The Trend of Boiler/Pressure Vessel Incidents: On the Decline?
Spring 1997
Category: Incidents
Summary: The following article is a part of National Board Classic Series and it was published in the National Board BULLETIN. (4 printed pages)
The release of the 1996 Incident Report marks the fifth anniversary of the new report form, which was changed to improve the accuracy and consistency of the data collected. To utilize this data as a meaningful tool and further enhance its value, a five-year trend analysis of boiler and pressure vessel-related incidents, injuries, and deaths is included.
The term "incident," for the purposes of the report and this article, is best described as an occurrence or failure resulting from one of the causes listed in the Incident Report. While an incident may not be a catastrophic failure, it is still considered to be an occurrence that results from a deficiency in mechanical operation, materials, human performance, or a combination thereof.
With that in mind, it is encouraging to report that the number of incidents in North America has decreased for the first time in five years, from 2,612 in 1995 to 2,087 in 1996. After a slight but steady increase in the numbers each year since 1992, the 1996 figures indicate a 20% decline in incidents. This is a significant drop, especially since the 1996 total represents a five-year low.
The number of injuries increased slightly from l995, about 3%, in keeping with a three-year trend of increases. This rise is understandable when incident figures also increase, but it is a disturbing statistic when there is a reduction in the number of incidents. The 1996 injury-to-accident ratio is the second most critical in the past five years, i.e., one injury for every 27 incidents. Only the 1993 ratio of one injury for every 23 incidents was more adverse.
A simple translation of the numbers is that more people are sustaining injuries from fewer occurrences. This can only mean that the incidents, while fewer in number, are greater in devastation. So, while 1996 was favorable in terms of the quantity of incidents, this is unfortunately negated by the greater destructive quality of those same incidents.
Boiler and pressure vessel-related deaths in North America decreased in 1996, perpetuating the cyclical trend of the past five years. Fatalities were down in 1992, went up in 1993, and have continued in that pattern since. However, the 1996 fatality decrease cannot be looked upon optimistically because past numbers indicate a probability of the trend continuing next year with an upswing. If the National Board uses information gathering for one of its intended purposes, as an early warning system, then preventing an increase in deaths in 1997 must be the focus.
A two-pronged approach to prevention of boiler and pressure vessel incidents (and thus injuries and deaths) is observed. First, if the deaths recorded in the Incident Reports of the past five years can be linked to the "off" year of a two-year inspection cycle, there is a clearly documented reason for annual inspections. Also, the installation of continually more complicated vessels may warrant review by the jurisdiction to increase its surveillance. If the jurisdiction's boiler and pressure vessel inspection program lacks adequate staff or funding to perform necessary inspections, then there is solid, statistical evidence to support the need for additional resources.
The second element of prevention involves violation tracking. A violation tracking program exists to record violations found on routine inspections and to show the number of incidents prevented due to inspections. This information helps jurisdictions focus on objects and causes which require stronger regulation. Violation data is useful in determining trends which affect safety, as well as in providing a statistical foundation for educating and informing legislators and the public.
However, if violations are not documented and reported, the potential effectiveness of an early warning system is diminished, and the basis from which to make adjustments to inspection requirements is lost. Ideally, the National Board will be alerted to areas of concern before incidents occur, rather than, as a result, analyzing what has already happened. The violation tracking program has helped the National Board advise its members of national trends and specific problems.
To put this in perspective, the category and cause information on the Incident Report should be examined closely. To begin, the objects experiencing the largest decrease in incidents are the steam heating boilers (low-pressure steam boilers), specifically occurrences related to low water condition. This may be attributed to a more vigorous effort by the jurisdictions to advise owners and to sponsor training for the proper methods of maintaining equipment.
Although the steam heating boiler category experienced a decrease in incidents, it is still the object that consistently records the highest number of occurrences. Each year it surpasses power boilers and the other categories in incidents because it is the type most frequently installed in the jurisdictions. The low-pressure steam boiler is also, perhaps, the type which does not generally receive the proper operator attention.
Within the object categories, there are several common causes of failure. Low water condition, operator error, and poor maintenance are the leading causes of incidents for the past five years. These vie for top position, nudging each other in and out of first place depending upon the year. Still, they remain the foremost reasons for incidents.
Turning this statistic around depends on operator training and partly upon the continued dissemination of safety information by various means available from the jurisdictions to the owners. Even in the category of unfired pressure vessels, where low water condition is not applicable, operator error and poor maintenance is the leading cause of incidents. The message is clear: the numbers reflect the need for properly trained, qualified operators. Boilers and pressure vessels can be safely operated and maintained only by individuals with the appropriate skills and training.
The inspectors of various jurisdictions have done what their job entails, and overall, violations were found to have been properly reported and adequately addressed. The presence of jurisdictional boiler inspection programs has an impact on preventing occurrences because violations far outnumber actual incidents.
However, because violations did occur, increased scrutiny of boiler and pressure vessel-related incidents is imperative. Inspectors representing various jurisdictions are impartial authorities with an agenda of safety and prevention. Enforcement of boiler and pressure vessel regulations to protect the public will continue in the coming years.
Editor's note: Some ASME Boiler and Pressure Vessel Code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition of the ASME Boiler and Pressure Vessel Code for current requirements.