Patent Publication Number: US-2022231500-A1

Title: Systems and methods for arc flash incident energy reduction

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under 35 U.S.C. § 119(e) of co-pending U.S. Provisional Patent Application No. 63/137,907 titled SYSTEMS AND METHODS FOR ARC FLASH INCIDENT ENERGY REDUCTION filed on Jan. 15, 2021, which is herein incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND OF DISCLOSURE 
     1. Field of Disclosure 
     Embodiments of the disclosure relate generally to safety features, and more specifically, to a safety assembly that is used within an equipment rack to prevent arc flash events from connecting and disconnecting electronic equipment from busbars and fan modules within the equipment rack. 
     2. Discussion of Related Art 
     Centralized data centers for computer, communications and other electronic equipment have been in use for a number of years. More recently, with the increasing use of the Internet, large scale data centers that provide hosting services for Internet Service Providers (ISPs), Application Service Providers (ASPs) and Internet content providers have become increasingly popular. It is often desirable to operate equipment within data centers seven days a week, 24 hours per day, with little or no disruption in service. To prevent any disruption in service, it is common practice in data centers to use uninterruptible power supplies (UPSs) provided in equipment racks to ensure that the equipment within the data centers receives continuous power throughout any black out or brown out periods. Typically, data centers are equipped with a relatively large UPS at the main power distribution panel for the facility. Often, the UPS is selected to have sufficient capacity to meet the power requirements for all of the equipment within the facility. 
     The use of the UPS to provide power to a critical load is well known in the art. The UPS is designed to protect electronic equipment from utility power blackouts, brownouts, sags and surges. The UPS may also protect electronic equipment from small utility fluctuations and large disturbances. In most rack configurations, the UPS provides battery backup until utility power returns to safe levels or the batteries are fully discharged. The configurable rack may include power distribution modules and batteries to form the UPS, and other pieces of equipment required to operate the uninterruptible power supply. These modules are rack-mounted in the well-known manner. 
     A typical power distribution unit consists of a rack frame chassis and removable power distribution modules or power modules for short, which are often removed for replacement or service. The power modules connect to a live busbar provided at a back of the equipment rack, and when the power module is removed, the live busbar is exposed. Often, the equipment rack includes a warning label to power down the equipment rack when working near the busbar to avoid hazards, such as arc flash, but such a label oftentimes can be ineffective. Other approaches have been tried, such as installing a blanking panel to block access to the live busbar. However, this approach, when implemented, requires additional time and parts. 
     Often, power modules and fan modules are removed and replaced from the equipment rack. Arc flashing can occur during such removal and replacement of such power modules and fan modules. 
     SUMMARY OF DISCLOSURE 
     One aspect of the present disclosure is directed to an assembly to contain energy from arc flash within a mounting slot of an equipment rack. In one embodiment, the assembly comprises a valve panel assembly including a first valve panel body secured to the frame members by a first hinge and a second valve panel body secured to the frame members by a second hinge. The first valve panel body and the second valve panel body are configured to rotate between closed positions and open positions. 
     Embodiments of the assembly further may include extending the first hinge along a top or side edge of the first valve panel body, with opposite ends of the first hinge extending through respective openings of the frame members. The second hinge may extend along a bottom edge of the second valve panel body, with opposite ends of the second hinge extending through respective openings of the frame members. The assembly further may include a spring to bias the second valve panel body to the closed position. The spring may be a coil spring that is mounted on one end of the second hinge, with the spring having one end configured to engage to the second valve panel body and another end that engages a portion of the frame members. At least one of the first hinge and the second hinge may include a torsion bar configured to bias the valve panel body in a closed position. The torsion bar may extend along an edge of the valve panel body, with the torsion bar having a bent section and a shaped section opposite the bent section, the shape section entering a shaped opening of a portion of the valve panel body to ensure that the valve panel body rotates when the torsion bar rotates. The assembly further may include a redirection plate secured to the chassis of the equipment rack. The redirection plate may be configured to direct arc flash along a plane of the redirection plate. The assembly further may include a fan shroud coupled to the chassis of the equipment rack. The fan shroud may be configured to receive a fan module to provide airflow to the electronic equipment. The fan shroud further may be configured to operate in an open position in which the fan module is received by the fan shroud and a closed position in which the fan shroud blocks arc flash when the fan module is installed or removed from the fan shroud. 
     Another aspect of the present disclosure is directed to a method of selectively blocking access to a portion of an equipment rack within a mounting slot of a chassis of the equipment rack with the assembly disclosed herein. 
     Yet another aspect of the present disclosure is directed to an equipment rack comprising a chassis, an open power source located at a back of the chassis, and a valve panel assembly including a first valve panel body secured to the frame members by a first hinge and a second valve panel body secured to the frame members by a second hinge. The first valve panel body and the second valve panel body are configured to rotate between closed positions and open positions. 
     Embodiments of the equipment rack further may include extending the first hinge along a top or side edge of the first valve panel body, with opposite ends of the first hinge extending through respective openings of the frame members. The second hinge may extend along a bottom edge of the second valve panel body, with opposite ends of the second hinge extending through respective openings of the frame members. The equipment rack further may include a spring to bias the second valve panel body to the closed position. The spring may be a coil spring that is mounted on one end of the second hinge, with the spring having one end configured to engage to the second valve panel body and another end that engages a portion of the frame members. The assembly further may include a redirection plate secured to the chassis of the equipment rack. The redirection plate may be configured to direct arc flash along a plane of the redirection plate. The assembly further may include a fan shroud coupled to the chassis of the equipment rack. The fan shroud may be configured to receive a fan module to provide airflow to the electronic equipment. The fan shroud further may be configured to operate in an open position in which the fan module is received by the fan shroud and a closed position in which the fan shroud blocks arc flash when the fan module is installed or removed from the fan shroud. 
     Another aspect of the present disclosure is directed to an assembly to contain energy from arc flash from an equipment rack. In one embodiment, the assembly comprises a redirection plate secured to a chassis of an equipment rack, the redirection plate being configured to direct arc flash along a plane of the redirection plate. 
     Another aspect of the present disclosure is directed to an equipment rack comprising a chassis, an open power source located at a back of the chassis, and a redirection plate secured to the chassis, the redirection plate being configured to direct arc flash along a plane of the redirection plate. 
     Another aspect of the present disclosure is directed to an assembly to contain energy from arc flash from an equipment rack. In one embodiment, the assembly comprises a fan shroud coupled to an equipment rack configured to support electronic equipment. The fan shroud is configured to receive a fan module to provide airflow to the electronic equipment. The fan shroud further is configured to operate in an open position in which the fan module is received by the fan shroud and a closed position in which the fan shroud blocks arc flash when the fan module is installed or removed from the fan shroud. 
     Another aspect of the present disclosure is directed to an equipment rack comprising a chassis, an open power source located at a back of the chassis, a fan module configured to be releasably coupled to the chassis, and a fan shroud coupled to the chassis configured to support electronic equipment. The fan shroud is configured to receive a fan module and to provide airflow from the fan module to the electronic equipment. The fan shroud further is configured to operate in an open position in which the fan module is received by the fan shroud and capable of providing airflow to the electronic equipment and a closed position in which the fan shroud blocks arc flash when the fan module is installed or removed from the fan shroud. 
     Another aspect of the present disclosure is directed to an assembly to contain energy from arc flash from an equipment rack. In one embodiment, the assembly comprises a fan shroud coupled to an equipment rack configured to support electronic equipment. The fan shroud is configured to receive a fan module. The fan shroud further is configured to operate in an open position in which the fan module is received by the fan shroud and a closed position in which the fan shroud blocks arc flash. 
     Another aspect of the present invention is directed to an equipment rack comprising a chassis, a power source located at a back of the chassis, a fan module configured to be releasably coupled to the chassis, and a fan shroud coupled to the chassis. The fan shroud is configured to receive a fan module. The fan shroud further is configured to operate in an open position in which the fan module is received by the fan shroud and a closed position in which the fan shroud blocks arc flash. 
     Another aspect of the present disclosure is directed to a method of assembling a system to contain energy from arc flash within a mounting slot of an equipment rack. In one embodiment, the method comprises: hingedly mounting a first valve panel body to a frame of the equipment rack by a first hinge; and hingedly mounting a second valve panel body to the frame of the equipment rack by a second hinge. The first valve panel body and the second valve panel body are configured to rotate between closed positions open positions. 
     Embodiments of the method further may include extending the first hinge along a top or side edge of the first valve panel body and extending the second hinge along a bottom edge of the second valve panel body. Hingedly mounting the first valve panel body to the frame of the equipment rack includes securing the first hinge to the frame by a first bracket and hingedly mounting the second valve panel body to the frame of the equipment rack includes securing the second hinge to the frame by a second bracket. The method further may include a spring to bias the movement of the second valve panel body to the closed position. The spring may be a coil spring that is mounted on one end of the second hinge. The spring has one end configured to engage to the second valve panel body and another end that engages a portion of the chassis. The method further may include securing a redirection plate to the chassis of the equipment rack, the redirection plate being configured to direct arc flash along a plane of the redirection plate. The further may include a fan shroud coupled to the equipment rack. The fan shroud may be configured to receive a fan module to provide airflow to the electronic equipment. The fan shroud further may be configured to operate in an open position in which the fan module is received by the fan shroud and a closed position in which the fan shroud blocks arc flash when the fan module is installed or removed from the fan shroud. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Various aspects of at least one example are discussed below with reference to the accompanying figures, which are not intended to be drawn to scale. The figures are included to provide illustration and a further understanding of the various aspects and examples, and are incorporated in and constitute a part of this specification, but are not intended as a definition of the limits of the disclosure. In the figures, identical or nearly identical components illustrated in various figures may be represented by like numerals. For purposes of clarity, not every component may be labeled in every figure. In the drawings: 
         FIG. 1  is a perspective view of a standard equipment rack; 
         FIG. 2  is an elevational cross-sectional view of the equipment rack; 
         FIG. 3  is an enlarged perspective view of an interior of the equipment rack; 
         FIG. 4  is an enlarged front view of mounting slots of the equipment rack; 
         FIG. 5  is a schematic elevational cross-sectional view of valve panel assemblies provided within a mounting slot; 
         FIGS. 6A-6C  are views showing a top valve panel assembly of an embodiment of the present disclosure; 
         FIGS. 7A-7D  are views showing a bottom valve panel assembly of an embodiment of the present disclosure; 
         FIGS. 8A-8D  are views showing a combination valve panel assembly of an embodiment of the present disclosure; 
         FIG. 9  is an exploded perspective view of the combination valve panel assembly; 
         FIG. 10  is a cross-sectional view of the combination valve panel assembly; 
         FIG. 11  is a perspective view of bottom valve panel assemblies and combination valve panel assemblies within the equipment rack; 
         FIG. 12  is a perspective view of top valve panel assemblies and combination valve panel assemblies within the equipment rack; 
         FIG. 13  is an elevational cross-sectional view of power modules being inserted into respective mounting slots of the equipment rack; 
         FIG. 14  is an elevational cross-sectional view of power modules fully inserted into respective mounting slots of the equipment rack; 
         FIG. 15  is an elevational cross-sectional view of an upper power module being fully inserted into its respective mounting slot and a lower power module being inserted into or extracted from its respective mounting slot; 
         FIG. 16  is an elevational cross-sectional view of an upper power module being inserted into or extracted from its respective mounting slot and a lower power module being fully inserted into its respective mounting slot; 
         FIG. 17  is a perspective view of an equipment rack having a redirection plate of an embodiment of the present disclosure; 
         FIG. 18  is a perspective view of the equipment rack with the redirection plate spaced from the equipment rack; 
         FIG. 19A  is a front perspective view of an exemplary equipment rack; 
         FIG. 19B  is a back perspective view of the equipment rack shown in  FIG. 19A ; 
         FIG. 20  is a back perspective view of another exemplary equipment rack showing openings for securing a redirection plate to the equipment rack; 
         FIG. 21  is a front view of a portion of an equipment rack having several fan modules; 
         FIG. 22  is a front view of the equipment rack with equipment removed to show a power terminal area and backsides of the fan modules; 
         FIG. 23  is a perspective view of a grille of a fan module; 
         FIG. 24  is a perspective view of a portion of a front of an equipment rack showing three fan modules, with one fan module being removed from the equipment rack; 
         FIG. 25  is a perspective view taken from behind the front of the equipment rack shown in  FIG. 24  showing fan shrouds of an embodiment of the present disclosure used to block access to the fan module; 
         FIG. 26A  is a cross-sectional view showing the fan module being removed from the equipment rack with the fan shroud shown in the closed position; 
         FIG. 26B  is a cross-sectional view showing the fan module secured to the equipment rack with the fan shroud in the open position; 
         FIGS. 27A and 27B  are cross sectional views of the fan shroud with the fan shroud in the closed position; 
         FIGS. 28A, 28B and 28C  are perspective views of the fan shroud with the fan shroud in the open position; 
         FIG. 29  is a perspective view of a base of the fan shroud; 
         FIG. 30  are views of an exemplary fan module; 
         FIG. 31  is a perspective view of a flap valve assembly of an embodiment of the present disclosure including a torsion bar to bias a flap valve panel; 
         FIG. 32  is a side view of a flap valve assembly of an embodiment of the present disclosure showing a torsion bar removed from a flap valve panel; 
         FIGS. 33A-33C  are perspective views of the torsion bar showing aspects of the torsion bar; 
         FIGS. 34A-34C  are perspective views of a flap valve assembly of an embodiment of the present disclosure showing frame members used to support a torsion bar; 
         FIGS. 35A and 35B  are perspective views of a portion of the flap valve assembly shown in  FIGS. 34A-34C ; 
         FIGS. 36A and 36B  are perspective views of another portion of the flap valve assembly shown in  FIGS. 34A-34C ; 
         FIG. 37  is an enlarged perspective view of a feature used to clamp or secure an end of the torsion bar; and 
         FIG. 38  is a perspective view of a flap valve assembly of an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The principles set forth in this disclosure are capable of being provided in other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     Mission-critical applications such as data centers, hospitals, airports, and military require high-availability power supply. One means of improving power availability is through modular design, which reduces mean time to recover (MTTR). For example, replacing a failed module in a UPS decreases recovery time while eliminating the downtime risk of transferring to bypass. This practice involves the ability to replace modules in any mode of operation. In addition to UPS, other low-voltage electrical equipment offered can be removed and replaced, such as cooling modules (e.g., fan modules), tap units on energized busway and circuit breaker modules on energized switchboard. 
     During such replacements, arc flash can occur. Specifically, energized-swapping activities can pose electrical hazards, such as shock and arc flash, to operators performing such replacements. A shock hazard may occur when the operator approaches energized electric conductors or circuit parts. The operator may inadvertently touch the part, i.e., due to disturbances, stumbling, or when in close proximity to de-energized parts. An arc flash may result when a fault occurs between two live conductors. Sources of an arc flash can be foreign elements, such as tools or dust/debris, defect or worn-down insulation material, poor design, poor installation, to name a few. Arc flash can be measured based on incident energy released through the air in the form of heat, sound, light, and explosive pressure, all of which can cause harm. Some specific injuries can include burns, blindness, electric shock, hearing loss, and fractures. 
     The present disclosure is directed to an assembly having valve panels that are configured to contain energy from arc flash, especially during replacements. Embodiments of the assembly disclosed herein are provided to ensure touch safety through the entire sequence of replacement. In some embodiments, the assembly is configured to limit potential arc flash incident energy to under 1.2 calories/cm 2 . 
     Flap Valves 
     Embodiments of the present disclosure are directed to valve panels that are operated by gravity or spring loaded to fall down or spring up respectively when a power module is removed from an equipment rack. The valve panels are provided to assist in reducing available incident energy below a tested threshold through all stages of a power module swapping. 
     Embodiments of the valve panels of the present disclosure enable no risk of touching the busbar and no increased risk of arc flash. 
     Embodiments of the valve panels of the present disclosure achieve arc incident energy reduction, which simplifies the design considerably. 
     Referring to  FIGS. 1 and 2 , an equipment rack or rack enclosure, generally indicated at  10 , is constructed in the well-known manner. In one embodiment, the equipment rack  10  includes a chassis, or frame structure, generally indicated at  12 , that defines an enclosure. In one embodiment, the equipment rack  10  includes a door, which is shown in the drawings in an open position. The chassis  12  includes an open front having several mounting slots, each indicated at  14 , that are each configured to slidably receive electronic components, such as power modules, each indicated at  16 . Once installed, the power modules  16  engage a busbar  18  ( FIG. 2 ) provided at a back of the chassis  12  in the well-known manner to provide power to the power modules. Although a busbar  18  is shown, the chassis  12  of the rack enclosure may include live wire provided to power equipment housed within the equipment rack, including the power modules  16 . 
     The exemplary equipment rack  10  shown in  FIGS. 1 and 2  illustrate power modules  16  installed within respective mounting slots  14  provided in the equipment rack  10 , with empty slots being covered by blanking panels. It should be noted that the equipment rack  10  can be configured to accommodate any number of power modules  16 , with the size of the mounting slots being dependent on the size of the power modules received within the mounting slots. In particular, the equipment rack  10  includes multiple mounting slots  14 , sometimes called bays, with each bay being configured to hold the power module  16  in place. As shown, the power modules  16  provided within the equipment rack  10  are stacked one above and adjacent one another; however, the equipment rack can be configured so that the power modules are oriented and positioned in any desired configuration. 
     In one embodiment, once installed, the power module  16  engages the busbar  18  to provide power to the power module. As mentioned above, the power module  16  can be removed from its respective mounting slot  14  to replace the power module or to repair the power module. Once removed, unless blocked off by a blanking panel mounted on a front surface of the equipment rack in front of the mounting slot  14  or within an interior of the equipment rack  10 , an operator or other person is able to access the busbar  18 , which can be dangerous if the operator is not careful. 
     Referring to  FIG. 3 , a portion of an interior of an equipment rack  30  is shown to disclose several mounting slots, each indicated at  32 . As shown, each mounting slot  32  includes a dead front barrier to an upper compartment, double insulated cables, and a connector  34  that is reinforced to be touch proof. A dead front barrier means that the equipment rack at the front is without live parts exposed to a person on the operating side of the equipment. 
     Referring to  FIG. 4 , valve panel assemblies of embodiments of the present disclosure are provided to contain energy from arc flash within a mounting slot  32  of an equipment rack. As shown, a first (top) valve panel assembly includes a top panel body  40  hingedly mounted by hinge  42  to a top wall  44  defining the mounting slot  32 . A second (bottom) valve panel assembly includes a bottom panel body  46  hingedly spring-mounted by hinge  48  to a bottom wall  50  defining the mounting slot  32 . The top panel body  40  of the first valve panel assembly is vertically oriented because of gravity, while the bottom panel body  46  of the second valve panel assembly is vertically oriented because of a spring mechanism associated with the hinge  48  of the bottom panel body, which will be described in detail below. As shown, a bottom edge of the top panel body  40  of the first valve panel assembly is spaced from a top edge of the bottom panel body  46  of the second valve panel assembly to define a gap  52 . The gap  52  between the bottom edge of the top panel body  40  of the first valve panel assembly and the top edge of the bottom panel body  46  of the second valve panel assembly can be varied based on the application. In one embodiment, the gap  52  provides a release for air pressure build up caused by an arc flash. 
     Referring to  FIG. 5 , the first (top) and second (bottom) valve panel assemblies are shown prior to inserting a power module into the mounting slot  32 . As shown, a busbar  54  includes two interface connectors, each indicated at  56 , which are used to connect the power module to the busbar. In one embodiment, the interface connectors  56  are touch “safe” in that an operator can touch or otherwise handle the connectors. The equipment rack further includes cables at the back of the equipment rack that connect to an input/output section provided above the mounting slot  32 . A steel plate  58  is provided to prevent an arc from propagating between the input/output section and the mounting slot  32 , indicated as the “power module cavity” in  FIG. 5 . The top and bottom valve panel assemblies, which are indicated as “flapper valves” in  FIG. 5 , provide protection against arc when removing a power module from the mounting slot  32 . 
       FIGS. 6A-6C  illustrate an embodiment of the top valve panel assembly, generally indicated at  60 , which is designed to hang down from the top wall of the mounting slot. In one embodiment, the top valve panel assembly  60  includes a top panel body  62  that is mounted to the top wall of the mounting slot by a bracket  64 . The top valve panel assembly  60  further includes a hinge  66  in the form of a pin to hingedly secure the top panel body to the bracket  64 . The top panel body  62  is formed by folding over side and end edges, with the side edges having openings formed therein to receive the hinge  66 . Since the top valve panel assembly  60  is mounted to the top wall of the mounting slot, the top panel body  62  of the top valve panel assembly is normally disposed in a vertical position. 
       FIGS. 7A-7D  illustrate an embodiment of the bottom valve panel assembly, generally indicated at  70 , which is designed to move from a biased vertical position to a generally horizontal position. In one embodiment, the bottom valve panel assembly  70  includes a bottom panel body  72  that is mounted to the bottom wall of the mounting slot. The bottom wall of the mounting slot is specifically configured to secure the bottom panel body  72  to the bottom wall. The bottom valve panel assembly  70  further includes a hinge  74  in the form of a pin to hingedly secure the bottom panel body to the bottom wall. The bottom valve panel assembly  70  further includes one or more coil springs together indicated at  76 , which are provided to bias the bottom panel body  72  in a vertical position. One free end of each spring  76  is positioned to engage the bottom panel body  72  and an opposite free end of each spring is positioned engaging a portion of the bottom wall of the mounting slot. 
       FIGS. 8A-8D  illustrate a combination top and bottom valve panel assembly, generally indicated at  80 , which is disposed between top and bottom adjacent mounting slots. As shown, the combination valve panel assembly  80  includes top panel body  82  and a bottom panel body  84 , with the top panel body being positioned below the bottom panel body since the top panel body operates within the bottom mounting slot and the bottom panel body operates within the top mounting slot. The top panel body  82  and the bottom panel body  84  are secured to a shelf  86  disposed between two mounting slots. In one embodiment, the shelf  86  is configured with an opening providing access to the top panel body  82  and the bottom panel body  84 . The combination valve panel assembly  80  further includes a hinge  88 , which is secured to the shelf by openings formed in the shelf  86 . The hinge  88  is configured to hingedly secure the top panel body  82  and the bottom panel body  84  to the shelf  86 . 
     As with the top panel body  62  of the top valve panel assembly  60  shown in  FIGS. 6A-6C , the top panel body  82  of the combination valve panel assembly  80  is free to hang from the hinge  88 . As with the bottom panel body  72  of the bottom valve panel assembly  70  shown in  FIGS. 7A-7D , the bottom panel body  84  is biased by one or more springs together indicated at  90  to the vertical position. The springs  90  are preloaded by sliding one end of each spring to engage the bottom panel body  84  of the combination valve panel assembly  80  and an opposite end of each spring to engage a base resting surface  92  of the shelf  86 . The shelf  86  further includes a stopping element  94  for limiting movement of the top valve panel and the bottom valve panel. 
       FIG. 9  illustrates an exploded perspective view of the combination valve panel assembly  80  shown in  FIGS. 8A-8D . As shown, the combination valve panel assembly  80  includes the top panel body  82 , the bottom panel body  84 , the hinge  88  and the spring  90 , which together are assembled to the shelf  86 .  FIG. 10  illustrates a cross-sectional view of the combination valve panel assembly  80 . 
       FIG. 11  illustrates the bottom valve panel assembly  70  and the combination valve panel assembly  80  in a position prior to receiving power modules within mounting slots, each indicated at  110 , of the equipment rack  112 . The bottom panel body  72  of the bottom valve panel assembly  70  is oriented in the biased generally vertical position. The top panel body  82  of the combination valve panel assembly  80  is disposed in a free hanging, vertical position. A gap  96  is shown between the bottom panel body  72  of the bottom valve panel assembly  70  and the top panel body  82  of the combination valve panel assembly  80 . The gap  92  is configured to provide a release for air pressure build up caused by an arc flash. 
       FIG. 12  illustrates the combination valve panel assembly  80  and the top valve panel assembly  60  in a position prior to receiving power modules within the mounting slots  110  of the equipment rack  112 . The bottom panel body  84  of the combination valve panel assembly  80  is oriented in the biased generally vertical position. The top panel body  62  of the top valve panel assembly  62  is disposed in a free hanging, vertical position. 
       FIG. 13  illustrates power modules, each indicated at  130 , being inserted into respective mounting slots  110  of the equipment rack  112 . As shown, the power modules  130  are illustrated prior to reaching the top valve panel assembly  60 , the bottom valve panel assembly  70  and the combination valve panel assembly  80 . In one embodiment, the valve panel assemblies  60 ,  70 ,  80  are shown to be positioned closer to a busbar  132  and a back of the equipment rack  112  than a front of the equipment rack to be closer to the arc should an arc be generated when removing the power modules. The top panel bodies  62 ,  82  and the bottom panel bodies  72 ,  84  are disposed in their respective vertical positions. 
       FIG. 14  illustrates power modules  130  fully inserted into respective mounting slots  110  of the equipment rack  112 . As shown, the power modules  130  are illustrated in positions in which they are mechanically and electrically coupled to interface connectors, each indicated at  134 , associated with the busbar  132 . The top panel bodies  62 ,  82  and the bottom panel bodies  72 ,  84  are disposed in their respective horizontal positions to enable the power modules  130  to be fully received within their respective mounting slots  110 . 
     It should be understood that the power modules  130  can be inserted into and extracted out of their respective mounting slots  110  independently from one another. For example,  FIG. 15  illustrates an upper power module  130  being fully inserted into its respective mounting slot  110  and a lower power module  130  being inserted into or extracted from its respective mounting slot  112 . Conversely,  FIG. 16  illustrates an upper power module  130  being inserted into or extracted from its respective mounting slot  110  and a lower power module  130  being fully inserted into its respective mounting slot  110 . 
     Embodiments of the valve panel assemblies enable the valve panel bodies to move to a deployed or blocking position in which the panel body drops down by gravity or springs up by a spring force when the power module is removed from the mounting slot of the equipment rack. Each valve panel body includes a sheet metal panel that can rotate around a hinge or spindle, which is fixed to a shelf of the equipment rack. The power module includes a rounded corner or push pins at the back of the module that function to move the valve panel body to avoid damaging the valve panel body when installing the power module. 
     The valve panel assemblies  60 ,  70 ,  80  can be mounted within the mounting slot  110  in any desired orientation. For example, the panel assemblies  60 ,  70 ,  80  can be suitably mounted within a mounting slot  110  on sides of the mounting slot so that the valve panel bodies  62 ,  72 ,  82 , respectively, extend in a horizontal direction within the mounting slot. To achieve this orientation, the valve panel assemblies  60 ,  70 ,  80  can be rotated 90 degrees. 
     One alternative to the bottom valve panel assembly and the combination valve panel assembly is to replace the spring with a magnet and/or provide a single spring instead of multiple springs. Another alternative to the top valve panel assembly and/or the combination valve panel assembly is to include a spring similar to the springs provided in the bottom valve panel assembly and the combination valve panel assemblies to spring load the top panel body. Another embodiment is to replace the hinge, e.g., the pin, with a standard hinge. Each valve panel body may include cutouts or openings to reduce its mass. 
     Although embodiments of the present disclosure illustrate power distribution modules being installed into and removed from the equipment rack, it should be understood that the assemblies of embodiments of the present disclosure can be employed within an equipment rack having any type of electronic module or device in a manner similar to the power distribution module. 
     Thus, it should be observed that embodiments of the present disclosure are directed to valve panel assembles function to reduce arc flash during removal of power modules and fan modules from the equipment rack. The valve panel assemblies block or otherwise reduce arc flash when removing such power modules and fan modules. 
     Redirection Plate 
     Referring to  FIGS. 17 and 18 , an equipment rack is generally indicated at  200 . A back of the equipment rack includes rear covers, each indicated at  202   a ,  202   b ,  202   c ,  202   d , which can be touch compliant. The rear covers  202   a - 202   d  are provided to prevent access into the equipment rack  200 . In one embodiment, the rear covers  202   a - 202   d  can be perforated or fabricated from mesh material to allow airflow through the equipment rack  200 . As described, arc flash incidents can occur when removing power modules from the equipment rack. The flapper valves described herein are provided to assist in protecting operators located at the front of the equipment rack  200 . To assist in protecting operators or personnel located at the back of the equipment rack  200 , a redirection plate generally indicated at  204  is mounted on the back of the equipment rack.  FIG. 17  illustrates the installed redirection plate  204  and  FIG. 18  illustrates the redirection plate being presented to the equipment rack  200  prior to installation. The redirection plate  204  is configured to direct arc flash upwardly and downwardly, as indicated by arrows  206 ,  208 . In some embodiments, the redirection plate  204  is configured to direct arc flash along a plane of the redirection plate.  FIGS. 19A and 19B  illustrate the front and back of an exemplary equipment rack, generally indicated at  190 , respectively. 
     In one embodiment, the redirection plate  204  is rectangular in construction and configured to cover rear covers  202   a ,  202   b ,  202   c , which for the equipment rack  200  shown is where arc flash incidents can occur. It should be understood that the rear covers can be configured to cover all or any part of the back of the equipment rack. As shown, the redirection plate  204  can be configured with raised portions  210   a ,  210   b , which provide a gap or space between a portion of rear cover  202   a  and rear covers  202   b ,  202   c  when the redirection plate is secured to the equipment rack  200 . 
     The rear covers  202   a - 202   d  and the redirection plate  204  enable touch and arc compliance from two separate structures. Thus, the provision of the rear covers  202   a - 202   d  and the redirection plate  204  enables enhanced air output through the perforated or meshed rear covers  202   a - 202   b  without excessive blocking of airflow from the redirection plate  204 . The redirection plate  204  provides redirection of arc flash up/down (arrows  206 ,  208 ) to protect an operator from a direct blast that may arise in the event of an arc flash incident inside the upper half of the equipment rack  200 . The provision of the redirection plate  204  further provides an additional covering behind the rear covers  202   a - 202   d  having the air exhaust openings. Further, the redirection plate  204  covers only a limited part of the total ventilation openings provided by the rear covers  202   a - 202   d  where incident energy is higher than a threshold limit. For example, the rear cover  202   d  is not covered by the redirection plate  204  because energies are lower in that location. 
     Referring to  FIG. 20 , in one embodiment, the redirection plate  204  is mounted to a frame  212  of the equipment rack  200  by fasteners (not shown), which are secured to the frame by tapped openings, each indicated at  214 , provided in the frame. In one embodiment, the redirection plate  204  is fabricated from galvanized plain carbon steel. The redirection plate  204  can be sized and shaped to a particular configuration based on where arc flash is to be reduced. 
     Fan Shroud 
     Referring to  FIG. 21 , a portion of the front of the equipment rack  200  is shown. As shown, the equipment rack  200  includes several fan modules, each indicated at  220 . Although four fan modules  220  are shown, it should be understood that any number of fan modules can be provided at desired locations at the front of the equipment rack  200  to provide cooling inside the equipment rack. 
     Referring to  FIG. 22 , the front of the equipment rack  200  is shown with equipment removed to show a power terminal area  222  and backsides of the fan modules. 
     Referring to  FIG. 23 , an exemplary grille  224  of a fan module is shown. The fan shroud described herein is designed to replace the grille  224  shown in  FIG. 23 . 
     Referring to  FIG. 24 , a portion of the front of equipment rack  200  is shown. As shown, two fan modules  220  are mounted on the front of the equipment rack with the lowermost fan module being partially removed from the front of the equipment rack. 
     Referring to  FIG. 25 , the backsides of the fan modules  220  of the equipment rack  200  are shown. As shown, fan shrouds, each generally indicated at  230 , of an embodiment of the present disclosure are used to block access to the fan modules  220 . In the shown embodiment, two fan shrouds  230  are illustrated in open positions to allow airflow from the fan modules  220  to the interior of the equipment rack  200 . The lowermost fan shroud  230  is illustrated in a closed position to block airflow from the fan module  220  to the interior of the equipment rack  200  and to block arc flash for reaching the operator removing the fan module. When the fan module is removed, a spring-loaded shutting mechanism can be provided to block an arc flash incident. 
       FIG. 26A  illustrates the fan module  220  being removed from the equipment rack with the fan shroud  230  shown in the closed position to block airflow and to block arc flash.  FIG. 26B  illustrates the fan module  220  fully secured to the equipment rack with the fan shroud  230  in the open position to allow airflow from the fan module to the interior of the equipment rack. In one embodiment, the fan shroud  230  includes a base  232  having a shutter assembly including a shutter  234  and a linkage arm  236  connected to the shutter to move the shutter between a closed position ( FIG. 26A ) and an open position ( 26 B). The fan shroud  230  further includes a spring  236  to bias the linkage arm  236  and the shutter  234  to the closed position. 
     The fan shroud  230  further includes a sliding mechanism  240  hingedly coupled to the base by a pin  242  and coupled to the linkage arm  236 . The sliding mechanism  240  is operated mechanically when receiving the fan module  220 , with a portion of the fan module engaging a portion of the sliding mechanism at  244 . When the fan module  220  is removed or inserted into the fan shroud  230  ( FIG. 26A ), the portion of the fan module engages the portion of the sliding mechanism  240  at  244  to move the linkage arm  236  against the bias of the spring  238 . Once seated, the linkage mechanism  236  and the shutter  234  are moved to the open position. The fan module  220  can include a seating pin  246  that is received within a pin positioner  248  provided on the base  232  of the fan shroud  230 . The fan module  220  is inserted into the fan shroud  230  about a hinge point provided at  250 . 
       FIGS. 27A and 27B  illustrate aspects of the construction of the fan shroud, including the base, the shutter, the linkage arm, spring, and the sliding mechanism. 
       FIGS. 28A, 28B and 28C  illustrate the fan shroud in the open position. 
       FIG. 29  illustrates the base  232  of the fan shroud. As shown, in one embodiment, the base  232  includes a grille portion  252  that enables airflow through the base. 
       FIG. 30  are views of an exemplary fan module. 
     Flap Valve with Torsion Bar 
     With arc flash assemblies, as described above, flap valves can be employed to contain energy from arc flash incidences. The arc flash assembly can include several parts to bias the flap (or flaps) in an operable position, which potentially can add to the cost of the arc flash flap assembly. As described above, the flaps can employ coil springs, which can be difficult to install and requires an appreciable amount of space to operate. 
     Referring to  FIGS. 31-38 , a flap valve assembly of another embodiment of the present disclosure is generally indicated at  310 . As shown, the flap valve assembly includes a valve panel body  312  that is secured to frame members  314 ,  316  by a torsion bar, which is generally indicated at  320 . It should be observed that embodiments of the present disclosure are directed to the provision of the torsion bar  320  that is configured to bias the valve panel body  312  and uses fewer, less expensive parts, is easier to install, and requires less room than coil spring assemblies. 
     As shown in  FIGS. 31 and 32 , the valve panel body  312  is hingedly secured to the frame members  314 ,  316  of a rack enclosure by the torsion bar  320 , which is provided to bias the valve panel body in an operable (vertical) position. In some embodiments, the torsion bar  320  can be fabricated from raw material that can be 3-10 millimeters (mm) diameter straight spring steel, which is cut to a required length and manipulated (tooling/compression/frustrating) to form a square section at one end and bent section at another end. 
     Referring to  FIGS. 33A-33C , the torsion bar  320  includes an elongate rod  322  having a square end section  324  at one end of the torsion bar ( FIG. 33B ) and a bent section  326  for clamping the torsion bar at the other end of the torsion bar in a fixed or secured condition with respect to the frame member, e.g., frame member  316 . 
     Referring to  FIGS. 34A-34C , the square end section  324  of the torsion bar  320  is sized to enter a square-shaped opening  328  formed in a portion  330  of the valve panel body  312  to ensure that the valve panel body rotates when the torsion rod is rotated. As shown in  FIG. 34B , the portion  330  extends perpendicularly from the valve panel body  312  and can be formed by bending the valve panel body. The free end of the square end section  324  extends through a circular opening  332  provided in the frame member  314 , with the circular opening being aligned with the square-shaped opening  328 . Accordingly, the square end section  324  is provided to drive the movement or rotation of the valve panel body  312 . The torque or drive force can be calculated by the torsion length of the rod  322  of the torsion bar  320  with a spring specification. As shown in  FIG. 34C , the bent section  326  is sized to enter a circular opening  334  formed in a portion  336  of the valve panel body  312  that is opposite to portion  330 , with the portions generally mirroring one another. The free end of the bent section  326  of the torsion bar  320  extends through a circular opening  338  provided in frame member  316 , with the circular openings being aligned with one another. The torsion bar  320  can rotate freely among the openings  332 ,  338  provided on the frame members  314 ,  316 , respectively, of the rack frame. 
       FIGS. 35A and 35B  illustrate the square-shaped opening  328  for tight tolerance with the square end section  324  of the torsion bar  320  to enable the torsion bar to drive the rotation of the valve panel body  312 . The square-shaped opening  328  is aligned with the circular opening  332  of the frame member  314  for free rotation of the torsion bar  320  and the valve panel body  312  with respect to the frame member. 
       FIGS. 36A and 36B  illustrate the circular opening  334  of the portion  336  of the valve panel body  312  positioned proximate to the circular opening of the frame member  316 , with the openings aligned with one another. This structure facilitates the rotation of the torsion bar  320  and the valve panel body  312 . Referring additional to  FIG. 37 , the frame member  316  includes a feature  340  that is provided to clamp or secure the free end of the bent section  326  of the torsion bar  320 . As shown, the free end of the bent section  326  of the torsion bar  320  is covered by the feature  340  and prevents the upward movement of the free end of the bent section of the torsion bar. 
       FIG. 38  illustrates the flap valve assembly in a fully assembled condition. During assembly, the bent section  326  of the torsion bar  320  is inserted into the opening  334  of the portion  336  of the valve panel body  312  and the opening  338  of the frame member  316 . The other end of the torsion bar  320  having the square end section  324  is inserted into the square-shaped opening  328  of the portion  330  of the valve panel body  312  and the opening  332  of the frame member  314 . The bent section  326  of the torsion bar  320  can be rotated with respect to the frame member  316  so that the free end of the bent section is captured by the feature  340 . 
     Thus, it is observed that the L-shaped torsion bar  320  is configured to maintain the valve panel body  312  in a closed position when no force is applied to the valve panel body. The valve panel body  312 , when closed, prevents or limits energy from arc flash in a UPS power module housing to protect an operator installing a power module or device. As the valve panel body  312  rotates (to an open position), the torsion bar  320  exerts a force on the valve panel body to return the valve panel body to a normal (closed) position. 
     Thus, it should be observed that the systems and methods disclosed herein, including the flapper valves, the redirection plate, and the fan shroud are designed to operate and reduce arc flash incident energy without human interaction. 
     In some embodiments, a mechanism that separates touch and arc compliance is provided. 
     In some embodiments, airflow throughput through the meshed hole pattern is achieved without undue restriction. 
     In some embodiments, touch compliance is provided by means of non-moving elements (no failing elements). 
     In some embodiments, arc compliance is provided by means of a shutter mechanism of the fan shroud that is controlled by a spring element to rest in or move to normal closed position when a fan module is being moved, inserted or is absent. 
     In some embodiments, the same shutter mechanism of the same shroud is pushed open by a driver part that translates the position of the fan module into a movement of the shutter mechanism so that when the fan module is fully inserted, the shutter mechanism is forced open to promote airflow. At this point arc compliance is ensured by the fan module. 
     In some embodiments, the linkage arm and the spring of the fan shroud may be replaced by an electrically operated motor so that the shutter mechanism can be closed remotely from a controller, so that the shutter mechanism is closed before the fan module replacement and/or repair begins. 
     In some embodiments, the linkage arm and the spring of the fan shroud may be replaced by a turning knob, so that the mechanism can be closed before replacement of the fan module. 
     In some embodiments, a fan/shutter mechanism may be configured so that in the event of a blast (pressure surge), a structural weak point will allow the fan module to fly out of its hinge. When the fan module is out of its hinge, the lever can move so the sliding element is opened, so that the spring can pull the shutter mechanism to closed state and stop the accident. 
     In some embodiments, the shutter mechanism is designed so that the pressure surge will force the shutter mechanism to return to closed position without the fan flying out of its hinge. The structural weak point would then be built into the shutter mechanism or the piston element. 
     In some embodiments, the fan shroud can be designed to function by gravity to block airflow and using the fan module airflow and pressure to open it. 
     In some embodiments, the fan shroud can be designed so that instead a piece of material yielding in on the event of an arc, a spring would yield in a non-destructive mode. 
     As used herein, an open power source may be a power source that is touch compliant and/or touch safe, or the like. 
     Having thus described several aspects of at least one embodiment of this disclosure, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the disclosure. Accordingly, the foregoing description and drawings are by way of example only.