Can a final element, such as an air-to-open control valve, be shared between a BPCS control loop that is the cause of a scenario, and an SIF that is an IPL for the same scenario?

If you used LOPA to determine if you need a SIF and to identify what SIL is required (if any), then you cannot share or partially share a final element.  So, if the BPCS control loop is the cause (initiating event) and that loop uses the final element in question, then that same final element [...]

By |2016-12-07T01:33:36-07:00January 29th, 2014|Uncategorized|2 Comments

When to Use a Risk Matrix and Risk Tolerable Criteria

We don't recommend using a risk matrix during PHAs/HAZOPs. matrices are good tools to teach risk concepts, but in a well led PHA/HAZOP they reduce quality more than they increase quality. To see much more details, download and read this free paper: http://www.process-improvement-institute.com/_downloads/Optimizing_PHA-HAZOP_While_Maximizing_Brainstorming.pdf We use a risk matrix and a risk tolerance criteria only when [...]

By |2013-09-06T11:08:30-07:00September 6th, 2013|Uncategorized|2 Comments

When should PHAs (HAZOPs, etc.) Be Performed During Major Projects?

The short answer is you need to perform PHAs in phases, from conceptual stage, through preliminary and detailed design, and then complete these during the pre-commissioning stages (as mentioned by Bryan). The PHAs build upon each other and the completion of the final phase PHA becomes the Baseline PHA. The tools used change from phase-to-phase, [...]

By |2016-12-07T01:33:36-07:00September 6th, 2013|Uncategorized|0 Comments

Use of Internal PSM Audits by OSHA Inspectors

Before the OSHA PSM standard became official (May 1992), OSHA said that they would not use 3rd party or even first party (internal audits) of PSM against a company, but then they add "initially".  When asked by us what this meant, they said the first few years of implementation of PSM; this was to encourage [...]

By |2016-09-05T09:48:16-07:00August 17th, 2013|Uncategorized|0 Comments

PSM (process safety management) – Basics: What it is and isn’t.

Firstly, you cannot "write a PSM" .... I'm not even sure what that would be. PSM is a not a document for compliance like some environmental studies. PSM, if done correctly, is a way to run a business. If developed and implemented right, it will control the human factors that control the human error that [...]

By |2016-12-07T01:33:36-07:00August 6th, 2013|Uncategorized|0 Comments


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 [...]

By |2016-09-05T09:50:36-07:00June 15th, 2013|Uncategorized|0 Comments

Target Mitigated Event Likelihood (TMEL) & ALARP (or ALARA)

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 [...]

By |2016-09-05T09:51:56-07:00May 29th, 2013|Uncategorized|1 Comment

The Value of LOPA (and other quantitative methods) versus HAZOP (and other qualitative methods)

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 [...]

By |2016-12-07T01:33:36-07:00April 2nd, 2013|Uncategorized|0 Comments

Benefits of Safety Instrumented System (SIS) Standards

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 [...]

By |2016-09-05T09:54:07-07:00April 1st, 2013|Uncategorized|0 Comments

Separate Analysis for SIL are NOT Needed; and Overuse of LOPA

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 [...]

By |2016-09-05T09:55:33-07:00July 15th, 2012|Uncategorized|0 Comments