Sil2 Loop for Shutdown Valve Upgrade

1) You Can Get Failure rates From Your Valve Vendor ,If its reputed manufacturer he may offer

Or

2) You can refer Oreda 2002 From where You can get lamda Dangerous for all types of Valves typically used for ESD , But that data was collected From North Sea area , & may vary depending upon the environment , So You have to Put some note in Your Scoping Paper and Present

Regards

Jose

by stating failures rate of valve means the MTBF number right? also, is there a rule of thumb for this; like we refer to the lowest rating in the loop. it doesn't make much sense for me considering having a really reliable control system, good sensors but using a non SIL certified valve. Wouldn't the whole loop be linked together and has the weakest final element. Confused...