Hydraulic rams

Abstract

There is disclosed an actuator for delivering a supplementary force to the piston of a shear ram in a blowout preventer (BOP), and a corresponding BOP. In one embodiment, a supplementary force actuator ( 12 ) is disclosed for use on a hydraulic ram ( 10 ), the actuator comprising an actuator body ( 30 ) connected to the hydraulic ram; first and second chambers ( 38, 36 ) located in the body, the chambers isolated from each other by an actuator piston ( 46 ); a rod ( 42 ) connected to an operating piston ( 24 ) of the hydraulic ram, passing through the first chamber and the actuator piston, and extending into at least a portion of the second chamber; wherein the actuator piston is releasably engageable to the rod by gripping means ( 48 ); and wherein the hydraulic ram is operated by a force from movement of the operating piston and by a supplementary force from movement of the actuator piston.

1 . A supplementary force actuator for use on a hydraulic ram, the actuator comprising;
 a) an actuator body connected to the body to a hydraulic ram;   b) first and second chambers located in the body, the chambers isolated from each other by an actuator piston;   c) a rod adapted to be connected to an operating piston of the hydraulic ram, pass through the first chamber and the actuator piston, and extend into at least a portion of the second chamber;   d) the actuator piston being releasably engageable to the rod by a gripping device; and   e) wherein the hydraulic ram is operated by a force from movement of the operating piston and by a supplementary force from movement of the actuator piston.   
     
     
         2 . A supplementary force actuator as claimed in  claim 1  wherein the actuator includes a release mechanism to operate the actuator piston. 
     
     
         3 . A supplementary force actuator as claimed in  claim 1  wherein a separation element is located between the hydraulic ram and the body. 
     
     
         4 . A supplementary force actuator as claimed in  claim 3  wherein one or more seals are arranged on the separation element to act upon the rod and prevent the release of hydraulic fluid from the body into a hydraulic chamber of the hydraulic ram. 
     
     
         5 . A supplementary force actuator as claimed in  claim 1  wherein the actuator includes an energy storage device arranged to provide a force to act upon the actuator piston. 
     
     
         6 . A supplementary force actuator as claimed in  claim 5  wherein the energy storage device comprises a mechanical means. 
     
     
         7 . A supplementary force actuator as claimed in  claim 6  wherein the mechanical means comprises one or more springs held in compression. 
     
     
         8 . A supplementary force actuator as claimed in  claim 6  wherein the mechanical means comprises a plurality of Bellville springs. 
     
     
         9 . A supplementary force actuator as claimed in  claim 5  wherein the energy storage device comprises is a hydraulic means. 
     
     
         10 . A supplementary force actuator as claimed in  claim 9  wherein the hydraulic means comprises hydraulic fluid held under pressure. 
     
     
         11 . A supplementary force actuator as claimed in  claim 1  wherein the actuator includes a resetting device configured to move the actuator piston back to its original operating position. 
     
     
         12 . A supplementary force actuator as claimed in  claim 11  wherein the actuator includes a ram setting device to move the operating piston back to its original position. 
     
     
         13 . A supplementary force actuator as claimed in  claim 1 , wherein the gripping device comprises a ball gripping device. 
     
     
         14 . A supplementary force actuator as claimed in  claim 13 , wherein the ball gripping device comprises a plurality of balls mounted in a ball mounting element having a plurality of apertures, each aperture associated with a corresponding ball. 
     
     
         15 . A supplementary force actuator as claimed in  claim 14 , wherein the actuator piston is adapted to urge the balls into engagement with the rod, to grip the rod. 
     
     
         16 . A supplementary force actuator as claimed in  claim 13 , wherein the ball gripping device is adapted to grip the rod during movement of the actuator piston in a first direction and to release the rod during movement in a second, opposite direction. 
     
     
         17 . A supplementary force actuator as claimed in  claim 14 , wherein the ball gripping device comprises a ball release mechanism for permitting relative movement between the ball mounting element and the actuator piston. 
     
     
         18 . A supplementary force actuator as claimed in  claim 17 , wherein the ball release mechanism comprises a shoulder adapted to abut the ball mounting element, to exert a force on the ball mounting element to disengage the balls from the rod during movement of the actuator piston in the second direction. 
     
     
         19 . A supplementary force actuator as claimed in  claim 18 , wherein the ball mounting element comprises a flange and at least one spring provided between the flange and the actuator piston. 
     
     
         20 . A method of operating a hydraulic ram comprising:
 a) releasing a first piston to act on a ram;   b) using the movement of the first piston to trigger a release mechanism; and   c) releasing a second piston on operation of the release mechanism, to act upon the ram.   
     
     
         21 . A method of operating a hydraulic ram as claimed in  claim 20  wherein the method includes the step of pressurising hydraulic fluid behind the first piston which is then used to operate the first piston. 
     
     
         22 . A method of operating a hydraulic ram as claimed in  claim 20  wherein the method includes:
 releasably engaging the second piston to the first piston, so that the second piston is stationary when the first piston operates and the second piston also moves the first piston upon operation of the second piston.   
     
     
         23 . A method of operating a hydraulic ram as claimed in  claim 20  wherein the release mechanism is triggered at or near the end of the stroke of the first piston. 
     
     
         24 . A method of operating a hydraulic ram as claimed in  claim 20  wherein the method includes:
 resetting the hydraulic ram by moving the first and second pistons back to their original operating positions.   
     
     
         25 . A blow out preventer for use in oil well drilling, the blow out preventer comprising:
 a pair of opposing hydraulic rams, each ram having a shear blade on a leading face; and   at least one supplementary force actuator as claimed in  claim 1  located on at least one of the hydraulic rams.   
     
     
         26 . A blow out preventer as claimed in  claim 25  wherein a supplementary force actuator is arranged on each of the hydraulic rams.