FORM 2 THE PATENT ACT 1970 (39 OF 1970) & The Patent Rules, 2003 COMPLETE SPECIFICATION (See Section 10 and Rule13)
1 TITLE OF THE INVENTION :A SYSTEM FOR LEVEL MEASUREMENT OF CONTENTS IN VESSEL / TANKS ESPECIALLY AT HAZARDOUS LOCATIONS

2 APPLICANT (S)Name: STEEL AUTHORITY OF INDIA LIMITEDNationality: A Govt. of India EnterpriseAddress: Bhilai Street Plant, Bhilai, State of Chattisgarh, India
3 PREAMBLE TO THE DESCRIPTIONCOMPLETEThe following specification particularly describes the invention and the manner in which it is to be performed

FIELD OF THE INVENTION
The present invention relates to a system for level measurement of liquid/solid contents in containers/vessels and ,in particular, to a system for level measurement of liquid/solid contents in containers/tanks/vessels at hazardous locations using ultrasonic instruments. The system is directed to avoid complications of installation and safety of operators while measuring levels in bunkers, hopper etc or liquid level in water tank/vessels in hazardous locations. This would favour fast and safe user friendly level measurement at hazardous locations involving ultrasonic instruments.
BACKGROUND ART
It is well known to use variety of systems for level measurement including at hazardous locations using ultrasonic instrument
In particular, it is known to use ultrasonic level measuring instrument to measure solid/liquid levels in bunker, hopper etc. or liquid level in water tank, vessel etc. Installations for such ultrasonic instruments usually recommend that the face of the ultrasonic sensor is parallel to the surface of the material. Also the sensor is required to be positioned at the center of the outflow funnel so that an echo is received till the silo is empty.
It is experienced that following such convention types of installations especially at hazardous locations where a person/operator can not go without proper shut down of the unit and further following proper safety precautions, reliable working of instruments and its proper maintenance is very difficult Importantly, it is found that such required shut down of operation tend to affect the production, therefore, not desirably occasioned frequently leading to possible delay in effective maintenance and proper use of such level measuring systems. Apart from such problems associated with shut down of the unit for maintenance and reliable working of the instruments, it is found that the environment in and around such hazardous locations of level measurement continue to be unsafe even after shut down, which always lead to safety concerns of people engaged in maintenance and/or operation of such level indicating systems.
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It is, therefore, required to provide better systems and method of measurement of levels especially at hazardous locations so that the complexities and problems of safety concerns of the people and operators are taken care of and the system can be safely and effectively maintained and used for proper level measurement including those at hazardous locations.
OBJECTS OF THE INVENTION
It is thus the basic object of the present invention to provide a system for level measurement at hazardous locations using ultrasonic instruments, which would avoid the discussed limitations and safety concerns of conventional installation for level measurement presently in use.
Another object of the present invention is to provide a system for level measurement at hazardous locations, which would avoid the problems concerning shut down and complex safety precautions required for installations and use of the ultrasonic level measuring instrument presently in use.
Yet another object of the present invention is directed to a system for level measurement at hazardous locations, which would ensure the safety of the instruments and human beings responsible for maintenance of the system for such level measurement without compromising on the efficacy and performance requirements of such ultrasonic level measuring system.
Yet another object of the present invention is directed to provide for a system for level measurement at hazardous locations using ultrasonic instruments, which would be simple and safe to install and would at the same time be effective and reliable in as far as ascertaining the level of contents in vessels/tanks etc. in hazardous locations.
Yet another object of the present invention is directed to a simple and cost effective system for level measurement of liquid/solid contents in tanks/vessels at hazardous locations, which could be easily obtained cost effectively and readily installed without involving technical complexities and/or avoid safety hazards while installing and/or during use.
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SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a system for level measurement of contents in vessels /tanks especially at hazardous locations comprising:
an ultrasonic wave reflector for disposition atop the vessel/tank containing the solid/liquid content of which the level is to be detected;
a conical wave guide cooperating with the above ultrasonic wave reflector ;
an ultrasonic instrument having sensor means cooperating with said conical wave guide to sense the level by generating ultrasonic wave and tracking the wave propagation by the sensor through the conical wave guide along the ultrasonic wave reflector and upto said level of the content in said vessel/tank without requiring disposition of the sensor facing the material surface.
Importantly, the above system for level measurement of contents in vessels /tanks include said ultrasonic wave reflector adapted to bend the waves for level measurement by 90 degrees. For such purpose, the said conical wave guide, and said ultrasonic instrument are supported with an instrument fixing stand having mounting matching flange.
In accordance with a preferred aspect the said conical wave guide have an angle of (a + 1)° wherein 'α' is the angle of propagation of the wave and the radius of the wave emanating from the wave guide after the wave reflection is defined by Radius (r) = tan (α/2)*L where V is the vertical distance between the sensor height with respect to the content of which the level is sensed.
An another aspect of the present invention is there is a provision of a method for level measurement at hazardous locations using the above system comprising:
mounting the ultrasonic instrument (sensor) horizontally away from the hazardous location;
providing the cooperating conical wave guide and said ultrasonic wave reflector such that the ultrasonic wave generated by the said ultrasonic instrument is reflected at 90° towards the content level to be sensed , thereby favouring the
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measuring of the level safely disposing the ultrasonic instrument away from the vertical top of the vessel/tank containing the content.
In the above method the wave guide cone used is based on the angle of propagation of the wave and the waves are bent at 90° with the use of the reflector.
Importantly, the conical wave guide used has angle of (o + l)°, where 'α' is the angle of propagation of the wave and the radius of the wave emanating from the wave guide ‘r’; where (r) = tan (α/2)*L (where L is the vertical distance between the sensor and the material whose level B to be measured.
It is thus possible by way of the above disclosed system for level measurement at hazardous locations using ultrasonic instruments to achieve simple yet effective installation of ultrasonic instrument for level measurement, which can be installed safely away from vicinity of the hazardous locations and facilitate safety related shut down of operations and/or for maintenance purposes of such measuring systems.
Advantageously, the above system of the invention could be developed after extensive studies of the sensor and the wave propagation pattern of the ultrasonic instrument based sensors. Importantly, the wave guiding cone used in the system of the invention has been developed by calculating the angle of the propagation of the waves. These waves are thereafter bent at 90° with the help of the reflector used in the system. It is by way of such selective provision of the wave guiding cone and the reflector it is possible to measure the level of solid or liquid at hazardous locations. Importantly, apart from facilitating safe measure of solid or liquid levels at hazardous locations the maintenance of the installed system, which is favorably located at safe location, as also been made safe, simple and cost effective.
The level measurement involving the system of the invention thus ensures safety of the instruments and also of the human being responsible for maintenance of such instruments. Importantly, while the system of the invention takes care of the drawbacks and limitation associated with the conventional level measuring systems also more importantly further ensures that the effectiveness and reliability of level measurement is maintained.
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The possible horizontal disposition of the system as compared to the vertical mounting of the instruments taught under the conventional art, ensure safe locations for the instruments as well as the user. The instrument under the present system is thus approachable with safety by any operating/maintaining personnel at any time as and when required. Importantly also, the maintenance and checking of the instrument in the system of the invention will be possible without requiring shut down. The manner of ultrasonic wave travel through wave guide in the system of the invention, which is maintained uninterrupted from any type of external obstruction, makes the material level measurement using the same possible without compromising with instrument performance.
The details of the inventions, its objects and advantages are explained hereunder in greater detail through illustrations as per the following accompanying drawings:
BRIEF DESCRIPTION OF THE FIGURES
Figure 1: illustrates the arrangement and installation of a conventional type level measurement using ultrasonic instrument;
Figure 2: illustrates the system of measurement of level at hazardous locations using ultrasonic instrument in accordance with the present invention.
Reference is first invited to accompanying figure 1, which illustrates in detail a conventional system for level measurement involving the ultrasonic instrument. Such ultrasonic instruments used for level measuring are conventionally known to be used to measure solid level in bunker, hopper etc or liquid level in water tank/vessel. As shown in said figure the installation of such ultrasonic level instrument (2) is recommended such that the face of the sensor is parallel to the surface of the material (5). In such system the sensor is thus required to be positioned at the center of the outflow funnel so that an echo is received till silo is empty. To facilitate the installation the mounting matching flange (1) is installed and the ultrasonic wave (4) is generated using the instrument (2). The angle (α) is the angle of the propagation of the wave while the radius ( r) = tan (α /2)* L wherein L constituents the distance between the sensor and the top of the material (5) of which the level is being measured contained in the hopper (3).
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It would be apparent from the above conventional type Ultrasonic Instrument Installation that such installations are hazardous, being directly facing possible contents and the operator/person installing/using can not reach the sensor installed without arranging proper shut down and following proper safety precautions. This necessarily affect the working of such instrument as well as its proper maintenance and it is found that even in case of shut down working in such an environment is highly unsafe.
Reference is now invited to accompanying figure 2, which illustrates the safe and user friendly horizontal installation of the ultrasonic instrument in the level measuring system of the invention. As dearly illustrated in said figure in the system of the invention the conventionally recommended installation of ultrasonic instrument such that the face of the sensor is parallel to the surface of the material is avoided to ensure easy installation and better safety of the instrument and the user. For the purpose in the system of the invention the ultrasonic instrument (3) is installed at 90° with respect to the material surface to favor uninterrupted ultrasonic wave travel from the instrument (3) towards the material surface (8). Importantly, the system provides for a conical wave guide (4) along with an ultrasonic wave reflector (5). The instrument as well as the wave guide is supported with respect to an instrument fixing stand (l). Such an arrangement facilitates the ultrasonic wave generated by the sensor to take a 90° turn at the reflector and then proceed towards the material surface for level sensing.
Importantly, as dearly apparent from the above the present system illustrated in figure 2 dearly avoids the vertical mounting of instrument at the center top of the bunkers/hoppers and make possible the mounting of the instrument horizontally away from the direct vicinity of the hazardous locations. Such an arrangement also favors approaching the instruments safely as and when required and enables maintenance of the instrument without requiring shut down.
In order to ascertain the performance of the present system for level measurement at hazardous locations as per the figure 2 above vis-à-vis the conventional systems as per figure 1 comparative experimental readings were carried out involving the systems as per figure 2 (present system) and figure 1 (conventional system) and the results are reproduced hereunder in Tables 1 & 2 respectively:
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TABLE 1
Experimental reading with sensor installed at a 90° to target (As per Figure 2)
Lm = 5.0 mt L = 7.0 mt

SI. No. Empty Distance MeasureValue(Mt) Actual Material level (Mt) Measuredmateriallevel(Mt) %Material Level Error (%)
1 2-23 2.22 4.77 4.78 95.40% 0.20%
2 2.5 2.5 4.5 4.5 90.00% 0.00%
3 3 2.99 4 4.01 80.00% 0.20%
4 3.5 3.49 3.5 3.51 70.00% 0.20%
5 4 3.99 3 3.01 60.00% 0.20
6 4.5 4.5 2.5 2.5 50.00% 0.00%
7 5 5.01 2 1.99 40.00% -0.20%
8 5.5 5.51 1.5 1.49 30.00% -0.20%
9 6 6 1 1 20.00% 0.00%
10 6.5 6.49 0.5 0.51 10.00% 0.20%
11 6-75 6.75 0.25 0.25 5.00% 0.00%
TABLE 2
Experimental reading with sensor directly facing target (As per Figure 1)
Lm = 5.0 mt. L = 5.5 mt

SI. No. Empty Distance MeasureValue (Mt.) ActualMateriallevel(Mt) Measuredmateriallevel(Mt) %MaterialLevel Error (%)
1 0.5 0.5 5 5 100.00% 0.00%
2 0.73 0.72 4.77 4.78 95.40% 0.20%
3 1 0.99 4.5 4.51 90.00% 0.20%
4 1.5 1.49 4 4.01 80.00% 0.20%
5 2 1.99 3.5 3.51 70.00% 0.20%
6 2.5 2.49 3 3.01 60.00 0.20%
7 3 2.99 2.5 2.51 50.00% 0.20%
8 3.5 3.5 2 2 40.00% 0.00%
9 4 4 1.5 1.5 30.00% 0.00%
10 5 5 0.5 0.5 10-00% 0.00%
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Importantly, the above readings confirm that the ultrasonic wave traveling through the wave guide in the system of the invention is maintained uninterrupted from any type of external obstruction and hence material level measurement is possible without comprising with instrument performance.
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WE CLAIM:
1. A system for level measurement of contents in vessels /tanks especially at
hazardous locations comprising:
an ultrasonic wave reflector adapted for disposition atop the vessel/tank containing the solid/liquid content of which the level is to be detected;
a conical wave guide cooperating with said ultrasonic wave reflector ;
an ultrasonic instrument having sensor means cooperating with said conical wave guide to sense the level by generating ultrasonic wave and tracking the wave propagation by the sensor through the conical wave guide along the ultrasonic wave reflector and upto said level of the content in said vessel/tank without requiring disposition of the sensor facing the material surface.
2. A system for level measurement of contents in vessels /tanks as claimed in claim 1 wherein said ultrasonic wave reflector is adapted to bent the waves for level measurement by 90 degrees.
3. A system for level measurement of contents in vessels /tanks as claimed in anyone of claims 1 or 2 wherein said conical wave guide and said ultrasonic instrument are supported with respect to an instrument fixing stand having mounting matching flange.
4. A system for level measurement of contents in vessels /tanks as claimed in anyone of claims 1 to 3 wherein said conical wave guide have an angle of (o + 1)° wherein a is the angle of propagation of the wave and the radius of the wave emanating from the wave guide after the wave reflection is defined by Radius (r) = tan (α/2)*L (where L is the vertical distance between the sensor height with respect to the content of which the level is sensed).
5.A method for level measurement at hazardous locations using the system as claimed in anyone of claims 1 to 4 comprising:
mounting the ultrasonic instrument and sensor horizontally away from the hazardous location;
providing the cooperating conical wave guide and said ultrasonic wave reflector such that the ultrasonic wave generated by the said ultrasonic instrument is
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reflected at 90° towards the content level to be sensed , thereby favoring the measuring of the level by safety disposing the ultrasonic instrument away from the vertical top of the vessel/tank containing the content.
6. A method for level measurement as claimed in claim 5 wherein the wave guide cone used was based on the angle of propagation of the wave and the waves are bent at 90° with the use of the reflector.
7. A method for level measurement as claimed in anyone of claims 5 or 6 wherein the conical wave guide use has angle of (α + 1)° wherein a is the angle of propagation of the wave and the radius of the wave emanating from the wave guide after the wave reflection is defined by Radius (r) = tan (α/2)*L (where L is the vertical distance between the sensor height with respect to the content of which the level is sensed).
8. A system for level measurement of contents in vessels /tanks at hazardous locations and the method of measuring the level of solid/liquid contents in vessels/tanks at hazardous locations using the same substantially as herein described and illustrated with reference to the accompanying figures.
Dated this 22nd Day of December, 2005

Anjan Sen
Of Anjan Sen & Associates
(Applicants Agent)
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ABSTRACT
A system for level measurement of liquid/solid contents in containers/tanks/vessels at hazardous locations using ultrasonic instruments. In the system the ultrasonic instrument having sensor means cooperate with a conical wave guide to sense the level by generating ultrasonic wave and tracking the wave propagation by the sensor through the conical wave guide along the ultrasonic wave reflector and upto said level of the content in said vessel/tank without requiring disposition of the sensor facing the material surface. The system is directed to avoid complications of installation and safety of operators while measuring levels in bunkers, hopper etc. or liquid level in water tank/vessels in hazardous locations. This would favour fast and safe user friendly level measurement at hazardous locations involving ultrasonic instruments.
(Figure 2)