Frequently Asked Questions

I have an application with 11 risers from sub-sea oil wells each having dual isolation valves in series, voted 1oo2. I have modelled the scenario assuming four risers and I need help on how to configure a voted group of 11oo11 where each leg has 1oo2 vote
Last Updated a year ago

First question I'd like to ask is do you really need to stop flow in all 11 risers? I have seen in the past examples that failure in any of the 11 can cause a high pressure event in a common header. Though one does not necessarily know which of the 11 is the culprit (and hence would want to close all 11) you would really only need to stop flow in the culprit. Therefore from a SIF perspective the final element configuration is a 1oo2 (in your case). The success (or failure) in the other 10 risers will not impact the success of the SIF trying to address the high pressure in the common header.
Assuming that you do need an 11oo11 over a 1oo2, you can model this as follows.
In your final SIF select 1 final element group. In the voting for this group select the MooN option and set this to 11oo11. For the final element use a "user defined" element and specify the failure rates as follows: Simplified solutions: LambdaDU = 0.10*LambdaDU of your solenoid+actuator+valve; LambdaSU = 2*LambdaSU of your solenoid+actuator+valve.
Alternatively create an intermediate SIF. In this SIF set the mission time to the proof test time of your final element. Set the demand mode to high. Create 1 final element group with the equipment you have voted 1oo2. The resulting PFH for the final element group is your LambdaDU, the resulting MTTFS can be used to calculate the LambdaSU.
What you have done in the intermediate SIF is determine the equivalent failure rates of the 1oo2 valve configuration. In your final SIF, when you select user defined as the equipment item selection you will be able to click on a button in the upper right hand corner where you can specify PFH and MTTFS which will then automatically determine the LambdaDU and LambdaSU to be used in the calculation.

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