A SIF uses a single, pneumatic, final element assembly consisting of a 3/2 pilot-operated spool solenoid valve, a spring-return scotch yoke actuator, and a trunnion ball valve. The application is close-to-trip.

MRTDU for failures detected during the proof test is 48 hours. The assembly can be fully tested after installation. Proof testing is planned for once a year during a process shutdown. The PT4 proof test is performed soon after the process shutdown, but because the final element assembly is not at operating pressure, PT5 cannot be claimed.

The process will run for 10 years before complete overhaul. Using the failure rate data and CPT data from Table 12-6, what is the PFDavg of the final element assembly?