The Trend of Boiler/Pressure Vessel Incidents: On the Decline?
Print Date: 7/28/2016 1:15:47 PM
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
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
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 and addenda of the ASME Boiler and Pressure Vessel Code for current requirements.