US3000385A

US3000385A - Pickling apparatus

Info

Publication number: US3000385A
Application number: US693369A
Authority: US
Inventors: Shay Eli
Original assignee: Wean Engineering Co Inc
Current assignee: Wean Engineering Co Inc
Priority date: 1957-10-30
Filing date: 1957-10-30
Publication date: 1961-09-19
Anticipated expiration: 1978-09-19

Description

Sept. 19, 1961 SHAY ,3

PICKLING APPARATUS Filed Oct. 30, 1957 2 SheetsSheet 1 ls k 23 m T Q3 \JLB3 29 31 X 20 2:5?- 30 X4 INVENTOR Eli Shay United States Patent 6 Filed Oct. 30, 1957, Ser. No. 693,369

Claims. (Cl. 13457) This invention relates to apparatus for the cleaning of products of substantial length by passing them in a substantially continuous manner through a pickling tank.

In the treatment and fabrication of many products of extended length, such as ferrous strip and wire products, for example, it is frequently necessary that the products be cleaned prior to performing a particular operation upon them. The cleaning process may be acid or alkaline and is generally known as pickling. Speaking by way of illustration, hot rolled steel strip is ordinarily covered with mill scale of ferrous oxides resulting from its exposure to air at elevated temperatures. The scale must be removed prior to cold rolling to avoid inclusions of scale in the cold rolled strip. The strip is, therefore, passed through a tank containing an acid pickling solution. The problems or" handling the strip at either end of the pickling tank, of welding coils to form a continuous strip before pickling, and of cutting the strip into manageable lengths after pickling, may reduce the strip speed in the pickling tank below the usual operating speed or require that the line be stopped momentarily. Despite such variations in speed and stops, the process is substantially a continuous one in which the product moves through the tank as an endless member approximating a predetermined speed.

It is necessary for eflicient operation to add acid and water continuously to the pickling bath to maintain a proper concentration of acid and iron in the bath for optimum removal of the mill scale from the product. Heretofore, acid and water have been added at a predetermined rate calculated from the average speed and width of strip passing through the pickling tank. Hourly or more frequent titrations have been necessary to check the acid concentration in the tank and to make fine adjustments in the acid and water flow, in accord with the results of the titrations. Regular corrections in the rate of acid and water flow have been necessary, and it has generally been necessary to overcorrect for the purpose of restoring a proper balance. To provide against insuificient pickling, an excess of acid has normally been carried resulting in a waste of acid and acid attacks on the product after removal of the scale. Regardless of the particular product being pickled, certain problems will usually be present in some degree. The flow of the pickling agent must be controlled to maintain a sufficient concentration for complete pickling, while holding attacks on the metal to a minimum. The maintenance of optimum conditions in the pickling tank reduces the amount of waste product which must be disposed of, and is highly desirable for this reason alone, the disposal of pickling waste being a major operating problem.

I provide means for continuously pickling a product comprising a pickling tank through which the product is passed, product measuring means to continuously measure the rate at which the product passes through the tank and control means to introduce a pickling agent into the tank at a rate proportional to the rate of passage of product through the tank. I prefer to provide product speed measuring means and means to indicate the product size whereby the product area rate of passage through the pickling tank may be determined. I prefer to provide product speed measuring means, pickling agent control means in connection therewith and pickling agent gauge means whereby the rate of flow of the pickling agent may Patented Sept. 19, 1961 ice be determined for further adjustment of said flow. I further preferably provide control means for a dilutent in operative connection with the pickling agent control means whereby the dilutent may be introduced into the pickling tank proportionally with the pickling agent.

Other details, objects, and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawings, I have illustrated a present preferred embodiment of my invention in which FIGURE 1 is a diagrammatic view showing a portion of a pickling tank with the associated controls being shown diagrammatically; and

FIGURE 2 is a side View of the exit end of a conventional pickle line embodying the invention, showing a portion of the pickling tank, the pinch rolls which pull strip through the pickling line and the strip washing and drying apparatus positioned between the pickling tank and pinch rolls.

in the accompanying drawing, a pickling tank is illustrated which is suitable for acid pickling of hot rolled strip prior to cold rolling. The handling of such strip is generally well-known. A particular type of installation is shown, for example, in United States Patent 2,196,600 to Raymond J. Wean and Donald A. McArthur. A portion of a pickling tank 1 is shown diagrammatically. The strip S passes into the pickling tank at irregular speeds because of normal operating conditions. The strip is pulled from the tank between a pair of conventional pinch rolls in a continuous operation, although the speed varies widely, and the strip may even be stopped at times. One of the I pinch rolls is illustrated at 2 and has a tachometer generator 3 connected to it. The pinch roll is continuously in contact with the strip whereby it and the connected generator will rotate at a speed proportional to the strip speed, producing a proportional electric signal. The sig nal is transmitted on wires 4 to a transmitter 5 which will deliver air to a pipe 6 at a pressure proportional to the generated voltage. A Foxboro E.M.F./pneumatic transmitter is a satisfactory instrument for this purpose. A manually set valve 7 supplies a regulated amount of air to a pipe 8. The valve supplies air at a reduced pressure which is proportional to the opening of the valve, and is calibrated in inches of strip width. Thus, by appropriate setting of valve 7, an air pressure in pipe 8 is maintained which is proportional to the strip width. A Foxboro pneumatic airdron type 20 supply regulator is suitable at this point. A multiplier 9 multiplies the pressures in pipes 6 and 8 and transmits a resultant pressure in pipe 10. Consequently, the pressure in pipe 10 will be proportional to the area of strip passing through and leaving the pickling tank. A Foxboro M/40 black box computer is a satisfactory instrument for these purposes. A recorder 11 of conventional design continuously records the pressures in pipes 6 and 8 on a chart to make a permanent record, as well as to give visual indication of the pressures at any moment.

Sulfuric acid used for pickling is maintained in a head tank 12 and feeds through a supply pipe 13 into the pickling tank at a discharge point 14. Pipe 10 leads to a controller 15 which transmits the pressure through the pipe 16 to valve 17 in acid supply pipe 13. Valve 17 opens an amount proportional to the air pressure in pipe 16, thereby allowing acid to pass into the pickling tank in an amount proportional to the area of strip then passing into the pickling tank. A Foxboro stabilfio wide range control valve is suitable for this purpose. A solenoid valve 19 is normally maintained in open position but may be operated to close pipe 16, thereby stopping acid flow into the tank. It will be apparent that small variations in the acid flow may occur due to variations of level in head tank 12, inaccuracies in valve and in strument settings, and the like. A magnetic flow meter 20, such as that employed in a Foxboro magnetic flow control meter system, is placed in acid supply pipe 13.

The Flow meter measures the rate of 130W of acid in supply pipe 13 and transmits a proportional electrical signal through wires 21 to a controller 15 such as a Poxboro dynalog electronic indicating controller transmitter with stabilog control mechanisms, Model No. 9653 44-4-8. By-pass valves 18 are provided around valve 17 and flow meter 20 for manual and emergency operation. I

Controller 15 is responsive to the voltage in wires 21. It then modulates the pressure in pipe :16 to maintain an accurate flow in supply pipe 13 which is proportional to the pressure in pipe 11. This feedback serves to check the actual acid input continuously and to match it accurately to the signal indicating the rate of strip passage through tank 1. Controller 15 also records the actual flow of acid in supply pipe 13 on a chart and transmits in pipe 22 a pressure proportional to the actual flow of acid in the supply pipe 13. A dial type recorder 23 such as a Foxboro integrating recorder maintains a record of the total amount of acid discharged into tank' l.

A proportioning controller 24 is connected to pipe 22 and delivers a controlled air pressure in pipe 25 which is proportional to the pressure in pipe 22. The ratio or proportion may be manually set on controller 24. A Foxboro recording receiver ratio cont-roller, type M/4O stabilog is suitable for this purpose. Air pressure in pipe 25 opens a pneumatic valve 26 proportionally, thereby discharging water through pipe 27 into the pickling tank at discharge point 28. A flow meter 29 connected across an orifice 30 records the actual flow of water in pipe 27. Manual by-passes 31 are provided around the valve 26 and orifice 30. The flow meter develops an air pressure in pipe 32 proportional to the actual flow of water through orifice 30. Pipe 32 connects to a proportioning controller .34 such as a Foxboro indicating flow transmitter and serves as a feedback from which controller 24 further adjusts valve 26 to maintain a correct flow of water in pipe 27. A dial type recorder 33, such as a Foxboro pneumatic receiver integrator, records the total gallons of water discharged into the pickling tank. Two pens in controller 24 continuously record the flow of acid and of water into pickling tank 1.

From the foregoing, it will be apparent that the area of strip passing through the pickling tank is constantly being determined and that acid is delivered'to the pickling tank in a fixed proportion thereto. The actual flow of acid is measured, and this information is fed back to the controller for further precise adjustment of the acid {flow control valve. In like manner, water is supplied to the pickling tank in an amount proportional to the acid flow. Similarly, the actual water flow is measured and fed back to the Water flow controller for further adjustment of the Water flow control valve. The acidwater ratio is adjusted manually to suit the particular operating conditions. Once set, this ratio is ordinarily maintained constant for given operating conditions, and future adjustments are made only infrequently, The amount of acid supplied may be cut ofi ,or increased through manual control to meet abnormal operations conditions or make corrections in the acid concentration if necessary. It has been found that the desired acid concentration is maintained much more closely than is possible with manual control. The time between titrations of the pickling tank solution has been increased, thereby reducing the labor required. Overly strong acid solutions are avoided, thereby making more efiective use of the acid and minimizing acid attack on the product. It will be apparent that use of the invention is not limited to wide thin strip or any other product, that it may be used with products of other types and cross SCfions,

such as wire, for example, and that any desired pickling agent may be employed.

While I have illustrated and described a present preferred embodiment of my invention, it is to be understood :that I do not limit my self thereto and that the invention may be otherwise variously practiced within the scope of the following claims.

I claim:

1. Apparatus for continuously pickling a product comprising a pickling tank through which said product is passed, measuring means to measure the speed at which the product passes through the tank, and means responsive to said measuring means to introduce a pickling agent into the tank whereby the pickling agent is introduced at a rate proportional to the measurement of said measuring means.

2. Apparatus for continuously pickling a strip product comprising a pickling tank into which said strip product is introduced, means to measure the rate of passage of the strip product through the tank, and means responsive to said first means to introduce a pickling agent into the tank at a rate proportional to said rate of passage of strip product, whereby the rate of introduction of the pickling agent varies with the rate of passage of the strip product through the pickling tank.

3. Means for continuously pickling a product of substantial length comprising a pickling tank through which said product is passed, measuring means to continuously measure the area of the product passing through the tank per unit of time, and means responsive to said measuring means to introduce a pickling agent into the tank at a rate proportional to the area of product passing through the tank.

4.. Means for continuously pickling a product of substantial length comprising a pickling tank through which the product is passed by concurrently introducing and removingthe product from the tank, means to measure the rate of removal of the product from the tank, and second means responsive to first said means to introduce a pickling agent into the tank at a rate proportional to the rate of removal of the product from the tank, whereby the rate of introduction of pickling agent is continuously varied with the rate of removal of the product from the tank.

5. Means for continuously pickling a product of substantial length comprising a pickling tank through which the product is passed, product speed measuring means adjacent the point of removal of the product from the tank, means in operative connection therewith adjustable for the size of the product being pickled whereby the area of product passing through the pickling tank is determined, and means controlled by the product speed measuring means and the means in operative connection therewith to introduce a pickling agent into the tank at a rate proportional to the rate removal of the product.

6. Means for continuously pickling a strip product of substantial length comprising a pickling tank through which the strip product is passed at a variable speed, strip speed measuring means adjacent the point of removal of strip from the tank and indicating the speed of removal of the strip, means to indicate the size of the strip, means responsive to both said means whereby the rate of strip product area passing through the pickling tank is determined, and means in operative connection therewith to feed a pickling agent to the tank at a rate proportional to the rate .at which strip product area is passing through the tank.

'7. Means for continuously pickling a product of substantial length comprising a pickling tank into which the product is introduced at varying speeds, speed measuring means to measure and indicate the speed of passage of product through the tank, indicating means in connection therewith and adjustable with the size of the product being introduced into the tank whereby the area of product passing through the tank may be determined,

means in operative connection with the speed measuring means and the indicating means to discharge a pickling agent into the tank at a rate proportional to the area rate of passage through the tank of the product, and means to concurrently discharge a proportioned amount of Water into the tank.

8. Means for continuously pickling a strip product of substantial length comprising a pickling tank through which the strip product is passed at a variable speed, strip speed measuring means, means in operative connection therewith to introduce a pickling agent into the tank at a rate proportional to the speed of passage of the strip product through the tank, and means to measure the rate of introduction of the pickling agent for further adjustment of the rate of introduction of said pickling agent.

9. Means for continuously pickling a product of substantial length comprising a pickling tank, product speed measuring means adjacent the pass line of the product, means responsive thereto to discharge an acid into the pickling tank at a rate proportional to the rate of passage of the product through the tank, and means to introduce Water into the tank proportionally with the acid.

10. Means for continuously pickling a strip product of substantial length comprising a pickling tank through which the strip product is passed, means to measure and indicate the speed at which the strip product passes through the tank, means in connection therewith to indicate the Width of the strip product whereby the area of strip product passing through the tank is determined, control means in operative connection with the speed measuring means and the indicating means to discharge acid into the tank proportionally with the rate of passage of strip product, acid gauge means to gauge the flow of acid for further adjustment of the control means, second control means to discharge Water into the tank proportionally with the rate of introduction of acid into the tank, and water gauge means to gauge the flow of water for further adjustment of the second control means.

References Cited in the file of this patent UNITED STATES PATENTS 2,334,177 Dishauzi Nov. 16, 1943 2,348,232 Trautman May 9, 1944 2,628,924 Johnston Feb. 17, 1953 2,661,009 Dunnegan Dec. 1, 1953 2,769,735 Miller Nov. 6, 1956