Abstract:
A silencer apparatus for attenuating noise in gas flow systems. The apparatus generally includes a housing having an interior cavity and a gas flow inlet and outlet that are adapted to be connected to a passage such that a gas flowing through the passage enters and exits the cavity of the housing through the inlet and outlet, respectively. A silencer cartridge unit is removably disposed within the interior cavity of the housing and defines a gas flow path fluidically connected to the inlet and outlet of the housing. The silencer cartridge unit has at least one sound-attenuating element that surrounds the gas flow path. The housing is further equipped with a closure that sealingly closes a portion of the housing, and is releasable from the housing to provide an access opening through which the silencer cartridge unit can be removed. The apparatus can also be adapted to include a filtration medium.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to equipment for attenuating noise in gas flow systems, including blowers, compressors, turbines, etc. More particularly, the present invention relates to silencer equipment containing a noise attenuation unit that can be removed and replaced as a unit to maintain the performance of the silencer equipment and, by disposing of the noise attenuation unit at the end of its useful life, protect downstream blowers, compressors, turbines, etc., from damage. The present invention can be applied in conjunction with all methods of attenuating noise caused by inlet or outlet gas streams. 
         [0002]    Certain equipment capable of noise/sound attenuation in gas (typically air) flow streams are commonly referred to as silencers in the art. Common sources of undesirable noise levels include, for example, blowers, compressors, turbines, etc., in a variety of installations, including manufacturing plants, bottling plants, laboratories, industrial plants, power generation facilities, waste water treatment plants, etc. Generally, a flowing gas stream through which undesirable noise is propagated from an upstream or downstream source is passed through a flow passage within a silencer, where the noise is attenuated using various means that are generally categorized as absorptive or reactive (also referred to as chambered). Absorptive silencers typically make use of barrier layers, typically steel or other materials known to be effective in interrupting the transmission of sound energy combined with layers of fibrous or cellular (fabric or foam) absorptive material that surrounds the flow passage and attenuates sound by transferring the energy of sound waves to the absorptive material, generally by converting the sound wave energy within the gas to vibrational and/or thermal energy within the absorptive material. Reactive silencers typically make use of pulse chambers connected to the flow passage, annular noise attenuation tubes, or axially-disposed noise attenuation tubes, into which the sound waves are conducted and suppressed. Hybrid silencers also exist that make use of both absorptive and reactive techniques. 
         [0003]    Silencers are typically manufactured as dedicated standalone units that are installed inline in a conduit, duct, pipe, or other passage through which the gas stream flows. Examples of conventional silencers include those sold by Universal Silencer of the Fleetguard/Nelson Company, Stoddard Silencer, and Burgess-Manning of Nitram Energy, Inc. Universal Silencer describes silencers in currently existing product instructional materials as “complete weldments or permanently assembled having no replaceable parts.” For air inlet applications, silencers are often used in combination with filters, though again typically as a standalone unit that is often connected between the filter housing and the noise source. However, integrated filter-silencer units are also commercially available, examples of which include the TRIVENT® Series P09 filter silencer manufactured by Endustra Filter Manufacturers, Inc. In a filter-silencer such as the Series P09, the silencer comprises a reactive chamber that forms an integral and permanent part of the filter housing, usually though not necessarily located immediately downstream of the filter element. The filter housing is configured so that the filter element is accessible for removal and replacement, but the components that make up the silencer are not as these components are, as in the aforementioned Universal Silencers, not removable or replaceable. Other commonly available integrated filter-silencers, such as those manufactured by several companies, among them Solberg Manufacturing, include reactive inlet tubes coupled with an absorptive silencer situated downstream or nested within the filter element. This reactive-absorptive filter silencer is again designed to provide access for filter element changes, but the silencer itself is an integral and permanent fixture of the housing, and is not intended to be removed or replaced. 
         [0004]    A problem encountered with silencers is the potential damage that can occur downstream as a result of degradation of the silencer components. For example, common dedicated silencers have an exterior primed surface and are designed to handle relatively moisture-free air. However, in virtually all industrial applications, intake air or gas is ambient and therefore only as dry as the relative humidity, and the compression of air and gases creates condensation. The resulting moisture laden air attacks and corrodes the interior surfaces of the silencers. Because silencers are typically downstream of the filter element, the resulting decay of the interior surfaces, as well as the absorptive materials, causes pieces of metal, scale, fabric, foam, etc., to be drawn into the machinery, and can and does cause permanent damage to the equipment. Dedicated reactive-absorptive filter silencers, in which the absorptive silencer unit is permanently located on the inside of or downstream of the filter element, pose the same problem. Even in situations where galvanized steel or stainless steel is employed to inhibit corrosion, these materials do not deter the decay or erosion of the absorptive material or foam, which accumulate moisture, dirt, and oils that have bypassed the filter element or have been transferred during filter changes or neglect. As a result, the absorptive material breaks down and becomes free to enter the equipment inlets, where they can and do cause permanent damage. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a silencer apparatus for attenuating noise in gas flow systems that contain a blower, compressor, turbine, or other source of noise that tends to propagate through gas compression or redirection. The silencer apparatus generally includes a housing having an interior cavity and a gas flow inlet and outlet that are adapted to be connected to a passage such that a gas flowing through the passage enters and exits the interior cavity of the housing through the inlet and outlet, respectively. A silencer cartridge unit is removably disposed within the interior cavity of the housing as a discrete and unitary component. The cartridge unit defines a gas flow path fluidically connected to the inlet and outlet of the housing, and comprises at least one sound-attenuating means, such as an absorptive, noise barrier or reactive element, that surrounds or interrupts the gas flow path as necessary to accomplish noise attenuation in the gas flow path. The housing is further equipped with a closure that sealingly closes a portion of the housing. The closure is releasable from the housing so as to provide an access opening in the housing through which the silencer cartridge unit in its entirety can be removed without dismantling or damaging the silencer cartridge unit. 
         [0006]    The silencer apparatus can also be adapted to include a filtration medium. For example, the silencer apparatus may include a separate filtration unit with a filtration medium enclosed therein, in which case the housing and filtration unit are coupled together so that gas flowing through the housing also flows through the filtration unit and the filtration medium. Alternatively, the filtration medium may be a component of the housing, in which case the silencer cartridge unit may be surrounded by the filtration medium. In either case, both the filtration unit and the silencer cartridge unit may be removed and disposed of when their useful lifespan has been expended. 
         [0007]    In view of the above, the silencer cartridge unit is adapted to be removed and replaced as a unitary discrete assembly from the housing without dismantling or damaging the silencer cartridge unit, and without damaging or dismantling the housing other than releasing or removing the closure. As such, the silencer apparatus is configured to allow the silencer cartridge unit to be removed, inspected, and then either cleaned and reinstalled or discarded and replaced with a second silencer cartridge unit of the same or different type. With this capability, the silencer apparatus can be used in a manner that greatly reduces the risk of damage to downstream components. In particular, the invention allows for and rightly assumes that the components of the silencer cartridge unit will inherently corrode and break down over time. To avoid pieces of metal, scale, fabric, foam, etc., from being drawn into downstream machinery, the silencer cartridge unit can be periodically removed, inspected, cleaned, and replaced as may be necessary. Further, and importantly, when its useful life has been fully exploited, the unit can be removed, disposed of, and replaced. The disposability feature, combined with the absorptive material being provided within a discrete cartridge rather than a permanent member of a welded structure, is a key aspect of the invention. 
         [0008]    Other objects and advantages of this invention will be better appreciated from the following detailed description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIGS. 1 and 2  show, respectively, side and end views of a silencer apparatus in accordance with a first embodiment of this invention, with the side view showing the interior of the apparatus exposed to reveal a removable and disposable silencer cartridge unit. 
           [0010]      FIG. 3  is a cross-sectional exploded view of the silencer apparatus of  FIGS. 1 and 2 , with a closure end of the apparatus removed to provide an access opening to the silencer cartridge unit within. 
           [0011]      FIGS. 4 ,  6 , and  8  represent three alternative configurations for the silencer apparatus of  FIG. 1 , in which a separate filtration unit is attached to the closure end of the apparatus, and  FIGS. 5 ,  7 , and  9  are cross-sectional exploded views of the silencer apparatuses of  FIGS. 4 ,  6 , and  8 , respectively. 
           [0012]      FIG. 10  is a partial cross-sectional representation of a silencer apparatus in accordance with another embodiment of the invention, in which the apparatus incorporates an integral filtration unit and the silencer cartridge unit is within the filtration unit. 
           [0013]      FIG. 11  is an exploded view of the apparatus of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIGS. 1 through 11  depict various embodiments of silencer apparatuses within the scope of the invention. The apparatuses find use for silencing noise generated by a variety of sources, including blower, compressors, turbines, and other sources of noise that propagates through the gas being worked on. The invention is particularly well suited for intakes of single and multistage axial, centrifugal, and reciprocating compressors and single-stage centrifugal blowers (turbines), multistage blowers, industrial fans, pressure blowers, and positive displacement blowers of types used in equipment found in manufacturing plants, laboratories, industrial plants, power generation facilities, etc. While the invention will be described in particular reference to silencing noise within air flow systems, the invention can be employed to attenuate noise in a wide variety of gases for various applications. As such, the term “air” will typically be used in reference to atmospheric air, though the principles of this invention and the apparatuses themselves apply to essentially any flowing gas over wide ranges of pressures and temperatures. 
         [0015]    With reference to  FIGS. 1 through 3 , a silencer apparatus  10  is shown as comprising a tubular-shaped silencer housing  12  that surrounds and encloses a silencer cartridge unit  14 , an inlet  16  located at one end  22  of the housing  12 , and an outlet  18  located at an opposite end  24  of the housing  12 . The housing  12  is depicted as having a unitary construction, though various other constructions are possible. The housing  12  coaxially positions and orients the silencer cartridge unit  14  within its interior cavity  13  ( FIG. 3 ) in a manner that encloses, seals, and protects the silencer cartridge unit  14  while also promoting the aerodynamic flow of air through the housing  12  and unit  14 . As will become evident from the following, the silencer housing  12  and silencer cartridge unit  14  are also configured to simplify the procedure for removing and replacing the silencer cartridge unit  14 . The inlet and outlet  16  and  18  are shown as comprising pipe sections terminating with flanges that enable the apparatus  10  to be connected to a conduit, duct, pipe, or other passage (not shown) through which the air stream flows. Alternatively, other types of connections could be used, including but not limited to NPT connections. As understood in the art, the housing  12  is sized to accommodate the gas flow for a given application. The length of the housing  12  can vary widely, depending on the particular application. For environmental resistance, the housing  12 , silencer cartridge unit  14 , inlet  16 , outlet  18  are preferably formed of corrosion-resistant materials such as a stainless steel, aluminum alloy, or plastic, and/or coated with a corrosion-resistant coating (e.g., paint or galvanized). 
         [0016]    The silencer apparatus  10  and its components are configured and sized relative to each other to provide for a flow path  20  through the silencer apparatus  10  that does not significantly resist air flow. In its simplest form, the silencer cartridge unit  14  has a tubular form (as shown) corresponding to the tubular shape of the silencer housing  12 , the flow path  20  within the silencer cartridge unit  14  is substantially coaxial with portions of the flow path  20  within the inlet and outlet  16  and  18 , and the portion of the flow path  20  within the silencer cartridge unit  14  is substantially equal in cross-sectional area to the portions of the flow path  20  within the inlet and outlet  16  and  18  such that the flow path  20  has a substantially constant cross-sectional area through the apparatus  10 , as evident from  FIG. 3 . However, variants are foreseeable. As also evident from  FIGS. 1 through 3 , the silencer cartridge unit  14  generally has a tubular shape, with a tubular-shaped core wall  26  that is at least semipermeable to air. A tubular-shaped outer wall  38  surrounds the core wall  26 , and the ends of the unit  14  are closed with end walls  39  to define an annular-shaped enclosure  28 . The core wall  26  circumferentially surrounds the flow path  20 , and in turn is circumferentially surrounded by an absorptive media  30  that preferably fills the entire annular enclosure  28 . 
         [0017]    In combination, the silencer housing  12 , core wall  26 , enclosure  28 , absorptive media  30 , and optionally the outer wall  38  are intended to provide a desired noise attenuation effect. The housing  12  acts as a noise barrier, and therefore must be formed of an impermeable material (such as a steel, plastic, etc.) to form an airtight seal surrounding the silencer cartridge unit  14 . The outer wall  38  of the silencer cartridge unit  14  does not need to be impermeable, and may even be omitted, as long as the unit  14  is installed in an appropriately-configured housing  12  (as shown in  FIGS. 1 and 2 ) that is air-impermeable and forms an airtight seal around the unit  14 . Nonetheless, improved noise attenuation can be achieved by forming the unit  14  to include the outer wall  38  and form the wall  38  of an impermeable material, thus adding an additional noise barrier. The core wall  26  of the silencer cartridge unit  14  must be permeable or at least semipermeable, such as a result of being formed of perforated or expanded metal or plastic. Sound waves are conducted through openings in the core wall  26  and into the enclosure  28 . The absorptive media  30  within the enclosure  28  serves as an absorptive silencer, and is preferably in the form of a consolidated mass that fills the enclosure  28 . The absorptive media  30  absorbs and converts the sound energy that has entered the enclosure  28  into thermal energy, and sound waves that are not converted are interrupted when they encounter the outer wall  38  of the silencer cartridge unit  14  (if the outer wall  38  is present and impermeable) or the silencer housing  12  (if the outer wall  38  is not present or present but permeable). The determination of a suitable opening cross-sectional area for a given application is within the skill of those knowledgeable in the art, and will vary widely based on the amount of noise attenuation desired in a given application. Suitable materials for the absorptive media  30  are also well known to those skilled in the art, with fibrous glass, polyester, polyurethane foam, and other materials being widely used as they are durable and nonreactive with air. The length and radial width of the enclosure  28  are shown as being determined by the housing  12 , inlet  16 , outlet  18 , core wall  26 , and optional outer wall  38 , all of which can be appropriately sized to achieve a desired attenuation effect for a given application. Chambers within the enclosure  28  are also foreseeable, as are other types of noise attenuators, absorbers, barriers, and interrupters. 
         [0018]    The inlet  16  is represented in  FIG. 3  as part of a removable closure of the silencer housing  12 , which when removed provides an access opening  32  whose diameter is essentially the same as the interior of the housing  12  that accommodates the silencer cartridge unit  14 , and therefore through which the entire silencer cartridge unit  14  can be removed from the silencer apparatus  10 . An outer rim  36  of the inlet  16  can be clamped or otherwise releasably secured to the housing  12  in any suitable manner, with the result that together the rim  36  and its inlet  16  define a removable closure for the housing  12 . The apparatus  10  is preferably a gas-tight assembly, and as such a ring-shaped gasket or sealant  34  is preferably provided to seal the rim  36  to the end  22  of the housing  12 . Suitable materials for the sealant  34  will depend on the particular gas being handled, as well as the temperature and pressure of the gas. Because only one end of the silencer housing  12  is required to be removable so as to permit removal of the silencer cartridge unit  14 , the outlet  18  can be permanently attached to the housing  12 , such as by welding, crimping, etc., again with the desire of forming a gas-tight connection. It is foreseeable that the outlet  18  could be adapted for removal instead of the inlet  16 , or both the inlet  16  and outlet  18  could be removable so that the silencer cartridge unit  14  can be removed from either end  22  and  24  of the housing  12 . 
         [0019]    The silencer cartridge unit  14 , including its core wall  26 , absorptive media  30 , outer wall  38  and end walls  39 , is a unit separate from the silencer housing  12  as a result of the core wall  26 , enclosure  28 , absorptive media  30 , outer wall  38  and end walls  39  not being secured to the housing  12 . As such, the housing  12  can be installed as an essentially permanent component of the air flow system in which it is used, whereas the silencer cartridge unit  14  can be manufactured as a disposable unit and simply replaced when its attenuation properties or overall condition degrades, as may result from wear, damage or accumulation of debris and particles from the air stream, aging, corrosion, scaling, and decomposition from weathering and corrosive agents in the air stream, etc., none of which is visible or otherwise readily apparent from the exterior of the silencer housing  12 . The silencer cartridge unit  14  can be easily removed and inspected on a regular schedule, and either refurbished or replaced before such degradation poses a risk to equipment and processes downstream of the unit  14 . As such, the silencer cartridge unit  14  is well suited for use under conditions that would be too severe or otherwise too quickly degrade the performance of a conventional silencer whose noise suppression components are integral and cannot be removed from their enclosure without cutting or otherwise damaging the enclosure. It is also foreseeable that the core wall  26  and absorptive media  30  could be formed of materials that are less expensive than those typically required for silencers, so as to provide for a low-cost silencer that can be routinely replaced with minimal impact on maintenance costs. 
         [0020]      FIGS. 4 and 5  represent an apparatus  40  similar to that of  FIGS. 1 through 3 , but with the inclusion of a filtration unit  42  coupled to the inlet  16  of the silencer housing  12 . (In the Figures, consistent reference numbers are used to identify functionally similar structures.) The preferred air flow path  20  through the apparatus  40  is indicated as being through the filtration unit  42  and then through the removable silencer cartridge unit  14  within the silencer housing  12 , which may be connected at its outlet  18  to an air flow system containing a source of noise that propagates through the air flow to the apparatus  40 . In this sense, the filtration unit  42  may be referred to as an air/gas intake or inlet filter, and the apparatus  40  may be referred to as a filter-silencer. The rim  36  of the inlet  16  is represented in  FIG. 4  as being clamped with a ring  54  to a flange  56  at the end  22  of the housing  12 , such that together the rim  36  and its inlet  16  define a removable closure for the housing  12 . The inlet  16  is further represented in  FIGS. 4 and 5  as having a pipe section (venturi) with a generally arcuate shape that provides a smooth transition from the inner diameter of the core wall  26  to the inner diameter of a filtration medium  44  within the filtration unit  42 . The filtration medium  44  may be, for example, a pleated filtration membrane secured between two plates  46  and  48 . The plate  46  is shown secured with a fastener system  50  to a bracket  52  attached to the other plate  48 , though other configurations and assembly techniques are foreseeable. Suitable materials for the medium  44  include essentially any air-permeable synthetic or natural materials that exhibit the required filtration efficiencies, flame resistance, recoverability, and other requirements known in the art, such as operating temperature as defined by the specific application. In practice, the filtration unit  42  may be an existing commercial product, such as the TRIVENT® Series P04 or P06 filters manufactured by Endustra Filter Manufacturers, Inc., or any other inlet filtration device suitable for the particular application and capable of being coupled to the silencer housing  12 . The filtration unit  42  could also be mounted directly to the silencer housing  12 , instead of the inlet  16  on the housing  12 , necessitating that the outlet  18  be removable to provide access to the removable, disposable, silencer cartridge unit  14  within the housing  12 . 
         [0021]      FIGS. 6 through 9  represent other filter-silencer apparatuses  60  and  70  similar to the apparatus  40  of  FIGS. 4 and 5 , but with their outlets  18  formed to have a ninety-degree bend to adapt the apparatuses  60  and  70  to other types of installations. As before, the rim  36  and its inlet  16  define a removable closure for the housing  12 . In  FIGS. 8 and 9 , the filtration unit  42  further includes a weather hood (lid)  72  that surrounds the filtration medium  44 , but is otherwise identical to the apparatus  60  of  FIGS. 6 and 7 . 
         [0022]      FIGS. 10 and 11  depict another configuration for a filter-silencer apparatus  80 , in which the filtration unit  42  is incorporated directly into the silencer housing  12  and surrounds the silencer cartridge unit  14 . The apparatus  80  is very compact and therefore advantageous for use in applications where space is limited or might not otherwise accommodate a conventional silencer or one of the silencer apparatuses of  FIGS. 1 through 9 . 
         [0023]    As in the previous embodiments, the silencer housing  12  has a tubular shape and the silencer cartridge unit  14  is contained within a cavity  13  of the housing and is essentially coaxial with the housing  12 . In contrast to previous embodiments, the housing  12  is defined by the filtration unit  42  and a plate  36  in which the outlet  18  (shown equipped with hose clamps) is provided, and the filtration unit  42  entirely surrounds the silencer cartridge unit  14 . Instead of the inlet  16  to the housing  12  being formed by a pipe section and rim as shown in  FIGS. 4 and 5 , the inlet  16  is defined by the entire cylindrical-shaped outer periphery of the housing  12 , at which the filtration medium  44  of the filtration unit  42  is installed. The filtration unit  42  is secured to the plate  36  with a fastening system  50  that includes a threaded rod  50 A that passes through an opening in a closed end cap  46  of the filtration unit  42 , and a nut  50 B threaded onto the rod  50 A. The rod  50 A is mounted to a bracket  52  attached to the plate  36 . The end  34  of the filtration unit  42  opposite the end cap  46  defines an opening  32  surrounded by a gasket, molded rubber or plastic, or other sealing means to enable the filtration unit  42  to create an airtight seal against the plate  36  via the pressure exerted via the fastening system  50 . Though not shown as being hooded, the filtration unit  42  could further include a weather hood, such as the hood  72  shown in  FIGS. 8 and 9 . 
         [0024]    The fastener system  50  may also be used to secure the silencer cartridge unit  14  within the housing  12 . However, in a preferred embodiment, a fastener system is not required to secure the silencer cartridge unit  14  within the housing  12 . Instead, the cartridge unit  14  is constructed to have an annular-shaped base  84  that fits over a tubular seating ring  86  on the plate  36  and surrounding the outlet  18 . The base  84  comprises a molded rubber or plastic that is pliable and resilient and defines a circumferentially-tapered opening  88  of appropriate size so that as the cartridge unit  14  is manually forced down over the seating ring  86 , the base  84  gradually applies increasing pressure on the seating ring  86  until the base  84  sufficiently deforms around the seating ring  86  to create a secure interference fit. The cartridge unit  14  can be removed by reversing this process. Other methods of seating the cartridge unit  14  could be employed, including but not be limited to clamps, fasteners, NPT connections, twist-locks, or other commonly known methods of fixing and seating annular devices. 
         [0025]    In the case of the apparatus  80  depicted in  FIGS. 10 and 11 , the outer wall  38  of the silencer cartridge unit  14  must be impermeable, acting as a noise barrier. Air is drawn through the filtration medium  44 , directed up through an annular-shaped channel  92  between the medium  44  and the outer wall  38  of the cartridge unit  14 , over the outer wall  38  of the cartridge unit  14 , and finally into the interior of the cartridge unit  14  through an opening  90  at the upper end of the unit  14 . The opening  90  is tapered to significantly reduce noise and restriction by creating an aerodynamic sloping surface with a low coefficient of drag over which the air travels. The redirection of airflow through the channel  92  and over the outer wall  38 , and the interruption of the sound waves, reactively suppresses noise. Once the airflow passes into the silencer cartridge  14 , the permeable inner core  26  allows sound energy to be absorbed by the absorptive media  30 , where it is converted to thermal energy. 
         [0026]    Though differing in its configuration, the filter-silencer apparatus  80  of  FIGS. 10 and 11  still provides the advantage of a unitary and disposable silencer cartridge unit  14  that can be readily installed and removed through the opening  32  in the filtration unit  42 , which is made accessible by detaching a removable closure (the plate  36 ) of the housing  12 . 
         [0027]    While the invention has been described in terms of a preferred embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, the physical configuration of the filtration system could differ from that shown, and materials other than those noted could be use. Therefore, the scope of the invention is to be limited only by the following claims.