Patent Publication Number: US-2020284274-A1

Title: Self actuating ram actuator for well pressure control device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Continuation of International Application No. PCT/US2018/049279 filed on Aug. 31, 2018. Priority is claimed from U.S. Provisional Application No. 62/554,670 filed on Sep. 6, 2017. Both the foregoing applications are incorporated herein by reference in their entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     Not Applicable. 
     BACKGROUND 
     This disclosure relates generally to the field of drilling wells through subsurface formations. More specifically, the disclosure relates to apparatus for controlling release of fluids from such wellbores, such devices called blowout preventers (BOPs). 
     BOPs known in the art have one or more sets of opposed “rams” that are urged inwardly into a housing coupled to a wellhead in order to hydraulically close a wellbore under certain conditions or during certain wellbore construction operations. The housing may be sealingly coupled to a wellhead or casing flange at the top of the well. The rams, when urged inwardly, may either seal against a pipe string passing through the BOP and/or seal against each other when there is no pipe (or when the pipe is present but must be cut or “sheared.” Movement of the rams is performed by hydraulically operated actuators. 
     BOPs known in the art used in marine operations may be coupled to a wellhead at the bottom of a body of water such as a lake or the ocean. In such BOPs, electrical power may be supplied from a drilling unit above the water surface, which may be converted to hydraulic power by a motor operated pump proximate the BOP. There may also be hydraulic oil tanks having hydraulic fluid under pressure proximate the BOP in order to provide the necessary hydraulic pressure to close the rams in the event of failure of the hydraulic pump or drive motor. 
     A typical hydraulically actuated BOP is described in U.S. Pat. No. 6,554,247 issued to Berkenhof et al. 
     SUMMARY 
     A method for operating a ram in a well pressure control apparatus according to one aspect includes communicating a control signal to at least one of a rotary motor and a source of pressurized fluid to operate at least one of the motor and the source of pressurized fluid to operate a ram actuator. “Fluid” in the present context is used to mean liquid, gas and/or combinations thereof. A parameter related to position of the ram actuator is measured during operation of the actuator. Operation of the ram actuator is automatically stopped when the measured parameter indicates the ram actuator is fully extended or fully retracted. 
     Some embodiments further include determining a performance of the ram actuator by comparing, in a controller disposed proximate the ram actuator, the measured parameter related to the position of the ram actuator to values of the control signal. 
     Some embodiments further include communicating the measured parameter to a location away from the ram actuator. 
     In some embodiments, the location comprises at least one of a platform on the surface of a body of water, a ram manufacturing facility and a ram repair and maintenance facility. 
     In some embodiments, the control signal is generated automatically by a controller disposed proximate the ram actuator in response to measurements of pressure in a well. 
     In some embodiments, the control signal comprises variable operating rate with respect to time. 
     In some embodiments, the variable rate with respect to time is optimized for conditions in a well. 
     Some embodiments further include measuring fluid pressure in the well, temperature proximate the ram actuator and using the measured parameter related to position, the measured fluid pressure and the measured temperature to adjust at least one parameter of the control signal. 
     Some embodiments include at least one of: determining when to remove the ram actuator from service when any parameter used to determine the performance of the ram actuator crosses a selected threshold; and measuring a parameter related to particle concentration in at least one of the pressurized fluid and fluid in an atmospheric pressure chamber, and determining when to remove the ram actuator from service when the parameter related to particle concentration crosses a selected threshold. 
     Some embodiments further include: removing the ram actuator from service; transporting the ram actuator to a facility for at least one of repair and remanufacturing; and returning the ram actuator to service after the at least one or repair and remanufacturing. 
     Some embodiments further include: generating an identification signal in the controller to enable remote identification of the ram actuator; and tracking movement of the ram actuator during each of a plurality of actions performed beginning with removal of the ram actuator from service and returning the ram actuator to service. 
     Some embodiments further include transmitting directly to at least one user at least the measured parameter related to position. 
     In some embodiments, the control signal is communicated from a mobile wirelessly connected device to the ram actuator by at least one of direct communication and Internet connected communication. 
     A pressure control apparatus according to another aspect comprises a housing having a through bore. A ram and actuator are affixed to the housing. A closure element is movable by the actuator to open and close the through bore. A controller is in signal communication with the actuator and is operable to cause movement of the actuator in response to a control signal detected by the controller. At least one position sensor is coupled to at least one of the actuator and the ram to measure a parameter related to position of the at least one of the actuator and the ram. A signal output of the position sensor is in communication with the controller. The controller is operable to automatically stop operation of the actuator in response to signals from the at least one position sensor indicative of the ram being fully closed and/or fully open. The controller is operable to start operation of the actuator in response to a control signal. 
     Some embodiments further comprise a communication device in signal communication with the controller, the communication device operable to transmit a signal indicative of output of the at least one position sensor and to receive the control signal. 
     In some embodiments, the actuator comprises a motor rotatably coupled to an actuator rod. 
     In some embodiments, the motor comprises an electric motor. 
     In some embodiments, the actuator comprises a piston disposed in a cylinder operatively coupled to a source of fluid pressure. 
     In some embodiments, the at least one position sensor comprises a pressure sensor. 
     Some embodiments further comprise a sensor responsive to solid particles present in fluid discharged by the source of fluid pressure. 
     Other aspects and possible advantages will be apparent from the description and claims that follow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example embodiment of marine drilling a well from a floating drilling platform wherein a blowout preventer is installed on the wellhead. 
         FIG. 2  shows a side view of an example embodiment of a well pressure control apparatus according to the present disclosure. 
         FIG. 3  shows a top view of the example embodiment of an apparatus as in  FIG. 1 . 
         FIGS. 4A and 4B  show an example embodiment of a self-actuating ram actuator. 
         FIG. 5  shows an example embodiment of the ram actuator of  FIGS. 4A and 4B  communicating performance information to a manufacturer or other pressure control apparatus service entity. 
         FIG. 6  shows an example apparatus as in  FIGS. 4A and 4B  being operated externally. 
         FIG. 7  shows example embodiments of ram operating strategies enabled by the apparatus shown in  FIGS. 4A and 4B . 
         FIG. 8  shows a flow chart of an example embodiment of the apparatus shown in  FIGS. 4A and 4B  wherein control parameters to operate the ram are updated based on measured response of the ram actuation to earlier values of control parameters. 
         FIG. 9  shows a flow chart of an automated maintenance and replacement method enabled by the apparatus shown in  FIGS. 4A, 4B and 5 . 
         FIGS. 10 and 11  show example embodiments of a subsea BOP stack and surface BOP stack, respectively, using ram actuators as shown in  FIGS. 4A and 4B / 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is provided to show an example embodiment of well drilling that may use well pressure control apparatus according to various aspects of the present disclosure. The example embodiment of drilling shown in  FIG. 1  is beneath a body of water, however an apparatus and method according to the present disclosure is not limited to marine drilling and the scope of the present disclosure is accordingly not so limited.  FIG. 1  shows a drilling vessel  110  floating on a body of water  113  and equipped with an apparatus according to the present disclosure. A wellhead  115  is positioned proximate the sea floor  117  which defines the upper surface or “mudline” of sub-bottom formations  118 . A drill string  119  and associated drill bit  120  are suspended from a derrick  121  mounted on the drilling vessel  110  and which extends to the bottom of a wellbore  122 . A length of structural casing  127  may extend from the wellhead  115  to a selected depth into the sub-bottom formations  118  above the wellbore  122 . Concentrically receiving the drill string  119  is a riser  123  which is positioned between the upper end of a blowout preventer stack  124  and the drilling vessel  110 . Located at each end of riser  123  are ball joints  125  to enable lateral movement of the drilling vessel  110  with reference to the wellhead  115 . 
     Positioned near the upper portions of the riser pipe  123  is a lateral outlet  126  which connects the riser pipe  123  to a low line  129 . An outlet  126  is provided with a throttle valve  128  (e.g., a controllable orifice choke). The flow line  129  extends upwardly to a separator  131  aboard the drilling vessel  110 , thus providing fluid communication from the interior of the riser pipe  123  through the flow line  129  to the drilling vessel  110 . Also aboard the drilling vessel  110  is a compressor  132  for conducting pressurized gas into a gas injection line  133  which extends downwardly from the drilling vessel  110  and into the lower end of the flow line  129 . The foregoing components may be used in so-called “dual gradient” drilling, wherein modification and/or pumping the returning drilling fluid to the drilling vessel  110  may provide a lower hydrostatic fluid pressure gradient in the riser  123  than would be the case if the drilling fluid were not so modified or pumped as it returns to the drilling vessel  110 . For purposes of defining the scope of the present disclosure, such fluid pressure gradient modification need not be used in any particular embodiment. The example embodiment disclosed herein is intended to serve only as an example and is not in any way intended to limit the scope of the present disclosure. 
     In order to control the hydrostatic pressure of the drilling fluid within riser  123 , in some embodiments drilling fluids may be returned to the drilling vessel  110  by means of the flow line  129 . As with ordinary marine drilling operations, drilling fluids are circulated down through the drill string  119  to the drill bit  120 . The drilling fluids exit the drill bit  120  and return to the riser  123  through the annulus defined by the drill string  119  and the wellbore  122 . A departure from ordinary drilling operations may then occur in some embodiments. Rather than return the drilling fluid and drilled cuttings through the riser  123  to the drilling vessel  110 , the drilling fluid may be maintained at a level in the riser  123  which is somewhere between the upper ball joint  125  and the outlet  126 . This fluid level may be related to the desired hydrostatic pressure of the drilling fluid in the riser  123  which will not fracture the sub-bottom formation  118 , yet which will maintain well control. The riser  123  may be connected to the top  116  of a wellhead (including components described with reference to numeral  124 ) or blowout preventer as in  FIGS. 2 and 3 , for example, using threaded couplings or bolted flanges. 
     In such embodiments, drilling fluid may be withdrawn from the riser  123  through the lateral outlet  126  and then returned to the drilling vessel  110  through the flow line  129 . The throttle valve  128 , which controls the rate of fluid withdrawal from the riser  123 , moves the drilling fluid into the low line  129 . Pressurized gas from compressor  132  may be transported down the gas injection line  133  and injected into the lower end of the flow line  129 . The injected gas mixes with the drilling fluid to form a lightened three-phase fluid consisting of gas, drilling fluid and drill cuttings. The lightened three-phase fluid has a density substantially less than the original drilling fluid and has sufficient “lift” to flow to the surface. 
       FIG. 2  shows a top view and  FIG. 3  shows a side elevation view of an example well pressure control apparatus  8  according to various aspects of the present disclosure. The well pressure control apparatus may be a blowout preventer (BOP) which includes a housing  10  having a through bore  11  for passage of well tubular components used in the drilling and completion of a subsurface wellbore. For clarity of the illustration, functional components of the BOP are shown on only one side of the housing  10 . It will be appreciated that some example embodiments of a BOP may include substantially identical functional components coupled to the housing  10  diametrically opposed to those shown in  FIG. 2  and  FIG. 3 . 
     The through bore  11  may be closed to passage of fluid by inward movement of a closure element  12  such as a ram into the through bore  11 . In some embodiments which include functional components on only one side of the housing  10 , the ram  12 , when fully extended into the through bore  11  may fully close and seal the through bore  11  as in the manner of a gate valve. In other embodiments of a BOP in which substantially identical components are disposed on opposed sides of the housing  10 , the ram  12  may when fully extended contact an opposed ram (not shown in the Figures) that enters the through bore  11  from the other side of the housing  10 . In the present example embodiment, the ram  12  may be a so called “blind” ram, which sealingly closes the through bore  11  to fluid flow when no wellbore tubular device is present in the through bore  11 . In some embodiments, the ram may be a so called “shear” ram that may be operated to sever a wellbore tubular or other device disposed in the through bore  11  so that the BOP may be sealingly closed in an emergency when removal of the tubular or other device is not practical. In other embodiments, the ram  12  may be a “pipe” ram that is configured to sealingly engage the exterior surface of a wellbore tubular, e.g., a segment of drill pipe, so that the wellbore may be closed to escape of fluid when the tubular is disposed in the through bore  11  without the need to sever the tubular. 
     The ram  12  may be coupled to a ram shaft  14 . The ram shaft  14  moves longitudinally toward the through bore  11  to close the ram  12 , and moves longitudinally away from the through bore to open the ram  12 . The ram shaft  14  may be sealingly, slidably engaged with the housing  10  so that a compartment usually referred to as a “bonnet”  16  may be maintained at surface atmospheric pressure and/or exclude entry of fluid under pressure such as ambient sea water pressure when the well pressure control apparatus  8  is disposed on the bottom of a body of water in marine drilling operations. 
     The ram shaft  14  may be coupled to an actuator rod  14 A. In the present embodiment, the actuator rod  14 A may be a jack screw, which may be in the form of a cylinder with helical threads formed on an exterior surface thereof. In the present example embodiment, the actuator rod  14 A may include a recirculating ball nut (not shown for clarity in the Figures) engaged with the threads of the actuator rod  14 A. A worm gear  18  may be placed in rotational contact with the ball nut, if used, or with the actuator rod  14 A. In some embodiments, other versions of a planetary roller type may be used to link the actuator rod  14 A to the worm gear  18 . Rotation of the worm gear  18  will cause inward or outward movement of the actuator rod  14 A, and corresponding movement the ram shaft  14  and ram  12 . 
     The worm gear  18  may be rotated by at least one, and in the present embodiment, an opposed pair of motors  30 . The motor(s)  30  may be, for example, electric motors, hydraulic motors or pneumatic motors. 
     An outward longitudinal end of the actuator rod  14 A may be in contact with a torque arrestor  22 . The torque arrestor  22  may be any device which rotationally locks the actuator rod  14 A. The piston  20  may be disposed in a cylinder  25  that is hydraulically isolated from the bonnet  16 . One side of the piston  20  may be exposed to an external source of pressure  24 , for example and without limitation, hydraulic pressure from an accumulator or pressure bottle, pressurized gas, or ambient sea water pressure when the pressure control apparatus  8  is disposed on the bottom of a body of water. The other side of the piston  20  may be exposed to reduced pressure  26 , e.g., vacuum or atmospheric pressure such that inward movement of the piston  20  is substantially unimpeded by compression of gas or liquid in such portion of the cylinder  25 . The other side of the piston  20  may be in contact with another torque arrestor  22 . The other torque arrestor  22  may be fixedly mounted to the cylinder  25 . 
     In the present example embodiment, a pressure sensor  21  may be mounted between the piston  20  and the torque arrestor  22 . The pressure sensor  21  may be, for example a piezoelectric element disposed between two thrust washers. The pressure sensor  21  may generate a signal corresponding to the amount of force exerted by the piston and the actuator rod  14 A against the ram  12  to open or close the ram  12 . Another pressure sensor  40  may be used as shown in  FIG. 2 . In some embodiments, a longitudinal position of the actuator rod  14 A or piston  20  may be measured by a linear position sensor  23 , for example a linear variable differential transformer or by a helical groove formed in the exterior surface of the piston  20  and a variable reluctance effect sensor coil (not shown). 
     As may be observed in  FIG. 2 , the motor(s)  30  may have a manual operating feature  31 , such as a hex key or other torque transmitting feature to enable rotation of the worm gear  16  in the event of motor failure. The manual operating feature  31  may be rotated by a motor, e.g., on a remotely operated vehicle (ROV) should such operation become necessary. 
     Referring once again to  FIG. 2 , in some embodiments, the well pressure control apparatus  8  may be made to operate in “closed loop” mode, whereby an instruction may be sent to the apparatus  8  to open the ram  12  or to close the ram  12 . For such purpose a controller  37 , which may be any form of microcontroller, programmable logic controller or similar process control device, may be in signal communication with the pressure sensor  21  and the linear position sensor  23 . A control output from the controller  37  may be functionally coupled to or conducted to the motor(s)  30 . When a command is received (see  37 B in  FIG. 4A ) by the controller  37  to close the ram  12 , the controller  37  will operate the motor(s)  30  to rotate the worm gear  16  and cause the actuator rod  14 A to move the ram  12  toward the through bore  11 . Fluid pressure acting on the other side of the piston  20  will increase the amount of force exerted by the actuator rod  14 A substantially above the force that would be exerted by rotation of the motor(s)  30  alone. When pressure measured by the pressure sensor  21  increases, and when the linear position sensor  23  measurement indicates the ram  12  is fully extended into the through bore  11 , the controller  37  may stop rotation of the motor(s)  30 . The reverse process may be used to open the ram  12  and stop rotation of the motor(s)  30  when the sensor measurements indicate the ram  12  is fully opened. In such manner, opening and closing the ram  12  may be performed without the need for the user to monitor any measurements and manually operate controls; the opening and closing of the ram  12  may be fully automated after communication of an open or close signal or command to the controller  37 . 
       FIGS. 4A and 4B  show an example embodiment of a ram actuator as explained with reference to  FIGS. 2 and 3 , which may include additional components to enable some degree of automation of operation of the ram actuator, and to store and communicate information related to the performance of the ram actuator so that ram actuator response to control signals can be periodically or continuously, and information concerning required maintenance may be automatically communicated to a service provider or manufacturer. 
     A pressure sensor  40  may measure hydraulic pressure on one side of the piston  20 , as in the embodiments shown in  FIGS. 2 and 3 . An optical sensor  23 B may be used in conjunction with the linear position sensor ( 23  in  FIG. 2 ) to determine position of the piston  20  within the cylinder  25 . Measurements from the optical sensor  23 B may also be used to determine a relative concentration of any solid particles present in pressurized fluid used to move the piston  20 . Such determination may be used in some embodiments, explained further below, to determine when the ram actuator requires removal and servicing. A second pressure sensor  23 A may be disposed in the bonnet  16  so that measurement of pressure in the through bore ( 11  in  FIG. 2 ) may be measured. A combination temperature/pressure/particle count (e.g., optical) sensor  33  may be arranged to measure temperature, pressure and a parameter related to particle count within fluid contained in an atmospheric pressure chamber  16 A enclosing the worm gear and actuator rod ( FIG. 2 ). Signals from the foregoing sensors may be communicated to the controller  37 . 
     An electrical power source  30 A may be provided to operate the motor(s)  30  and the controller  37 . The electrical power source  30 A may be self-contained, such as batteries disposed in the atmospheric chamber  16 A, or may be conducted over an electrical cable ( FIGS. 9 and 10 ) from the drilling vessel ( 10  in  FIG. 1 ), or a combination thereof. 
     In the present example embodiment, the controller  37  may comprise a processor, programmable logic controller, programmable microcomputer or any similar device, shown at  37 A) that can execute instructions stored on a computer readable medium or stored in a storage device within the processor  37 A. The processor  37 A may be in signal communication with a transceiver  37 B. The transceiver  37 B may be “hard wired” to a communication device in signal communication with another controller deployed on the drilling vessel ( 110  in  FIG. 1 ) for water-bottom deployed ram actuators (see  FIG. 10 ) or may be a wireless communication device, for example and without limitation, radio, wireless Internet, BLUETOOTH transceiver or any other two way communication device. BLUETOOTH is a registered trademark of Bluetooth Special Interest Group (“SIG”), Inc., Suite 350, 5209 Lake Washington Boulevard, Kirkland, Wash. 98033. 
       FIG. 5  shows an example embodiment of the apparatus shown in  FIGS. 4A and 4B  wherein signals corresponding to measurements made by the various sensors shown in those figures may be communicated to a maintenance and/or manufacturing facility  42  on a periodic or continuous basis. The signals communicated may comprise values of control signals used to operate the motor ( 30  in  FIG. 2 ) and hydraulic pressure used to move the piston ( 20  in  FIG. 2 ) and values of the measurements made by the sensors shown in  FIGS. 4A and 4B . The facility  42  may have disposed therein computers or computer systems (not shown) that can calculate the performance status of the ram actuator. In some embodiments, such performance status may comprise comparing control signal values, for example, control signals to operate the motor ( 30  in  FIG. 4B ) and to enable hydraulic pressure to be applied to the piston ( 20  in  FIG. 4B ), and their corresponding expected sensor measurements to the actual sensor measurements made and communicated to the controller ( 37  in  FIGS. 4A and 4B ). Anomalous sensors measurements, for example, those indicative of excessive motor temperature when moving the ram actuator, excessive hydraulic fluid pressure, slow measured rate of movement of the ram actuator with respect to hydraulic pressure and motor rotation, and excessive particle concentration in the fluid used to operate the piston ( 20  in  FIG. 4B ) may be used to determine faulty operation of the ram actuator and/or changes in actuator performance that may be known to be associated with or may be indicative of future faulty performance of the ram actuator. The foregoing will be explained in further detail with reference to  FIG. 9 , wherein an automated maintenance and replacement method is described. 
       FIG. 6  shows an example of autonomous or automatic control of operation of the ram actuator by programming suitable instructions in the controller  37 . When so programmed, the controller  37  may automatically operate the motor ( 30  in  FIG. 2 ) and supply hydraulic pressure to the piston ( 20  in  FIG. 2 ) in response to measurements of linear position, hydraulic pressure, motor rotation, temperature and fluid pressure in the throughbore ( 11  in  FIG. 2 ) so that the ram actuator may operate fully autonomously. Full autonomous operation may include measurement of pressure in the throughbore ( 11  in  FIG. 2 ) and a response by the controller  37  to close the ram ( 12  in  FIG. 2 ) when the measured pressure and/or a time derivative of the measured pressure crosses a selected threshold. In some embodiments, a command signal may be communicated from an external source  44  to the controller  37  to open or to close the ram actuator; in such embodiments, detection of the “open ram” or “close ram” signal by the controller  37  may cause the controller to operate the motor ( 30  in  FIG. 4A ) and supply/relieve hydraulic pressure to the piston ( 20  in  FIG. 4A ) to automatically close and/or open the ram actuator. 
       FIG. 7  shows graphs of ram actuator position with respect to time for different ram actuator operating characteristics that may be programmed into the controller ( 37  in  FIG. 4A ) to operate the ram actuator to open and close at different and selectable time variable rates. For example, one opening and closing rate is shown as a linear function of position with respect to time at STRATEGY  1 . A “stair step” opening/closing position function with respect to time (e.g., alternating rapid movement and slow movement) is illustrated as STRATEGY  2 . A variable stair step (which may include opening and closing rate reversals as well as monotonic and/or stair step increases/decreases) opening/closing position with respect to time is illustrated at STRATEGY  3 . In some embodiments, the controller  37  may be programmed to automatically optimize the ram actuator position with respect to time for different ram actuator operating characteristics. 
       FIG. 8  shows a block diagram of using the measurements made by the sensors shown in  FIGS. 4A and 4B  in the controller to automatically change the control parameter signals generated by the controller  37  to operate the ram actuator. For example and without limitation, if the STRATEGY  1  is implemented by the controller  37  and measurements made by the sensors are indicative of position with respect to time changing more slowly than what has been programmed as STRATEGY  1  (in  FIG. 7 ), then the controller  37  may adaptively increase either or both of the pressure applied to the piston ( 20  in  FIG. 2 ) and the operating speed of the motor ( 30  in  FIG. 2 ) so that the measured position with respect to time more closely matches the preprogrammed position with respect to time. A performance weight matrix  41  allows identical controllers to behave differently based on operational parameter changes (e.g., mud weights, well depths, operational stage, etc.), specific RAM performance (based on measured performance during calibration) and environmental changes (such as water depth, temperatures, etc). Since there is a wireless connection this weight matrix can be updated if and when needed“. The ability to tune the controller is of great operational advantage” Other possible control parameter updating methods will occur to those skilled in the art. Such updating of control parameters may be performed automatically on a periodic or continuous basis, or may be performed when a signal is communicated externally from a signal source  44  to the controller  37 . The signal source  44  may be wired and/or wireless as explained with reference to  FIGS. 4A, 4B and 5 . 
       FIG. 9  shows a flow chart of an automated method for determining when a ram actuator should be removed from service for repair, maintenance and/or reconditioning. As explained with reference to  FIG. 8 , performance of the ram actuator may be continuously determined in the controller  37  by comparing the sensor measurements ( FIGS. 4A and 4B ) to the values of the control signals used to operate the motor ( 30  in  FIG. 2 ) and/or the piston ( 20  in  FIG. 2 ). At  50 , the ram actuator performance may be continuously monitored along with the total time the ram actuator has been in service and the number of times the ram actuator has been tested and/or used in service to control well pressure (“service parameters”). If during the performance monitoring all service parameters indicative of a need to remove the ram actuator from service are within predetermined limits or have not crossed respective thresholds, the ram actuator will remain in service as shown at  52 . If any one or more service parameters is determined in the controller  37  to be outside the predetermined limits or crosses a predetermined threshold, a signal may be generated and communicated at  54  (e.g., using the communications transceiver  37 B in  FIG. 4A ) to advise the operator and/or the service facility that the ram actuator should be removed from service, at  56 . When such signal indicating the need to remove the ram actuator from service is generated, the ram actuator may be removed from service at  58 . For purposes of the method described with reference to  FIG. 9 , service procedures applicable to the ram actuator may be likewise applied to the ram ( 12  in  FIG. 2 ), wherein the ram actuator and ram are acted upon as a unit. The removed ram actuator may be transported at  60  to the facility ( 42  in  FIG. 5 ). At  62 , the facility may recondition or remanufacture the ram actuator. The facility  42  may perform certification testing on the ram actuator at  64 . The facility  42  may store or conserve the ram actuator at  66  for eventual transport, at  68 , to the drilling or production platform where the ram actuator was previously used, or may transport the ram actuator to any other drilling or production platform having a BOP stack or single BOP housing (see  FIGS. 10 and 11 ) that is compatible with the particular ram actuator. The ram actuator may be stored, at  70 , at the location of the drilling or production platform for eventual installation if and as necessary. If and as necessary a same type of ram actuator installed on the BOP stack or BOP housing ( FIGS. 9 and 10 ) may be replaced, at  72 , by the stored ram actuator. By implementing the method shown in flow chart form in  FIG. 9 , maintenance and replacement scheduling for the ram actuator(s) may be automated, as well as automating inventory tracking of to be serviced and fully serviced ram actuators. 
       FIG. 10  shows a BOP stack  124  including a plurality of rams/ram actuators as explained with reference to  FIGS. 2 through 5 . The BOP stack  124  shown in  FIG. 10  may be affixed to a wellhead  115  proximate the water bottom in a sub-bottom well. The BOP stack  124  may be affixed to the top of a surface casing  127  as explained with reference to  FIG. 1 . The sub-bottom well may comprise an intermediate casing  127 A, shown in  FIG. 10  for illustrative purposes only and not to limit the scope of the present disclosure. In  FIG. 10 , a power supply cable  80  may be connected to each ram actuator  8  either or both to operate the electrical components therein and to keep batteries therein fully charged. The power supply cable  80  may also be used to communicate signals between each controller ( 37  in  FIG. 4A ) and the drilling platform ( 110  in  FIG. 1 ) for such water bottom deployed BOP stacks  124 . In some embodiments, signals may be communicated between the ram actuators and the surface using acoustic telemetry through the water. Such telemetry systems are known in the art. 
       FIG. 11  shows a corresponding BOP stack  124 A used at the surface. The surface may be, for example, on the drilling platform ( 110  in  FIG. 1 ) or on the land surface for land-based wells. In the embodiment of  FIG. 11 , the transceivers ( 37 B in  FIG. 4A ) may be wireless as explained with reference to  FIG. 4A . In some embodiments, operational and condition monitoring data can be transmitted directly to other users in addition to or in substitution for communicating such data to the facility ( 42  in  FIG. 9 ). In some embodiments, a power cable  80 A may supply electrical power to operate the respective motor ( 30  in  FIG. 2 ) and controller ( 37  in  FIG. 4A ) in each ram actuator. 
     In some embodiments, the ram actuator may be controlled with wirelessly connected mobile devices such as tablets, smart phones and the like. In some embodiments, the communication device ( 37 B in  FIG. 4A ) may be directly or indirectly in signal communication with the Internet. In such embodiments, the wirelessly connected mobile devices may be used to operate and/or monitor performance of the ram actuator using an Internet connection. In some embodiments, the wirelessly connected mobile devices may be in signal communication with the communication device ( 37 B in  FIG. 4A ) directly such as by radio signal, WiFi communication protocol (IEEE standard 802.1(a) et seq.), BLUETOOTH communication protocol or any other wireless communication protocol. 
     In some embodiments, e.g., for multiple ram actuators such as shown in  FIGS. 10 and 11 , each ram actuator may be in signal communication with other ram actuators in the BOP stack and the respective controllers ( 37 A in  FIG. 4A ). In such embodiments, the respective controllers may be programmed to synchronize operation of each ram actuator to the operation of one or more of the other ram actuators in the BOP stack ( 124  in  FIGS. 10 and 124A  in  FIG. 11 ). 
     While the invention 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 invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.