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This application claims priority to U.S. Provisional Patent Application Ser. No. 60/658,640 filed on Mar. 4, 2005 entitled, “Electric Control System for a Pressure Control Device in a Hazardous Area” incorporated herein by reference for all purposes. 

   BACKGROUND OF INVENTION 
   High pressure valves, or chokes, are often positioned at the wellhead to control flow. There are three main types of chokes: manual chokes, which require the user to be physically in the manifold and operate the choke by hand as the gas flows through; hydraulic chokes, which allow the user to operate the choke remotely from the drilling floor or doghouse; and electric chokes, which also allow the user to operate the choke remotely and are able to perform consistently in varying environmental conditions as well as add digital capabilities to the choke. 
   At locations where oil or gas wells are being drilled, a number of flammable gases may be present, including mixtures of oxygen, methane, ethane, propane, hydrogen sulfide and others. Similar potentially dangerous environmental conditions exist in locations in which petroleum products are being recovered, refined or processed. Standardized classifications for various types of hazardous locations have been adopted and assigned by regulatory agencies according to the nature and type of hazard that is generally present or that may occasionally be present. 
   Because electrical components, by their nature, may generate heat and sparks sufficient to ignite a flammable gas or other flammable mixture under even normal operating conditions, such components must be carefully selected and installed when used in an area that is classified as hazardous. More specifically, the components must exceed certain minimum standards as to such characteristics as power consumption, operating temperature, current and voltage requirements, and energy storage capabilities. These standards are also established by regulatory authorities and vary depending upon the particular hazardous environment. 
   Chokes positioned at the wellhead are often located in areas that are classified as hazardous. As such, the use of electric chokes may be limited to uses where they are not at the wellhead or in a hazardous area. It would be an improvement to have an electric choke that could be used at the wellhead or in other hazardous areas. 
   SUMMARY 
   In one aspect, the present invention relates to an apparatus for controlling a choke assembly, wherein the choke assembly includes a housing having an inlet and an outlet in fluid communication with a wellbore, a fixed plate located between the inlet and the outlet and having an orifice therethrough for communicating fluid from the inlet to the outlet, a choke plate rotatably retained against the fixed plate and having an orifice therethrough, wherein the choke plate is rotatable to adjust a size of an orifice resulting from the relative positions of the orifice through the choke plate and the orifice through the fixed plate and is further rotatable to close the resulting orifice to prevent fluid communication therethrough. The apparatus may include an air source, an air purge system in fluid communication with the air source, a remote operating panel receiving data from at least one remotely located wellbore sensor, a local operating panel in electronic communication with the remote operating panel, and an actuator coupled to the assembly to control pressure within the wellbore. The remote operating panel may include an airtight housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the housing, a plurality of operator controls for manually controlling operation of the pressure control assembly, and a display for visually displaying values of data received from the wellbore sensor. The local operating panel may include an airtight panel housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the panel housing, and a local operator controller having an operator interface for receiving operator instruction input into the local panel, and operable to receive operator instructions from the remote panel and transmit operator instructions. The actuator may include a motor in an explosion-proof housing coupled to the choke plate and operable to adjust the orifice through the choke plate, wherein the motor receives electronic communication of the operator instructions transmitted by the local operator controller, and a position indicator coupled to the choke plate for sensing the orifice opening and providing feedback of the choke plate position to the motor. 
   In another aspect, the present invention relates to an apparatus for a plurality of choke assemblies, wherein each choke assembly includes a housing having an inlet and an outlet in fluid communication with a wellbore, a fixed plate located between the inlet and the outlet and having an orifice therethrough for communicating fluid from the inlet to the outlet, a choke plate rotatably retained against the fixed plate and having an orifice therethrough, wherein the choke plate is rotatable to adjust a size of an orifice resulting from the relative positions of the orifice through the choke plate and the orifice through the fixed plate and is further rotatable to close the resulting orifice to prevent fluid communication therethrough. The apparatus may include an air source, an air purge system in fluid communication with the air source, a remote operating panel receiving data from at least one remotely located wellbore sensor, a local operating panel corresponding to each choke assembly being controlled, wherein each local operating panel is in electronic communication with the remote operating panel, and an actuator corresponding to each choke assembly and coupled thereto. The remote operating panel may include an airtight housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the housing, a toggle switch for selecting one of the choke assemblies to be controlled, a plurality of operator controls for manually controlling operation of the selected choke assembly, and a display for visually displaying values of data received from the wellbore sensor. Each local operating panel may include an airtight panel housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the panel housing, and a local operator controller having an operator interface for receiving operator instruction input into the local panel, and operable to receive operator instructions from the remote panel and transmit operator instructions. The actuator may include a motor in an explosion-proof housing coupled to the choke plate and operable to adjust the orifice through the choke plate, wherein the motor receives electronic communication of the operator instructions transmitted by the local operator controller, and a position indicator coupled to the choke plate for sensing the orifice opening and providing feedback of the choke plate position to the motor. 
   In yet another aspect, the present invention relates to an apparatus for controlling pressure in a wellbore including a choke assembly, wherein the choke assembly includes a housing having an inlet and an outlet in fluid communication with the wellbore, a fixed plate between the inlet and the outlet having an orifice therethrough for communicating fluid from the inlet to the outlet, a choke plate rotatably retained against the fixed plate and having an orifice therethrough, wherein the choke plate is rotatable to adjust a size of an orifice resulting from the relative positions of the orifice through the choke plate and the orifice through the fixed plate and is rotatable to close the resulting orifice to prevent fluid communication therethrough. The apparatus may also include an air source, an air purge system in fluid communication with the air source, a remote operating panel receiving data from at least one remotely located wellbore sensor, a local operating panel in electronic communication with the remote operating panel, and an actuator coupled to the assembly to control pressure within the wellbore. The remote operating panel may include an airtight housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the housing, a plurality of operator controls for manually controlling operation of the pressure control assembly, and a display for visually displaying values of data received from the wellbore sensor. The local operating panel may include an airtight panel housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the panel housing, and a local operator controller having an operator interface for receiving operator instruction input into the local panel, and operable to receive operator instructions from the remote panel and transmit operator instructions. The actuator may include a motor in an explosion-proof housing coupled to the choke plate and operable to adjust the orifice through the choke plate, wherein the motor receives electronic communication of the operator instructions transmitted by the local operator controller, and a position indicator coupled to the choke plate for sensing the orifice opening and providing feedback of the choke plate position to the motor. 
   Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic of a control system for automatic pressure control. 
       FIG. 2  is a front view of a remote actuator panel. 
       FIG. 3  is a side view of a remote actuator panel. 
       FIG. 4  is a front view of a local panel. 
       FIG. 5  is a top view of the actuator with a cutaway view of a proximity switch guard. 
       FIG. 6  is a side view of the actuator with a cutaway view of the hand wheel section. 
       FIG. 7  is an end view of the actuator with the hand wheel removed to show the belt drive. 
       FIG. 8  is a cross sectional side view of a choke assembly. 
       FIGS. 9A-C  depict choke plate positioning with respect to a fixed opening. 
       FIG. 10  is a cross sectional view of the position indicator. 
       FIG. 11  is a schematic of a control system for dual choke valve pressure control including a second pressure control device. 
   

   DETAILED DESCRIPTION 
   In one aspect, embodiments disclosed herein are directed to an apparatus for controlling a pressure control device. In another aspect, embodiments disclosed herein are directed to an apparatus for controlling a plurality of pressure control devices. In yet another aspect, embodiments disclosed herein are directed to an apparatus for controlling pressure of a fluid in a weilbore. In each embodiment disclosed, the apparatus meets the requirements of Class 1, Division 1 standards as established by the American Petroleum Institute (API) and published in the API “Recommended Practice for Classification of Locations for Electrical Installations at Petroleum Facilities,” API Recommended Practice 500 (RP500), First Edition, Jun. 1, 1991, specifically incorporated herein by this reference. 
   Referring to  FIG. 1 , an apparatus for controlling a pressure control device is shown generally as  100 . The terms “pressure control device,” “pressure control assembly,” and “choke assembly” are used herein, interchangeably, to refer to an apparatus that is used to regulate the pressure in a wellbore. 
   Referring to  FIG. 8 , the choke assembly  106  with which the apparatus  100  is to be used has a fluid inlet  108  and a fluid outlet  110 , which are typically oriented such that they are right angles. An actuator end  112  is located opposite the fluid outlet  110 . The fluid path between the fluid inlet  108  and the fluid outlet  110  is controlled by a rotatable choke plate  116  and a fixed plate  120 . As shown in  FIGS. 9A-C , in one embodiment, the rotatable choke plate  116  has a half-moon shaped aperture  118  through its surface and the fixed plate  120 , downstream from the choke plate  116  has a fixed aperture  122  through it. A fluid aperture  124  is defined when the choke plate aperture  118  and the fixed aperture  122  overlap to provide fluid communication through both apertures  118  and  122 , as may be seen in  FIGS. 9B and 9C . As the choke plate  116  is rotated relative to the fixed aperture  122  the size of the fluid aperture  124  varies. In this embodiment, the choke plate  116  is rotatable between a full closed position, shown in  FIG. 9A , and a full open position, shown in  FIG. 9C . In one embodiment, an actuator fork  114  coupled to the choke plate  116  is rotated to rotate the choke plate  116 . Pressure within the wellbore is controlled and adjusted by varying the fluid aperture  124  through the choke assembly  106 . 
   Referring, again, to  FIG. 1 , in one embodiment, the apparatus  100  includes a remote panel  130 , a local panel  150 , an actuator  170 , and at least one sensor  126 . In one embodiment, the remote panel  130  is located in a doghouse or on a drilling floor of a rig  103 . In one embodiment, the local panel  150  is located at a choke manifold  104 . In one embodiment, the local panel is located within 30 feet of the actuator  170 . The actuator  170  is coupled to the actuating end  112  of a choke assembly  106 . One or more sensors  126  are located within the wellbore  102  to measure predetermined parameters. 
   The remote panel  130  of the control system  100  is shown in  FIGS. 2 and 3 . In one embodiment, the remote panel  130  includes a housing  132  within which controls  134  are included. In one embodiment, controls  134  include a speed dial, an open/close lever, a contrast, and/or a stroke reset switch. In one embodiment, analog gauges  136  are included to provide information to the operator regarding relevant conditions in the wellbore  102 . A digital display  138  provides data from one or more choke assemblies  106  to the operator. In one embodiment, the digital display  138  also provides visual menus to the operator. In one embodiment, menus guide an operator through calibration of the actuator controls and choke  106  adjustments. Referring to  FIG. 3 , a plurality of electronic inputs  140  are included through housing  132  to provide input of electronic data from one or more sensor communication cables  128  connecting one or more sensors  126  to the remote panel  130 . A panel communication cable  142  also connects the local panel  150  to the remote panel  130  electronically. 
   Referring again to  FIG. 1 , an air purge system  144  ensures that the remote panel  130  is safe for operation in an area that is classified as hazardous. An air source  146  provides air to the air purge system  144 . In one embodiment, the air source  146  for the air purge system  144  is from the rig. In another embodiment, the air source  146  is a separate air source dedicated to the apparatus  100 . The air purge system  144  is in fluid communication with the housing  132  of the remote panel  130 , which is airtight. The purge system  144  includes feed lines  148  and intake lines  149  to communicate air into and out of the housing  132 . The clean air provided to the remote panel  130  prevents any hazardous gases from entering the housing  132 . 
   The local panel  150  provides a secondary interface for an operator to control the choke assembly  106 . The local panel  150  has a local panel housing  158 . 
   Referring to  FIG. 4 , in one embodiment, the local panel  150  includes one or more basic controls  156 . In this embodiment, the controls  156  allow the operator to operate the choke  106  from the local panel  150 . In one embodiment, basic controls  156  include an open/close lever. In this embodiment, the open/close lever allows the operator to electronically actuate the choke  106  from the manifold  104 . In one embodiment, no speed control is provided on the local panel  150  and the lever operates differently from the open/close lever on the remote panel  130 . In this embodiment, as the lever on the local panel  150  is moved to either an open or closed mark, the actuator  170  begins to rotate at a percentage of its maximum speed. The actuator rotation speed accelerates to full speed within a predetermined time allowing the operator to make fine tuned movements in short bursts and to also fully open/close the valve quickly. In another embodiment, a speed controller is provided on the local panel  150 . 
   In one embodiment, an electronic input  160  is included through the side of housing  158  to provide electronic data along a sensor communication cable  128  to the local panel  150  from a sensor  126  in the wellbore  102 . In one embodiment, a plurality of electronic inputs  160  are included through the side of housing  158  to provide electronic data to the local panel  150  from a plurality of sensors  126  in the wellbore  102 . In one embodiment, an electronic interface  160  is also included for the panel communication cable  142  between the local panel  150  and the remote panel  130 . 
   The air purge system  144  ensures that the local panel  150  is safe for operation in an area that is classified as hazardous. The purge system includes feed lines  148  and intake lines  149  to communicate air into and out of the local panel  150  through an air feed opening  162  and air discharge  164 , respectively, in local housing  158 . Local housing  158  is airtight to prevent the entry of hazardous gases. 
   In one embodiment, the local panel  150  includes an emergency stop button  152 . In this embodiment, actuation of the emergency stop button shuts off power to the actuator  170 , thereby providing a class A shutdown of the choke  106 . 
   In one embodiment, the local panel  150  includes a digital display  154 . In this embodiment, an operator can observe measurements taken by one or more sensors  126 . 
   The actuator  170  is shown in  FIGS. 5-7 . The actuator  170  is coupled to the choke assembly  106  and provides an interface between the remote panel  130  and/or the local panel  150  and the choke assembly  106 . In one embodiment, the actuator  170  includes an actuator housing  172 , a hand wheel  240 , a motor  212 , a position indicator  188 , and a belt drive  220 . In one embodiment, the actuator housing  172  includes an adapter  174 , an actuator guard  176 , a motor housing  178 , a motor guard  180 , and a belt guard  182  and belt guard lid  184 . 
   The motor  212  is housed within the motor housing  178 , which is coupled to the belt guard  182 . To ensure that the motor  212  is safe for use in a hazardous area, the motor housing  178  is explosion proof. Further, a junction box  214  is provided to receive the control communication cable  166  from the local panel  150  and the switch communication cable  196 . The junction box  214  is also explosion proof, with the control and switch communication cable inputs  218  being armored. The control communication cable  166  and switch communication cable  196  are also armored to ensure they are safe for use in a hazardous area. The junction box  214  is attached to the motor housing  178  and such that the power and sensor feedback are connected to the motor  212  within an enclosure formed by the junction box  214  and the motor housing  178 . The motor  212  is connected to the belt drive  220 . 
   Referring to  FIG. 7 , the belt guard  182  and the belt guard lid  184  form an enclosure within which the belt drive  220  is retained. In one embodiment, the belt drive  220  includes a first sprocket  222 , a second sprocket  230 , and a belt  238 . In this embodiment, the first sprocket  222  has a first diameter  224  and includes a first groove  226  around its side  228 . The second sprocket  230  has a second diameter  232  and includes a second groove  234  around its side  236 . The first sprocket  222  is spaced apart from the second sprocket  230  within the belt guard  182  such that the belt  238  is taut about opposing portions of the first and second sprockets  222  and  224  and rests within the respective grooves  226  and  234 . Output from the motor  212  interfaces with the first sprocket  222  of the belt drive  220  through corresponding holes in the motor housing  178  and the belt guard  182 . Rotation by the first sprocket  222  is transferred to the second sprocket  230  by the belt  238 . The first diameter  224  is less than the second diameter  232  resulting in more than one rotation of the first sprocket  222  being required to rotate the second sprocket  230  one full rotation. Factors used to determine the desired ratio between the first diameter  224  rotation and the second diameter  232  include the top motor speed, the speed at which it is desired that the choke plate  116  go from a full open position to a full closed position, the precision with which it is desired that the choke plate aperture  118  be positioned relative to the fixed aperture  122 , and the variability of the control of the speed of the motor  212 . 
   In one embodiment, an actuator fork  114  interfaces with the second sprocket  230 . In this embodiment, the actuator fork  114  extends through a second hole in the belt guard  182  and is coupled to the choke plate  116 . 
   In one embodiment, the hand wheel  240  provides manual control of the actuator fork  114  to rotate the choke plate  116  in the event of power loss or system failure. The hand wheel  240  is connected to a gear reducer (not shown) to increase the number of revolutions required to open and close the choke assembly  106 . After the local panel  150  has been disabled, the manual hand wheel  240  can be used to fully open and close the choke plate  116  in a predetermined number of revolutions. The position of the choke plate  116  can be determined by observing the position indicator  188 . 
   The position indicator  188  is housed by the adapter  174 , which is coupled to the actuator end  112  of the choke assembly  106 . In one embodiment, shown in  FIG. 10 , the position indicator  188  includes a proximity switch  190  and an indicator ring  198 . In this embodiment, the indicator ring  198  is cylindrical about a center axis  200  and has an indicator side  202 . The indicator ring  198  is rotationally retained within the adapter  174  through its center axis  200 . The indicator ring  198  is coupled to the choke plate  116 . Thus, rotation of the indicator ring  198  corresponds to rotation of the choke plate  116 . 
   In one embodiment, a magnet  204  is housed by the indicator ring  198 , flush within the indicator side  202 . In this embodiment, when the magnet  204  engages the proximity switch  190 , a homing response is recognized by the motor  212 . As the operator commands an open/close request to the motor  212  the motor  212  uses preprogrammed algorithms to interpret a homing response and turn the motor  212  a predetermined number of revolutions as required to open/close the choke plate  116 . 
   In one embodiment, the proximity switch  190  is coupled to the adapter  174  such that a sensor end  192  is less than a predetermined distance  210  from the indicator side  202 , but far enough from the indicator side  202  that the indicator ring  198  does not contact the sensor end  192  when rotating. The distance  210  between the indicator side  202  and the sensor end  192  is within the range in which the proximity switch  190  can sense the presence of the magnet  204 . Thus, as the indicator ring  198  is rotated, the proximity switch  190  detects the magnet  204 , which corresponds to a predetermined position of the choke plate  116 . 
   In one embodiment shown in  FIGS. 5-7 , the proximity switch  190  is surrounded by a proximity switch guard  186  affixed to the adapter  174 . The proximity switch guard  186  protects the proximity switch  190  from becoming dislodged or moved from position. 
   The proximity switch  190  has a connector end  194  to which a switch communication cable  196  is attached. In one embodiment, the switch communication cable  196  connects to the motor  212  through an open end of the proximity switch guard  186  to provide feed back to the motor  212  of whether the magnet  204  is in front of the sensor end  192  of the proximity switch  190 . When the magnet  204  is detected by the proximity switch  190  a predetermined quantity of times corresponding to a desired choke plate  116  position, the feedback signal stops the motor  212 . 
   In one embodiment, the adapter  174  is of a tubular construction wherein an operator can view the indicator ring  198  through an open side of the adapter  174 . In one embodiment, marks on the indicator side  202  can be viewed and the alignment compared with stationary marks on the adapter  174  to determine the position of the choke plate  116 . When an operator uses the handwheel  240  to manually rotate the choke plate  116 , the position indicator  188  is used to indicate the position of the choke plate  116  relative to the fixed plate  120 . In one embodiment, the operator looks through the tubular adaptor  174 , between the choke assembly  106  and the actuator housing  172  and lining up the markings on the indicator ring  198  with the corresponding markings on the top of the adapter  174 . 
   One or more sensors  126  are located within the wellbore  102  to measure predetermined parameters. In one embodiment, sensor communication cables  128  connect the sensors  126  and the local panel  150 . In one embodiment, the remote actuator panel  130  includes preprogrammed algorithms operative to interpret measurement data and transmit responsive instruction to the motor  212  to open or close the choke plate  116 . In one embodiment, wherein the local panel  150  includes the emergency stop button  152 , instruction from the remote actuator panel  130  to the motor  212  is routed through the local panel  150  because the emergency stop cannot be bypassed. In one embodiment, the local panel  152  includes preprogrammed algorithms operative to interpret measurement data and transmit responsive instruction to the motor  212 . 
   The apparatus  100  provides the operator with three methods of control. The first method is electronically through the use of the remote panel  130  from a remote location such as the doghouse  103 . The second method allows the operator to control the choke assembly  106  electronically from the local panel  150  in the manifold shack  104 . The final method of control is by using the manual hand wheel  240  coupled to the back of the actuator  170 . 
   All of the electronic components are housed in air tight housings  132 ,  158  within which continual air purge is provided. The motor housing  178  is explosion proof and an explosion proof junction box  214  receives armored switch and control communication cables  196  and  166  directed to the motor  212 . Thus, the control system  100  is safe for use in a hazardous area pursuant to Class 1 Division 1 standards. 
   Referring to  FIG. 11 , in one embodiment, there is provided an apparatus for pressure control of a fluid system having at least one redundant, or back-up pressure control device, or choke assembly  106 ,  106 ′. This system, generally designated  300 , includes a remote panel  330 , a plurality of local panels  350 ,  350 ′, a plurality of actuators  370 ,  370 ′, and at least one sensor  326 . 
   The choke assemblies  106 ,  106 ′ each have a configuration such as that previously described. The single fluid path to the set of chokes  106 ,  106 ′ divides to provide an individual fluid path to each choke assembly  106 ,  106 ′. A valve may be present to direct flow into one of the individual fluid paths. 
   In this embodiment, the remote panel  330  includes a choke selection switch  310  on the panel. In one embodiment, the switch  310  is toggled between two or more detent locations corresponding to the two or more choke assemblies  106 ,  106 ′. In one embodiment, the digital display  338  provides data from a selected choke assembly  106  or  106 ′. In another embodiment, the digital display provides data from both choke assemblies  106 ,  106 ′ simultaneously. A panel communication cable  342  splits into corresponding segments  342 ′,  342 ″, etc. to provide electronic communication between the remote panel  330  and each local panel  350 ,  350 ′. In one embodiment, a molded junction box  345  is present at the intersection of the communication cables. 
   To ensure that the remote panel  330  is safe for operation in an area that is classified as hazardous, the housing  332  is air-tight and the air purge system  344  provides clean air into the housing  332 . The air purge system  344  also provides air circulation through each local panel  350 ,  350 ′, etc. 
   The local panels  350 ,  350 ′, located at the choke manifold  104 , provide the secondary interface for the operator to control the chokes  106 ,  106 ′. In one embodiment, controls  356  and displays  354  are present. In one embodiment, an emergency stop button  352 ,  352 ′ is located on each local panel  350 ,  350 ′. Each communication cable segment  342 ′,  342 ″ is connected to the corresponding local panel  350 ,  350 ′. 
   An actuator  370 ,  370 ′ is attached to the actuator end  112 ,  112 ′ of a corresponding choke assembly  106 ,  106 ′. In one embodiment, each actuator  370 ,  370 ′ includes a manual hand wheel  440 ,  440 ′, providing manual control of each choke assembly  106 ,  106 ′. The local panels  350 ,  350 ′ provide electronic control of the corresponding choke assembly  106 ,  106 ′. The remote panel  330 , provides remote electronic control of each choke assembly  106 ,  106 ′ independently by selecting the appropriate choke  106 ,  106 ′ with the choke selection switch  310 . 
   It will be understood by those of skill in the art that any number of choke assemblies  106 ,  106 ′ may be controlled with the control system  300  described. An actuator  370 ,  370 ′ is to be operatively attached to the actuator end of each choke  106 ,  106 ′ to be controlled. A local panel  350 ,  350 ′ electronically communicates with each actuator  370 ,  370 ′. Only one remote panel  330  is required, wherein a choke selection switch  310  is used to select control of any one of the choke assemblies  106 ,  106 ′. 
   In one aspect, the present invention generally relates to a control system for a pressure control device, or choke assembly, which can be used in a hazardous area and meets standards established by the American Petroleum Institute (API). The pressure control device, or choke, may be used in conjunction with a BOP (Blow Out Preventer) to allow safe evacuation of high-pressure gas/fluids from the well bore during a well control situation (kick). This is accomplished by varying the opening size of the choke valve through which the fluid/gas is flowing to increase/decrease flow in order to maintain a stable drill pipe or casing pressure, depending on the situation. 
   While the claimed subject matter has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the claimed subject matter as disclosed herein. Accordingly, the scope of the claimed subject matter should be limited only by the attached claims.

Summary:
An apparatus operable is a hazardous area for controlling a choke assembly includes an air source, an air purge system in fluid communication with the air source, a remote operating panel receiving data from at least one remotely located wellbore sensor, a local operating panel in electronic communication with the remote operating panel, and an actuator coupled to the assembly to control pressure within the wellbore. The remote operating panel includes an airtight housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the housing, a plurality of operator controls for manually controlling operation of the pressure control assembly, and a display for visually displaying values of data received from the wellbore sensor. The local operating panel includes an airtight panel housing in fluid communication with the air purge system, wherein air from the air purge system is circulated through the panel housing, and a local operator controller having an operator interface for receiving operator instruction input into the local panel, and operable to receive operator instructions from the remote panel and transmit operator instructions. The actuator includes a motor in an explosion-proof housing coupled to the choke plate and operable to adjust the orifice through the choke plate, wherein the motor receives electronic communication of the operator instructions transmitted by the local operator controller, and a position indicator coupled to the choke plate for sensing the orifice opening and providing feedback of the choke plate position to the motor.