Claims:We claim:

1. A dust-collection chamber equipped with an automatic fire-extinguishing system connected to a shot-blasting chamber via a spark arrester / cyclone separator by means of a pipeline to carry shot-blasting dust produced therein, wherein the dust-collection chamber comprise an elongated dust-collection chamber of substantially uniform cross-section including:

(a) an upper sub-chamber fitted with an air-blower;
(b) a lower sub-chamber; and
(c) an intermediate dust filtering chamber disposed between the upper and lower sub-chambers;

wherein the dust filtered and separated by the filter bags by means of a forced air suction by the air-blower disposed in the upper chamber and the filtered and separated dust falls down on the lower chamber equipped with an automatic fire-extinguishing system configured as a plastic piping covering the entire area thereof and the plastic piping being connected to a pressurized water supply line.

2. Shot-blasting dust-collection chamber as claimed in claim 1, wherein the dust-collection chamber is configured in substantially rectangular cross-section and the upper, lower and intermediate chambers are disposed vertically one over the other.

3. Shot-blasting dust-collection chamber as claimed in claim 1, wherein the top of the intermediate chamber is configured by a partition wall provided with at least four apertures for fixing a respective filter bag suspended therefrom in the intermediate chamber.

4. Shot-blasting dust-collection chamber as claimed in claim 1, wherein the top cover of the upper chamber is configured as a hinged cover to facilitate opening thereof for removing and/or replacing and/or cleaning the filter bags suspended in the intermediate chamber.

5. Shot-blasting dust-collection chamber as claimed in claim 1, wherein the air-blower is laterally fitted in one of the vertical sides of the upper chamber.

6. Shot-blasting dust-collection chamber as claimed in claim 1, wherein the plastic piping is connected at one end to a pressurized water supply line and closed at the other end thereof keep the pipe pressurized.

7. Shot-blasting dust-collection chamber as claimed in claim 1, wherein the plastic piping comprises the melting pipe of the plastic pipes is lower than the fire starting point in the dust-collection chamber, preferably in a range of 60 to 650C.

8. A dust-collection chamber equipped with an automatic fire-extinguishing system connected to a shot-blasting chamber via a spark arrester / cyclone separator by means of a pipeline to carry shot-blasting dust produced therein, wherein the dust-collection chamber comprise an elongated dust-collection chamber of substantially uniform cross-section disposed vertically and including:

(i) an upper sub-chamber laterally fitted with an air-blower creating a forced air-suction therein;
(ii) an intermediate dust filtering chamber disposed between the upper and lower sub-chambers having a partition wall at the top provided with a plurality of apertures for suspending a respective filter bag;
(iii) a lower sub-chamber supplied with the shot-blasting dust adjacent the bottom surface thereof;

wherein the lower chamber is connected to the shot-blasting chamber by means a pipeline via a spark arrestor / cyclone separator for filtering and separating dust particles by passage through the plurality of filter bags suspended in the intermediate chamber by means of a forced air-suction by the air-blower laterally disposed in the upper chamber of the dust collection chamber.

9. Dust-collection chamber as claimed in claim 8, wherein the plastic piping is connected at one end to a pressurized water supply line and closed at the other end thereof to keep the pipe under pressure and the melting point of the plastic piping is selected lower than the fire starting point in the dust-collection chamber so that before reaching the fire starting point of the dust collected at the bottom of the lower chamber at any point of the plastic piping, the plastic piping gets punctured in that region to spray pressurized water for prevent start of any fire in the dust collection chamber, thereby acting as an automatic fire extinguisher.

10. Method for automatic fire extinguishing in a dust collection chamber of a shot-blasting chamber, the method comprises the following steps:

- conveying gaseous shot-blast containing gas and dust mixture produced in the shot blasting chamber via a pipeline to the spark arrestor / cyclone separator;

- conveying further cleaned gas/dust mixture to the lower chamber of the dust-collection chamber for further dust separation;

- sucking air from the air-blower disposed laterally in the upper chamber of the dust-collection chamber for forced evacuation of air;

- filtering and separating dust particles by means of filter bags suspended in the intermediate chamber of the dust-collection chamber, which are collected at the bottom of the lower chamber of the dust-collection chamber;

wherein the automatic fire-extinguishing system consisting of a plastic piping carrying pressurized water gets punctured over the region on reaching close to the fire starting point of the dust particles that region in the lower chamber of the dust-collection chamber for spraying pressurized water for preventing commencement of a fire in the filtered and separated dust particles in the dust-collection chamber.

Dated this 30th day of December, 2015. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT , Description:FIELD OF INVENTION

The present invention relates to preventing fires in shot-blasting dust collector. In particular, the invention relates to an arrangement for extinguishing fires caused in shot-blasting dust collector. More particularly, the invention relates to a simple and effective system to extinguish fires caused in shot-blasting dust collector timely and from spreading in the entire shot-blasting system.

BACKGROUND OF THE INVENTION

Shot blasting is a process used for cleaning, strengthening or peening or polishing metal-components. Shot blasting is extensively used in almost every industry using metal and metal components, such as automotive, aerospace, construction, foundry, shipbuilding, rail and such other processes etc. This includes cleaning and descaling metal by shot peening or using a stream of abrasive powder blown through a nozzle under air pressure in a range 30 to 150 pounds/inch2 (200-1000 kPa). For example, the metallic components are cleaned by blasting steel shots, e.g. at about 2800 RPM against components. During this process, the shots also get broken into fine dust particles, which get mixed with carbon, thereby forming a homogeneous combustible mixture, which is used as a raw material for making explosives. This combustible mixture dust is removed by suction blower using the dust filters fitted in-line. Accordingly, this dust is collected at the bottom of the dust collector.

DISADVANTAGES WITH THE PRIOR ART

The major disadvantages with the existing arrangement of shot blasting dust collectors are as under:

• Dust particles carry carbon, which is highly inflammable, particularly because shots containing Phosphorous hit the components to be shot-blasted, thereby causing an oxidation inside the shot blasting chamber.

• Combination of fine metallic dust powder and sparks are generated inside the shot blasting chamber - because of thousands of steel shots impacting the components to be shot-blasted.

• Some Spark manages to travel through the ducting and gets settled at the bottom of the Dust collector along with other dust. This dust than glows and smoldering takes place like an intense stick. Thus, nearby dust also starts smoldering and area gets heated up. This smoldering and heating may take place at any portion of the bottom Dust collector to start with.

• Now in due course of time, because of suction blower, carbon combustible dust and heat, fire is started. This fire immediately spreads within the entire dust collector.

• By the time the fire starts, all the bags are already burned down and often the damages motor and wirings on the periphery of the chamber. Meanwhile, the self-burning dust has already spread throughout the inner periphery of the ducting and it is impossible to extinguish the dust burning within the ducting.

• The only possibility is to allow the powder to burn off by itself and then to clean dust collector. But this takes about 2 days to restore machine.

The various fire categories have been considered as the cause of the phenomena:

- Spark / heated particles entering the dust collector.

- Static charge due to shot flow and oxidation of dust accumulated inside the shot blasting chamber.

- External conditions such as:
(i) External fire,
(ii) Bottom hopper of dust collector not cleaned properly, and
(iii) Dust collecting trolley.

However, for avoiding the dust catching fire in the dust collectors used in the shot blasting process, different manufacturers opt for various measures.

These solutions are discussed below in short:
(i) External fire is addressed by:
• Equipping the dust collector with Spark arrestor,
• Equipping the dust collector with Cyclone separators,
• Deploying CO2 extinguisher (although it “extinguishes” and does not prevent such fire),
• Using fire-retardant bags,
• Flooding the dust chamber with Nitrogen,
• Equipping the dust collector with water sprinkler system, and
• Cooling of dust particles by equipping the ducts with water tank and heat exchanger.

(ii) Bottom hopper of dust collector not cleaned properly can be corrected by:
• By providing .the dust collector with an earthing.

(iii) Dust collecting trolley: Regular cleaning of dust collection trolley.

Ideally, the spark or ignition should be avoided in the shot blasting process, but the process inherently involves spark generation. So, the best possible solution would be to quench the start of dust from getting heated well before it starts burning and spreads fire to other areas in the dust collector.

A possible solution could be fitting temperature sensors and/or activating water sprinklers. But a fire can start from any corner or face or side of the dust collector, so this solution of equipping temperature sensors to the entire periphery of the dust collector is not economically viable.

Similarly, Auto Fire Extinguisher, such as CO2, i.e. using CO2 flooding also has two distinct disadvantages:

• it activates only after fire occurs, and
• it requires expensive system, such as CO2 Gas Cylinders, Flame sensors.

In some existing dust collector arrangements, the rotary valve is replaced by a sliding valve. This helps when dust particles become very hot due to continuous operation and if there is no door opening at the end of the cycle and when the chamber volume is small. In this case of replacing the rotary valve with a sliding valve, an intermittent opening the sliding valve is possible for purging air from the top. For example, the sliding valve is opened for just two seconds every five minutes. This helps in allowing the accumulated dust and granular particles to fall down on the dust chamber floor. Further, hot air exits from below the dust collector chamber due to air-purging from the top and thereby cools the dust collector chamber.

Further, Spark quencher / Cyclone Separator are used to quench the sparks generated in the shot blasting chamber, which ignite fires. This spark quencher quenches the sparks and cools the dust particles. The cyclone separator creates turbulence to extinguish any spark generated inside the dust collector chamber.

Another improvement was replacing the filter type dust collectors by bag type dust collector, which are 25% less expensive than the filter type ones. The removal of bags is also easier making their replacement convenient and fast.

Some existing arrangement also used Nitrogen flooding along with quick opening covers. Although, this reduced the fire occurrence substantially, it could not completely eliminate it.

It was also attempted to install temperature sensors within the dust collector chamber for issuing an alarm to operator, if the temperature rise within the dust collector chamber. Even a controller can be fitted for raising the alarm and to start a water sprinkler system to douse the fire in the dust collector. However, it is impossible to fit temperature sensors all across the periphery of the dust collector. So, the regions devoid of any temperature sensor will become hot and the filter bags disposed in that region will ignite immediately, even before a corrective action is done based on an alarm issued by the sensor fitted in another region.

Finally, boiler has Fusible plugs, but these plugs are made of special material; which blow off at more than 1000 Celsius.
Despite all above improvements in the existing dust collector chambers in shot-blasting arrangements available until now, the fires are frequently occurring, which lead to substantial losses of machinery and production stoppages. This necessitates high costs for replacing damaged equipment.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a reliable device for timely arresting the fire caused in the dust collector of the shot blasting arrangement.

Another object of the present invention is to provide a cost-effective device.

Still another object of the present invention is to provide an arrangement of shot blasting dust collector, whereby the dust filter bags are easily replaced.

These and other objects and advantages of the present invention will become more apparent from the following description when read with the accompanying figures of drawing, which are, however, not intended to limit the scope of the present invention in any way.

DESCRIPTION OF THE PRESENT INVENTION

Accordingly, a simple and effective arrangement of extinguishing fire due to dust accumulated in the shot blasting chamber by providing at least one plastic pipe throughout the dust collection area. The plastic pipe is closed at one end and connected to the pressurized water supply line at other end. For this purpose, only plastic pipes having a melting point lower than the fire starting point in the dust chamber are used. As soon as the combination of shot-lasted metallic dust particles and carbon collected inside the dust collector becomes hotter than the firing point of the plastic pipe in any specific region thereof, the portion of the plastic pipe disposed in that region melts immediately. As a result of this, the water present under pressure inside the plastic pipe is sprayed on the hot dust particles, which were otherwise prone to getting burned and generating fire. This cools pipe to avoid any fire being started in that that hot dust containing region. Moreover, due to water spillage visible below the dust collector, the operator immediately becomes aware of hazardous hot conditions prevailing inside the dust collector and can immediately stop the dust collector air-blower. This prompt action also helps further in avoiding catching of fire, which would have otherwise spread due to the air being blown by the air-blower. Advantage of this plastic pipe auto fire-extinguisher arrangement is that the plastic pipe melts just before reaching the firing temperature of hot dust powder. So, only those plastic pipe can be selected, which gets punctured or melted even with a temperature prevailing in the range of 60-650 Celsius. Since, the plastic pipe is connected to a pressurized water supply; water immediately comes out from punctured or melted plastic pipe at the relevant hot regions of the dust collector and immediately cools the smoldering dust and exactly in the effected hazardous hot area of the dust collector.

SUMMARY OF THE INVENTION

A dust-collection chamber equipped with an automatic fire-extinguishing system connected to a shot-blasting chamber via a spark arrester / cyclone separator by means of a pipeline to carry shot-blasting dust produced therein, wherein the dust-collection chamber comprise an elongated dust-collection chamber of substantially uniform cross-section including:

(a) an upper sub-chamber fitted with an air-blower;

(b) a lower sub-chamber; and

(c) an intermediate dust filtering chamber disposed between the upper and lower sub-chambers;

wherein the dust filtered and separated by the filter bags by means of a forced air suction by the air-blower disposed in the upper chamber and the filtered and separated dust falls down on the lower chamber equipped with an automatic fire-extinguishing system configured as a plastic piping covering the entire area thereof and the plastic piping being connected to a pressurized water supply line.
Typically, the dust-collection chamber is configured in substantially rectangular cross-section and the upper, lower and intermediate chambers are disposed vertically one over the other.

Typically, the top of the intermediate chamber is configured by a partition wall provided with at least four apertures for fixing a respective filter bag suspended therefrom in the intermediate chamber.

Typically, the top cover of the upper chamber is configured as a hinged cover to facilitate opening thereof for removing and/or replacing and/or cleaning the filter bags suspended in the intermediate chamber.

Typically, the air-blower is laterally fitted in one of the vertical sides of the upper chamber.

Typically, the plastic piping is connected at one end to a pressurized water supply line and closed at the other end thereof keep the pipe pressurized.

Typically, the plastic piping comprises the melting pipe of the plastic pipes is lower than the fire starting point in the dust-collection chamber, preferably in a range of 60 to 650C.

The present invention also includes a dust-collection chamber equipped with an automatic fire-extinguishing system connected to a shot-blasting chamber via a spark arrester / cyclone separator by means of a pipeline to carry shot-blasting dust produced therein, wherein the dust-collection chamber comprise an elongated dust-collection chamber of substantially uniform cross-section disposed vertically and including:

(i) an upper sub-chamber laterally fitted with an air-blower creating a forced air-suction therein;

(ii) an intermediate dust filtering chamber disposed between the upper and lower sub-chambers having a partition wall at the top provided with a plurality of apertures for suspending a respective filter bag;

(iii) a lower sub-chamber supplied with the shot-blasting dust adjacent the bottom surface thereof;
wherein the lower chamber is connected to the shot-blasting chamber by means a pipeline via a spark arrestor / cyclone separator for filtering and separating dust particles by passage through the plurality of filter bags suspended in the intermediate chamber by means of a forced air-suction by the air-blower laterally disposed in the upper chamber of the dust collection chamber.

Typically, the plastic piping is connected at one end to a pressurized water supply line and closed at the other end thereof to keep the pipe under pressure and the melting point of the plastic piping is selected lower than the fire starting point in the dust-collection chamber so that before reaching the fire starting point of the dust collected at the bottom of the lower chamber at any point of the plastic piping, the plastic piping gets punctured in that region to spray pressurized water for prevent start of any fire in the dust collection chamber, thereby acting as an automatic fire extinguisher.

In accordance with the present invention, there is also provided a method for automatic fire extinguishing in a dust collection chamber of a shot-blasting chamber, the method comprises the following steps:

- conveying gaseous shot-blast containing gas and dust mixture produced in the shot blasting chamber via a pipeline to the spark arrestor / cyclone separator;

- conveying further cleaned gas/dust mixture to the lower chamber of the dust-collection chamber for further dust separation;

- sucking air from the air-blower disposed laterally in the upper chamber of the dust-collection chamber for forced evacuation of air;

- filtering and separating dust particles by means of filter bags suspended in the intermediate chamber of the dust-collection chamber, which are collected at the bottom of the lower chamber of the dust-collection chamber;

wherein the automatic fire-extinguishing system consisting of a plastic piping carrying pressurized water gets punctured over the region on reaching close to the fire starting point of the dust particles that region in the lower chamber of the dust-collection chamber for spraying pressurized water for preventing commencement of a fire in the filtered and separated dust particles in the dust-collection chamber.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, which include:

Figure 1 shows a perspective schematic view of the arrangement of a conventional shot-blasting arrangement.

Figure 2 shows a perspective view of the dust collector in the shot-blasting arrangement depicted in Figure 1.

Figure 3 shows a perspective view of the improved dust collector in the hot-blasting arrangement in accordance with the present invention.

Figure 4a shows a detailed perspective view of a further improved dust collector as depicted in Figure 3 also equipped with plastic pipe above the region of the collected dust particles.

Figure 4b shows a detailed perspective view of the dust collector depicted in Figure 4a after dust particles become hot during shot-blasting process due to smoldering taking place.

Figure 4c shows a detailed perspective view of the dust collector depicted in Figure 4a after puncturing and/or melting of the plastic pipe depicted in Figure 4a due to the high temperature of the dust particles.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, different embodiments of the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1 shows a perspective schematic view of the arrangement of a conventional shot-blasting arrangement. The shot-blasting arrangement includes a shot-blasting chamber 10 connected to an inlet 14 of the spark arrestor/cyclone separator 20 via a pipeline 12. The arrows 16 indicate the flow path of the metallic dust particles, potentially containing carbon particles as well. The outlet 18 of the spark/cyclone separator arrestor 20 is connected via another pipeline 22 to the dust collection chamber 30 at an inlet 34 disposed adjacent the bottom of the dust collector 30 for receiving dust for further filtering. The duct collector 30 includes a hollow chamber, preferably divided in two sub-chambers, i.e. a bottom sub-chamber 32 for receiving dust coming from the shot-blasting chamber 10 after passage through the spark arrestor/cyclone separator 20 and a top sub-chamber 38 equipped with an air-blower 50 for sucking out the clean air filtered by means of a plurality of dust filters 40 provided in the partition wall 36 between the top sub-chamber 38 and bottom sub-chamber 32 of the dust collector 30. A cover 42 is also provided on one side wall of the dust collector 30 for removing and cleaning the dust filtering bags 40. The separated dust particles 60 fall down from the bottom of the dust collector 30 and the clean filtered air 54 is sucked out by the blower 50 to outside of the duct collector 30.

Figure 2 shows a perspective view of the dust collector in the shot-blasting arrangement as depicted in Figure 1. As already described in connection with Figure 1 above, the dust collector 30 includes a partition wall 36 dividing the dust collector 30 into a top sub-chamber 38 and a bottom sub-chamber 32. The partition wall 36 is provided with a plurality of openings (e.g. 4 here) for fitting a respective removable filter bag 40 for filtering the dust contained in the shot-blast received from the shot-blasting chamber 10 (Fig. 1) after passing through the spark arrestor/cyclone separator 20 (Fig. 1). In this conventional arrangement of the dust collector 30, the air-blower 50 is fitted at the top of the dust collector 30 and the cover 42 for removing and cleaning the filter bags 40 is provided on a vertical/side face of the dust collector 30.

Figure 3 shows a perspective view of the improved dust collection chamber 100 in the hot-blasting arrangement in accordance with the present invention. The dust collector in accordance with the present invention includes a partition wall 136 provided with a plurality of openings for fitting a respective removable filter bag 140. However, in this novel arrangement of the dust collector, the top of the dust collector is made as a hinged cover 152 (closed position 152-I) , which can be opened (opened position 152-II) for easy removal of the filter bags 140 from the top for cleaning thereof. Here, the weight of each filter bag is normally of the order of about 7.5 kg. In contrast to dust collector shown in Figures 1 and 2, the air-blower 150 is now fitted on one of the side faces of the dust collector 130, which reduces the height for accessing the air-blower 150 by the operator for maintenance and repair activities. In addition, this reduces the chances of fire, since even if blower spark occurs, the same cannot enter the dust chamber 130 due to sidewise positioning of the air-blower 150.

Figure 4a shows a detailed perspective view of the improved dust collection chamber 130 as depicted in Figure 3. In which, the additional arrangement includes equipping the lower-most dust collector chamber 162 with a plastic pipe line 164 above the region of the collected dust particles. This pipe line 164 is supplied with pressurized water from a source 170at one end thereof and the other end thereof is closed.

Figure 4b shows a detailed perspective view of the dust collection chamber depicted in Figure 4a after dust particles become hot and a particular region 180 within the dust chamber becomes excessively hot prone to cause a fire, however, the temperature are still below the melting point of the plastic pipe line 164, which is filled with pressurized water supplied from water source 170.

Figure 4c shows a detailed perspective view of the dust collection chamber depicted in Figure 4a after puncturing and/or melting of the plastic pipe line 164 depicted in Figure 4a in the region 180. Here, due to a high temperature higher than the melting point of the plastic pipe line 164 of the dust particles due to fire caused in this region 180, a puncturing or melting of pipe line 164 occurs at point 190, which releases pressurized water in the overheated region and thereby extinguishes the fire immediately.

Although, the dust collector shown here is in a cuboidal shape, however it may be of any shape.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The device and method configured in accordance with the present invention has the following advantages:

• Fire can be extinguished immediately on occurrence thereof.

• Offers a very cost-effective device.

• Dust filter bags can be easily replaced from sides.

• Spark arrestor/cyclone separator can be easily and regularly cleaned.

• Air-blower can be easily maintained and repaired.

• Dust and granular particles can be intermittently purged by the air from the top of dust collection chamber.

• Machine is recovered within 3-4 hours instead of 2 days earlier.

Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention.
The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention.

Although, only the preferred embodiments have been described herein, the skilled person in the art would readily recognize to apply these embodiments with any modification possible within the spirit and scope of the present invention as described in this specification.

Therefore, innumerable changes, variations, modifications, alterations may be made and/or integrations in terms of materials and method used may be devised to configure, manufacture and assemble various constituents, components, subassemblies and assemblies according to their size, shapes, orientations and interrelationships.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.