Abstract: A riser recoil control system (10) adjusts tension forces (F1, F2) applied to a marine riser (60), which is attached to an anchored, floating vessel (30) and a wellhead (80). The riser (60) is attached to the vessel (30) using tension forces (F1, F2) asserted by riser tensioners (20). Each tensioner (20) has an air shutoff valve (110), and an orifice-controlled fluid valve (120). A disconnection sensing means (200) provides a disconnect signal when the riser (60) is disconnected from the wellhead (80), which closes the valves (110, 120) and adjusts the tension forces (F1, F2) applied by the tensioners (20). The invention includes a method for adjusting the tension forces (F1, F2) applied to the riser (60), including sensing the disconnect signal and adjusting the tension forces (F1, F2) supplied to the riser (60) by closing the air shutoff valves (110) and partially closing the orifice-controlled fluid valves (120).

Abstract: An automated riser recoil control system (10) including a plurality of riser tensioners (20), a vessel heave measurement system (210) and a control processor (70) with each tensioner (20) having a piston travel indicator (27) which signals the processor (70) and a method of operation is disclosed.

Abstract: A rotary electric actuator module has a plurality of actuators for actuating a device in a subsea wellhead assembly. The module is arranged to receive primary power and control signals from an external source in order to actuate the subsea devices. Each actuator in the module has a back-up power supply, each power supply having a self-contained electrical storage unit providing a source of secondary power. Each actuator has a motor driven by the electrical storage unit. A control system is provided to detect the interruption of the primary power or the control signals and, if the subsea device is in an unsafe operating position, cause the subsea device to move into a safe position using the secondary power.