Choosing Consequence or Chance Reduction Strategies to Manage Operating Risk Matters if You Want Operational Excellence

The vital difference between using consequence or chance reduction strategies if you want Operational Excellence results, is consequence reduction requires repairs and maintenance, whereas chance reduction removes repairs and maintenance.


In reading “Enterprise Asset Management Success the Plant Wellness Way for CEOs and Senior Executives” I was interested in your table on page 15 that showed risk based inspection and condition based monitoring techniques as consequence reduction strategies.

My understanding is that both RBI and CBM are specifically designed to prevent failure through reducing the likelihood of failure i.e. by detecting failure before it happens within timescales that allow mitigation action to be taken. In the API 581 RBI standard, consequence is treated as a constant over time so the methodology specifically targets risk reduction through more effective inspection or design changes.

I appreciate that this is only a small point in terms of the overall approach and key messages challenging readers, but if you have time to reply I would like to understand the reasoning behind not viewing RBI and CBM as chance reduction.


Hello Paul,

When I developed the table I decided that if a technique or methodology required a failure to start in order to provide evidence that failure had been initiated, then it fell into the consequence reduction strategy. Once an embryonic failure existed then the eventual outcome COULD be complete failure if circumstances went badly. CBM and RBI look for evidence of failure, in fact they need a failure to have started in order to provide the signal that the P-F degradation has begun.

Vibration analysis (a CBM technique) needs a rolling bearing to start failing in order to generate the noise signature that a failure has begun. Oil wear particle analysis requires the oil to be contaminated before it tells you that the oil is contaminated by wear particles. RBI requires a vessel or pipe wall thickness to start thinning, or the wall to start cracking/pitting, so that it can tell you that the vessel wall is thinning or a crack/pit has been initiated. None of the failure events are prevented; only discovered after embryonic failure is already present. Now all that you can do is fix them, replace them, or live with the failure and derate the equipment. There goes more money down the drain!

Chance reduction techniques intentionally seek to limit failure initiating situations from even arising. There will be no problem to ever find because the circumstances that generate the failure are prevented from happening in the first place. You can do away with RBI and CBM in that case. That will save/make you a lot of money.

We do need RBI and CBM so that we can find the presence of embryonic failure in companies that do follow chance reduction practices, but they are consequence reduction strategies because they detect a problem and then allow us to mitigate the now existing problem so catastrophe does not occur. But RBI and CBM do not prevent the problem’s existence.

The differentiation between chance reduction and consequence reduction is important to understand, as it greatly impacts the plant and equipment operating and maintenance strategy you use. Consequence reduction will always require repairs and maintenance. Chance reduction will remove the need for repairs and maintenance.

I hope that these thoughts are of use to you as you develop your understanding of what leads to maintenance and operational excellence.

My best regards to you,

Mike Sondalini

P.S. If you have questions on life cycle asset management, equipment maintenance strategy, defect elimination and failure prevention, or plant maintenance and reliability, please feel free to contact me by email.