This disclosure generally relates to a flameless venting system for a protected volume within a vessel, building structure, piping or duct system, or other enclosed processes.
A fire or explosion can result from ignition of a combustible material, such as dust, gas, or vapor, when mixed with oxygen present in the environment. When such ignition takes place within a protected volume contained by a vessel, such as a process or storage enclosure, the rapid rise in pressure developed may exert destructive forces within a few milliseconds, which may place both personnel and equipment at risk.
A number of industries may face the danger of ignition in an enclosed system or building structure, including plastics, food and dairy, pigments and dyes, wood processing, grain processing, coal processing, pharmaceuticals, grain ethanol, chemicals, metals, and agrochemicals. Within and/or beyond those industries, particular applications may pose the danger of such ignition. For example, cyclones, bag houses, cartridge filters, pneumatic conveying systems, milling processes (including pin milling, ball milling, etc.), bucket elevators, dust collectors, bins, dryers, ovens, roller mills, grinding applications, and buildings may all pose the danger of ignition causing fire or explosion.
The destructive forces associated with a fire or explosion may take the form of a detonation (i.e., an expanding flame ball that proceeds at a speed in excess of the speed of sound in air) or a deflagration (i.e., an expanding flame ball that proceeds below the speed of sound in air).
Most materials handling, processing, and storage equipment is not designed to resist the pressure of an explosion. To survive a deflagration, for example, processing and storage equipment typically must be designed to resist the maximum pressure (Pmax) developed by the combustion process. Such design may be prohibitively expensive, however, because Pmax may exceed 75 psig (5.2 bar) in typical cases. Therefore, to address combustion, a process or storage enclosure may be provided with a system to allow pressure and/or a flame from an explosion to escape the enclosure.
An explosion venting system provides an explosion vent as part of the process, building, piping, ducting or storage enclosure. The explosion vent may include an explosion panel, burst panel, rupture disk, or other pressure-release mechanism.
Combustion within the enclosure may create an increased pressure (i.e., overpressure), which in turn can lead to opening of the explosion vent. When an explosion vent opens, a flame ball may be released from the enclosure. The flame ball may be released directly to the atmosphere. Alternatively, if the explosion vent is deployed within a building or structure, a duct may be used to direct the flame ball away from the enclosure, e.g., to the exterior of the building or structure. An explosion venting system may do little to mitigate a flame of a flame ball, and may still result in a pressure wave resulting from combustion, or particulates resulting from the combustion.
A flame arrestor system may be provided as part of the process or storage enclosure. A flame arrestor may comprise a filter component such as a coiled-ribbon-type mesh, woven metallic mesh, or ceramic matrix, which is designed to provide a series of small flow paths through the flame arrestor's structure. When the flame passes through the small flow paths of the filter, it tends to be suppressed or extinguished as the heat is absorbed by the filter material and the combustion process is momentarily starved of oxygen. A flame arrestor is typically deployed in a combustible gas or vapor application, although the extinguishing of flame also may be effective with combustible dusts, mists, and vapors. A flame arrestor may provide effective mitigation of a flame, thereby acting as a barrier to the flame's progress.
A flameless venting system provides a combination of an explosion vent and a quenching module (which may be a flame arrestor or include a flame arrestor), and is designed to absorb a flame ball arising from the combustion of a dust, gas, vapor, mist, or combination thereof. Depending on the design of the flameless venting device, it may mitigate the flame ball, reduce a pressure pulse emitted by the combustion, and absorb some or all of the particulates arising from, e.g., a combustible dust explosion. Thus, a flameless venting system may be particularly desired in circumstances in which an ejected flame ball or ejected particulates are unacceptable. For example, flameless venting systems may be particularly suited to installation in confined indoor spaces where personnel may be in the vicinity, or where secondary risks of combustion are present.
A flameless venting system may be a round system (as might be used with a circular vent) or a rectangular system (as might be used with a rectangular vent). In general, round devices are conducive to a large ratio between vent area and flame-arresting area (typically greater than 5:1), which makes round devices superior for dust absorption. Round devices include, e.g., the IQR™ device of BS&B Safety Systems. Also in general, rectangular devices have a smaller ratio between vent area and flame arresting area (typically greater than 2:1), which typically makes their dust-absorption more limited. Rectangular devices include, e.g., the R-IQR™ device of BS&B Safety Systems.
In some applications, a flameless venting system may be mounted on a curved surface, such as the cylindrical surface of a storage silo or the cylindrical surface of a round-body dust collector. Known flameless venting systems require using an adapter to transition from such curved surfaces to the flat-flanged mounting arrangement of a known flameless venting system. In other words, known flameless venting systems cannot mount directly to a curved surface. Using an adapter to mount a flameless venting system is often inconvenient or undesirable. The adapter may add cost, weight, and/or size to the flameless venting system. Additionally, the adapter may add a ledge, a corner, or some other geometrical complexities that may attract contamination and/or may otherwise be difficult to clean. In “clean product” industries, such as the food industry and pharmaceutical industry, it is desirable to avoid or eliminate any such opportunities for contamination.
In a known system using a flameless venting system, an explosion vent is first installed on a vessel containing a protected volume. A flame arrestor component is then positioned and installed over the explosion vent, perhaps as part of a quenching module. Such known systems present significant drawbacks in installation. For example, an explosion vent is typically made of a relatively light-gauge material (e.g., from 0.020-inch to 0.080-inch or 0.5-mm to 2.0-mm thick), and is carefully calibrated to open in response to a particular pressure differential. A flame arrestor component and/or quenching module is much heavier by comparison. For example, a quenching module/flame arrestor component of a flameless venting device is typically a fabricated structure made of sheet metal and angled metal of typical thickness between 0.080-inch to 0.250-inch, or 2.0-mm to 6.5-mm, which results in a mass perhaps an order of magnitude (or more) greater than the mass of the explosion vent. As one example, the combined weight of a flameless venting system (i.e., an explosion vent and flame arrestor) may exceed 200 pounds or 90 kg, whereas the weight of an explosion vent alone may be around 20 pounds or 9 kg. During installation of a known flameless venting system, the relatively lightweight vent must be held in place gently while the heavy arrestor mechanism and/or quenching module are mounted above the vent and the whole arrangement is bolted to a vessel containing a protected volume. Often, such flameless venting systems are installed on substantially vertical surfaces (e.g., the side wall of a silo), and/or on a surface that is difficult to access. As such, the installation process is difficult and presents the risk that the heavy arrestor mechanism may damage the relatively delicate (and often carefully calibrated) explosion vent.
A known flameless venting system also presents difficulties in inspection and maintenance. Applicable codes and standards require components (e.g., explosion vents and flame-arrestor filters) to be inspected periodically. In a known system, such inspection typically requires removal of the flame arrestor (a process that may necessitate full replacement of the explosion vent) or requires an inspector to enter the protected volume to inspect the explosion vent from the process side. Inspection from the process side may be difficult, particularly if the vent is positioned in a difficult-to-access part of the process. Also, inspection from the process side may be undesirable, to the extent that inspection creates the risk of an inspector contaminating or damaging the protected volume. Also in known flameless venting systems, the flame-arrestor filter may only be inspected externally, because the interior of the flame arrestor is inaccessible. Further, in a known flameless venting system, the explosion vent may only be replaced via removal of the flame arrestor—i.e., it is not possible to replace the explosion vent while the heavy flame arrestor or quenching module remains mounted in position on the protected enclosure.
In view of the foregoing, it may be desirable to provide a flameless venting system that may mount directly onto a curved surface without an adapter. It also may be desirable to provide a flameless venting system in which a flame arrestor may be mounted on a vessel more easily, and/or such a system in which an explosion vent or other flameless venting system components may be installed, inspected, and maintained more easily (e.g., without removing the flame arrestor).
The disclosure herein provides a device, system and associated methods that may achieve one or more advantages over the known devices, systems and methods in the art, including such art described above.
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments and together with the description, serve to explain principles of the disclosure.
Reference will now be made in detail to the present exemplary embodiments, examples of which are illustrated in the accompanying figures.
In use, an explosion vent within the flameless venting system 100 may be positioned over an opening in the vessel containing a protected volume, and the explosion vent and/or flameless venting system 100 may be secured to the vessel via mounting flange 111. A gasket (not shown) may be provided between the flange 111 and a mated flange of the vessel (not shown). The explosion vent may be configured to burst in the event of an explosion within the protected volume, which will allow a pressure wave, propagating flame, gases, and/or debris (as applicable) to escape into the interior of the flameless venting system 100 to be absorbed or retained by the filter 120 to prevent or reduce one or more of the pressure wave, propagating flame, gases, and/or debris from escaping the system into the environment.
Because the mounting flange 111 is curved, the embodiment of
Although the embodiments in
The rear hatch 330 may allow inspection of the vent without removal of the full flameless venting system 300 and quenching module body 310 from service. For example, a rear hatch 330 opening may allow periodic inspections in compliance with NFPA 68 or other applicable codes or requirements. During operation, the hatch 330 may be closed using a door, as illustrated. Other hatch closures are contemplated, including heat shields, mesh, or other suitable barrier to limit egress of heat, flame, dust, or other materials through the hatch. Covering the hatch in such a manner may provide safety for the system and operators. Additionally, covering the hatch may force escaping heat, flame, dust, or other materials toward the filter 320 of the quenching module, so that the filter may absorb or retain the heat, flame, dust, or other materials as needed.
As illustrated in
Additional detail of the relationship between the body flange 311 and explosion panel flange 352 is provided in
The disclosed flameless venting system may be provided to fit a vessel outlet of any suitable size. By way of non-limiting example, the disclosed system may be configured to fit an outlet of 920 mm×586 mm, 610 mm×610 mm, 490 mm×590 mm, 350 mm×650 mm, 305 mm×610 mm, 300 mm×500 mm, 270 mm×458 mm, or 170 mm×470 mm. In addition, an embodiment of the disclosed system may be deployed with a non-rectangular (e.g., circular or round) interface, which may be suitable for use with a circular or round explosion vent, or an irregular shape to suit specific application constraints.
The disclosed flameless venting system may be used with any suitable explosion vent. As one example, a quenching module may be deployed with a Vent-Saf Plus™ (“VSP”) vent of the type sold by BS&B Safety Systems, including VSP-L and VSP-D type vents. More specifically, a flameless venting system according to the present disclosure has been tested using a 0.75 psi (5171 Pa) vacuum-resistant VSP-L vent. Another system according to the present disclosure has been tested using a 2.9 psi (19,995 Pa) vacuum-resistant VSP-D vent. The typical nominal set pressure of exemplary explosion vents tested with one embodiment of a flameless venting system is 0.1 bar, but additional set pressures are contemplated. For example, set pressures may be below or above 0.1 bar.
Although an explosion vent is described above, the disclosure is not limited to such configurations. For example, a flameless venting system 300 may be used in conjunction with a burst panel, rupture disk, or other mechanism configured to release pressure, gas, debris, or flame from a protected volume in the event of an explosion.
Whereas
A curved outlet (such as depicted in
Although
Returning to flameless venting system 300,
In the event of an explosion in the system 300, an explosion vent (not shown in
A flameless venting system 300 may be suitable for use in applications such as bucket elevators, dust collectors, bins, or other applications in which a protected volume poses a risk of ignition. A flameless venting system 300 also may be suited for use with cyclones, bag houses, cartridge filters, pneumatic conveying systems, milling processes (including pin milling, ball milling, etc.), dryers, ovens, roller mills, grinding applications, and buildings.
In operation, a flameless venting system may reach high temperatures and may exhaust high-temperature gas or other materials through the filter. Thus, it may be necessary or desirable to create a “safety zone” within a certain distance from the quenching module. Personnel, flammable materials, and/or temperature-sensitive equipment may be restricted outside of the safety zone during operation, to avoid the risk of injury, damage, or fire during operations that may lead to an explosion being quenched in the quenching module. The size of any required safety zone may be decreased by using protection shields or other mechanisms (not shown) placed between the outlet of system 300 and personnel or sensitive materials or equipment. In one embodiment, the operation of a quenching module may be improved by maintaining a distance between the quenching module and any walls or nearby equipment, so that venting through the filter is not obstructed.
The present disclosure provides an advantageous method of installing a flameless venting system, such as the system embodiments described above. In one embodiment, a quenching module body (e.g., 310 in
A sealing gasket may be provided between mated flanges to provide seal(s) between one or more of the explosion vent, vessel, and quenching module body. A gasket may be a separate component, or may be provided integrally with the vent, vessel, and/or quenching module body. A suitable gasket may be made, e.g., from EPDM, silicone, or other suitable materials.
After the quenching module body 310 is fixed to the vessel, an explosion panel 350 (or burst panel or other pressure relief device) may be installed to cover the vessel opening. The vessel opening may be accessed, as illustrated in
Once the vessel opening is accessed, an explosion panel 350 may be secured within the quenching module, as illustrated in
An explosion vent sensor also may be installed and configured to provide an indication when the explosion vent opens. In one embodiment, the explosion vent sensor may be provided integrally with the explosion vent, such that the sensor is installed concurrently with the explosion panel. In another embodiment, the explosion vent sensor may be installed separately from the explosion panel. The explosion vent sensor may be connected to the explosion vent panel. Additionally or alternatively, an explosion vent sensor may be mounted on the quenching module, as illustrated, for example, in
Before operation, it may be desirable to install one or more conductive grounding straps. As illustrated in
Embodiments of the disclosed flameless venting system also may be used with a method of sizing a flame quenching module of a flameless venting system. According to the method, a normal vent area requirement may first be calculated based on the needs of an application (e.g., based on the maximum anticipated pressures, particulate sizes, and other parameters). Additionally or alternatively, a normal vent area requirement may be determined by looking up known requirements for known applications. Next, a vent efficiency correction factor associated with the flameless venting system may be applied. For example, if an application is determined to require a vent area of 3 ft2, and a flameless venting system has been demonstrated to have a 64% efficiency, then the necessary flameless venting system exit area size may be calculated by dividing 3 ft2 by 0.64 to reach 4.69 ft2. Thus, a flameless venting system having at least that exit area may be used. As another example, if an application is determined to require a vent area of 5 ft2, and a flameless venting system has been demonstrated to have an 87% efficiency, then the necessary exit area for the flameless venting system may be calculated by dividing 5 ft2 by 0.87 to reach 5.75 ft2. In both examples, an exemplary 920 mm×586 mm flameless venting system, having a 6 ft2 exit area may be used to achieve the necessary 4.69 ft2 or 5.75 ft2 exit areas.
Embodiments of the present disclosure have been tested and demonstrated to achieve certain performance advantages. For example, an embodiment of the disclosed flameless venting system may have significant Kst capability, including Kst≤350. In a dust application, Kst is the deflagration index of the dust, and is an expression of its reactivity. Kst is a parameter critical to the sizing of all explosion venting devices, including flameless venting devices. Based on observed Kst values, an embodiment of the disclosed vent may be used for agricultural and/or organic dusts.
The disclosed flameless venting system may achieve standards for flameless venting, including, e.g., EN 16009:2011 (the only global standard dedicated to flameless venting devices), EN 14491-2012, EN 14797-2007, and/or NFPA 68-2007. Furthermore, the disclosed flameless venting system may be ATEX certified and/or CE marked. The disclosed venting system may meet standard INERIS 15ATEX0016X. In one embodiment, the disclosed venting system may discharge in ATEX Zone 21 & 22, on protected equipment with dust concentration up to 300 g/m3 and particle size up to 50 μm.
It is contemplated that individual features of one embodiment may be added to, or substituted for, individual features of another embodiment. Accordingly, it is within the scope of this disclosure to cover embodiments resulting from substitution and replacement of different features between different embodiments.
The above described embodiments and arrangements are intended only to be exemplary of contemplated systems and methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein.
Number | Date | Country | Kind |
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2915307 | Dec 2015 | CA | national |
This is a continuation of U.S. Nonprovisional application Ser. No. 16/061,914, filed Jun. 13, 2018, which is a National Phase of International Application No. PCT/US2016/066404, filed Dec. 13, 2016, which claims the benefit of U.S. Provisional Application No. 62,267,084, filed Dec. 14, 2014, and Canadian Application No. 2915307, filed Dec. 14, 2014. The entire contents of the above-referenced applications are expressly incorporated herein by reference.
Number | Date | Country | |
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Parent | 16061914 | Jun 2018 | US |
Child | 17933636 | US |