Claims:We Claim:
A method for determining an allowable catenary depth (Acd) of a strip (103) in a trapezoidal shaped pickling tank (108), the method comprising:
receiving by a control unit, dimensional parameters of the pickling tank (108) including height (h), width (w) and base length (lb) from a memory unit;
receiving by the control unit, dimensional parameters of the strip (103) including, width, thickness, and weight of the strip (103) from the memory unit;
determining, by the control unit, a side wall length (lb) of the pickling tank (108) based on received dimensional parameters of the pickling tank (108);
determining, by the control unit, a base angle (d) of the pickling tank (108) based on the height (h) of the pickling tank (108) and the determined side wall length (lb) of the pickling tank (108);
determining, by the control unit, the allowable catenary depth (Acd) of the strip (103) in the pickling tank (108) based on the dimensional parameters of the strip (103) and the determined base angle (d) of the pickling tank (108).

The method as claimed in claim 1 comprises, determining by the control unit, the base length (lb) of the pickling tank (108) by estimating the half of the width (w) of the pickling tank (108).

The method as claimed in claim 1 wherein, the side wall length (lb) of the pickling tank (108) is determined by computing square root of difference between twice the base length (lb) of the pickling tank (108) and twice the height (h) of the pickling tank (108).

The method as claimed in claim 1 wherein, the base angle (d) of the pickling tank (108) is determined by computing the product between a first subset of parameters and a second subset of parameters wherein, the first subset of parameters is the tangent function of the height of the pickling tank (108) divided by the side wall length (lb) of the pickling tank (108).

The method as claimed in claim 4 wherein, the second subset of parameter is 180 divided by p.

The method as claimed in claim 1 wherein, the allowable catenary depth (Acd) of the strip (103) in the pickling tank (108) is determined based on an empirical expression as an algebraic sub of a first allowable catenary depth (Acd1) of the strip (103) in the pickling tank (108) and a second allowable catenary depth (Acd2) of the strip (103) in the pickling tank (108).

The method as claimed in claim 6 wherein, the first allowable catenary depth (Acd1) of the strip (103) in the pickling tank (108) is determined by estimating a multiple of half of the width (w) of the strip (103) and a tangent function of the base angle (d) of the pickling tank (108).

The method as claimed in claim 6 wherein, the second allowable catenary depth (Acd2) of the strip (103) in the pickling tank (108) is determined by the control unit, a multiple of thickness (t) of the strip (103) and a tangent function of the base angle (d) of the pickling tank (108).

The method as claimed in claim 1 comprises, varying by the control unit, a speed of a flattener roller (107) and a speed of an encoder roller (113) based on the determined allowable catenary depth (Acd) of the strip (103) in the pickling tank (108).

Dated this 30th day of March 2021.

GOPINATH A.S
OF K&S PARTNERS
IN/PA 1852
AGENT FOR THE APPLICANT
, Description:TECHNICAL FIELD

Present disclosure relates in general to a field of manufacturing technology which includes surface treatment for hot rolled strips. Particularly, but not exclusively, the present disclosure relates to an aspect of determining an allowable catenary depth of a strip in a trapezoidal shaped pickling tank. Further, embodiments of the disclosure, discloses a method of employing a computational solution for quantifying and measuring the allowable catenary depth of the strip during continuous surface treatment of the strip in the pickling tank.

BACKGROUND OF THE DISCLOSURE

Steel is an alloy of iron, carbon, and other alloying elements. Because of its high tensile strength and low cost, steel may be considered as most viable choice for major components manufacturing in a wide variety of applications. Some of the applications of the steel may include buildings, ships, tools, automobiles, machines, bridges, and numerous other applications.

Steel may be generally manufactured as steel slabs by processes such as casting including but not limiting to continuous casting, and then the steel is formed into various shapes depending on the application. One such common form of steel is a steel sheet which is obtained by converting the steel slab into steel sheet by series of metal forming processes to find its use in the sheet metal industry. During drawing of the steel sheet from steel slabs, processes such as hot rolling and cold rolling are carried out.

Conventionally, hot rolling may be performed in a Hot Strip Mill (HSM) which is an integral part of a steel plant. The primary objective of HSM is to make strips from slabs and acquire intended properties in the strips. Typically, HSM has two sections- Roughing Mill and Finishing Mill. Roughing Mill is essentially a single strand reversing mill whose function is to reduce the thickness of the slabs as well as break the cast structure. After roughing, strips go into the finishing mill. The job of a finishing mill is to reduce the thickness of the strips and incorporate requisite properties into the strips. The strips may be used for producing various products like cutting saws, automotive components (Circlips, Washers, Springs, and Recliner, Driven and disc plate), gardening tools, surgical blades, springs, measuring devices, wire rods, tire bead wires, deep drawn high strength wires, wires for suspension bridges, and others.

Generally, the hot rolled strip or sheet is subjected to a pickling process. The pickling process is performed for removing scales and other surface defects on the strip. Post this process, the strip is subsequently subjected to rinsing. Further, pickling refers to a treatment that is used to remove impurities such as rust and scale from the surface of the strip. During hot working processes, an oxide layer (referred to as “scale”, due to the scaly nature of its appearance) develops on the surface of the metal. Before subjecting the steel sheet or strip to cold rolling processes, hot rolled steel goes through a pickling line to remove the scales from the surface and make it easier to work. To restore the best corrosion resistant performance, the damaged metal layer must be removed, exposing a fully alloyed steel strip surface. The oxide layer and the impurities on the surface of the strip is removed by dipping the strip into a pickle liquor. The pickle liquor may be hydrochloric or sulfuric acid. For steels that have a higher carbon content, a two-step pickling process is required, with additional acids used. The pickling process chemically removes oxides and scales that are from both the top and bottom surfaces of the strip.

The pickling process involves pulling of the strip by a motor driven bridle rollers or by a tension bridle in a catenary fashion under a controlled speed through a series of several troughs or tanks. The strip may be pulled through three to eight pickling tanks, combined measure adding up to seventy to a hundred meters in length and each pickling tank may be rectangular or isosceles/ trapezoidal in shape. The hot rolled strips are conveyed continuously in the pickling tank by having it pass through deflector rollers and helper rollers which act to move the strip. A substantial tension is created in the initial section of the strip by placing a drag on the pay-off reel which create catenary profile on the strip inside the pickling tank. Here the substantial tension created by the tension reel develops the velocity difference between encoder reel and pay of reel. If the tension applied to the strip is relatively too high, the velocity differences along the prescribed addressed section is negligible which results in catenary lifting process and the said strip passes over the liquid surface, leading to poor pickling. Conversely, if the tension applied is small or negligible, the velocity difference along the prescribed addressed section is relatively higher which results in catenary bottom sliding in which the strip comes into sliding contact with the side wall surface of the pickling tank. The catenary bottom sliding may cause scratches on the surface of the strip. The existing or the instant catenary depth of the strip may initially be determined and may be compared with an allowable depth of the strip to determine a safe operational condition of the strip.

Conventional methods for determining the allowable depth of the strip is conducted manually based on the dimensions of the tank and the strip. The accuracy of such methods is low, and the obtained results are often not reliable. Inaccurate manual methods for determining the allowable depth often results in inaccurate results on the operational state of the strip. Consequently, the strip may undergo bottom or side sliding when the comparison of the catenary depth of the strip with the determined inaccurate allowable depth of the strip does not indicate the accurate operational conditions of the strip.

The present disclosure is directed to overcome one or more limitations stated above or any other limitations associated with the conventional arts.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of the prior art are overcome by a method and a product as claimed and additional advantages are provided through the method as described in the present disclosure.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure.

In one non limiting embodiment of the disclosure, a method for determining an allowable catenary depth of a strip in a trapezoidal shaped pickling tank is disclosed. The method involves steps of a control unit receiving dimensional parameters of the pickling tank including height, width, and base length from a memory unit. The control unit also receives dimensional parameters of the strip including, width, thickness, and weight of the strip from the memory unit. Further, the control unit determines a side wall length of the pickling tank based on received dimensional parameters of the pickling tank. The next step involves the control unit determining a base angle of the pickling tank based on the height of the pickling tank and the determined side wall length of the pickling tank. Subsequently, the control unit determines the allowable catenary depth of the strip in the pickling tank based on the dimensional parameters of the strip and the determined base angle of the pickling tank.

In an embodiment, the control unit determines the base length of the pickling tank by estimating the half of the width of the pickling tank.

In an embodiment, the control unit determines the side wall length of the pickling tank by computing square root of difference between twice the base length of the pickling tank and twice the height of the pickling tank.

In an embodiment, the control unit determines the base angle of the pickling tank by computing the product between a first subset of parameters and a second subset of parameters wherein, the first subset of parameters is the tangent function of the height of the pickling tank divided by the side wall length of the pickling tank. Further, the second subset of parameter is 180 divided by p.

In an embodiment, the control unit determines the allowable catenary depth of the strip in the pickling tank based on an empirical expression as an algebraic sub of a first allowable catenary depth of the strip in the pickling tank and a second allowable catenary depth of the strip in the pickling tank.

In an embodiment, the first allowable catenary depth of the strip in the pickling tank is determined by estimating a multiple of half of the width of the strip and a tangent function of the base angle of the pickling tank.

In an embodiment, the second allowable catenary depth of the strip in the pickling tank is determined by estimating a multiple of thickness of the strip and a tangent function of the base angle of the pickling tank.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

The novel features and characteristics of the disclosure are set forth in the appended description. The disclosure itself, however, as well as a preferred mode of use, further objectives, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying figures. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals represent like elements and in which:

Fig. 1 is a schematic drawing of continuous pickling line, according to an exemplary embodiment of the present disclosure.

Figure 2 schematic drawing of catenary formation in continuous pickling line, according to an exemplary embodiment of the present disclosure.

Figure 3 shows a perspective view of the pickling tank, according to an exemplary embodiment of the present disclosure.

Fig. 4 is a flowchart illustrating the method for determining an allowable catenary depth of a strip in a trapezoidal shaped pickling tank, according to an exemplary embodiment of the present disclosure.

Fig. 5 illustrates a block diagram of a system for monitoring and controlling the catenary depth of the strip in the pickling tank, according to an exemplary embodiment of the present disclosure.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

The foregoing has broadly outlined the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter which form the subject of the description of the disclosure. It should also be realized by those skilled in the art that such equivalent methods do not depart from the scope of the disclosure. The novel features which are believed to be characteristics of the disclosure, as to method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.

In the present document, the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments.

While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the disclosure to the form disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the spirit and the scope of the disclosure.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a method that comprises a list of acts does not include only those acts but may include other acts not expressly listed or inherent to such method. In other words, one or more acts in a method proceeded by “comprises… a” does not, without more constraints, preclude the existence of other acts or additional acts in the method.

Embodiments of the present disclosure discloses a method for determining an allowable catenary depth of a strip in a trapezoidal shaped pickling tank. The strip is made to pass though the pickling tank for surface treatment of a hot rolled strip. In some scenarios, if a tension applied to the strip is relatively high, the velocity differences is negligible which results in catenary lifting process and the strip passes over the liquid surface, causing poor pickling. Conversely, if the tension applied is small, the velocity difference is relatively higher which results in catenary bottom sliding in which the strip comes into sliding contact with the side wall surface of the pickling tank. The catenary bottom sliding may cause scratches on the surface of the strip. The existing or the instant catenary depth of the strip may initially be determined and may be compared with an allowable depth of the strip to determine a safe operational condition of the strip. Conventional methods for determining the allowable depth of the strip were conducted manually based on the dimensions of the tank and the strip. The accuracy of such methods was low, and the obtained results were often not reliable.

According to various embodiments of the disclosure, a method for determining an allowable catenary depth of a strip in a trapezoidal shaped pickling tank is disclosed. The method includes steps of a control unit receiving dimensional parameters of the pickling tank including height, width, and base length from a memory unit. The control unit also receives dimensional parameters of the strip including, width, thickness, and weight of the strip from the memory unit. Further, the control unit determines a side wall length of the pickling tank based on received dimensional parameters of the pickling tank. The next step involves the control unit determining a base angle of the pickling tank based on the height of the pickling tank and the determined side wall length of the pickling tank. Subsequently, the control unit determines the allowable catenary depth of the strip in the pickling tank based on the dimensional parameters of the strip and the determined base angle of the pickling tank.

Henceforth, the present disclosure is explained with the help of figures of a method for determining an allowable catenary depth of a strip in a trapezoidal shaped pickling tank. However, such exemplary embodiments should not be construed as limitations of the present disclosure since the method may be used on other types of steels where such need arises. A person skilled in the art may envisage various such embodiments without deviating from scope of the present disclosure.

Fig. 1 is a schematic drawing of continuous pickling line (100) and Fig. 2 is schematic drawing of catenary formation of a strip (103) in the continuous pickling line (100). The continuous pickling line (100) may include a plurality of pickling tanks (108) for the surface treatment of the strip (103). Each of the plurality of pickling tanks (108) may be filled with a suitable pickle fluid and the pickle fluid in an embodiment may be a suitable acid. The surface of the strip (103) may be treated by means of an acid bath including but not limited to hydrochloric acid.

With reference to Fig. 1, the continuous pickling line (100) may include a plurality of un-coilers or pay of reels. The continuous pickling line herein includes a primary pay of reel (101) and a secondary pay off reel (102). The hot rolled strip (103) that is initially received from a hot strip mill, may be unwrapped for processing by a processor (104). The primary pay of reel (101) and the secondary pay off reel (102) are used to guide the strip (103) to the processor (104) and may also break the oxide scale present over the strip (103). The processor (104) receives the strip (103) and may be directed though a breaker roll [not shown] housed in the processor. The breaker roll may minimize the tendency of the strip (103) to break. The strip (103) is further guided to a welder assembly (105). The strip (103) in the welder assembly (105) may be reshaped or cut suitably and may be welded to impart square shape throughout the length of the strip (103). The assembly (105) may cut and weld the edges of the strip (103) to impart the square shape to the strip (103). The continuous pickling line (100) also includes a primary guide roll (106) and a secondary guide roll (111). The primary guide roll (106) and the secondary guide roll (111) may guide the strip through the plurality of pickling tanks (108) and a rinsing assembly (109). The primary guide roll (106) and the secondary guide roll (111) convey the strip (103) throughout the entry and exit of the processing line. The primary guide roll (106) initially conveys the strip (103) from the welder assembly (105) into the plurality of pickling tank (108) through a flattener roller (107). The continuous pickling line (100) including the flattener roller (107) receives the strip (103) form the primary guide roll (106) and imparts a pre-determined speed to the strip (103) while guiding the strip (103) into the plurality of pickling tank (108). The flattener roller (107) provides a flattener reference ratio which facilitates and enables the entry speed of strip (103) inside the pickling tank (108). The flattener roller (107) may be any known mechanism or method in the art for imparting speed to the stirp (103), as the strip (103) traverses through the pickling tank (108).

The pickling tank (108) may include pickle fluid and the strip (103) may be guided through the pickle fluid inside the pickling tank (108). As the strip (103) traverses through the pickling tank (108) and the pickling fluid, a chemical reaction take place with the pickle fluid where, black oxide scales from the surface of the strip (103) is generated during hot rolling process which are suitably removed. The strip (103) from the pickling tank (108) may further be guided through the rinsing assembly (109) where, the residual acid on the surface of the strip (103) from the plurality of pickling tanks (108) is removed. The rinsing assembly (109) may also include a provision for drying the strip (103). Excess water on the strip (103) may be removed or dried to prevent the formation of rust. The strip from the rinsing assembly (109) may further be guided through an oiler (110). The oiler (110) may add a thin layer of oil on the surface of the strip (103). The thin layer of oil may be added for preventing the formation of rust on the surface of the strip (103). The strip (103) from the rinsing assembly (109) may be received by the secondary guide roll (111) and the strip (103) may be coupled to an edge cutter (112). The edge cutter (112) may remove the edges of the strip (103) to ensure that there are no edge defects to the strip (103). Defects such as cracks or minor edge damages may be sheared suitably to guarantee a continuous and uniform strip (103) width. The strip (103) is coupled to an encoder roller (113) which also imparts speed to the strip (103) traversing throughout the continuous pickling line (100) similar to the flattener roller (107). The encoder roller (113) may be an assembly of an encoder and the edge cutter where, the encoder imparts speed to the strip (103) and the edge cutter trims the edges of the strip (103). The encoder roller (113) may maintain the desired tension by means of a tension reel (114). The tension reel (114) may maintain the desired tension throughout the continuous pickling line (100) and a binding reel (115) may be used to coil the pickled strip (103) suitably.

The flattener rollers (107) and the encoder rollers (113) are configured to impart a drooping structure or a catenary shaped structure to the strip (103). The flattener roller (107) and the encoder roller (113) may be operated at differential speeds. Initial threading process of the strip (103) is set by maintaining the speed or tension on the flattener roller (107) and the encoder roller (113) in equilibrium. The speed of the flattener roller (107) and the encoder roller (113) is initially maintained at very low magnitude. The speed for threading lies between 40 meter per minute to 60 meter per minute. Further, once the threading is completed, the speed of the flattener roller (107) is considerably increased (107) by 1.001 to 1.5 times with respect to fixed line speed of the encoder roller (113). The speed of the flattener roller (107) and the encoder roller (113) may be fixed based on various parameters of the strip (102) including width, thickness, and grade of the strip (103). The speed of the secondary guide roll (111) is directed through the tension reel (114) by the application of encoder roller (113). Whereas speed of the primary guide roll (106) is directed through the encoder roller (113). Hence, the difference in speed is created along the flattener roller (107) and the encoder roller (113) which leads to a differential speed. Due to the differential speed, the flattener roller (107) seeks to pass more length of the strip (103) to the encoder roller (113), but the encoder roller (113) does not receive the whole length of the strip (103) because of lesser speed. Therefore, drooping characteristic is predominant between the flattener roller (107) and the encoder roller (113). Consequently, the catenary shape is imparted to the strip (103) traversing through the plurality of pickling tanks (108). The catenary shape that is imparted to the strip (103), causes the strip (103) to accumulate inside the plurality of pickling tanks (108).

In an embodiment, plurality of pickling tanks (108) may be used for removing the surface impurities of the strip (103). More particularly three to eight pickling tanks (108) which when combined and measured reads 70 to a 100 meter in length may be used. Each individual pickling tank (108) consists of primary bridal roll (203) and secondary bridal roll (204) at entry and exit, respectively.

With reference to the Fig. 2 catenary formation in the continuous pickling line (100) with the plurality of pickling tanks (108) is shown. The strip (103) may be traversed though multiple pickling tanks (210, 211,212, 213 and 214). Each pickling tank (210, 211,212, 213 and 214) may be trapezoidal in shape as seen from the Fig. 3. Each of the plurality of pickling tanks (108) may include two side walls (404 and 405) that are parallel to each other and these two side walls (404 and 405) may be interconnected with a front wall (301) and a rear wall (302) that are oriented in a non-parallel orientation to define a trapezoidal shape to the plurality of pickling tank (108). The front wall (401) and the rear wall (402) may be defined at a pre-determined angle (306) with respect to the side walls (404 and 405). The angle (306) may vary between 1° to 89° degree for a trapezoidal shaped pickling tank (108) and may be 90° rectangular shaped pickling tank (108).

Further, each pickling tank (210, 211,212, 213 and 214) may include a primary bridal roll (203) and a secondary bridal roll (204). The primary bridal roll (203) plays a pivotal role to entry of the strip (103) at higher speed and the secondary bridal roller (204) plays pivotal role to deliver the strip (103) to the next pickling tank (211,212, 213 and 214). The secondary bridal roller (204) may operate at lower speeds and the secondary bridal roller (204) may be coupled to the encoder roller (113). Whereas the primary bridal roll (203) may be coupled to the flattener roller (107). The differential speed between the primary bridal roller (203) and the secondary bridal roller (204) imparts the catenary shape to the strip (103) inside each pickling tank (210, 211,212, 213 and 214). The method of determining the allowable catenary depth (Acd) of the strip (103) inside each pickling tank (108) is explained in detail below.

Figure 3 shows a perspective view of the pickling tank (108). The pickling tank (108) may be of the trapezoidal shape. The pickling tank (108) may be defined by a base wall and two non-parallel side walls. The top end of the pickling tank (108) may be open to accommodate the strip (103). The angle between the base and the side walls of the pickling tank (108) may be herein defined by the term “d”. The pickling tank (108) may be of a pre-determined height, herein defined by the term “h”. Further, the length of the side walls and the base wall may be defined by the term “ls” and “lb” respectively. The pickling tank (108) may be filled with an acid up to a pre-determined point, herein defined by the term “X”. The strip (103) may be immersed in the acid of the pickling tank (108) for surface treatment of the strip (103). The calculated catenary depth of the strip (103) may be herein defined by the term “Ccd” and the allowable depth of the stirp (103) may be herein defined by the term “Acd”.

Fig. 4 is a flowchart illustrating the method for determining the allowable catenary depth (Acd) of a strip (103) in the trapezoidal shaped pickling tank (108). The first step 301 involves, receiving the dimensional parameters of the pickling tank (108). The dimensional parameters of the pickling tank (108) include length of the side wall (ls), length of the base (lb), height (h) of the pickling tank (108), acid level (X) in the pickling tank (108), the angle (d) between the base and the side walls of the pickling tank (108), the width (w) of the pickling tank (108) and the calculated catenary depth (Ccd) of the strip (103). The next step 302 involves receiving by the control unit, the dimensional parameters of the strip (103). The dimensional parameters of the strip (103) may include thickness, length, width, self-weight of the strip (102) and the grade of metal used for manufacturing the strip (103). Further, the next step involves determining a side wall length (ls) of the pickling tank (108) from the below equation (1).

base length= (Top width of tank)/2….. equation (1)
From the above equation (1), the control unit determines the base length (lb) of the pickling tank (108) by estimating the half of the width (w) of the pickling tank (108).
The next step involves 303 the aspect of determining the side wall length (ls) of the pickling tank (108) from the below equation (2).
side wall length (ls) = v(?base length (lb)?^2-?height of trapezoid (h)?^2 ) ….. equation (2)
From the above equation (2), the control unit [not shown] associated with the pickling line determines the the side wall length (ls) of the pickling tank (108) by computing square root of difference between twice the base length (lb) of the pickling tank (108) and twice the height of the pickling tank (108).
Further, the step 304 involves determining a base angle (lb) of the pickling tank (108) from the below equation (3).
base angle (d)=Atan((height of trapezoid (h))/(Side wall length (ls)))*(180/p) ….. equation (3)
From the above equation (3), the base angle (d) of the pickling tank (108) is determined by the control unit by computing the product between a first subset of parameters and a second subset of parameters. The first subset of parameters is the tangent function of the height of the pickling tank (108) divided by the side wall length (lb) of the pickling tank (108). The second subset of parameter is 180 divided by p.
The next step 305 involves determining the allowable catenary depth (Acd) of the strip (103) in the pickling tank (108).
Initially, a first allowable catenary depth (Acd1) of the strip (103) in the pickling tank (108) is determined by estimating a multiple of half of the width (w) of the strip (103) and a tangent function of the base angle (d) of the pickling tank (108) as described in the below equation (4).
first allowable catenary depth (Acd1)=( width of strip)/2*tan?d….. equation (4)
Further, a second allowable catenary depth (Acd2) of the strip (103) in the pickling tank (108) is determined by the control unit by a multiple of thickness (t) of the strip (103) and a tangent function of the base angle (d) of the pickling tank (108) as described in the equation (5).
second allowable catenary depth (Acd2)=( Thickness of strip)/1*tan?d….. equation (5)
Lastly the allowable catenary depth (Acd) of the strip (103) in the pickling tank (108) is determined based on an empirical expression as an algebraic sub of the first allowable catenary depth (Acd1) of the strip (103) in the pickling tank (108) and the second allowable catenary depth (Acd2) of the strip (103) in the pickling tank (108) as described in the below equation (6).
Total allowable catenary depth (Acd)= (Acd1) + (Acd2) ….. equation (6)
The determined allowable catenary depth (Acd) of the strip (103) in the pickling tank (108) from the above-mentioned method may be recorded by the control unit.
Fig. 5 illustrates a block diagram of a system (500) for monitoring and controlling the catenary depth of the strip (103) in the pickling tank (108). The system may include an input module (501) that is communicatively coupled to a control unit (503). The control unit (503) may also be communicatively coupled with the flattener roller (107) the encoder roller (113). The control unit (503) may receive and control the operational speed of the flattener roller (107) the encoder roller (113). The control unit (503) may also receive data on the calculated or the instant catenary depth (Ccd) of the strip (103) as the strip (103) traverses through the pickling tank (108) through the input module (501). Further, the control unit (503) may compare the calculated catenary depth (Ccd) with the determined allowable catenary depth (Acd) of the strip (103). Based on the comparison, the control unit (503) may vary the speed of the flattener roller (107) and the speed of the encoder roller (113). The calculated catenary depth (Ccd) of the strip (103) inside the said pickling tank (108) may be compared with the allowable catenary depth (Acd) of the pickling tank (108). If the calculated catenary depth (Ccd) of the strip (103) lies below to the allowable catenary depth (Acd), the control unit interprets that the strip (103) is too close and colliding with the bottom surface or side walls of the tank (108). Consequently, computational method provides a new differential speed to the flattener roller (107) and the encoder roller (113) for correcting the catenary depth of the strip (103). The speed may be determined to operate the flattener roller (107) and the encoder roller (113) such that the catenary depth of the strip (103) is sufficient to prevent catenary lift and catenary bottom/side sliding condition inside the pickling tank (108) in normal operating practice of the continuous pickling line (100). In an embodiment, catenary depth of strip (103) which may be controlled and varied by the control unit may be applicable for all types of pickling line, cold rolling mill, push-pull pickling line, continuous pickling line, semi continuous pickling line etc.
With reference to the below Table 1, the user interface (502) associated with the control unit (503) may generate an alarm if the calculated catenary depth (Ccd) of the strip (103) is lesser than the allowable catenary depth (Acd). The control unit may set off alarm through the user interface (502) indicative of bad or risk condition of catenary depth for faulty operating practices to operator. The control unit may suggest the optimal operating practices as well. If the operating conditions are good i.e., the calculated catenary depth (Ccd) of the strip (103) is greater than the allowable catenary depth (Acd), the control unit (503) will not set of an alarm and the operational conditions may be tabulated for further reference.
Width Thickness Flattener roller Encoder roller Catenary depth Allowable depth Condition/alarm
mm mm mpm mpm m m
1220 2.4 136.5 130 0.221 0.174 good
1220 2.4 137.15 130 0.197 0.174 good
1220 2.4 137.8 130 0.172 0.174 bad
1250 2.5 131.25 125 0.221 0.178 good
1250 2.5 131.87 125 0.192 0.178 good
1250 2.5 132.7 125 0.171 0.178 bad
1540 2.4 103 100 0.298 0.22 good
1540 2.4 103.5 100 0.266 0.22 good
1540 2.4 104 100 0.218 0.22 bad

In an embodiment, the above-mentioned method of determining the allowable catenary depth (Acd) for the strip (103) in the pickling tank (108) is completely computational without any additional use labour or sensors. Consequently, the method of determining the allowable catenary depth (Acd) of the strip (103) is cost-effective. The above-mentioned allowable catenary depth (Acd) for the strip (103) in the pickling tank (108) provides results with greater accuracy when compared to the conventional manual methods of measuring the allowable depth. In an embodiment, the method of determining the allowable catenary depth (Acd) of the strip (103) inside the pickling tank (108) of the present disclosure is applicable for trapezoidal shaped tanks (108). Since the method of determining the allowable catenary depth (Acd) of the strip (103) inside the pickling tank (108) is computational and relies only on the specification of the strip (103) and pickling tank (108) without any user intervention, the determined allowable catenary depth (Acd) of the strip (103) is accurate.
Equivalents:

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., "a" and/or "an" should typically be interpreted to mean "at least one" or "one or more"); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to "at least one of A, B, and C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, and C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to "at least one of A, B, or C, etc." is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., "a system having at least one of A, B, or C" would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" will be understood to include the possibilities of "A" or "B" or "A and B."

While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals

Referral Numerals Description
100 Continuous pickling line
101, 102 Pay off reels
103 Strip
104 Processor
105 Welder assembly
106 Primary guide roll
107 Flattener roller
108, 210, 211, 212, 213, 214, 215 Pickling tank
109 Rinsing assembly
110 Oiler
111 Secondary guide roll
112 Edge cutter
113 Encoder roller
114 Tension reel
115 Binding reel
203 Primary bridal roll
204 Secondary bridal roll
H Height of the pickling tank
ls Length of side walls in the pickling tank
lb Length of base in the pickling tank
w Width of the pickling tank
d Angle between the base and the side wall of the pickling tank
X Acid level in the pickling tank
Ccd Calculated catenary depth of the strip in the pickling tank
Acd Allowable catenary depth of the strip in the pickling tank