FIELD OF THE INVENTION
The present invention relates in general to detecting fluid levels within a fluid
storage tank and more particularly to a laser based fluid level detection system
and a laser based fluid level detection method for measuring levels of fluid such
as acid contained in acid regeneration tanks of an acid regeneration plant (ARP)
where an acid regeneration tank supplies regenerated acid to pickling tanks of
continuous pickling line-tandem cold mill (PLTCM).
BACKGROUND OF THE INVENTION
Indication of fluid or liquid level is a critical variable in process control, storage
tank monitoring, and mechanical systems where fluids are contained. Fluid level
indication is of particular importance in pickling of steel. Pickling is a treatment
process in which an oxide scale present on the surface of steel plates, such as
cold rolled steel plates, hot rolled steel plates to be subjected to cold rolling, hot
rolled steel plates which are in the form of final products, is removed by
immersing the steel plates in a pickling solution of hydrochloric acid, sulfuric
acid, etc., or by spraying a pickling solution at the surface of the steel plates.
Pickling is performed, for example, by continuously passing steel plates through
a continuous pickling line in which a plurality of pickling tanks containing a
pickling solution are arranged in series in the direction of movement of the
plates. In pickling performed using such a continuous pickling line, the acid level
in each pickling tank, and particularly in the last pickling tank, greatly
influences the efficiency of removal of oxide scale. Therefore, in pickling using
such a continuous pickling line, it is necessary to accurately monitor the acid
levels in the acid regeneration tanks of the Acid regeneration plants (ARPs)
through which the acid is passed to pickling tanks of continuous pickling line-
tandem cold mill (PLTCM) purge tube.
For example, the most commonly used fluid level detection process used in the
pickling industry involves a PLTCM Purge Tube and differential pressure switch
are used to measure the acid level of regenerated acid tank. The process is based
on the concept of measurement of pressure of a liquid of known height using the
relation “P = h*ρ*g”, where P= Pressure h= height of the liquid ρ=density of the

liquid and g = acceleration due to gravity (Fig.1). The problem with the above
approach is that the system needs accurate calibration of differential pressure
ttransmitter (DPT), maintenance of constant air/nitrogen pressure, ensuring
that there is no leakage inside purge tube and pneumatic line making such
systems very prone to malfunction.
Other commonly known approaches use sensors for detection of the fluid level.
As the float moves vertically with the fluid level, the electrical resistance of the
sensor changes typically from 30 to 270 ohms. In most sensors, a sliding or
moving contact attached to the float establishes a resistive circuit based upon
the position of the contact with respect to a wire wound resistor or a thick film
resistor printed on an insulating base or substrate. The problem with such
systems is sensors are put inside the fluid storage tanks which are not
desirable as it affects the accuracy of detection of the fluid levels.
To address all of the drawbacks of the prior art, there is therefore a need to
develop a dedicated, portable, simple to calibrate and easy to install fluid/acid
level measurement system and method to be used for measurement of acid level
in the acid regeneration tanks during the pickling process.
OBJECTS OF THE INVENTION
It is therefore an object of the invention is to overcome the aforementioned and
other drawbacks existing in prior fluid detection systems.
Another important object of the present invention is to provide an automatic
system and method for detecting dynamic level of fluid in a tank.
Still another object of the present invention is to provide a system for detecting
acid level in an acid regeneration chamber during pickling process.
Yet another object of the present invention is to provide a fluid level detection
system which is portable, simple to calibrate and easy to install.

Still further object of the present invention is to provide a fluid level detection
system where sensing unit (laser distance meter) has no contact with the fluid
contained in the tank.
These and other objects and advantages of the present invention will be
apparent to those skilled in the art after a consideration of the following
detailed description taken in conjunction with the accompanying drawings in
which a preferred form of the present invention is illustrated.
SUMMARY OF THE INVENTION
In an aspect, the present application discloses a system for automatically
detecting dynamically changing level of fluid stored in a tank having known
cross-sectional characteristics. The method comprises a reference object (1)
having a stem (2) where the reference object (1) floats in the fluid contained in
the tank (5), a reflector (3) contactly attached to the stem (2) of the reference
object (1), a sensor which is a laser distance meter (7) disposed outside the
tank (5) on a platform (6) positioned on roof of the tank (5), where the sensor
(7) aligned with the reflector (3) such that that laser rays (8) emitted by the
sensor (7) hits the reflector (3) and reflected back, a measuring scale (4)
disposed on the platform (5) and aligned alongside the stem (2) of the reference
object (1), a controller (9) electronically coupled to the sensor (7) for receiving
output from the sensor (7) and calibrating the received electrical signal to
output the fluid level, a display unit (10) electrically coupled to the controller
(9) for displaying the output from the controller (9).
In an aspect, the present application discloses a method for automatically
detecting dynamically changing level of fluid stored in a tank having known
cross-sectional characteristics. The method comprises placing a reference
object (1) inside a tank (5), wherein the reference object (1) floats in the fluid
contained in the tank (5), placing a measuring scale (4) aligned stem (2) of the
reference object (1), positioning a reflector (3) and a sensor (7) outside the tank
(5) such that laser rays (8) emitted by the sensor (7) hits the reflector (5) and

reflected back, electronically measuring fluid level based on electrical current
signal generated by the sensor (7) and displaying the measured fluid level.
The above and additional advantages of the present invention will become
apparent to those skilled in the art from a reading of the following detailed
description when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The above brief description, as well as further objects, features and
advantages, of the present invention can be fully appreciated by reference to
the following detailed description. These features of the present invention will
become more apparent upon reference to the drawings, wherein:
Fig. 1: Conventional fluid level measurement system.
Fig. 2a: Illustrates lower position of float indicating low level of acid in the acid
regeneration tank.
Fig. 2b: Illustrates raised position of float indicating high level of acid in acid
regeneration tank.
Fig. 3: Illustrates design of the acid level detection system.
Fig. 4: Illustrates block diagram of the automatic acid level detection system.
Fig.5: Illustrates deployment of the system in the acid regeneration tank of the
acid regeneration plant (ARP).
DETAILED DESCRIPTION OF THE INVENTION
Although the disclosure hereof is detailed and exact to enable those skilled in
the art to practice the invention, the physical embodiments herein disclosed
merely exemplify the invention which may be embodied in other specific
structure. While the preferred embodiment has been described, the details may

be changed without departing from the invention, which is defined by the
claims.
It will be apparent, however, to one of ordinary skill in the art that the present
invention may be practiced without specific details of the well known
components and processes. Further specific numeric references should not be
interpreted as a literal sequential order. Thus, the specific details set forth are
merely exemplary. The specific details may be varied from and still be
contemplated to be within the scope of the present invention. The features
discussed in an embodiment may be implemented in another embodiment.
Moreover, occasional references to the conventional systems are made in order
to better distinguish the present inventive disclosure discussed later in greater
detail. Few of the details pertaining to said system/process are well known in
the art and therefore, are described herein only in the detail required to fully
disclose the present invention while unnecessarily obscuring the present
invention.
Improving upon and addressing the problems discussed at length above
(background), in the present disclosure a system for automatically detecting
dynamically changing level of fluid stored in a tank such as the dynamically
changing level of acid in the acid regeneration tank as illustrated in the Figures
clearly makes the proposed system advantageous over the existing approaches
as would also become clearer to the knowledgeable in the art with the
particulars of the aforesaid unique system/process being described below in
greater details. The present invention will be described in detail below with
reference to embodiments as shown in the drawings.
Fig. 2a shows a lower position of float indicating low level of acid in the
acid regeneration tank and Fig. 2b shows a raised position of float
indicating high level of acid in acid regeneration tank.
In an embodiment, a reference object 1 fitted with a stem 2 combinedly called a
scaled float mechanism (1, 2) is mounted on the tank roof on which is placed a

platform 6. In an embodiment, the platform may have a groove/hole. In an
embodiment, the reference object 1 is a float floating in the fluid in a tank such
as acid in the acid regeneration tank (5). Further, when tank’s liquid level
increases float rod raised (Fig.2a) and when tank’s liquid level decreases float
rod lowers down (Fig.2b) proportionately and attached measuring scale 4
shows the level of the tank 5. In an embodiment, the measuring scale 4
disposed on the platform 5 and aligned alongside the stem 2 of the float 1.
Fig. 3 shows a design of the acid level detection system.
Fig. 3 shows that the proposed system has a float 1 with a stem 2 floating in
the acid in the acid regeneration tank 5. In an embodiment, a reflector 3 is
attached with the float mechanism 1, 2 and the sensor 7 which in a preferred
embodiment is a laser distance meter is placed outside the tank 5 on a platform
6 positioned on roof of the tank 5. In an embodiment, the sensor 7 aligned with
the reflector 3 such that that laser rays 8 emitted by the laser distance meter 7
hits the reflector 3 and reflected back. In an embodiment, the reflector 3 is
square shaped.
Fig. 4: Illustrates block diagram of the automatic acid level detection
system.
In operation, the laser distance meter 7 on the platform 6 emits laser rays 8
which hit the square shaped reflector 3 attached to the stem 2 of the float 1
and is reflected back. Further, electronically calculating the distance from the
reflector which is calculated based on the time of travel and known speed of
laser). Laser distance meter 7 is coupled to the controller 9 which in an
embodiment may be a Distributed control system (DCS) and/or Programmable
Logic Controller (PLC). The Laser distance meter 7 outputs the calculated
“distance” above in terms of 4 to 20 mA and as the reflector 3 is physically
attached with the float 1 and when the float level varies with the variation in
liquid/acid, generated is the exact proportionate electrical signal from the laser
distance meter, this electrical signal (4 to 20 mA) is input to the PLC/DSC 9
which calibrates the signal to get the exact level of liquid/Acid which is

displayed through the display unit 10. In an embodiment the display unit may
be a Human Machine Interface (HMI). Fig. 5 shows deployment of the system in
the acid regeneration tank of the acid regeneration plant (ARP).
In an embodiment, the measuring scale 4 is pre-calibrated with the specific
liquid along with float mechanism. Thus, this scale will be required in case of
change of laser sensor/laser distance meter or in case of any physical position
change of sensor or reflector.
In another embodiment, the measuring scale 4, the calibrated scale can be
prepared with float and liquid of different specific gravity.
The foregoing is considered as illustrative only of the principles of the
invention. Furthermore, since numerous modifications and changes will readily
occur to those skilled in the art, it is not desired to limit the invention to the
exact construction and operation shown and described. While the preferred
embodiment has been described, the details may be changed without departing
from the invention, which is defined by the claims.

We claim:
1. A system for automatically detecting dynamically changing level of fluid
stored in a tank having known cross-sectional characteristics, the system
comprising:
a reference object (1) having a stem (2), wherein the
reference object (1) floats in the fluid contained in the tank (5);
a reflector (3) contactly attached to the stem (2) of the
reference object (1);
a sensor (7) disposed outside the tank (5) on a platform (6)
positioned on roof of the tank (5), said sensor (7) aligned with the
reflector (3) such that that laser rays (8) emitted by the sensor (7)
hits the reflector (3) and reflected back;
a measuring scale (4) disposed on the platform (5) and
aligned alongside the stem (2) of the reference object (1);
a controller (9) electronically coupled to the sensor (7) for
receiving output from the sensor (7) and calibrating the received
electrical signal to output the fluid level;
a display unit (10) electrically coupled to the controller (9) for
displaying the output from the controller (9).
2. The system as claimed in claim 1, wherein the sensor (7) is a laser
distance meter.
3. The system as claimed in claim 2, wherein the output from the laser
distance sensor is in form of electrical current signal in range of 4-20mA.
4. The system as claimed in claim 1, wherein the reference object (1) is a
float floating in the fluid.

5. The system as claimed in claim 1, wherein the controller (9) is at least one
of Distributed Control System (DCS) or Programmable Logic Controller
(PLC).
6. The system as claimed in claim 1, wherein the reflector (3) is square
shaped.
7. The system as claimed in claim 2, wherein the laser distance meter (7) is
powered with a 24V DC supply by the controller (9).
8. The system as claimed in claim 1, wherein the display unit (10) is a
Human Machine Interface (HMI).
9. A method for automatically detecting dynamically changing level of fluid
stored in a tank having known cross-sectional characteristics, the system
comprising:
placing a reference object (1) inside a tank (5), wherein the
reference object (1) floats in the fluid contained in the tank (5);
placing a measuring scale (4) aligned stem (2) of the
reference object (1);
positioning a reflector (3) and a sensor (7) outside the tank
(5) such that laser rays (8) emitted by the sensor (7) hits the
reflector (5) and reflected back;
electronically measuring fluid level based on electrical
current signal generated by the sensor (7); displaying the
measured fluid level.