Claims:We Claim:

1. Protective enclosure for protecting electronic gadgets including sensors in arduous and corrosive environments at top of coal silos and the like comprising :

a main protective enclosure stably supporting and housing the electronic gadgets including sensor against any mechanical damage and the like;

said main enclosure including at the top thereof cooperative with an angle adjuster means for desired angular direction for the electronic gadget/ sensor housed in the said main protective enclosure; and

a top cover for said main protective enclosure adapted for top protection of said electronic gadget including sensor against any mechanical damage due to moving machinery including conveyor belt , tripper and the like.

2. Protective enclosure as claimed in claim 1 for non-contact RADAR type level measurement sensors suitable for arduous and corrosive environments at top of coal silos and the like comprising :

a main protective enclosure stably supporting and housing the non-contact RADAR type level sensor with downwardly looking position at the silo top ;

said main enclosure at the top thereof cooperative with an angle adjuster means for desired angular direction for the sensor housed in the said main protective enclosure such that the RADAR beam focusses at the center of the storage bunker;

a cooperative antenna protector adapted to protect the downward looking antenna of sensor emitting electronic wave at continuously varying frequency for desired level measurement based on reflected beam wave received by the antenna and cooperative transmitter electronics for determine solo level based on frequency phase shift and travel time of electronics wave;

a cover for top protection with operative cable entry provision.

3. The protective enclosure as claimed in anyone of claims 1 or 2 wherein said main protective enclosure stably supporting and housing the non-contact RADAR type level sensor comprises of stainless steel protective enclosure and adapted for mounting at the silo top without any projections to avoid any mechanical damage of any moving machinery.

4. The protective enclosure as claimed in anyone of claims 1 to 3 including provisions for air and/or nitrogen purging comprising a mechanism for connecting air and/or nitrogen supply to the enclosure and piping arrangement for cleaning radar antenna with air and/or nitrogen against deposit of coal dust and moisture.

5. The protective enclosure as claimed in anyone of claims 1 to 4 wherein said cooperative angle adjustment means include means for adjustment of mounting angle comprising a mechanical rotation arrangement thereby adjusting the enclosure angle with respect to horizontal base frame fixture.

6. The protective enclosure as claimed in anyone of claims 1 to 5 including means for convenient installation and removal for maintenance including cemented fixed base frame below the conveyor belts at the silo top and removable flange and adjustable removable fixture to support / hold the enclosure body.

7. The protective enclosure as claimed in anyone of claims 1 to 6 comprising of level measurement sensors based on 80 GHz W-Band radar, including frequency modulated continuous wave method (FMCW) for level sensing.

8. The protective enclosure as claimed in anyone of claims 1 to 7 which is adapted to house the level sensor and installed below running conveyor belt.

Dated this the 30th day of March, 2021
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199

, Description:FORM 2
THE PATENT ACT 1970
(39 OF 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

1 TITLE OF THE INVENTION :
A PROTECTIVE ENCLOSURE FOR PROTECTING ELECTRONIC GADGETS INCLUDING SENSORS IN ARDUOUS AND CORROSIVE ENVIRONMENTS AT TOP OF COAL SILOS.



2 APPLICANT (S)

Name : STEEL AUTHORITY OF INDIA LIMITED.

Nationality : Indian.

Address : Research & Development Centre for Iron & Steel,
Doranda, Ranchi, Jharkhand, India. PIN-834002.





3 PREAMBLE TO THE DESCRIPTION

COMPLETE

The 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 protective enclosure for protecting electronic gadgets including sensors in arduous and corrosive environments of coal silos. More particularly, the present invention is directed to a special protective enclosure for sensors including Radar Type Level Transmitters for installation at arduous location of Coal Silos for ease of installation and maintenance ensuring safe and reliable performance of the instruments. The level measurement sensor is non-contact type, W-band, RADAR based on Frequency Modulated Continuous Wave (FMCW) technology. The enclosure is extremely essential and useful as it facilitates appropriate angular adjustment of level measurement sensor inside the storage bunker. The enclosure also provides protection of instrument against any mechanical damage and corrosion inside the arduous and dusty environment of coal storage bunkers.

BACKGROUND OF THE INVENTION

At Applicant’s Durgapur Steel Plant (DSP), coal is filled into the storage bunkers from the top at a height of 28 metres (approx.) through inclined feeding conveyor and tripper car assembly. Tripper car collects the coal from feeder conveyor and refill the same into the storage bunkers through two nos. of chutes. There is provision for mounting level measurement sensor at the top of all the silos in old silo section of coal handling plant(CHP), DSP. A top view of the silo top indicating coal feeding hole and sensor mounting location is shown in Fig 1. The diagram shows the mounting location of the level transmitter with respect to the floor of the storage bunker top. Sensor mounting hole is a circular opening of approximately 430 mm diameter and is available over each silo under the feeding conveyor. The level transmitter is mounted inside the aforesaid opening of the silo. The allowable vertical distance between the instrument mounting hole and the feeding conveyor above is approximately 400 mm.
Level measurement sensors are Through-Air-Radar (TAR) technology based non contact type transmitters. The transmitters are based on 80 GHz W-Band radar, which uses frequency modulated continuous wave method (FMCW) for level sensing. The antenna emits an electromagnetic wave at a continuously varying frequency. This wave is reflected by the product and received again by the antenna. The transmitter electronics calculates the coal level based on frequency phase shift and travel time of electronics wave.
Level measurement sensors are exposed to very rough and arduous environment of coal dust inside the storage bunkers. Further proper angular adjustment of sensors are extremely essential in order to ensure proper focusing of sensor beams w.r.t. all possible coal levels from full bunker to completely empty condition. Coal dust accumulation over sensor radar also obscures the field of view of sensor. Generally the sensors are mounted either directly inside the silos or inside some kind of enclosures which does not facilitate angular adjustment and prolonged resistance against corrosive environment. Prolonged exposure of critical level measuring sensor and its electronics with coal dust causes wear and tear, corrosion and ultimately untimely failure of entire sensor and associated electronics.
Drawbacks of the Known Art:
The known art suffers from following major drawbacks:
i) Direct exposure of costly level sensors and associated electronics results in early failure of entire sensor.
ii) Improper enclosure cannot sustain prolong exposure of corrosive coal dust, wear and tear.
iii) In absence of proper angular adjustment, proper focusing of sensor beams are not possible causing erroneous measurement.
iv) No provision of air purging causes dust accumulation over sensor radar resulting in erroneous measurement.

OBJECTIVES OF THE INVENTION
The basic objective of the invention is to provide a protective dust proof enclosure for non contact type level measurement sensors for continuous measurement of level of coal inside storage bunkers.

The other objectives to provide a protective enclosure for level measurement sensor are as follows:
i) The Level measurement sensors are installed inside a harsh arduous environment of coal dust which causes frequent accumulation of powders / lumps covering the sensor. The heap of powder / lump is manually removed using shovel and other hard objects and the area is also subjected to impact of torn conveyor with huge force. Therefore, the enclosure shall not only protect the level transmitter from ingression of coal powder and water flow from the environment but also protect from mechanical damage and impact of external forces.
ii) The Level measurement sensors are installed over the top of the storage bunker with downward looking position. Also, all the operations related to coal charging inside bunkers are done from the top. Therefore, to avoid operational difficulties, the enclosure shall have provisions for maintenance free installation. This includes proper electrical connections and provision of nitrogen / air purging connections under the floor of the storage bunker without any kind of projection outside the bunker roof. Any projection outside the bunker roof may cause mechanical damage due to moving conveyors and tripper car.
iii) It is essential to focus the sensor beam only on the coal surface and not on the bunker walls or any other attachments fixed to walls.
iv) Angular adjustment of sensor beam to coal level ranging from empty bunker to full bunker condition.
v) The enclosure has provisions for easy removal and re-insertion from / to the mounting hole for repair / periodic maintenance of the level transmitter. Material of the body of the enclosure and all components like nuts, bolts, hinges etc. has been designed of stainless steel suitable for above mentioned environment.

SUMMARY OF THE INVENTION

The basic aspect of the present invention is directed to provide a protective enclosure for protecting electronic gadgets including sensors in arduous and corrosive environments at top of coal silos and the like comprising :

a main protective enclosure stably supporting and housing the electronic gadgets including sensor against any mechanical damage and the like;

said main enclosure including at the top thereof cooperative with an angle adjuster means for desired angular direction for the electronic gadget/ sensor housed in the said main protective enclosure; and

a top cover for said main protective enclosure adapted for top protection of said electronic gadget including sensor against any mechanical damage due to moving machinery including conveyor belt , tripper and the like.

A further aspect of the present invention is directed to said protective enclosure for non-contact RADAR type level measurement sensors suitable for arduous and corrosive environments at top of coal silos and the like comprising :

a main protective enclosure stably supporting and housing the non-contact RADAR type level sensor with downwardly looking position at the silo top ;

said main enclosure at the top thereof cooperative with an angle adjuster means for desired angular direction for the sensor housed in the said main protective enclosure such that the RADAR beam focusses at the center of the storage bunker;

a cooperative antenna protector adapted to protect the downward looking antenna of sensor emitting electronic wave at continuously varying frequency for desired level measurement based on reflected beam wave received by the antenna and cooperative transmitter electronics for determine solo level based on frequency phase shift and travel time of electronics wave;

a cover for top protection with operative cable entry provision.

A still further aspect of the present invention is directed to said protective enclosure wherein said main protective enclosure stably supporting and housing the non-contact RADAR type level sensor comprises of stainless steel protective enclosure and adapted for mounting at the silo top without any projections to avoid any mechanical damage of any moving machinery.

A still further aspect of the present invention is directed to said protective enclosure including provisions for air and/or nitrogen purging comprising mechanism for connecting air and/or nitrogen supply to the enclosure and piping arrangement for cleaning radar antenna with air and/or nitrogen against deposit of coal dust and moisture.

Another aspect of the present invention is directed to said protective enclosure wherein said cooperative angle adjustment means include means for adjustment of mounting angle comprising a mechanical rotation arrangement thereby adjusting the enclosure angle with respect to horizontal base frame fixture.

Yet another aspect of the present invention is directed to said protective enclosure including means for convenient installation and removal for maintenance including cemented fixed base frame below the conveyor belts at the silo top and removable flange and adjustable removable fixture to support / hold the enclosure body.

A further aspect of the present invention is directed to said protective enclosure comprising of level measurement sensors based on 80 GHz W-Band radar, including frequency modulated continuous wave method (FMCW) for level sensing.

A still further aspect of the present invention is directed to said protective enclosure which is adapted to house the level sensor and installed below running conveyor belt.

The above and other objects and advantages of the present invention are described hereunder in greater details with reference to the following accompanying non limiting illustrative drawings.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 : shows Silo Top View.
Fig. 2: shows the Level Sensor.
Fig. 3 : illustrates the Sensor beam angle.
Fig. 4 : shows the variation and significance of sensor beam angle adjustment.
Fig. 5 : shows Line diagram and Photo of enclosure body.
Fig. 6 : shows Line diagram and photo of Complete enclosure of sensor and RADAR antenna.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS

The present invention is directed to provide a protective enclosure based on the requirement of mounting of Level measurement sensors with downward looking position at the silo top. Level sensors are mounted inside the enclosure, which facilitates mechanical protection and ensures its installation at desired angle w.r.t. storage bunker top surface. Level measurement sensors are mounted at the storage bunker top and antenna is directed inside the bunker. Level measurement sensors are Through-Air-Radar (TAR) technology based non contact type sensor. Level measurement sensors are based on 80 GHz W-Band radar, which uses frequency modulated continuous wave method (FMCW) for level sensing. Fig. 2 depicts level measurement sensor. The downward looking antenna of sensor emits beam of electromagnetic wave within a solid angle of 4 degrees at a continuously varying frequency. This wave is reflected by the product and received again by the antenna. The transmitter electronics calculates the silo level based on frequency phase shift and travel time of electronics wave.

Beam angle of Level sensor is defined as angle ‘a’, where energy density of the radar waves reaches half the value of maximum energy density (3 DB width). Microwaves are also emitted outside the signal beam and can be reflected off to interfere with bunker structure. Beam angle is illustrated in Fig. 3. The sensor averages the distance measurement signal from the solid angel area defined by diameter ‘W’ as shown in Fig. 3.
As indicated above, for the type of level sensor used at DSP the value of ‘a’ is 4o. Accordingly the beam width diameter ‘W’ at different height of storage bunker height is indicated in Table 1. It is important that the sensor shall be mounted in such a way that the beam width does not interfere with any silo material.

Distance 'meter' Beam width diameter 'W' 'meter'
2 0.14
4 0.28
6 0.42
8 0.56
10 0.70
12 0.84
14 0.98
16 1.12
17 1.19
18 1.26
20 1.40
22 1.54
24 1.68
26 1.82
28 1.96

As indicated in Fig. 1, the diameter at top of the silo is 10000 mm and total height is 28000 mm. The centre point of level sensor mounting hole is approximately 3300 mm away from the centre point of x-axis of silo and just over the y-axis of silo. Sometimes, coal deposit inside silos tends to form ‘rat holes’ due to deposition of coal over the silo wall. In view of the above, the level sensors are equipped with adjustable signal focusing facility to focus the RADAR beam at suitable spot. Hence, it is extremely important to adjust the angle of level sensor w.r.t. silo top surface, so that RADAR beam focuses over the surface of coal. The invented enclosure is designed to project RADAR beam exactly over coal surface. Special thrust has been given to design the enclosure such that sensor can be mounted to focus the RADAR beam at desire location within the bunker as per site requirement.
The invention is very critical for successful operation of level sensors as it features to adjust the mounting angle. The requirement of angle adjustment feature of mounting enclosure is illustrated in Fig. 4. It is essential that beam angle of sensor and mounting angle of enclosure is adjusted in such a way that beam focuses as indicated in ‘CASE II’ of Fig. 4 i.e. at the centre of storage bunker. In case of ‘CASE I’ and ‘CASE III’, the beam will be focused at the sides and will reflect wrong signal. This will give erroneous level measurement output from sensor. Hence proper focusing of level sensor and its mounting enclosure is very critical.
As indicated above, the Coal Handling Plant (CHP) area is highly prone to accumulation of coal dust, a special type installation with a protective enclosure is essential. Further, the arrangement has to be made so that level sensor can focus entire solid angle up-to the bottom of the silo to cover entire workable silo height as shown in CASE– II of Fig. 4. Hence the sensor enclosure with angle adjustment provision is required to achieve the same. As the level transmitters are installed below running conveyor belt, it also needs protection from damage by moving machineries around. Fig. 5 illustrates the sketch of sensor enclosure. Fig. 6 illustrates the sketch of total invention. In view of above, a special customized enclosure has been designed for the level transmitters having following crucial features:
i) Stainless steel protective enclosure for the radar type level transmitter suitable for arduous environment of coal silos.
ii) Mounting of the enclosure with Level Transmitter at silo top without having any projection over the floor to avoid any mechanical damage by moving machineries around.
iii) Angle adjustment feature to cover entire height of silo.
iv) Provision for air / nitrogen purging.
v) Convenient arrangement for installation and removal for maintenance purpose.

Best mode of working the invention is thus directed to facilitate mechanical mounting arrangement for non-contact type RADAR antenna based solid level measurement sensor. The invention is more suited for installation of sensor in arduous and corrosive environment of coal dust or any other solid material with dielectric constant less than 4.0. The invention is also suited where there is a critical need of angle adjustment in order to properly focus the RADAR antenna. The invention is applicable, where there is requirement of protecting the costly electronics equipment against mechanical damage due to moving machinery like conveyor belt, tripper car etc. The invention is also applicable where there is need of air / nitrogen purging of sensor.

It is thus possible by way of the present invention to provide a protective enclosure for level measurement sensor disposed at silo top, and below the feeding conveyor to ensure following advantageous features:
i) Provision of a special stainless steel protective enclosure for non-contact RADAR type level measurement sensor suitable for arduous and corrosive environment of coal storage bunkers.
ii) Convenient and maintenance free mounting of the enclosure with level measurement sensor at silo top without having any projection over the floor to avoid any mechanical damage by moving machineries around.
iii) Angle adjustment feature to cover entire height of storage bunker.
iv) Provision of air / nitrogen purging facility
v) Convenient arrangement for installation and removal for maintenance purpose.