ReAct

REAct is a pressure balanced subsea electric fail-safe linear actuator for isolation valves. The springs used in the REAct actuator to close/open the valve in an emergency are energised and locked in place before the valve is operated.

In the System-Module application the fail-safe mode is specified as closed, though, if required, the fail-safe mode can be specified as open. On initial actuation, the actuator first compresses the spring stack, which has sufficient force to close (open) the valve under shutdown conditions, before normal valve operation takes place.

The difference between REAct and other spring energised actuators is that once these springs have been fully compressed they are latched in position with an electromagnet which continues to hold the spring force until the current to the electromagnet circuit is removed.

The advantage of this mechanism is that once the springs are energised and latched in position, the valve can be operated without having to act against the springs thereby considerably reducing the forces needed to operate the valve. This can be very significant when available power is limited, and also allows for a much smaller valve/actuator envelope with the associated savings in weight and cost.

ReACT Valve

The REAct drive mechanism is such that when the actuator motor and drive is deenergised the valve will maintain position, with no back driving, until the fail-safe mode is initiated by removing power to the electromagnet circuit.

The current status of the design is at the MkII stage with many improvements being incorporated as a result of the continued testing programme for PROAct. This has resulted in further savings in weight, size and standardisation on parts.