Process Improvement Institute Blog – news related to process safety, process reliability, and human reliability

The CCPS book clearly states LOPA uses a single cause-consequence pair, the worst combination, for the order-of-magnitude risk estimate. Other methods, especially Fault Tree, are more appropriate to treat multiple initiating events. Many times simply summing the initiating events is not appropriate due to limitations in the simplifying assumptions behind the development of LOPA. There are several reasons outlined in …

There is a lot of discussion elsewhere on ALARP (and/or ALARA).  However, a company can add too many protection layers and invite shortcuts of one or more of the IPLs over the long-term, since staff are pretty sharp at figuring out when the “plumbing is over-tinked”.  We advise folks to reach barely tolerable on each scenario and then stop; BUT …

I like LOPA as well as the next person; I’m one of the two co-originators as you likely know.  But all of the quantitative methods use “statistical” values (but not as statistical as most think) that have in fact been “voted” upon by “experts”, so you can either let LOPA or QRA analyst use factors voted on by others or …

The main benefit to a business (set aside any “government regulator” issues for now, since that should not be very important) in implementing SIS standards is the consistency in understanding the safeguard level for an instrumented safety system. But, there are disadvantages to following “only” IEC 61508/61511. One disadvantage is that the PFDavg calculated for a SIF of a given …

Since I’m one of the two originators of LOPA in 1995 and one of the two primary authors of the CCPS books on LOPA (2001 and 2012), I (and many others) believe we are doing Too Many analysis. A well-structured and well led PHA team does 95% of the risk analysis and 99% of the risk identification. LOPA is only …

Double-jeopardy is NOT a discussion of (or failure of) multiple layers of protection. Nearly every scenario should have multiple layers of protection against the ultimate (unmitigated) consequence. Double jeopardy is also NOT a deviation combined with failure of a safeguard that then “lies in wait.” Double jeopardy is the occurrence of two deviations or two initiating events at the same …

Trouble-Shooting guides is the term many folks use to for the list of steps and decisions necessary to tale when a deviation from the normal opertion occurs. It is what an operator does to prevent a deviation from leading to an emergency shutdown or worse. (Trouble-Shooting guides are significant extensions of waht some call Operating Limits Tables.) The standard way …

Many (perhaps even most) EPCs and Owner companies do not really understand best practices related to risk analysis and independent protection layers (IPLs). This is unfortunate. This lack leads to a lot of wasted resources. Also, many owner companies do not implement the management systems and discipline needed to maintain IPLs once identify. It is Far more important to properly …

“Are You conducting SIL assessment session along with HAZOP?” Note that this question does not include the term LOPA. We do not use LOPA during a HAZOP (unless clients make us) and yet we identify most of the SIFs and we set the needed SIL at that time (no numbers; no other analysis). We do the same as we discuss …

Though consequence severity can (and is) used to decide when a LOPA is needed, the Best trigger for doing a LOPA is when the HAZOP team is confused. More than likely the HAZOP team is Not confused even for high severity. For instance, we were on a high severity ($100,000,000 loss potential, multiple death) consequence today in our HAZOP (Crude …