GCI TECH NOTES ©
Revised October 1, 2004
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
|
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 |
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 |
|
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