Because of recent involvement with products and systems that have Safety Integrity Level (SIL) ratings, I read the comment (below) in the PSA Deepwater Horizon review with interest. While administrative and effectiveness issues must be carefully assessed, the application of SIL should be part of the BOP performance dialogue. SIL ratings may also be appropriate for entire well control or well integrity systems.
Today’s requirements stipulate a risk analysis for the control system of a drilling BOP, with specified minimum requirements for its safety integrity level (SIL). As a result of the DwH incident and of the fact that blowouts are not confined to drilling operations, the question is whether such an analysis, with a specified minimum SIL level, should also apply to all types of BOPs, including well-intervention models. In addition, consideration should be given in this context to whether other control and management systems related to well integrity/control exist which should be subject to such requirements.
Bud's Offshore Energy (BOE) 
I feel in the ops. of BOP’s if we refer to Macondo and the various comments and reports (the official DNV version which spent months onshore investigating) there are 2 specific parts :
The control system versus the BOP action itself.
1- Failure of the control to activate the BOP : loss of surface and subsea communications, no one activating the BOp or too late and wrongly ? poor or false feed back or non coherent infos ? unsufficient hyd/electrical power ?
Because all the software and surface equipment has sunk with the rig this area of comments and conclusions is limited.
2- Failure of the activated BOP to close on the pipe : This part of it was investigated, and indicated that the the drill pipe was jammed between the ram block having found a place “off center” unlike the general concensus that the suspended pipe is vertical and concentric to BOP bore. Further indication and comments have focuses on the movement of rig / riser pulling the pipe tight in an offset and preventing the ram to drive it in the center ?
And the scenario of buckling effect which deflected the pipe below the ram cavity and jammed it in a partially close bag preventer.
My own view is that much more work has to be done on the various BOP control sequences and feed back of pressure, pipe position ect.
If thy particular BOP model or manufacturer cannot cut a pipe off center , how are the other BOP’s performing ? and what is been done on this subject interest me as an observer.
Thanks JL. Good input.