Abstract:
A system and method for testing a valve actuator is provided, where an electrical motor is operatively connected to the valve actuator operatively connected to the valve. The system can include a main motor driver connecting the electrical motor to a primary power source, a first sensor to monitor the primary power source, a second sensor to monitor the flow of current to the electrical motor, a third sensor to monitor the angular rotation of the valve, and an emergency shut down (“ESD”) controller to operate the main motor driver in the event of an alarm condition to actuate the valve to a fail-safe position. The method includes the steps of providing the system, actuating the valve, monitoring the rotation of the valve and generating an alarm if the valve does not rotate in response to the step to actuate it.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure is related to the field of electric valve actuators, particular those used for surface and subsurface safety valves in oil and gas operations and more so to electrically-actuated valves used in a system as a Emergency Shut Down fail safe feature, in particular, systems and methods for testing the valve actuators. 
       BACKGROUND 
       [0002]    An electric Emergency Shut-Down (“ESD”) valve actuator is relied upon to actuate a valve to a fail-safe position in the event of a system control failure. An example of such a system failure would be when a separator floods on an oil or gas well. When the master control system detects such a control failure, it can actuate the ESD to the fail-safe position stopping the flow of incoming oil or gas. As a critical element in a safety system, it is important that the ESD valve works correctly in all situations, even if abnormal. There are four abnormal major failure modes in a typical system protected with an electrical ESD valve. The first, when the main power fails, can be solved with either a mechanical or battery-based backup energy storage system that has enough energy to actuate the valve when this failure occurs. The other three failure modes occur when the ESD controller, the backup energy source or the master controller fails. If any of these three items cease to function, the fail-safe feature will compromised and catastrophic failure can occur. In systems where this failure cannot be tolerated, it is important to minimize the risk of any of these three failure modes occurring. 
         [0003]    It is, therefore, desirable to provide a system and method that can minimize these risks. 
       SUMMARY 
       [0004]    A system and method for testing a valve actuator is provided. In some embodiments, the system can comprise an electrical valve actuator that can test itself automatically for common failures and detect when the system controller that normally actuates the valve fails. This can be useful when electrically actuated valves are used in Emergency Shut Down (“ESD”) systems, where system failure cannot be tolerated and risk reduction is necessary. In some embodiments, an electrical ESD controller with four safety mechanisms can be provided that can be used in whole or in part to lower such risk depending on the situation. 
         [0005]    In some embodiments, ESD failure detection can be provided by an ESD controller periodically testing the ESD valve to ensure it can actuate. The detection can be done by measuring the angular position of the valve and/or by monitoring the current draw by the electric motor that actuates the valve. If failure is detected, a alarm condition can be sent to a master controller. 
         [0006]    In some embodiments, the ESD backup energy supply can be tested periodically to verify that it has enough energy to actuate the valve if the main power fails. Like a valve failure, the system master controller can be informed of the alarm condition upon detection of a malfunctioning energy storage device. 
         [0007]    In some embodiments, the ESD controller can be protected by an external watchdog circuit that can detect a failure of the ESD controller. If not reset by the ESD controller periodically to indicate that the ESD controller is operating, the external watchdog circuit can be capable of separately actuating the valve to the fail-safe position. 
         [0008]    In some embodiments, the ESD controller can further comprise a separate master controller watchdog that can be reset by the master controller. If the master controller ceases to function, the ESD controller can actuate the valve to the fail-safe position. 
         [0009]    Broadly stated, in some embodiments, a system is provided for actuating a valve comprising an electrical motor operatively connected to a valve actuator operatively connected to the valve, the system comprising: a main motor driver operatively connecting the electrical motor to a primary power source, the main motor driver configured to control the flow of current from the primary power source to the electrical motor; a first sensor configured to monitor the voltage of the primary power source; a second sensor configured to monitor the flow of current from the main motor driver to the electrical motor; a third sensor configured to monitor the angular rotation of the valve; and an emergency shut down (“ESD”) controller operatively connected to the main motor driver, the first sensor, the second sensor and the third sensor, the ESD controller configured to operate the main motor driver in the event of an alarm condition to actuate the valve to a fail-safe position. 
         [0010]    Broadly stated, in some embodiments, a method is provided for testing a valve actuator operatively connected to a valve, the valve actuator comprising an electrical motor operatively connected thereto, the method comprising the steps of: providing a system comprising: a main motor driver operatively connecting the electrical motor to a primary power source, the main motor driver configured to control the flow of current from the primary power source to the electrical motor, a first sensor configured to monitor the voltage of the primary power source, a second sensor configured to monitor the flow of current from the main motor driver to the electrical motor, a third sensor configured to monitor the angular rotation of the valve, and an emergency shut down (“ESD”) controller operatively connected to the main motor driver, the first sensor, the second sensor and the third sensor, the ESD controller configured to operate the main motor driver in the event of an alarm condition to actuate the valve to a fail-safe position; actuating the valve; monitoring the angular rotation of the valve; and generating an alarm if the valve does not rotate in response to the step to actuate the valve. 
         [0011]    Broadly stated, in some embodiments, a system is provided for testing a valve actuator operatively connected to a valve, the valve actuator comprising an electrical motor operatively connected thereto, the system comprising: first means for controlling the flow of current from a primary power source to the electrical motor; means for monitoring the voltage of the primary power source; means for monitoring the flow of current from the primary power source through the first controlling means to the electrical motor; means for monitoring the angular rotation of the valve; means for actuating the valve to a fail-safe position in the event of an alarm condition; and means for generating an alarm in the event that the valve cannot be actuated to the fail-safe position. 
         [0012]    Broadly stated, in some embodiments, a method is provided for testing a backup power source operatively connected to a valve actuator, the valve actuator operatively connected to a valve, the valve actuator comprising an electrical motor operatively connected thereto, the method comprising the steps of: providing a system comprising: a main motor driver operatively connecting the electrical motor to a primary power source, the main motor driver configured to control the flow of current from the primary power source to the electrical motor, a first sensor configured to monitor the voltage of the primary power source, a second sensor configured to monitor the flow of current from the main motor driver to the electrical motor, a third sensor configured to monitor the angular rotation of the valve, and an emergency shut down (“ESD”) controller operatively connected to the main motor driver, the first sensor, the second sensor and the third sensor, the ESD controller configured to operate the main motor driver in the event of an alarm condition to actuate the valve to a fail-safe position; disconnecting the primary power source; actuating the valve with the backup power source; monitoring the angular rotation of the valve; and generating an alarm if the valve does not rotate in response to the step to actuate the valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a block diagram depicting a system for testing and actuating a valve. 
           [0014]      FIG. 2  is a flowchart depicting the operation of an emergency shutdown controller. 
           [0015]      FIG. 3  is a flowchart depicting the operation of an emergency shutdown watchdog. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0016]    Referring to  FIG. 1 , a block diagram of a system for testing and actuating a valve is shown. In normal operation, ESD controller  1  can open and close valve  5  via electric motor  4 . When master controller  11  receives information from sensors  11   b  such that valve  5  needs to be closed, master controller  11  can send a signal via communication path  11   a  to ESD controller  1 . Upon receiving a valid command from master controller  11 , ESD controller  1  can transmit a signal via signal path  2   a  to main motor driver  2  to supply power to electric motor  4  to actuate the valve  5  via valve actuator  4   a.    
         [0017]    In order to verify that valve  5  can be actuated in the event of a emergency, valve  5  can be periodically tested for actuation failure. In order to determine if valve  5  can be actuated, position sensor  6  can be used to send a signal corresponding to the angular position of valve  5  via signal path  6   a  to ESD controller  1 . If valve  5  has failed to actuate, or if valve position sensor  6  itself has failed, an alarm condition can be sent from ESD controller  1  to master controller  11  via signal path  11   a.  What actually failed depends on the feedback signal received from valve position sensor  6  and motor current sensor  2   b  via signal path  2   c.  If valve  5  cannot mechanically turn, and there is a high current measured by current sensor  2   b,  a locked rotor condition alarm can be generated. If current sensor  2   b  senses that the current flowing to motor  4  is too low, this can indicate either a failure of electric motor  4  or of main motor driver  2 . In both conditions, an alarm can also be generated. In addition, backup motor driver  3  can be activated to attempt to actuate valve  5  via backup motor driver  3  as a backup to main motor driver  2 . In this situation, current sensor  3   b  can monitor the current flowing to motor  4  and send a feedback signal to ESD controller  1  via signal path  3   c.    
         [0018]    To verify that the mechanical or electrical back up power supply  7  has enough energy to actuate valve  5 , a test can be carried out wherein switch  8  can be opened to disconnect the main power supply. In some embodiments, backup power supply  7  can comprise a mechanical backup power source (not shown) such as a spring-operated or functionally equivalent biasing mechanism as well known to those skilled in the art that can operate valve actuator  4   a.  In other embodiments, the mechanical backup power source can further comprise a reset mechanism that can reset the spring or biasing mechanism to an “armed” position wherein the spring or biasing mechanism is set to operate valve actuator  4   a  again. 
         [0019]    ESD controller  1  can monitor valve  5  if it has actuated from the signal received from sensor  6 . If the test fails, then an alarm condition can be sent from ESD controller  1  to the main controller  11  via  11   a.  If backup power source  7  comprises an electric backup power supply, testing can be done by opening switch  8  to disconnect main power supply  9 . Then, ESD controller  1  can either use a built in load resistor to test the current flow from backup power source  7 , or activate main motor driver  2  via communication path  2   a  to provide an electrical load to backup power source  7 . By monitoring the current flow with current sensor  2   b  and the voltage of backup power source  7  with voltage sensor  7   a  operatively connected to ESD controller  1  via signal path  7   b,  ESD controller  1  can determine whether backup power source  7  can operate when needed (ie, is “good”) or whether backup power source  7  is failing or has failed. 
         [0020]    To detect when ESD controller  1  itself has failed, the system can comprise, in some embodiments, external ESD controller watchdog  10 . In other embodiments, ESD controller watchdog  10  can be embodied, embedded or integrated functionally or physically in ESD controller  1 . ESD controller  1  can communicate with ESD controller watchdog  10  via signal path  1   a  to determine whether ESD controller  1  is functioning correctly. When ESD controller watchdog  10  no longer received communication from ESD controller  1  on signal path  1   a,  ESD controller watchdog  10  can conclude that ESD controller  1  has failed. In this event, ESD controller watchdog  10  can independently actuate valve  5  via signals sent along signal path  10   a  to main motor driver  2  to operate valve  5  to the fail-safe position. In the event that main motor driver  2  has failed or is inoperable, ESD watchdog can independently actuate valve  5  via signals sent along signal path  10   b  to backup motor driver  3  to operate valve  5  to the fail-safe position. 
         [0021]    In normal operation, a periodic signal can be transmitted to ESD controller  1  from master controller  11  to master controller watchdog  1   b  via signal path  11   a  to indicate that main system controller  11  is operating correctly. In the event of a failure of the periodic signal from master controller  11  to master controller watchdog  1   b  disposed within ESD controller  1 , which can indicate a failure of master controller  11 , ESD controller  1  can actuate valve  5  to the fail-safe position via a signal sent along signal path  2   a  to main motor driver  2  to supply current to motor  4  to actuate valve  5 . 
         [0022]    In some embodiments, the system can detect when there is a failure of primary power supply  9 . Voltage sensor  9   a  can monitor the voltage of primary power source  9 . When the voltage of primary power source changes or drops, sensor  9   a  can send a signal to ESD controller  1  via signal path  9   b  to indicate an alarm condition. ESD controller  1  can then actuate valve  5  to the safe position. 
         [0023]    In some embodiments, each of ESD controller  1  and ESD controller watchdog  10  can comprise discrete electronic or electro-mechanical components, such as transistors, field-effect transistors (“FETS”), diodes, triacs, optocouplers, operational amplifiers, relays, solenoids, resistors, capacitors and inductors, and any other discrete or integrated electronic device or component as well known to those skilled in the art wherein ESD controller watchdog  10  can operate either of main motor driver  2  or backup motor driver  3  in response to a triggering event as discussed above. In other embodiments, either or both of ESD controller  1  and ESD controller watchdog  10  can comprise a microprocessor, a microcontroller, integrated logic circuits, timer circuits, programmable gate arrays, field-programmable gate arrays or application specific analogue devices as well known to those skilled in the art. In representative embodiments, ESD controller watchdog  10  can comprise a model ADM6316 series supervisory circuit as manufactured by Analog Devices, Inc. of Norwood, Mass., U.S.A. In further embodiments, ESD controller  1  can comprise any or all of the aforementioned electronic components and devices in combination, as well known to those skilled in the art. 
         [0024]    Referring to  FIG. 2 , a flowchart of process  200  that can be carried by ESD controller  1  in some embodiments is shown. Process  200  can begin at step  204  and then carry out step  208  where ESD controller  1  can query whether a standard communication has been received from master controller  11 . If “yes”, then ESD controller  1  can carry out any process as set out in the standard communication at step  212 . If “no”, then ESD controller  1  can determine whether master controller watchdog  1   b  has received communication from master controller  11  at step  216 . If “yes”, then master controller watchdog  1   b  can be reset at step  220  whereupon ESD controller  1  can proceed to step  232 . If “no”, then ESD controller  1  can determine whether master controller watchdog  1   b  has timed out at step  224 . If “yes”, then ESD controller  1  can proceed to actuate valve  5  to a safe position and generate an alarm at step  228 , and then proceed to step  232 . If “no”, ESD controller  1  can proceed to step  232 . 
         [0025]    At step  232 , ESD controller  1  can send a reset request to ESD controller watchdog  10  and then proceed to step  236 . At step  236 , ESD controller  1  can determine whether it is time to run a test procedure, such as testing the operation of valve  5  or testing backup power source  7 . If the answer to the query at step  236  is “yes”, then ESD controller  1  can carry out the testing procedure or operation at step  240 . At step  244 , a query can be made to determine if the testing procedure or operation passed. If “yes”, process  200  can proceed to step  252 . If “no”, ESD controller  1  can generate an alarm and optionally actuate valve  5  to a safe position at step  248  and then proceed to step  252 . If the answer to the query at step  236  is “no”, then process  200  can proceed to step  252 . 
         [0026]    At step  252 , ESD controller  1  can carry out other process measurement and control tasks, which can include measuring voltages and currents and detecting the angular position of valve  5  from the sensors disposed in the system. After step  252 , process  200  can proceed to step  256  where it can then loop back to step  204  and repeat itself. 
         [0027]    Referring to  FIG. 3 , a flowchart of process  300  that can be carried by ESD controller watchdog  10  in some embodiments is shown. Process  300  can begin at step  304  and then carry out step  308  where ESD controller watchdog  10  can query whether it has received communication from ESD controller  1  along signal path  1   a.  If “yes”, then ESD controller watchdog  10  can be reset at step  312 , and process  300  can then proceed to step  324 . If “no”, then a query can be made at step  316  to determine if ESD controller watchdog  10  has timed out. If “yes”, then ESD watchdog  10  can actuate valve  5  to a safe position at step  320 . If “no”, then process  300  can proceed to step  324 . At step  324 , ESD controller watchdog  10  can then carry out any remaining housekeeping tasks as programmed therein. After step  324 , process  300  can then proceed to step  328  where it can then loop back to step  304  and repeat itself. 
         [0028]    In some embodiments, either or both of master controller watchdog  1   b  and ESD controller watchdog  10  can comprise discrete active and passive electronic components or integrated analogue and/or digital electronic devices and components, or a combination thereof, as well known to those skilled in the art, wherein watchdogs  1   b  and  10  can be external or not integrated with ESD controller  1 . In other embodiments, either or both of master controller watchdog  1   b  and ESD controller watchdog  10  can be integrated or embedded in ESD controller  1 , either in terms of electronic components or embodied as “virtual components or circuits” wherein the functions of watchdogs  1   b  or  10  can be carried out by a microprocessor or microcontroller disposed in ESD controller  1  following a series of steps programmed in a computer-readable memory disposed thereon or therein, as well known to those skilled in the art. 
         [0029]    Although a few embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the invention is defined and limited only by the claims that follow.