DESC:
FIELD OF THE INVENTION:
The present subject matter relates to a floating roof tanks, and in particular relates to a fire detection and its extinguishment mechanism in rim seal area of the floating roof tank.

BACKGROUND OF THE INVENTION:

Flammable liquids such as gasoline, oil, and alcohol can be stored in floating roof tanks. Floating roof tanks are usually installed for environmental or economic reasons to limit product loss and reduce the emission of volatile organic compounds. Additionally, floating roof tanks are used to store flammable liquids because fumes of such materials can pose extreme risks of fire and/or explosion. Floating roof tanks therefore may be used to reduce the exposed surface area and reduce the vapor space of the flammable liquids, thereby reducing the risk of fires and/or explosions.

Lightning and/or other electrical discharges at or near the floating roof tanks, however, pose a serious risk of fire and/or explosion if the discharge ignites the fumes of the flammable liquids. This risk is particularly high at or near the rim of the floating roof of floating roof tanks, as an air gap typically exists between the floating-roof and the shell of the floating-roof tank. In fact, rim seal fires are the most common type of fire in floating roof tanks, particularly external floating roof tanks.

To mitigate the risk of rim seal fires, it is common to equip floating roof tanks with shunts around the rim of the floating roof. The shunts are spring loaded wiping contacts that engage the shell, thereby creating an electrical connection between the floating roof and the shell. The shell typically is connected to a grounding system, and therefore the floating roof can be grounded using shunts or other electrical connections between the floating roof and the shell. Thus, the threat of rim seal fires caused by electrical arcing or other electrical discharges between the floating roof and the shell can be reduced if the shunts and shells are maintained in working order.
The shunts, however, tend to wear out over time. Similarly, sludge and/or other materials can accumulate along the wall of the shell, preventing or degrading electrical connections between the shunts and the shell. As such, maintenance of floating roof tanks often includes inspection and/or repair of shunts, if the shunts are visible. Because shunts sometimes are submerged in the flammable liquids held by the floating roof tanks, such an inspection may be difficult if not impossible without first draining the floating roof tanks. Thus, data indicates that proper inspections of shunts and/or other floating roof tank structures may be properly performed at least once every five years. As such, these and other maintenance procedures may be inadequate for detecting degrading shunts and/or other structures, and therefore may fail to reduce the risk of rim seal fires.

US8096708B2 discloses linear heat detector with thermocouple heat confirmation uses two different conductors sheathed in thermal polymers terminated with end of line resistor at tank roof. This includes a monitoring circuit through which a monitoring current passes continuously through detector configured to monitor resistance along first and second conductors.

US20100142584A1 discloses linear heat detector uses two similar conductors sheathed in thermal polymers terminated with end of line resistor a tank roof. Continuous current passes through detector through a monitoring circuit. Heat detection method comprises monitoring resistance along first and second conductor of digital linear heat detector.

US4064944 discloses floating tank rim seal fire detection and extinguishing system which includes an enclosure secured to tank roof. Enclosure carries an agent tank, an expellant tank and an accumulator tank .A heat sensitive pilot conduit is disposed along rim of tank roof and fluidly connects the expellant conduit.

RSFPS by Vimal Fire Control Ltd: SS tube along with detection unit by Securiton is used for fire detection. Pressurized foam vessels are kept on roof of tank. Continuous 24V dc power supply and 80 mili-ampere current is necessary at tank roof to run the system

To name a few, disadvantages as arising out of the above mentioned prior-arts may be as follows:
• Continuous current is required at tank roof
• Load of Pressurized foam vessels
• Pressurized nitrogen gas is essentially needed.
• False alarm of low pressure, low foam level will occur
• Substantial signalling and power-cables are required.
• Foam solution is limited for forty seconds only.
• No signal for a connection failure between solenoid valve (SOV) and foam-actuation valve is available
• Usage of bulky components such as Solenoid valve, pressure switches and foam actuation valve.
• Maintenance of pressurized foam vessels at the tank roof is difficult.
• Mounting of such pressurized foam vessels is prone to damage tank roof in long run.

Accordingly, there lies a need to provide an improved method for fire detection at the rim-seal area in respect of floating-roof tank.

There lies another need to provide a cost-effective and simpler method of generating and discharging foam solution into the floating-roof tank for extinguishing the fire.

Overall, there lies a need to provide an easily operable and cost-effective fire-detection and extinguishment mechanism in the floating-roof tank

Summary of the invention:

This summary is provided to introduce a selection of concepts in a simplified format that are further described in the detailed description of the invention. This summary is not intended to identify key or essential inventive concepts of the claimed subject matter, nor is it intended for determining the scope of the claimed subject matter.

Accordingly, in accordance with the purposes of the invention, the present invention as embodied and broadly described herein provides a method for detecting and extinguishing fire within a floating-roof tank. The method comprises: signalling rise in temperature around the roof of a floating-roof tank by a linear heat sensing element to a processing device, said rise in temperature being above a threshold- level; actuating an electronically operable valve by said processing device to permit flow of water from a hydrant line to a foam-inductor, and delivering foam solution by said foam-inductor, two flexible stainless-steel (ss) pipes and foam spray nozzles positioned around said floating-roof tank.

In other embodiment, the present invention as embodied and broadly described herein provides an apparatus for detecting and extinguishing fire within a floating-roof tank. The apparatus comprises: a linear heat sensing element connected to a floating roof of said tank to detect rise in temperature above a threshold level around said floating-roof; a processing device to receive a detection signal from said sensing element; an electronic valve actuated by said processing device to permit flow of water from a hydrant line to a foam-inductor, wherein said inductor is kept at gauger’s platform; two flexible SS pipes connected to foam inductor outlet and foam spray nozzles positioned around the floating-roof to deliver foam solution into rim seal area of said tank.

At least by virtue of aforesaid, the present invention overcomes the technical short comings of the conventional fire detection and extinguishment mechanisms in floating-roof tanks and provides an improved mechanism which neither requires the usage of heavy pressurized foam vessels maintained atop the floating-roof tank, nor a continuous-current flow is required at the floating roof of the tank. Accordingly, the present invention not only saves the floating roof of the tank from bearing the weight of heavy foam tanks, but also does away with the requirement of a micro processor unit, electric panel and an electric current at tank roof.

More specifically, the present invention at least overcomes the limitation of conventional mechanisms, which completely rely upon heavily loaded nitrogen-pressurized foam tanks and are able to discharge the foam for only 40 seconds into the floating-roof tank. In contrast, the present invention appropriates a hydrant line pressure to generate and discharge foam solution and is able to maintain such discharge for at least 180 seconds.

Description of the drawings:

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Fig. 1 illustrates a method of operation of a fire detection and extinguishment mechanism for a floating-roof tank rim seal fire, in accordance with an embodiment of the present subject matter;

Fig. 2 illustrates a digital linear heat-sensing element in accordance with an embodiment of the present subject matter;

Fig. 3 illustrates a firedetection and extinguishing apparatus in accordance with an embodiment of the present subject matter;

Fig. 4 illustrates a top view of a floating-rook tank, in accordance with an embodiment of the present subject matter;

Fig. 5 illustrates an isolated-barrier, in accordance with an embodiment of the present subject matter;

Fig. 6 illustrates an entire architecture of the fire detection and extinguishing system connected to the floating-roof tank, in accordance with an embodiment of the present subject matter.

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

Description of the invention:

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

According to one embodiment, the present invention provides a new method on Floating roof tank rim seal fire detection and fire extinguishing system.
Now referring to Figure 1, it can be seen that the present invention provides a method of detecting and extinguishing fire within a floating-roof tank, in accordance with an embodiment of the present subject matter. The method comprises signalling (step 102) within 30 millisecond after rise in temperature around rim seal area of floating-roof tank by a linear heat sensing element to a processing device, wherein said rise in temperature is detected within ten second of temperature rise above a threshold- level. Thereafter, said processing device actuates (step 104) an electronically operable valve to permit flow of water from hydrant line to a foam-inductor inlet, and inductor is kept at gauger’s platform of floating-roof tank. The foam solution is discharged (step 106) into rim seal area by said foam-inductor via two flexible SS pipes and foam spray nozzles positioned around said floating-roof.
Fig. 2 illustrates a digital linear heat sensing (LHS) cable 202 as a component of the fire detection and extinguishing apparatus, in accordance with an embodiment of the present subject matter. One end of two cores of tri-metallic (tinned copper over steel) conductors of digital linear heat sensing cable 202 is laid around rim of floating roof tank. The digital linear sensing cable 202, which may be also referred as a sensing element 202, consists of two-core tri-metallic conductors individually insulated with thermal polymer. The polymer melts at pre-determined temperature and the conductors or wires contact each other upon such melting.
The ends of two-core metallic conductors of the cable 202 are placed in open position at the tank-roof and not terminated with any resistor or wire. Accordingly, the digital linear heat sensing cable 202 as laid around the floating-roof tank rim does not require a flow of continuous current. The linear heat sensing cable 202 is connected with a junction box 204 to keep the LHS cable 202 in its position during movement of the floating-roof. The other end of the two core LHS cable 202 is connected to an input of an isolated barrier 206 as shown in Figure. 2. A first output of the isolated barrier 206 is connected with a push button of a limit switch of Motor operated valve (MOV), while a second output from the barrier 206 is connected with audio-visual alarm. The MOV 302 is an electronically operable valve, while the isolated barrier may be signal splitter or a controlling device.
Further, a push button 208 is provided in the form of ‘test-key’ to forcefully short the wires within the LHS 202 and test the operation in the absence of fire-breakage or the accidental rise in temperature. When the push button 208 is activated, the two core linear heat sensing cable 202 outputs digital input signal to the barrier 206 and the barrier 206 in turn sends two output signals. While one signal operates the MOV, and other one leads to alarm signalling at a remotely located control room. MOV can also be closed from control room via 2 core wire.
In an example, the LHS 202 is adapted to operate in temperature range of about minus 40 degree Celsius to 120 degree Celsius and exhibits a negligibly small current flow of about 8 milli Ampere at the time of fire or temperature rise only. Maximum voltage rating of the LHS 202 may be about 30V AC or 42V DC. A capacitance exhibited may be in the range of 88 to 150 pF/m, while inductance as exhibited may be in the range of about 540 to 1050 nH/m. In addition, the LHS 202 may be UL/FM approved LHS cable.
Fig. 3 illustrates a fire detection and extinguishing apparatus 300 broadly comprising the LHS 202, the isolated barrier 206, a motor-operated valve 302, and a hydrant line 304 connected to a foam inductor. In an example, the isolated barrier 206 and a motor operated valve (MOV) 302 may be powered with 24V DC and 440V AC power-supply, respectively. In addition, the MOV 302 is integrated with the digital linear heat sensing cable 202 through the barrier 206. The MOV 302 in maintained in a closed condition between the pressurized hydrant line 304 and the foam inductor (shown in Fig. 4), which in turn is positioned at a gauger’s platform (shown in Fig. 6).
In operation, a foam solution supply is provided for at least 180 seconds at the rate of 18 lpm/m2 of rim seal area through the hydrant line 304 into a rim-seal area of the floating-roof tank. The hydrant line 304 connects inline-foam inductor inlet and foam container is connected with foam inductor. The foam inductor discharges pressurized foam in real-time and thereafter introducing the generated foam solution into said rim-seal area using hydrant line pressure. The hydrant line 304 may be a pipe having a 100 mm diameter and connected with foam-inductor inlet placed at the gauger’s platform. Accordingly, an existing hydrant line pressure is appropriated to generate and discharge foam solution into rim seal area.
Fig.4 illustrates a view 400 of a floating-roof tank when seen from the top, in accordance with an embodiment of the present subject matter. Two flexible SS pipes 402 connect circular SS pipe 404 or galvanized iron pipes 404 at the same elevation as the tank roof with the inline foam inductor’s 406 outlet at the gauger’s platform. A vertical riser is connected with inlet of inline foam inductor 406 at the gauger’s platform to connect with the hydrant line 304. Further, the circular pipes 404 are located around the rim-seal area of the floating roof tank. More specifically, a number of foam spray nozzles 408 are connected with these circular stainless pipes 404 all along the rim-seal of the floating-roof of the tank and protrude radially outwards of said circular-pipe 404.
Fig.5 illustrates the isolated barrier 206, in accordance with an embodiment of the present subject matter. As also stated aforesaid, one end 502 of two core digital linear heat sensing cable 202 is communicated with the input of barrier, and the other end of the LHS 202 is kept free and allowed to short in case of fire or temperature-rise. Further, a barrier output signal 504 from the isolated barrier 206 is integrated with a push-button of the motor operated valve 302, while the other barrier signal output 506 is communicated to an audible alarm. The motor operated valve 302 may be a 6 inch valve and receives a power-supply of 440V AC supply, while the isolated barrier 206 receives the 24V dc power supply.
Further, in operation, when the free end of two-core heat sensing cable 202 contact each other owing to fire detection, the foam solution discharge into the rim seal area of the floating-roof tank starts within a substantial short time, e.g. 18 seconds after fire detection/temp rise at tank roof. This duration may be also further reduced by changing size or torque of the MOV 302. The time-duration as set for the discharge may be verified and tested by activating push button 208. According to an embodiment of the present invention, the overall operation in accordance with the components depicted in Fig 2 till Fig. 4 may be depicted through Fig. 6 as follows:
Step 1: Temperature rise above threshold/fire occurs within rim seal area of the floating-roof tank.
Step 2: A thermal-polymer wound around two core of linear heat sensing cable 202 in rim seal area melts.
Step 3: Two core or wires of linear heat sensing (LHS) cable 202 contact each other
Step 4: The mechanical-contact as taken place at the step 3 serves as digital input signal for the isolated barrier 206, which is mounted away from the tank at a ground level
Step 5: The isolated barrier 206 upon being actuated by the mechanical-contact, due to shorting of 2 core wires in the step 4, outputs two output signals.
Step 6: The first and second output leads to actuation of the audio-visual alarm and the motor operated valve 302, respectively.
Step 7: The foam inductor 406 delivers foam solution with the hydrant line pressure on the tank roof. As seen from the figure, the foam inductor 406 is maintained at the gauger’s platform 602.
Step 8: The foam spray nozzles 408 accordingly discharge a foam solution into the rim seal area of floating roof tank.
While steps 1 to 4 as depicted correspond to the step 102 of Fig. 1, the steps 5 and 6 correspond to the step 104. Finally, the steps 7 and 8 correspond to the step 106 of Fig.1.
The present invention at least overcomes the limitation of conventional mechanisms, which completely rely upon heavily loaded nitrogen-pressurized foam tanks and are able to discharge the foam for only 40 seconds into the floating-roof tank. In contrast, the present invention appropriates a hydrant line pressure to generate and discharge foam solution and is able to maintain such discharge for at least 180 seconds. Such time of discharge is also scalable by increasing the amount of foam-concentrate in foam container near foam inductor.

Further, the present invention also does away with the requirement of continuous current within the LHS cable 202. Overall, the present invention is not only cost-efficient owing to non-employment of heavier components say, nitrogen-pressurized foam vessels, but also technically advantageous than the convention mechanisms at least by providing a substantially small amount of time for initiating the discharge upon detection of fire, but also a scalable time-duration (i.e. minimum 180 seconds) of foam-discharge into the rim seal area.

While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.

The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein.

Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.
,CLAIMS:We claim
1. A method of detecting and extinguishing fire within a floating-roof tank rim seal area, said method comprising:
signalling (step 102) rise in temperature around the roof of a floating roof tank by linear heat sensing element to a processing device, said rise in temperature being above a threshold- level;
actuating (step 104), by said processing device, an electronically operable valve to permit flow of water from a hydrant line to a foam inductor inlet, wherein said inductor is maintainable at a gauger’s platform of floating-roof; and
delivering (step 106) foam using hydrant line pressure by said foam inductor, and a number of foam spray nozzles positioned around said floating roof of the tank.
2. The method as claimed in claim 1, said signalling comprises signalling the rise in temperature occurring at a rim-seal area around said floating roof.
3. The method as claimed in claim 1, wherein signalling comprises generating a digital signal by said linear heat sensing element.
4. The method as claimed in claims 1 and 3, said signalling comprises communicating said digital signal to the processing device, upon mechanical contact of wires within the sensing-element due to said rise in temperature.
5. The method as claimed in claim 1, wherein actuating said electronically operable valve comprises actuating a motor operated valve actuated by the processing device.
6. The method as claimed in claims 1 and 2, wherein said delivering comprises generating pressurized foam in real-time and thereafter introducing the generated foam into said rim-seal area utilizing hydrant line pressure.
7. The method as claimed in claim 6, wherein said delivering comprises maintaining said foam-inductor at said gauger’s platform of said floating roof.
8. The method as claimed in claim 1, wherein said delivering comprises delivering said foam solution from said foam-inductor to circular stainless steel pipes or galvanized iron pipes through flexible stainless-steel pipes .
9. The method as claimed in claim 8, wherein said delivering comprises delivering the foam solution by the circular stainless steel pipe through said nozzles protruding radially outwards from said circular-pipe.
10. The method as claimed in claim 1, wherein said actuating comprises actuating an alarm by said processing device upon occurrence of said rise in temperature.
11. An apparatus (600) for detecting and extinguishing fire within a floating-roof tank rim seal area, said method comprising:
a linear heat sensing element (202) connected to a floating roof of said tank to detect rise in temperature above a threshold level around said floating-roof rim seal area;
a processing device (206) to receive a detection signal from said sensing element (202);
an electronic valve (302) actuated by said processing device (206) to permit flow of water from a hydrant line to foam-inductor (406), wherein said inductor (406) is kept at gauger’s platform of said tank; and
a number of foam-spray nozzles (408) connected with said foam inductor (406) and positioned around the floating roof of the tank to discharge foam solution utilizing a hydrant line pressure.
12. The apparatus (600) as claimed in claim 11, said element (202) detects the rise in temperature occurring in rim seal area around said floating roof.
13. The apparatus (600) as claimed in claim 11, wherein said linear heat sensing element (202) is a two-core metallic wire laid along to the rim of said floating roof tank without being terminated with a resistor and capable of generating a digital signal as a part of said signalling.
14. The apparatus (600) as claimed in claims 11 and 13, said sensing element (202) communicates said digital signal to the processing device (206), upon shorting of wires within the sensing-element (202) due to said rise in temperature.
15. The apparatus (600) as claimed in claim 11, wherein said electronically operable valve (302) is a motor operated value actuated by the processing device (206).
16. The apparatus (600) as claimed in claims 11 and 12, wherein said foam inductor (406) is adapted to generate pressurized foam in real-time and thereafter introduce the generated foam solution into said rim-seal area utilizing hydrant line pressure.
17. The apparatus (600) as claimed in claim 16, wherein said foam-inductor (406) is placed at a gauger’s platform (602) and mounted externally to said floating roof.
18. The apparatus (600) as claimed in claim 11, wherein said foam inductor (406) is connected to circular stainless steel pipes (404) or galvanized iron pipes (404) through flexible stainless steel pipes to insert foam solution into the rim-seal area of the tank.
19. The apparatus (600) as claimed in claim 18, wherein the circular stainless steel pipe (404) connected with said multiple foam spray nozzles (408) protruding radially outwards to discharge pressurized foam solution into the rim-seal area.
20. The apparatus (600) as claimed in claim 11, wherein said processing device (206) is a signal splitter or an isolated barrier and adapted to actuate an alarm upon occurrence of said rise in temperature.