Safety Loop Solutions

A Yokogawa integrated safety solution ensures your process availability and safety. Functionality needed to properly integrate field devices is built-in.

For example, the 61508 certified EJX transmitter will indicate an internal problem including plugged impulse line by sending a 3.8 mA signal. ProSafe-RS recognizes this signal as a diagnostic and sends an alarm to the DCS alerting the operators to fix the problem. No shutdown is needed. To achieve this functionality in a non-integrated system, careful application level programming involving analog filtering and comparison is needed between the sensors and the logic solver, as well as complex engineering to send alarms from the logic solver to the control system.

Such collaborative functionalities ensure maximum process availability by avoiding unwanted shutdown.

In a comparison study by exida the two designs show a significant difference in PFDavg, a measure of safety integrity and MTTFS, mean time to failure spurious (false trip). The ad hoc solution uses conventional design techniques including three transmitters, a SIL3 logic solver and remote actuated valve.
The Yokogawa integrated solution utilizes a single EJX certified pressure transmitter, a ProSafe-RS SIL3 certified logic solver and a single remote actuated valve with the SVI II digital positioner configured for automatic partial valve stroke testing every week (168 hours).

As compared to the ad-hoc solution, the Yokogawa integrated solution doubles safety loop availability, triples safety and extends valve proof test interval by ten times.
The results show significant differences. When one considers the lower capital cost of the integrated solution, the differences look even better. When life cycle cost is considered (more frequent proof testing), the integrated solution looks even more superior.