Renaissance for solid state safety

Yokogawa added safety systems to their portfolio with the acquisition of GTI Industrial Automation in 1997. GTI had a proven track record with programmable solid state safety systems. With the advancement of certified systems, including Yokogawa’s ProSafe-RS, GTI's solid state technology has become overshadowed. Nevertheless, ProSafe is still the system of choice for the highest-integrity safety applications such as High Integrity Pressure Protection Systems (HIPPS). The ProSafe-SLS system is now generating renewed interest for more than just small HIPPS solutions due to a number of unique features which fit well with the increasing focus on longer lifecycle costs.

ProSafe-SLS
ProSafe-SLS in its current format is 20-years old. An additional 10 years can be added due to earlier versions. However, all work versions work on the same principle of magnetic core technology. Oscillating magnetic fields created by passing current through windings in combination with 1 millisecond timing are configured to create logic functions, supplemented by Input/Output modules which include further configuration options in all safety saystems. But, what makes ProSafe-SLS special for its users?

ProSafe-SLS was the first (by a lot years) safety system to be certified up to SIL4 without redundancy. This high integrity is uniquely combined with the highest availability due to the stress tolerance of the circuits. It is virtually impossible to create a nuisance trip of ProSafe-SLS logic without physically damaging the modules. The integrity of the system arises from the principle of operation rather than dependence on high quality components, external testing or extensive diagnostics. This is attractive as it means the logic can be located in the harshest environments and be trusted to operate reliably for many years, an attribute proven by the use of ProSafe-SLS in subsea HIPPS systems or sealed in explosion-proof enclosures in the turrets of FPSOs.

Combine this reliability with high-speed operation (total propagation time is typically 20 milliseconds) regardless of system size, 1 millisecond event capture for every input and logic gate, and a communications network allowing multiple systems to be managed with 1 millisecond synchronisation and one understands why the systems is worth a second look.

ProSafe-SLS, working for 10 years with no failures and decreasing the fuelling cycle time to give major cost benefits, has also proven itself in complex interlocking systems on the fuelling machines of nuclear reactors. In the North Sea, most of the Shell production platforms rely on ProSafe-SLS for all their protection logic -- not just on the highest integrity levels. This decision was reinforced by studies into lifecycle ownership costs. A global analysis showed that ProSafe-SLS systems were far more reliable than all other programmable systems, even where redundant fault tolerant programmable systems were used.

ProSafe today
Today, Yokogawa offers ProSafe-RS for programmable solutions and ProSafe-SLS for diverse technology, high-integrity solutions. Both are integrated with the CENTUM VP Distributed Control System. However, the ProSafe-SLS technology is still available for larger systems and the lifecycle ownership issues can still be applied for remote, unmanned and/or harsh locations. Yokogawa can, therefore, reduce all riskd aspects of process operations by offering solutions for all safety requirements perfectly suited to particular conditions, operating philosophies and lifecycle models.