Hi all. I would like to hear everyone’s views and opinions on having one valve for control and one valve for safety, Or if they would have one valve that does both. If you have one valve what’s are your argument for, independence, CCF, and control system errors.

Hi all, thanks for accepting. First of all, I am new in functional safety and sorry for my bad english😊. Actually I have some doubt about one of variable in PFDavg calculation namely mission time, couple of question to all: 1. What will happen in the end of mission time?should end user decommissioned the plant?or just replace everything and the mission time will get restarted? 2. If it depend on end user, than based on what consideration usually for them to determine the correct mission time?and what is the reason behind that? 3. Since by the time PFDavg will get derated, and SIL claimed may decreased over the time, shouldn't end user decide to set the mission time before the SIL/RRF drops beyond the rating it should be? Hope you guys can share your knowledge. Thanks,

Hi all (again), I am currently working with a Client which has asked me to carry out a C&I compliance assessment on vendor skid coming from China. The skid is fair size (approx. 400m²) as it contains a full Pyrolysis unit along with it's own BPCS Control System and Independent Fail Safe Controller. Among all the other C&I compliance checks I am doing, the Functional Safety checks is one of the main items on my radar. My initial TQ's to this particular vendor contain queriers around how they have managed their SIL rated trips, i.e. which Safety Standard have they complied with? and also what lifecycle documentation they can provide, i.e. Hazard Study Reports, SRS, SIL Verification Calcs, SIF Validation evidence etc? (I am awaiting their response) .. I often hear that we should treat Vendor packages as black boxes, however I believe there must be some level of assessment which must be carried out by the Principal Designer to ensure the equipment being supplied is compliant to our standards, and has followed robust safety lifecycle? My question to the team is, what sort of assessment would you carry out on 3rd party skids the size of this? Again, any opinions on this one would be hugely appreciated!

Hi All, I am currently writing a proof test procedure for a High-High Temperature SIF. The sensor is 3-wire RTD. After carrying out all the proof testing checks, I have included for an RTD Calibration check to be carried out at the end, using a decade box or loop calibration device e.g. Fluke 754). Reason being, I wanted to ensure the loop was functioning correctly still after disconnecting sensor wires etc, during the proof test. However, my Client has requested this to be removed from the Proof Test as this is done as part of other existing maintenance routines. Just want to get anyone's thoughts on this, as to whether it is overkill to include an RTD check, and I should simply just ask the user to check the RTD is within it's prescribed calibration date? Any opinions on this would be appreciated!

Hi All. Just thought I would post in here to get others thoughts on a scenario I have come across recently. I know it’s best practice to avoid a single element being used in multiple SIFs, but are there any factors to take into consideration for the calculation. For example, several vessels have a common feed supply and whilst each have their own level sensor and logic solver, the common feed line overfill trip valve is shared for all vessels. Each SIF will have a calculation of all components, but all are actually using the same valve. My understanding is no common cause can really be applied as all have a 1oo1 output function. On another note, the configuration would also result in more demands on the valve with it being shared. Downtime and maintenance would also be impacted if shared. Again, just to get other thoughts on other factors that should be taken into account in this scenario. Thanks, Craig