RU2786558C1 - Cooling section with valves and pressure tanks to prevent water shocks - Google Patents

Abstract

FIELD: mill products.

SUBSTANCE: invention relates to a device for cooling rolled metal. The device for cooling rolled metal has several cooling devices, to each of which water is supplied through the corresponding dead-end pipeline (7). In dead-end pipelines, there are valves through which the water flow running through the corresponding dead-end pipeline is adjusted. The valves are correspondingly correlated with the actuator by which the corresponding valve is activated. The cooling devices form several groups, each of which is equipped with its own pressure tank. Each pressure tank at the appropriate connection point is connected to the corresponding supply pipeline, through which water is supplied to the dead-end pipelines of the cooling devices of the corresponding group. In the direction of the water flow, each connection point is located in front of the valves of the corresponding group of cooling devices.

EFFECT: as a result, hydraulic shocks are prevented when the rolled products are cooled with water.

6 cl, 6 dwg

Description

Technical field

The present invention relates to a device for cooling rolled metal rolled in a group of rolling stands,

- moreover, this device has several cooling devices, to each of which water is supplied through the corresponding dead-end pipeline, and through which water is applied to the rental;

- at the same time, in the dead-end pipelines, there is a valve, by means of which the water flow flowing through the corresponding dead-end pipeline is adjusted;

- in this case, the valves are respectively assigned to the drive, with which the corresponding valve is activated.

State of the art

Such a device is known, for example, from WO 2018/080 669 A2. This device has one separate bypass pipeline parallel to dead-end pipelines. By means of this bypass line, water hammer is to be prevented, which would otherwise occur when the bulk flow through the stub lines is quickly interrupted. This bypass pipeline must actively open and close.

From EP 2 767 353 A1 a cooling section for flat products is known, this cooling section having a plurality of spray bars, each of which is preceded by a valve.

Also known from WO 2013/143 902 A1 is a device for cooling rolled metal rolled in a group of rolling stands. With this device, the cooling nozzles of the cooling section present there are connected by a supply line to a water tank. The water supply to the cooling nozzles is controlled by a single valve or multiple valves. There is a pressure tank, which is located in front of this valve or, respectively, these valves. This pressure tank is partly filled with water and partly with air. In this embodiment, water hammer, which may otherwise occur when the volume flow through the stub pipes is quickly interrupted, is prevented or at least reduced in magnitude due to the buffering action of the pressure tank.

Brief summary of the invention

In the cooling section of the rolling mill, after rolling the rolled metal, this rolled product is cooled. Precise temperature control is generally accepted in the cooling section in order to adjust and thus maintain as constant as possible the desired properties of the material. At the same time, several cooling devices are mounted in the direction of transport of the rolled stock, by means of which water is applied to at least one side of the rolled stock. These cooling devices can be made, for example, in the form of chilled beams. The amounts of water applied by the cooling devices are adjusted by means of valves located in front of the cooling devices. It is problematic in particular if these valves close quickly. After all, when valves close too quickly, pressure shocks often occur, also called water hammer in professional circles. Therefore, in order to avoid excessive loads, the switch-off duration is usually limited to 1 second. This applies even if the valves could close faster.

In the prior art, as a rule, pneumatic valves are used. As a rule, they cannot turn on faster than 1 second. However, in some cases shorter switching times of 0.6 seconds can also be achieved.

From WO 2018/080 669 A2 a cooling section of a rolling mill is known, in which the cooling devices are switched on by means of electrically actuated valves.

From WO 2013/143 902 A1 it is known to connect a pressurized tank in a supply line to a cooling section. This pressure tank mainly serves to maintain a constant pressure when supplying the cooling section, but also contributes to some extent to the reduction of water hammer. The available pressure tank is designed for a volume of several cubic meters. Specifically, WO 2013/143 902 A1 names a characteristic volume of 10 to 20 cubic meters.

The object of the present invention is to provide a device for cooling rolled metal rolled in a group of rolling stands, which has superior performance properties.

The problem is solved using a device for cooling rolled metal, rolled in a group of rolling stands, with the features of claim 1 of the claims. Preferred embodiments of the device are the subject of dependent claims 2-6.

In accordance with the invention, a device for cooling rolled metal, rolled in a group of rolling stands, of the above type is made in such a way that

- that the cooling devices form several groups, each of which is proprietary equipped with its own pressure tank;

- that each pressurized tank is connected at the respective connection point to a supply pipe, through which water is supplied to the stub pipes of the cooling devices of the respective group, so that, looking in the direction of the water flow, the corresponding connection point is located before the valves of the respective group of cooling devices.

The device can be made in the form of a cooling section, which is located after a group of rolling stands. Alternatively, the device can be made in the form of a group of inter-stand coolings, while one of these inter-stand coolings is located between each two rolling stands of the rolling stand group. In a separate case, the device can also be located in front of a group of rolling stands, for example, when the device is located between (at least) one roughing stand and a multi-stand group of finishing stands. Mixed forms are also possible.

Rolled stock often consists of steel. This can be, in particular, flat products, that is, a strip or a thick sheet. In the case of flat products, the cooling devices may alternatively supply water to the flat products only on the top side, only on the bottom side, or both on the top and bottom side.

For cooling devices, the amount of water applied by them to the rental can be individually adjusted using their valves. It is possible for the cooler groups to be "true" cooler groups that each include more than one cooler. However, in many cases, at least some of the groups of cooling devices include only one single cooling device. In particular, it is even possible for all groups to include only one single cooling device each. In this case, the groups of cooling devices are degenerate.

The actuators associated with the valves can be made according to the needs. In particular, they can be made in the form of electric drives, for example, in the form of stepper motors.

Proprietary component of each group of cooling devices pressure tank has a certain volume of the tank. This tank volume is preferably from n x 20 l to n x 200 l, where n is the number of cooling devices of the respective group. Particularly preferably, the volume of the tank is from n x 50 l to n x 125 l.

Preferably, a corresponding flow resistance is located between each connection point and the corresponding pressure tank. That is, there is a device, the meaning and purpose of which is to oppose resistance to water flow (= hydraulic resistance).

As already mentioned, a respective volumetric flow flows in each supply line when the valves of the cooling devices of the respective group are all fully open. In this state, each inlet pipeline has a corresponding pipeline pressure in the area of the corresponding connection point. The respective flow resistance is preferably chosen in such a way that the respective volumetric flow, when it flows through the respective flow resistance, causes a pressure drop which is at least 25% and at most 75% of the respective pipeline pressure, in particular about half the magnitude of the respective pipeline pressure. . However, small deviations are acceptable.

Brief description of the drawings

The above described features, features and advantages of this invention, as well as how they are achieved, become clearer and more clearly understood in the context of the following description of exemplary embodiments, which are explained in more detail with reference to the drawings. In this case, the schematic image shows:

figure 1: rolling stand and cooling section;

figure 2: part of the cooling section;

figure 3: section of the cooling;

figure 4: time graph of the degree of filling and

figure 5: time plot of the volumetric flow,

Fig. 6: time plot of pressure.

Description of Embodiments

In accordance with figure 1 in the group of rolling stands rolled 1. In figure 1 shows only the last rolling stand 2 multistand group of rolling stands. Rental 1 is often a flat rental, that is, a strip or a thick sheet. However, rental 1 may have a different format. For example, it can be a profile or a bar 1. The bar 1 often consists of steel, sometimes aluminum and, in rare cases, some other metal or, respectively, some appropriate alloy.

After the group of rolling stands there is a section 3 for cooling. In section 3 cooling rolled 1 is cooled. The cooling section 3 is thus a device for cooling the rolled metal 1 rolled in the rolling stand group. With reference to the cooling section 3 shown in FIG. 1, which is located after the group of rolling stands, the present invention will be explained. That is, the term "cooling section" is used in the sense of the named device. However, the present invention can also be implemented when the device is located in a group of rolling stands, that is, between rolling stands 2 of a multi-stand group of rolling stands. In addition, it can also be implemented when the device is located in front of a group of rolling stands.

The cooling section 3 has, in accordance with FIG. 1, several cooling devices 4 . By means of these cooling devices 4, water 5 is applied to the rolled 1. The cooling devices 4 are usually made in the form of spray beams, which apply water 5 to the rolled 1 over the entire width of the rolled 1. Water 5 in its entirety is supplied to the cooling section 3 along the supply pipeline 6. In section 3 cooling water 5 is distributed until it enters the dead-end pipelines 7, through which water 5 is supplied to each device 4 cooling. In dead-end pipelines 7, one (1) valve 8 is located, by means of which the amount of water 5 that is supplied to the corresponding cooling device 4 per unit of time can be adjusted. Thus, there is a 1:1 correspondence between cooling devices 4, dead ends 7 and valves 8. The amount of water 5 that is supplied to each cooling device 4 per unit time is the corresponding water flow.

Figure 1 shows a total of eight cooling devices 4, and in the image in accordance with figure 1, one part of the cooling devices 4 applies water to the rental 1 from above, and the other part of the cooling devices 4 applies water 5 to the rental 1 from below. In addition, the cooling devices 4, when viewed in the direction x of transporting the rolled steel 1, are arranged in stages one after the other. However, these situations are purely exemplary. Thus, there may well be more or less than eight cooling devices 4 as well. It is also possible for water to be applied to the rolled product 1 exclusively from above or exclusively from below by means of the cooling devices 4 . If the rolled product 1 is a flat product, it is also possible, according to the depiction in FIG. It is decisive that a corresponding valve 8 is located in each stub pipe 7, by means of which the corresponding water flow through the respective stub pipe 7 can be adjusted.

The valves 8 are each equipped with an actuator 9 as an actuating device. Drives 9 according to the image in figure 2 are made in the form of electric drives. Each actuator 9 activates the corresponding valve 8. This situation also occurs with the valves 8 of FIG. However, this is not shown in FIG. 1 so as not to overload FIG. Due to the design of the actuating devices as electric actuators for the valves 8, duty cycles can be realized that are significantly less than 1 second, for example 0.2 seconds or less. In addition, very fast fine tuning of electric actuators is possible. Therefore, both quick and fine adjustment of each valve position is possible.

Electric drives can be made, for example, in the form of stepper motors. Stepper motors can easily be moved 90° in less than 0.2 seconds. This angle also corresponds to the rotation angle of the conventional valve 8 between fully closed and fully open position. At the same time, at a time of 0.2 seconds or less, each valve 8 can be transferred from a fully closed position to a fully open position and vice versa. In addition, the repositioning of a stepper motor is usually done in angular steps that are significantly less than 1° (mechanically), for example 0.1° (or a similarly small angle). In this case, it is possible to move each valve 8 between a fully closed and fully open position in steps of 0.1° (or similarly small angle). In addition, the control electronics of the electric drive is quite simple and economical. Wear and failure is many times less than that of a pneumatic actuator. The required sealing against splash water and the like (eg protection class IP 65) can be implemented without difficulty. This applies both to each electric drive itself and to its control electronics.

Regardless of the particular geometrical arrangement of the cooling devices 4, the cooling devices 4 also form, according to the representation in FIG. 3, several groups. These groups are each proprietary equipped with their own pressure tank 10. The term "proprietary equipped" should mean that each pressure tank 10 interacts with the cooling devices 4 of this group and interacts only with these cooling devices 4. In particular, each pressure tank 10 is connected in the respective connection point 11 to the respective inlet pipeline 12. Water 5 is supplied through the respective pipeline 12 to the dead-end pipelines 7 of the cooling devices 4 of the corresponding group. In this case, when viewed in the direction of flow of water 5, each connection point 11 is located in front of the valves 8 of the corresponding group of cooling devices 4. In contrast, this supply line 12 does not supply water 5 to dead-end pipes 7 of other cooling devices 4. In this case, when viewed in the direction of the flow of water 5, each connection point 11 is not located in front of the valves 8 of other groups of cooling devices 4. In this case, each pressurized tank 10 defines a respective group of cooling devices 4: all cooling devices 4 whose water 5 flows through the corresponding connection point 11 form one (1) group of cooling devices 4 . All other cooling devices 4 do not belong to this group.

Each connection point 11 for the respective pressure tank 10 must be located as close to the valves 8 of the respective group as possible. If - see figure 3 on the left - the corresponding group of cooling devices 4 includes only one single cooling device 4, the corresponding connection point 11 should be located as close as possible to the valve 8 of this cooling device 4. If - see figure 3 on the right - the corresponding group of cooling devices 4 includes several cooling devices 4, the corresponding connection point 11 should be located as close as possible to the distribution point 13 at which the supply line 12 first branches to the cooling devices 4 of the corresponding groups.

According to the image in figure 3, some of the groups of devices 4 cooling includes only one single device 4 cooling. In the image of FIG. 3, this is specifically the case for the two cooling devices 4 shown on the left. In these cases, the respective supply line 12 is identical to the respective stub line 7. Alternatively, it is also possible for the groups of cooling devices 4 to include several cooling devices 4 each. In the image of figure 3, this is specifically the case with the cooling devices 4 shown on the right. In these cases, each supply pipeline 12 is located in front of the corresponding dead-end pipelines 7.

The decisive criterion for the arrangement of the pressure tanks 10 is the amount of water 5 that is between each connection point 11 and the corresponding valves 8, or, in the case of a single one located after the valve 8, the corresponding valve 8. After all, this amount of water cannot be redirected to the corresponding pressure vessel 10. This quantity must therefore, when the respective valves 8 close quickly, immediately and quickly brake in front of the respective valves 8. As a rule, this is not critical if the distance from the respective valves 8 to the respective pressure vessel 10 is sufficiently small, e.g. 10 m or less, in particular less than 5 m. This should be explained using the example of one individual valve 8.

Let us assume that the flow rate of water 5 in the corresponding dead-end pipeline 7 is 3 m/s. Each valve 8 will close completely within 0.2 seconds. Then the water 5 must slow down from 3 m/s to 0 m/s within 0.2 seconds. In this case, an average acceleration of 15 m/s ² is obtained, i.e. approximately 1.5 times the acceleration of free fall. In addition, it is known that a water column 10 m high creates a pressure of 1 bar. The same applies to a 10 m long water column, which is decelerated with free fall acceleration. Let us also assume that the distance from the corresponding connection point 11 to the corresponding valve 8 is 5 m. 5 times free fall acceleration. Thus, this water column under these operating conditions, when braking from 3 m/s to 0 m/s within 0.2 s, creates a pressure of 0.75 bar.

By closing the corresponding valve 8 quickly without pressure tanks 10, in contrast, a high pressure surge would occur, since in this case the water 5 flowing in the supply line 12 would also have to be decelerated, since it is located when viewed in the direction of flow water 5, in front of the corresponding connection point 11. However, such pressure surges can be significantly mitigated by pressure tanks 10, since in this case the water 5 flowing in the corresponding supply line 12 is redirected to the pressure tank 10, which is proprietary to the corresponding group of cooling devices 4.

As is well known, pressure tanks 10 serve to equalize the water balance. Therefore, depending on the need, firstly, with a rapid decrease in water demand 5, they must be able to receive water 5 from the supply pipeline 12 to which they are connected, and secondly, with a sudden increase in water demand 5, be able to feed water 5 back into the supply pipe 12. In order for the pressure tanks 10 to receive and feed back this water 5, the pressure tanks 10, according to the image in figure 3, are each filled partially with water 5 and partially with air 14 during operation. As a rule, one should strive for degree F filling with water 5 (see figure 4) approximately 50%. However, some deviations are quite possible - for example, from 40% to 60%. That is, the pressure tanks 10 are designed to be partially filled with water 5 and partially with air 14 during operation.

In order to be able to adjust the respective filling degree F, the pressure tanks 10 can, for example, have a corresponding air valve 15. Through this respective air valve 15, air 14 can be supplied to the corresponding pressure tank 10, or air 14 can be drained from the corresponding pressure tank 10. In the simplest case, the corresponding air valve 15 is a manually actuated check valve (such as, for example, the valve of a bicycle or some other road vehicle having air-filled tires). In this case, the respective pressure vessel 10 preferably has a fill level indicator and/or a pressure indicator. The filling level indicator can be, for example, a simple sight glass, the pressure indicator is a conventional pressure gauge. Alternatively or additionally, the corresponding air valve 15 can be activated by a control device (not shown) of the cooling section 3 . In this case, the respective air valve 15 is preferably divided into two valve paths, whereby one of the two valve paths for replenishing air 14 in the corresponding pressure tank 10 is connected to the compressed air supply, and the other of the two valve paths for bleeding air 14 from the corresponding pressure tank 10 has a release to the environment. Furthermore, in this case, the respective filling degree F and/or the pressure acting in the respective pressure tank 10 is preferably detected by measuring technology and transferred to said control device.

Thus, with the help of the corresponding pressure tank 10, the amount of water moving in the corresponding supply line 12 is smoothly slowed down. Due to the fact that the groups of cooling devices 4 are generally relatively small - most often no more than six to ten cooling devices 4 - relatively small dimensions can also be chosen for pressure tanks 10 . This is explained below with reference to FIGS. 4-6 for the embodiment in which the corresponding group of cooling devices 4 includes only one single cooling device 4. However, the respective embodiments are also applicable when the respective group of cooling devices 4 includes several cooling devices 4 . In this case, the subsequent embodiments must be modified in terms of starting from the joint activation of the valves 8 of the respective group.

If the corresponding valve 8 is fully open, in the corresponding supply line 12 - which in the case of a group having one single cooling device 4, is identical to the stub pipe 7 - flows a corresponding volumetric flow V of water 5, for example 100 liters per second. This state is shown in Fig. 5 on the left. The degree of filling F is, according to the image in figure 4, initially about 50%. That is, the corresponding pressure tank 10 is filled in equal proportions with water 5 and air 14.

By the time t0, the corresponding valve 8 is transferred from a fully open to a fully closed position. The transition from the fully open to the fully closed position is carried out as quickly as possible, for example in 0.1 seconds or 0.2 seconds. In order to be able to better explain the selection of the dimensions of the respective pressure vessel 10, it is assumed below that the closing of the respective valve 8 takes place very abruptly, i.e. the time required for closing can be disregarded as such.

If there were no corresponding pressure tank 10, when the corresponding valve 8 is closed, a high pressure surge would occur, since the volume flow V flowing in the corresponding supply line 12 would have to drop sharply to zero. However, thanks to the corresponding pressure tank 10, the corresponding volume flow V can be redirected to the corresponding pressure tank 10. As a result, the corresponding pressure tank 10 continues to be filled above its previous degree of filling F. However, due to the filling of the corresponding pressure tank 10, the air 14 contained in the respective pressure tank 10 is compressed, so that the air pressure present there is increased. The increased air pressure opposes the further supply of water 5 to the corresponding pressure tank with increasing resistance. Therefore, the corresponding filling degree F initially increases from time t0, but then reaches a maximum and then drops again. Under certain conditions, a small, most often noticeably damped, oscillation can occur. This is best seen in FIG. 5 by the sign change in front of the volumetric flow number. The maximum degree of filling F is reached in most cases in 1 second, sometimes even in less time, for example only 0.5 seconds.

At the time t0 itself, i.e. at the beginning of the braking, according to the image in Fig. 4, the entire previously current volume flow V should be received. t0 time would be completely filled, for example, after 0.5 seconds. In this case, 50% of the volume of the corresponding pressure tank 10 would flow into the corresponding pressure tank 10 in 0.5 seconds. Therefore, 100% of the volume of the corresponding pressure tank 10 would flow into the corresponding pressure tank 10 in 1 second. In this case, in accordance with the image on 4, the quotient of the volume of the respective tank (unit: liter or cubic meter) and the respective volume flow V (unit: liter/second or cubic meter/second) is 1 second. Although some deviations from this value (1 second) are possible. Preferably, however, the said quotient should be between 0.2 seconds and 2.0 seconds. In practice, for a single cooling device 4, this corresponds to a volume of 20 l to 200 l, most often in the range of 50 l to 125 l, in particular about 100 l. If a group includes several cooling devices 4, the named volume values must be scaled accordingly.

Due to the resistance that - counting from the respective connection point 11 - each stub pipe 7 and each cooling device 4 have, in the state from which the figures 4 and 5 are first taken - that is, when the corresponding valve 8 is in the fully open position - in the area of the corresponding connection point 11 is affected by the corresponding pressure p0 in the pipeline. That is, the current corresponding pressure p in the pipeline has the value p0. This is shown in Fig. 6 on the left. Since the state of equilibrium is in effect until the time t0, the air 14 in the corresponding pressure tank 10 is also under pressure p0. By the time t0, i.e. by the time the respective valve 8 is closed, the volume flow V flowing in the respective supply line 12 must first be completely redirected to the corresponding pressure tank 10. The volume flow V through the supply line 12, measured at the respective connection point 11 and shown 5 causes, on its way from the respective connection point 11 to the respective pressure tank 10, a pressure drop δp at the respective hydraulic resistance 16, which is located between the respective connection point 11 and the respective pressure tank 10. This pressure drop δp is preferably equal to half the value of the corresponding pressure p0 in the pipeline. Therefore, the corresponding pressure p in the pipeline must rise sharply to a value that corresponds to about 1.4 times to 1.6 times the value of p0, that is, about 1.5 times. In absolute terms, this pressure drop δp in practice is most often of the order of 1 bar. After that, the corresponding pressure p in the pipeline drops again.

As a result, each flow resistance 16 can be adjusted by appropriately sizing each connection pipe between the respective connection point 11 and the respective pressure tank 10, in particular by selecting the cross-sectional dimensions of the entire respective connection pipe or the cross section of a section of the respective connection pipe. By properly sizing the hydraulic resistance 16, in particular, the tendency to oscillate is suppressed and damped.

The present invention has many advantages. In particular, water hammer can be prevented, although the valves 8 are switched on very quickly (with a switch-on time of much less than 1 s). The influence of the pressure tanks 10 on the quantities of water actually supplied to the cooling devices 4 can be taken into account by a corresponding model of the cooling section 3 or simply equalized by means of basic automation of the cooling section 3 . With the help of pressure tanks 10, pressure fluctuations in the hydraulic system (consisting of the supply pipeline 6, supply pipelines 12 and dead-end pipelines 7) are also prevented. This simplifies the control of the pumps which pump the water 5. This applies in particular when pressure measurements are used to control the pumps. In addition, pressure disturbances are also reduced when the valves 8 are connected, since in this case the water 5 from the pressure tanks 10 is fed into the corresponding supply lines 12. The design of the actuators 9 as electric actuators in a simple manner makes it possible to activate the valves 8 reliably and quickly.

Although the invention has been illustrated and described in detail with reference to the preferred embodiment, the invention is not limited to the disclosed examples, and other variations may be deduced from the skilled person without departing from the scope of the invention.

LIST OF REFERENCES

1 rental

2 rolling stand

3 Cooling section

4 Cooling devices

5 Water

6 Supply pipeline

7 Dead ends

8 Valves

9 Electric drives

10 Pressure tanks

11 Connection points

12 Supply pipes

13 Distribution point

14 Air

15 Air valves

16 Water resistance

F Degree of filling

p, p0 Line pressure

t0 Time

V volume flow

x Direction of transport

y Width direction

δp - pressure drop

Claims (14)

1. A device for cooling rolled metal (1) rolled in a group of rolling stands, - moreover, the device has several cooling devices (4), each of which is supplied with water (5) through the corresponding dead-end pipeline (7), and through which water (5) is applied to the rental (1); - at the same time, in the dead-end pipelines (7), respectively, there is a valve (8), by means of which the water flow flowing through the corresponding dead-end pipeline (7) is adjusted; - while the valves (8) are respectively correlated with the drive (9), with which the corresponding valve (8) is activated; different in that - that the cooling devices (4) form several groups, each of which is proprietary equipped with its own pressure tank (10), - that the corresponding pressure tank (10) is connected in the corresponding connection point (11) to the corresponding supply pipeline (12), through which water (5) is supplied to the dead-end pipelines (7) of the cooling devices (4) of the corresponding group, so that, if you look in the direction of water flow (5), the corresponding connection point (11) is located in front of the valves (8) of the corresponding group of cooling devices (4). 2. Device according to claim 1, characterized in that at least part of the groups of cooling devices (4) includes only one single cooling device (4). 3. The device according to claim 1 or 2, characterized in that the drives (9) are made in the form of electric drives. 4. The device according to claim 3, characterized in that the electric drives are made in the form of stepper motors. 5. The device according to one of claims 1 to 4, characterized in that - that the pressurized tank (10) associated with each group of cooling devices (4) has the capacity of the tank, and - that this tank volume is from nx20 l to nx200 l, where n is the number of cooling devices (4) of the respective group. 6. A device according to one of claims 1 to 5, characterized in that a corresponding hydraulic resistance (16) is located between the respective connection point (11) and the respective pressure tank (10).

Images