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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.

HAZARDOUS AND OPERABILITY STUDY WORKSHEET

Site:

Plant:

Line/Equipment

Guide Word

Deviation

Cause

Consequence

Action

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 1


Table 1

Guide Word

 

Deviation

 

Flow

 

 

More
No
Less
Reverse
Other
Also

 

Pressure

 

 

More
Less

 

Temp

 

 

More
Less

 

Viscosity

 

 

More
Less

 

Relief

 

 

Other

 

Samples

 

 

Other

 

Instruments

 

 

Other

 

Corrosion

 

 

More

 

Erosion

 

 

More

 

Services

 

 

Other

 

Maintenance

 

 

Other

 

Static

 

 

Other



Table 2

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:

ACTION ON:

RESPOND BY:

ACTION NO:

MEETING DATES:

DOCUMENT REFERENCE:

TITLE:

REVISION:

ITEM:

CAUSE:





CONSEQUENCE:





SAFEGUARDS/COMMENTS:





ACTION:



RESPONSE: DATED:



















SIGNED:

Figure 2