About Bill Bridges

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So far Bill Bridges has created 59 blog entries.

Come See Us at the 13th Global Congress on Process Safety in San Antonio!

Come by and see us at the AIChE 13th Global Congress on Process Safety in San Antonio, Texas March 26th thru 29th, 2017! We'll be presenting papers and speaking on multiple topics at the conference, and will also have a booth set up in the exhibit hall, so come by and sell hello, and let's [...]

By | 2017-03-27T13:02:14+00:00 March 25th, 2017|Events, PSM|0 Comments

Keys to Avoid Making A Dog’s Breakfast Out of Your MOC System

In an invaluable addition to the Process Improvement Institute compendium of Free Resources, PII colleagues Revonda Tew and Tim Waugh present an important paper that discusses how to ensure the Management of Change system addresses a change’s effect on implementation of other process safety management systems and discusses common MOC workflow weaknesses that can undermine [...]

By | 2017-02-19T13:08:52+00:00 January 6th, 2017|MOC|0 Comments

New Papers in Free Resources on Identifying SIF-SIL as part of PHA/HAZOP, PHA of Non-Normal Operation Modes, and Writing Operating Procedures and Troubleshooting Guides

Just posted in the Free Resources section of the Process Improvement Institute website are three new and invaluable papers related to issues important to process safety management professionals everywhere: Identify SIF and Specify Necessary SIL, and other IPLs, as part of PHA/HAZOP Learn why it is not necessary to “Boldly Go Beyond HAZOP and LOPA.” [...]

By | 2016-12-07T01:33:30+00:00 April 22nd, 2016|HAZOP, PHA, SIF, SIL|0 Comments

Does LOPA really replace 90% of the QRA?

Well, that depends on what you call QRA. Some companies (the folks they have taught) define QRA as only the high level risk assessment that may be performed at the early design phase of a project to make large siting and fire protection (and other mitigation) decisions. LOPA does not replace that specific QRA. But [...]

By | 2016-09-05T05:54:22+00:00 August 26th, 2015|CCPS, HAZOP, LOPA, PHA, QRA|0 Comments


In the world of HAZOP/PHA, double-jeopardy (D-J) is defined as a scenario where two independent causes exist at the same time. One Cause (in LOPA terms, one Initiating Event) can occur in time much earlier than another, and not be corrected or maybe not even discovered. Then a second cause occurs and the scenario progresses. [...]

By | 2016-12-07T01:33:33+00:00 August 14th, 2015|Double-Jeopardy|1 Comment

ESTIMATES of ACCIDENT FREQUENCY – Per Scenario and per Site

Do Not believe the math as black and white or as accurate. When we accept a risk of 10-3 per year per facility, we are not necessarily saying we accept 1/10 deaths per year for the facility... we are actually guessing at both factors. 1) The factors we use for LOPA (and for SIF need [...]

By | 2016-09-05T08:47:42+00:00 August 14th, 2015|LOPA, PHA, SIF|0 Comments

Is Consideration of Double-Jeopardy valid in PHA/HAZOP Discussion?

Double-jeopardy (D-J) is NOT an independent protection layer (IPL) failure after an initiating event (IE). All PHA/HAZOP scenarios are of the type of: IE occurs, then IPL 1 fails, then...., leading to Consequences. However, the definition of double jeopardy (D-J) is when two initiating events, which are independent (or we had hoped they were so), [...]

By | 2016-09-05T08:48:48+00:00 August 13th, 2015|Double-Jeopardy, HAZOP, PHA|0 Comments


We use the terms of tool and method interchangeably. Methods/tools include HAZOP of continuous mode, HAZOP of steps for non-continuous modes of operation, What-if, Checklist. The scope and goals establish the Qualitative Hazard Evaluation that you need to accomplish using one or more of these tools/methods. So, a Process Hazard Analysis (PHA) is a specific [...]

By | 2016-12-07T01:33:33+00:00 June 29th, 2015|HAZOP, PHA|0 Comments

Enroll in a Process Safety Course from Process Improvement Institute!

Process Improvement Institute, Inc. (PII) has 15 experts on staff (each with over 25 years of industry experience; including 10 to 35 years of process safety experience) who teach PSM, PHA Leadership, MOC, LOPA, Procedure Writing, and other specific courses on process safety, as well as Human Factors. You can attend publicly available courses or [...]

By | 2016-12-07T01:33:33+00:00 June 15th, 2015|Human Error, OSHA, PHA, PSM|0 Comments