Linear actuator with ex-zone 1 rated housing

Abstract

A linear actuator assembly that can include an electric motor contained in an explosive (EX) certifiable housing, a linear actuator external to the EX certifiable housing, the linear actuator coupled to and driven by the electric motor, the linear actuator having a first axis and a body, and a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first axis and the second axis being parallel and spaced apart. The electrically operated linear actuator assembly can provide up to 700 kN clamping force when engaging a tubular. A plurality of the linear actuator assemblies can provide up to 250 kNm of torsional force to a tubular string joint when used in a wrench assembly.

1 . A tool for conducting a subterranean operation, the tool comprising:
 a linear actuator assembly that comprises:
 an electric motor contained in an EX certifiable housing; 
 a linear actuator external to the EX certifiable housing, wherein the linear actuator is coupled to and driven by the electric motor, and wherein the linear actuator includes a first axis and a body; and 
 a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first axis and the second axis being parallel and spaced apart. 
   
     
     
         2 . The tool of  claim 1 , wherein the linear actuator is coupled to the electric motor via gears disposed in a fluid filled chamber. 
     
     
         3 . The tool of  claim 2 , wherein seals disposed between the EX certifiable housing and the fluid filled chamber prevent pressurized gas from entering the fluid filled chamber and prevent fluid from the fluid filled chamber from entering the EX certifiable housing. 
     
     
         4 . The tool of  claim 1 , wherein the EX certifiable housing receives pressurized gas through a gas inlet and exhausts the pressurized gas from the EX certifiable housing via a gas outlet, such that the pressurized gas in the EX certifiable housing is continually replaced with the pressurized gas received through the gas inlet. 
     
     
         5 . The tool of  claim 1 , wherein the linear actuator further comprises a structure mounted to an end of the piston, wherein the structure is configured to:
 engage a tubular,   transfer a longitudinal force of the piston to the tubular, and   direct a torsional force, applied to the tubular by the structure, away from the piston.   
     
     
         6 . The tool of  claim 5 , wherein the structure comprises a gripper that is removably attached to the structure, the gripper being configured to engage the tubular when the piston extends toward the tubular. 
     
     
         7 . The tool of  claim 1 , wherein the linear actuator assembly provides up to 700 kN clamping force when engaged with a tubular, and wherein a first overall volume includes the EX certifiable housing, the body of the linear actuator, and a gear box for coupling the linear actuator to the electric motor, and wherein the first overall volume is less than 32K cubic cm. 
     
     
         8 . The tool of  claim 1 , wherein the linear actuator assembly provides up to 700 kN clamping force when engaged with a tubular, and wherein a vertical height of the EX certifiable housing is less than 200 mm. 
     
     
         9 . A system for conducting a subterranean operation, the system comprising:
 an iron roughneck comprising a torque wrench having a plurality of actuator assemblies circumferentially positioned around an opening through the iron roughneck, wherein the opening is configured to receive a tubular string, and wherein each of the actuator assemblies comprise:
 an electric motor contained in an EX certifiable housing; 
 a linear actuator with a piston that extends or contracts in response to rotation of a coupling between the electric motor and the linear actuator; and 
 a structure attached to an end of the piston, the structure being configured to engage the tubular string with a gripper when the piston is extended toward the tubular string and transfer a torsional force away from the piston when the gripper is engaged with the tubular. 
   
     
     
         10 . The system of  claim 9 , wherein the torque wrench is configured to transfer up to 250 kNm of torsional force to the tubular string when the torque wrench is engaged with the tubular string. 
     
     
         11 . The system of  claim 9 , wherein each of the actuator assemblies is rigidly attached to a body of the torque wrench, and wherein the torque wrench is configured to transfer a torsional force to the tubular string when the torque wrench is engaged with the tubular string, and wherein the structure transfers the torsional force to the body of the torque wrench and away from the piston. 
     
     
         12 . The system of  claim 9 , wherein each of the actuator assemblies is rigidly attached to a body of the torque wrench, and wherein the torque wrench is configured to transfer a torsional force to the tubular string when the torque wrench is engaged with the tubular string, and wherein the structure comprises:
 a head portion;   the gripper removably attached to the head portion; and   a T-shaped protrusion that extends from the head portion, wherein the T-shaped protrusion is slidingly engaged with a groove in the body of the torque wrench, and wherein the groove is complimentarily shaped to receive the T-shaped protrusion.   
     
     
         13 . The system of  claim 9 , wherein the iron roughneck further comprises a backup tong spaced vertically away from the torque wrench, the backup tong having another plurality of the actuator assemblies circumferentially positioned around the opening in the iron roughneck. 
     
     
         14 . The system of  claim 9 , wherein the iron roughneck further comprises a backup tong spaced vertically away from the torque wrench, the backup tong having another plurality of the actuator assemblies circumferentially positioned around the opening in the iron roughneck, and wherein the iron roughneck is configured to produce a minimum vertical distance from a top of one of the grippers in the backup tong to a bottom of one of the grippers in the torque wrench, and wherein the minimum vertical distance is 60 mm (2.36 inches). 
     
     
         15 . The system of  claim 14 , wherein a maximum height from a top of the torque wrench to a bottom of the backup tong is less than 500 mm when the torque wrench is positioned adjacent the backup tong with the grippers in the backup tong being separated from the grippers in the torque wrench by the minimum vertical distance, with the maximum height including combined vertical heights of the backup tong, the torque wrench, and a vertical space between the backup tong and the torque wrench. 
     
     
         16 . The system of  claim 15 , wherein the torque wrench and backup tong are configured to transfer up to 250 kNm of torsional force to the tubular string when the torque wrench and the backup tong are engaged with the tubular string. 
     
     
         17 . A method for making or breaking a joint in a tubular string, the method comprising:
 positioning the joint within a vertical opening that extends through an iron roughneck, with the iron roughneck comprising a torque wrench and a backup tong;   engaging the joint with the backup tong and the torque wrench, wherein an overall height of an engagement of the joint is less than 400 mm, and wherein the overall height is defined as a distance along the joint from a top of an engagement of the torque wrench to a bottom of an engagement of the backup tong; and   making or breaking the joint by rotating the torque wrench relative to the backup tong.   
     
     
         18 . The method of  claim 17 , further comprising:
 engaging the joint via first grippers in the torque wrench and second grippers in the backup tong; and   positioning the torque wrench adjacent the backup tong, such that grippers in the torque wrench are spaced away in a vertical direction from grippers in the backup tong by a vertical distance less than 60 mm; and   applying up to 250 kNm of torsional force to the joint via the torque wrench and the backup tong.   
     
     
         19 . The method of  claim 18 , operating an electric motor in a linear actuator assembly to extend or retract one of the first grippers or the second grippers toward or away from the joint. 
     
     
         20 . The method of  claim 18 , wherein the iron roughneck comprises a linear actuator assembly for each one of the first grippers and the second grippers, and wherein the linear actuator assembly comprises:
 an electric motor contained in an EX certifiable housing;   a linear actuator external to the EX certifiable housing, the linear actuator coupled to and driven by the electric motor, the linear actuator having a first axis and a body; and   a piston of the linear actuator that extends or retracts relative to the body when the linear actuator is driven by the electric motor, the piston having a second axis, with the first and second axes being parallel and spaced apart.