It depends on what does one expect from FEED, and what is the project in question.
I remember having a few projects where it was virtually impossible to step into EPC (I don't think anybody will go for separate Detailed Design and PCC phases with different contractors, for many reasons) immediately after the Selection or Pre-Feasibility phase. They were all revamp, brownfield projects. Even if you get all the main equipment selected and sized to the tiniest details during pre-feasibility stage, it is very hard to imagine how will all this fit into a predefined plot space, predefined utilities, safety constraints, shutdown frame of the existing facilities, etc. etc. This was the moment for performing FEED engineering - taking care of the layouts, constructability, SIMOPS, expansion of Utilities, safety studies. Sometimes, you could see how a perfect concept for a greenfield environment simply doesn't work for a brownfield project. I don't see how all this important stuff can be performed during pre-feasibility stage. If someone finds out and develops complete methodology, I will propose this person for Nobel prize.
For greenfield projects (vast majority of them), added value of FEED is almost always insignificant. If you have done the project economics well, price variations arising from inaccuracies in equipment and materials calculations in pre-feasibility phase can be pretty much well covered by the contingency. The conclusion based on 13 years in this business is that requirements for FEED should be assessed on a case to case basis. Performing FEED for every project, or not performing FEED for any project - I have found out that this strict rule simply does not work for me. I think you and Dave are saying something very similar to that.
Dejan IVANOVIC
Process Engineer, MSChE