum values when the discharge flow rate and the speed command value have been set at the maximum values.

In step S8, the high-level tank water level monitoring unit 242 compares the data c of the actual high-level tank water level value with the high-level tank decelerated water level Cth again. If the data c is the high-level tank slowdown possible water level Cth or higher, the process proceeds to step S9. If the data c is lower than the high-level tank slowdown possible water level Cth, the high-level tank water level monitoring unit 242 proceeds to step S10.

In step S9, the high-level tank water level monitoring unit 242 supplies a deceleration permission signal for permitting the lift pump 9 to decelerate to the calculation unit 23. The calculation unit 23 receives a signal from the PLC50 that the rolled material has left the final stand 5g, starts the deceleration of the lift pump 9, and decelerates to the minimum value Gmin in accordance with the calculated deceleration time Td.

In step S10, the high-level tank water level monitoring unit 242 supplies a deceleration prohibition signal for prohibiting the speed of the lift pump 9 from being decelerated to the calculation unit 23. The high-level tank water level monitor 242 returns the process to step S6.

In this manner, the speed control device 20 of the embodiment can operate.

The speed control device 20 of the lift pump 9 is, for example, a computer device such as a server, and may include an arithmetic device such as a CPU or MPU that operates by executing a program. Such an arithmetic device executes a read program to realize a part or all of the functions of the above-described modules or the operations of the steps.

The effect of the speed control device 20 of the embodiment will be described.

In the speed control device 20 of the embodiment, the data a of the initial flow rate setting information and the data V of the rolling speed setting value can be acquired from the CTC30 and the finish rolling setting calculation device 40, and the usage flow rate of the CTC can be predicted based on these data. Therefore, the flow rate of the cooling water for pumping can be determined based on the data E of the water injection amount calculated by prediction, and the speed of the lift pump 9 can be suppressed when the water injection amount is small. Therefore, the drive power of the lift pump 9 can be suppressed, and energy saving of the pass line can be achieved.

The data A, V can be received before the timing at which the feedback of the actual value of the use of the cooling water and the actual value of the rolling speed can be obtained, and the required acceleration time can be calculated by using the plant length d of the ROT 6. Therefore, the lift pump can be accelerated without causing a control delay such as feedback control, and a desired discharge flow rate can be realized in a required acceleration time.

The deceleration time of the lift pump can be calculated in advance by using the equipment length of the ROT6 and the data V, and the speed controller 20 can start deceleration at an appropriate timing such as the timing when the tail end of the rolled material leaves the final stand 5 g. Therefore, the lift pump 9 is appropriately stopped without reducing the water storage amount in the high water level tank 6 a.