Abstract:
A lock-out bracket secures the position of a shaft extending through a pneumatic actuator, the shaft having a first end and a second end, the first end being operative for controlling a valve, the second end being coupled to a limit switch mounted on a limit switch bracket mounted to the actuator. The lock-out bracket includes a substantially flat base plate and a substantially flat lock-out tab substantially perpendicular to the base plate, the base plate defining an opening configured for matingly fitting over, receiving, and engaging the second end of the shaft. The lock-out tab defines a first hole adapted for alignment with a corresponding second hole defined on the limit switch bracket for facilitating the insertion of a lock shackle through the first hole and the second hole to secure the lock-out bracket relative to the actuator and prevent movement of the shaft and valve coupled to the shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. Pat. No. 8,806,906, formerly co-pending patent application Ser. No. 13/622,265, filed on Sep. 18, 2012, and issued on Aug. 19, 2014, and claims the benefit of U.S. Provisional Application No. 61/631,202, filed Dec. 29, 2011, both of which applications are hereby incorporated herein by reference, in their entirety. 
    
    
     TECHNICAL FIELD 
     The invention relates generally to actuators adapted for controlling valves and, more particularly, to a system and method for locking actuators to prevent movement of a valve controlled by the actuator. 
     BACKGROUND 
     Process manufacturing companies, chemical companies, food industries, water treatment facilities, and the like are, on a daily basis, taking the safety of their employees more and more seriously and, accordingly, are continually looking for ways to improve their safety records by minimizing the number of injuries at their work place. Employee safety is further encouraged by the Occupational Safety and Health Administration (OSHA) which requires that companies insure that their employees have a safe working environment, and that companies develop policies and procedures for maintaining operating equipment. 
     In view of the foregoing, most manufacturing facilities have developed procedures referred to as “lock-out” and “tag-out” procedures for employees to implement whenever a piece of equipment needs to be isolated or brought down for maintenance. In most cases, such procedures require that valves and electric motors be locked, de-energized, or fixed so they are inoperable. Most valves have actuators mounted on them to allow computers and other programmable logic controllers (PLCs) to open and close such valves. There are, however, a number of shortcomings with such procedures. For example, some procedures require devices that are prohibitively expensive, or such devices failed to do what they were supposed to do, or they were simply too difficult and/or time-consuming to install or make work. Such devices, when not being used, also require storage space and some means of tracking the devices. 
     In other cases, rather than using devices to lock-out valves, the air supply to the respective actuators that control the valves is removed in an attempt to prevent the valves from opening during preventive maintenance or a major shutdown. A drawback with this method is that the valves controlled by actuators are valves, such as butterfly valves, which open or close with a turn of about 90°. When pressure builds up or is exerted against the valve seat of such valves; the valve will tend to open, if only slightly, but even if only slightly, fluid that leaks by such a valve could render a work area, such as the interior of a vessel, hazardous. 
     Accordingly, a continuing search has been directed to the development of a simpler and more secure way to lock-out and secure an actuator and valve so that the valve cannot leak fluid when closed, and thereby maintain safety for men working and/or repairing equipment. 
     SUMMARY 
     The present invention, accordingly, provides a lock-out bracket configured to secure the position of a shaft extending through an actuator, the shaft having a first end operative for controlling a valve, and a second end coupled to a limit switch mounted on a limit switch bracket mounted to the actuator. The lock-out bracket preferably includes a substantially flat base plate and a substantially flat lock-out tab substantially perpendicular to the base plate, the base plate defining an opening configured for matingly fitting over, receiving, and engaging the second end of the shaft. The lock-out tab defines a first hole adapted for alignment with a corresponding second hole defined on the limit switch bracket for facilitating the insertion of a lock shackle through the first hole and the second hole to secure the lock-out bracket relative to the actuator and prevent movement of the shaft and valve coupled to the shaft. 
     In a method for configuring an actuator to secure a closed position of a shaft extending through the actuator, the limit switch bracket and limit switch are removed from the actuator. A lock-out bracket is mounted onto the second end of the shaft, and the lock-out bracket includes a lock-out tab that defines a first hole. The limit switch bracket and limit switch are then mounted onto the actuator, and the limit switch is coupled to the second end of the shaft. The valve is then closed; and a second hole is formed in the limit switch bracket that aligns with the first hole of the lock-out tab. To secure the valve in a closed position, a shackle of a lock is extended and secured through the first hole and the second hole. 
     By using the lock-out bracket of the present invention, operations and/or maintenance personnel can secure a valve in a closed position so that, for example, maintenance personnel can work on or in vessels without concern about chemicals leaking into the vessel. 
     The present invention also allows for normal operation of an actuator without removal of the lock-out bracket. Once the lock-out bracket is installed, it can remain permanently installed for use whenever it is needed without interrupting normal operation of the actuator. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a conventional actuator and limit switch mounted on a pipe and coupled to a valve in the pipe; 
         FIG. 2  is a perspective view of a lock-out bracket embodying features of the present invention; 
         FIG. 3  is a plan view of the lock-out bracket of  FIG. 2  taken along the line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is an elevation view of the lock-out bracket of  FIG. 2  taken along the line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is a perspective view of a portion of the actuator with the limit switch mounted thereon taken along the line  5 - 5  of  FIG. 1 , and including placement of the lock-out bracket of  FIGS. 2-4  mounted thereon and for an open valve unsecured in accordance with principles of the present invention; 
         FIG. 6  is a perspective view of the actuator, limit switch, and lock-out bracket of  FIG. 5  showing the lock-out bracket of  FIGS. 2-4  mounted thereon for a closed valve unsecured in accordance with principles of the present invention; 
         FIG. 7  is a perspective view of the actuator, limit switch, and lock-out bracket of  FIG. 6  with the addition of a lock to secure the lock-out bracket and closed valve in accordance with principles of the present invention; 
         FIG. 8  is a flow chart exemplifying steps for configuring the actuator to secure a valve in a closed position, in accordance with principles of the present invention; 
         FIG. 9  is a flow chart exemplifying steps for securing a valve coupled to the actuator of  FIG. 8  in a closed position; and 
         FIG. 10  exemplifies a perspective view of a portion of an alternative embodiment of the invention utilized in connection with an actuator without a limit switch. 
     
    
    
     DETAILED DESCRIPTION 
     In the discussion of the FIGURES, the same reference numerals will be used throughout to refer to the same or similar components. In the interest of conciseness, details concerning various other components known to the art, such as actuators, limit switches, and the like necessary for the operation of valves, have not been shown or discussed in detail inasmuch as such details are not considered necessary to obtain a complete understanding of the present invention, and are considered to be within the skills of persons of ordinary skill in the relevant art. Additionally, as used herein, the term “substantially” is to be construed as a term of approximation. 
     Referring to  FIG. 1  of the drawings, the reference numeral  100  generally designates a system embodying features of the prior art. The system  100  includes an actuator  102  and a limit switch  103  mounted on the actuator via a limit switch bracket  105 , all of which are well known in the art. The actuator  102  is preferably a pneumatic actuator, and includes a shaft  104  extending through the actuator upwardly, as shown, and downwardly (not shown). The upward extension of the shaft  104  is preferably coupled to the limit switch  103  via a short rod  122  ( FIG. 5 ), and the downward extension of the shaft  104  is typically coupled to a process system valve  107  operable within a pipe  101 . The valve  107  is exemplified as a butterfly valve in a closed position, but could, by way of example but not limitation, be a ball valve or any valve operable for being opened or closed by being rotated through an angle of approximately 90° in one direction or another in a conventional manner well-known in the art. Operation of the actuator  102  is preferably automated via a computer, a programmable logic controller (PLC), or the like (not shown), coupled to the actuator to open and close the valve  107 , or to move or change the position of the valve  107 . 
       FIGS. 2-4  exemplify perspective, plan, and elevation views, respectively, of a lock-out bracket  106  embodying features of the present invention. The lock-out bracket  106  preferably comprises a flat base plate  110  that, as viewed in  FIGS. 2 and 4 , is generally horizontally oriented, and a flat lock-out tab  112  that is preferably perpendicular to the base plate and generally vertically oriented, as viewed in  FIGS. 2 and 4 . The base plate  110  and the lock-out tab  112  are preferably formed from a single plate bent at a crease  108 , but may be formed in alternative manners, such as two pieces of flat plate joined (e.g., welded) at the crease  108 . The lock-out bracket  106  is preferably fabricated from a stainless steel, such as 11 or 12 gauge 304 or 316 L stainless steel, though any material suitable for restraining movement of the shaft  104  may be used. 
     The base plate  110  of the lock-out bracket  106  defines a hole  114  sized (e.g., as a square, depicted) to matingly receive and fit over the shaft  104  (exemplified having a generally square cross-section) so as to securely engage the shaft. The hole  114  is preferably further configured so that the lock-out bracket  106  will be oriented as depicted in  FIG. 6  when the valve  107  is closed. The lock-out tab  112  of the lock-out bracket  106  defines a hole  116  sized and positioned to align with a corresponding hole  124  on the limit switch bracket  105 , discussed in further detail below with respect to  FIGS. 5-8 . The lock-out bracket  106  further preferably includes a first chamfer  118  on the base plate  110 , and a second chamfer  120  on the lock-out tab  112 , the two chamfers preferably being generally contiguous and sized for facilitating rotation of the lock-out bracket  106  within the confines of the limit switch bracket  105 . 
       FIG. 5  depicts the limit switch  103  mounted on the limit switch bracket  105  mounted on the actuator  102  for a valve  107  in an open position. As shown in  FIG. 5 , movement of the shaft  104 , and hence valve  107 , is not restrained by the lock-out bracket  106 , typical when the valve  107  operated by the actuator  102  is in an open position. 
       FIG. 6  depicts the shaft  104  rotated through an angle of 90° so that the lock-out bracket  106  is likewise rotated through an angle of 90° until the hole  116  of the lock-out bracket  106  is aligned with a hole  124  defined on the limit switch bracket  105 . This position of the bracket and shaft would be typical when the valve  107  operated by the actuator  102  is in a closed position. 
       FIG. 7  exemplifies how the lock-out bracket  106  is secured so that it is restrained from movement, and so that the valve  107  operated by the actuator  102  is maintained in a closed position. This is achieved by extending a shackle  132  of a lock  130 , such as a key lock or a combination lock, through the aligned holes  116  and  124 , thereby securing the alignment of the holes and restraining movement of the lock-out bracket  106 , shaft  104 , and thus valve  107  coupled to the downward portion of the shaft  104 . 
       FIG. 8  depicts a flowchart  800  which exemplifies steps of a method for configuring the limit switch bracket  105  and assembling the lock-out bracket  106  onto the actuator  102 . Accordingly, in step  802 , the limit switch bracket  105 , as well as the limit switch  103  secured to the limit switch bracket, are removed from the actuator  102 . 
     In step  804 , preferably with the valve  107  in an open position, the hole  114  ( FIGS. 2 and 3 ) of the lock-out bracket  106  is positioned to receive the shaft  104 , so that the lock-out bracket is positioned on the shaft  104  as shown in  FIG. 5 . The shaft  104  is then engaged with the lock-out bracket  106 , so that the shaft and lock-out bracket move together with the same degree of freedom or restraint, as the case may be. 
     In step  806 , the limit switch bracket  105  and limit switch  103  are re-installed onto the actuator  102 , as shown in  FIG. 5 . In step  808 , the valve  107  is closed, as shown in  FIG. 6 . In step  810 , a hole  124  is drilled in the limit switch bracket  105  that lines up with the hole  116  defined on the lock-out bracket  106 . The hole  124  may be formed in the limit switch bracket  105  in any conventional manner, such as by marking the location with a marker extending through the hole  116  to the limit switch bracket  105 , and a hole drilled where marked. The diameter of the holes  116  and  124  is preferably sized to allow the shackle  132  of the lock  130  to fit snugly therethrough. 
       FIG. 9  depicts a flowchart  900  which exemplifies steps of a method for restraining a closed valve  107  from movement. Accordingly, in step  902 , the actuator  102  is used to close the valve. In step  904 , with the holes  116  and  124  aligned, the shackle  132  of the lock  130  is passed through the holes  116  and  124  to thereby restrain movement of the lock-out bracket  106 , shaft  104 , and valve  107 . 
     In step  906 , a first part of two parts of a tag (not shown) is preferably secured to or proximate to the lock  130 . The first part of such tag preferably includes at least an identifying number and optionally the purpose for which the valve  107  is locked. A second part of each tag preferably includes the same identifying number as on the first part of the tag, as well as further identifying markings such as, by way of example but not limitation, the location of the tag, the valve  107  the lock is placed on, and the purpose for which the valve is locked-out. In step  908 , the second half of the tag, as well as the key to the lock (assuming the lock is a key lock) is preferably placed in a security box that is preferably locked, thereby preventing quick and easy access to the lock. 
       FIG. 10  exemplifies an alternative embodiment of the invention that may be utilized in connection with an actuator  102  configured without a limit switch bracket  105  (and hence without a limit switch) to which the lock-out bracket  106  may be secured. According to this embodiment, the lock-out bracket  106  is preferably sized large enough to extend across a bolt hole  102   a  in the actuator  102 . A hole  106   a  is formed in the lock-out bracket  106  for alignment with the hole  102   a  when the lock-out bracket  106  is positioned on the shaft  104  with the valve  107  in a closed position. The hole  106   a  is suitably-sized for snugly receiving a bolt  134  that will threadingly engage the hole  102   a . In operation, when the actuator  102  closes the valve  107 , the valve is secured in the closed position by passing the bolt  134  through the hole  106   a  and screwing it into the hole  102   a . Optionally, a tag may be attached to the hole  116  as described above. 
     By the use of the present invention, a valve may be secured in a closed position to thereby promote the safety of persons who may work on equipment in fluid communication with the valve. 
     It is understood that the present invention may take many forms and embodiments. Accordingly, several variations may be made in the foregoing without departing from the spirit or the scope of the invention. For example, the embodiment of  FIG. 10  could be used with a limit switch bracket and limit switch positioned on the actuator of  FIG. 1 , and/or integrated into the embodiment of  FIGS. 2-9 . 
     Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.