The question often raised is “Should LOPA be combined with HAZOP meeting.” To set the background, I’m one of the three originators of LOPA in the mid-1990s and co-authored the first textbook on LOPA (CCPS/AIChE, 2001) and am primary author of the second textbook issuing in a few months: Guidelines for Independent Protection Layers and Initiating Events (CCPS/AIChE, 2012). We have led thousands of PHAs (HAZOPs), either with LOPA integrated or without. On the ones with LOPA included, we have done with ALL scenarios requiring LOPA (100% LOPA) to 10% of scenarios requiring LOPA during the meetings. Based on these trials, it is MUCH better to do LOPA after the HAZOP is completed and to use LOPA only for those scenarios that the HAZOP team found too confusing to make a qualitative risk decision in the HAZOP setting.

There are many reasons, based on data, for this decision, which include:

  • Brainstorming in the HAZOP is maximized because you analytical discussions in the HAZOP meetings. The HAZOP (or qualitative analysis approach using brainstorming methods) is your only chance to Find scenarios (LOPA does not help with that chore) and so you should do nothing to limit brainstorming.
  • LOPA can easily be done by one analyst (no need for a team and a team is not even recommended; read the LOPA book and the many papers since then for a description of same). So why waste everyone else’s time on LOPA when one can do it very well (with a little help from one or more folks on some LOPA)?
  • Only about 3-5% of scenarios are complex enough to need LOPA; why do LOPA or more than is needed.
  • Doing LOPA in the meetings will frustrate many team members as they will see it as a waste of time; this will further hurt brainstorming.

We realize many are pushing LOPA + HAZOP combos as something “new and improved”… it is not… in fact LOPA was invented to remove semi-quantitative analysis from HAZOP meetings. So, combining LOPA + HAZOP is taking a step 20 years back in time and ignores one of the main reasons for the develop of the rules for LOPA.

To find out more, visit and download the papers there on LOPA. Or schedule to attend our course on LOPA: