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Gossman Consulting, Inc

GCI TECH NOTES©

Volume 4, Number 08                  A Gossman Consulting, Inc. Publication                   August, 1998

Revised October 1, 2004

HAZOP REVIEWS

David Gossman

Recently Gossman Consulting, Inc. had the opportunity to perform a HAZOP (hazard and operability) review for a facility in Europe. While such a review is common for industrial facilities in Europe, it is only commonly performed in the United States at chemical facilities usually as a requirement of the OSHA Process Safety Management regulations (29 CFR 1910.119). A more common practice in the United States is a facility audit which looks at a variety of health, safety and regulatory issues and may loosely prioritize a series of recommended improvements as a result. The more formal HAZOP review uses a list of keywords to examine each part and operation of a facility to determine both the probability and consequence of each mode of failure. Based on this combination of probability and consequence, the risk is determined. Any unacceptable risk requires a high priority corrective action.

The first step in a HAZOP is to break the facility down into subsections, either lines or individual pieces of equipment such as a tank, pump, agitator, etc. The degree to which this first step is done often determines how rigorous the HAZOP will be. HAZOPs are often done to different levels of rigor. We performed, and I will be describing, a medium level HAZOP; although different companies have established company/ industry specific definitions and procedural issues for such levels.

Figure 1 provides a form that can then be used to evaluate a specific line or piece of equipment. Table 1 provides a list of guide words and deviations that are used to evaluate each piece of equipment/line. Given a guide word and deviation produced by a theoretical cause the consequences must then be determined. Each consequence is evaluated against frequency and severity. Finally, after each consequence is evaluated, a form similar to Figure 2 is completed to determine corrective actions for each unacceptable consequence.

A HAZOP review can be performed based on drawings prior to construction, just prior to startup or periodically during operation of a facility. The review can identify significant flaws in facility design and operations and thereby reduce the risks to human health and safety and the environment.

Site:

Plant:

Line/Equipment

Figure 1

Table 1

PRIORITIZATION OF SAFETY, HEALTH AND ENVIRONMENT ISSUES

ASSESSMENT KEY

CONSEQUENCE CATEGORY	PROPOSAL FOR EXPENDITURE - SAFETY, HEALTH OR ENVIRONMENT IMPROVEMENT
CATEGORY 5 EXTREMELY SERIOUS CONSEQUENCE	TOLERABLE BAND
CATEGORY 4 MAJOR CONSEQUENCES		TOLERABLE BAND		UNACCEPTABLE
CATEGORY 3 SEVERE CONSEQUENCES			TOLERABLE BAND
CATEGORY 2 SERIOUS CONSEQUENCES		TOLERABLE		TOLERABLE BAND
CATEGORY I SIGNIFICANT CONSEQUENCES					TOLERABLE BAND
EVENT FREQUENCY PER YEAR	10-7                10-6     10-5                 10-4     10-3                 10-2             0.1                     1                      10 EXTREMELY             VERY UNLIKELY           UNLIKELY                                    POSSIBLE                      PROBABLE UNLIKELY
FREQUENCY CATEGORY	1	2	3	4	5
Example                Consequence Category 3 and Frequency Category 4                         3-4

 

PRIORITIZATION OF SAFETY, HEALTH AND ENVIRONMENT ISSUES

GUIDANCE FOR CONSEQUENCES CATEGORIES 

	CATEGORY 1 EVENT SIGNIFICANT CONSEQUENCES	CATEGORY 2 EVENT SERIOUS CONSEQUENCES	CATEGORY 3 EVENT SEVERE CONSEQUENCES	CATEGORY 4 EVENT MAJOR CONSEQUENCES	CATEGORY 5 EVENT SERIOUS CONSEQUENCES
TYPICAL MEDIA ATTENTION	Noted in Local Press, TV & Radio Few telephone calls	Significant local attention, interviews Adverse local comment	Considerable local, some national attention Local outcry	Headline  national, continuing local attention	International news, outcry threatens to close operation
TYPICAL ACTION BY AUTHORITIES	Notifiable	Warning	Prosecution	Severe Fine	Prohibition
ACUTE INJURY INCIDENT - on-site effects	Minor/classified injury  Low  probability of Lost Time Accident	Lost Time Accident Low probability of  major injury	Major injury Multiple injuries Low probability of fatality	Fatalities or few employee fatalities Low probability of many fatalities	Many fatalities (ie 5 or more)
ACUTE INJURY ACCIDENT - off-site effects	Nuisance off-site- see Environmental	People affected- short term minor	Few people require hospital treatment	Serious injuries 10s in hospital	Fatality or fatalities off site; many injuries
CHRONIC HEALTH OR PHYSICAL CONDITION - on-site effects	Occasional releases above Occupational Limits - OEL or STEL - low hazard materials Unpleasant conditions	Persistent releases above limits - 2 to 6 times Occupational Limits - non-carcinogen Harmful conditions	Distressing exposure Significant health effects Harmful, irreversible, unacceptable effects Sensitization effects	Employee exposure to high levels of carcinogens, e.g. asbestos, benzene, vinyl chloride, or life-threatening conditions	Many cases of ill health and resultant fatalities Health risk unacceptable due to continuous or discrete large releases

HAZARD AND OPERABILITY STUDY ACTION SHEET

DATA FILE:

Figure 2