Accidents in technical industrial plants
A safety-related analysis of damage events in Germany
BAuA systematically investigates accidents in industrial plants. Why are we doing that? Because you can learn from accidents! In so doing, we aim at generating knowledge as to how the safety of systems and employees can be improved.
In order to use events (damage events) in process systems in order to be able to draw lessons against any repetition of these events and regarding the orientation of the failure-preventing and failure-limiting measures, respectively, data is analysed according to industrial health and safety criteria. Reports on reportable events pursuant to the Major Accidents Ordinance, reports on fatal industrial accidents, datasets on non-reportable events provided by the Committee "Ereignisauswertung" (event analysis) of the Commission on Process Safety (AS-Er of the KAS, successor of the sub-committee "Ereignisauswertung" (event analysis) of the Major Accidents Commission) and information from technical literature are present. For efficient data collection and analysis, a database was created that is described in the research report Fb 1022. Building upon this collection and analysis, the data is processed continuously, which will be described in the following for the years of 2004-2006.
An overview of the damage events
Since 1 January 2004, 136 new datasets were entered into the database. Thereof, only 91 events actually occurred after this date, however. This shows that a significant number of events are entered in a delayed manner. In this, the data was collected from the following sources:
Thereof, the following events actually occurred since 2004:
Among these 91 events, there were 20 accidents with lethal consequence and 21 accidents where people were injured.
A more profound analysis shows that a substance was released without any fire and explosion in most events:
As in the previous years, the majority of the damage events occurred for the system type "Chemical products, pharmaceuticals, mineral oil refining" (42 datasets). In contrast, only eight datasets regarding the system type "Management and elimination of waste and other substances" could be entered as events reportable pursuant to the Major Accidents Ordinance. However, at least 30 events in recycling and waste management companies were published as press releases on the Internet for 2005 and 2006 alone (source: Federal Environment Agency). This shows that only a low number of actual damage events in recycling and waste management companies is captured via the reporting obligation according to the Major Accidents Ordinance.
In contrary to the previous years, it was possible to capture about 30 datasets on incidents in connection with vessels. These datasets specifically provided findings regarding hazards caused by foreign substances, deposits, substance intolerances, static charging, and poor preparation of the vessel regarding repair and cleaning work, respectively. The analysis of the data for hazardous substances causally or decisively involved in the events did not show any significant accumulation regarding specific substances. In at least seven events since 2004, a corrosion resulted in a loss of function of safety-relevant facilities.
New findings from accident analyses are incorporated in the technical rules
Due to the events entered retrospectively, it was possible to perform an analysis of the findings regarding the technical provisions and rules concerned. This way, it was possible to identify 128 events and 25 events having occurred since 2004 from all entries in the database that provided indications to the creation of new texts on technical rules and the application of existing rule texts in practice. Below, there are some examples in this regard:
- A lethal accident was caused by a nitrogen line being confused with a compressed air line, with this being the cause of the suffocation of the employee during sandblasting work. Another accident resulted in one severely and two slightly injured employees, because two immediately adjacent extraction connections were confused and thereby an acetylene-oxygen mixture escaped unnoticed through a hose behind an equipment cabinet. An explosive mixture was formed within the cabinet which ignited due to dripping slag parts caused by flame cutting activities performed above the cabinet. The confusion of gas connections was discussed in the Committee on Occupational Safety and is discussed in the Committee for Event Analysis of the Commission on Process Safety. The discussion includes additional protective measures, such as the spatial separation of the gas connection exceeding the identification of these connections pursuant to the technical rule for workplaces "Sicherheits- und Gesundheitsschutzkennzeichnung" (Safety and health protection labels) (ASR A1.3).
- Regarding corrosion as interaction of work equipment with substances, findings from several events were incorporated in the development of the technical rule for operational safety "Gefährdungen durch Wechselwirkungen" (hazards caused by interactions) (TRBS 2210). This TRBS contains specific notes regarding hazards caused by corrosion for chlorine gas and contact with water. The exemplarily mentioned measures are, among others, based on two events: When hydrogen chloride was to be extracted from a transport vessel using a hose line, hydrogen chloride was released. It was not possible to rotate the valve spindle for opening the vessel, since it was corroded due to being exposed to acid. As a consequence, the head screw loosened instead of the spindle. In the second event, four bolts that were corroded due to a creeping leakage suddenly failed in a discharge line of a smelting reactor, among others filled with sodium hydroxide solution. The analysis of additional events occurred since 2004 did not provide any information on the execution of general measures against corrosion, such as "korrosiv wirkende Ablagerungen vermeiden" (avoid deposits causing corrosion).
- For example, the following damage event provided indications of hazards due to the "Reaktionsfreudigkeit" (reactivity) between compressed oxygen and greases in the TRBS 2210: a metal fire occurred on a piston compressor for compressing oxygen despite a comprehensive sealing system, because oil traces remained on the sealing rings and the piston rod after conversion work.
Violation of rules and provisions is the primary cause of accidents
Far more frequently than an incomplete rule text, a violation of the existing requirements from provisions and rules was observed. Thereof, two events shall be represented, with relatively detailed information regarding the provisions and rules concerned being present for the two events:
- in one accident, the safety interlock of the protective lining causing the machine to be shut down if the lining is opened was bypassed in a casting unit. When a temporary employee who did not know about this bypass wanted to insert strainer baskets into the sand mould, the employee was squeezed lethally when entering the area of the moulding press. Pursuant to annex 1 no 2.8 Operational Safety Ordinance (BetrSichV), it must not be possible to easily bypass or render ineffective safeguards. The technical rule for operational safety "Gefährdungen an der Schnittstelle Mensch-Arbeitsmittel - Ergonomische und menschliche Faktoren" (hazards at the human-work equipment interface - ergonomic and human factors) (TRBS 1151) specifically mentions measures against mistakes by bypassing safeguards (the TRBS 1151 was adopted by the Committee on Occupational Safety and will be published soon on BAuA's website).
- While filling an underground tank using a road tanker, the tank was overfilled and ethanol escaped to the gravel bed of the tank. According to the delivery note, the delivered volume of ethanol should have fitted into the tank - without exceeding the specified filling degree of 95 %. However, the vehicle contained more product. The tank was equipped with a level gauge and an overfill protection device that had been, however, disabled in the distribution box within the framework of maintenance work and not been re-enabled prior to commissioning. The system did not display the missing activation and thereby this was a passive error. Furthermore, there was no interlock or alarm via the level display of the tank. The overfill protection system did not comply with the information for error monitoring pursuant to the technical rule for combustible liquids "Richtlinie/Bau- und Prüfgrundsätze für Überfüllsicherungen" (guideline construction and testing principles for overfill protection devices) (TRbF 510) annex 2 no. 5.1, according to which overfill protection devices, in the event of a loss of auxiliary power or an interruption of the connecting lines between the parts of the system, have to report this failure or display the maximum level. No equivalent protective measures were taken either. Furthermore, the disabled overfill protection device could have been discovered within the framework of a post-maintenance inspection specified according to § 10 section 3 BetrSichV and/or within the framework of a post-installation inspection required according to annex 2 no. 6 of the TRbF 510. It is important that, within the framework of the succeeding rules prior to suspending the TRbF 510, these protective measures are continued to be mentioned specifically and the professional public is made aware of their necessity.
The accident analysis - an important prevention instrument!
When reading the first chapters, it becomes apparent that the number of newly entered data and the number of events thereof that actually occurred since 2004 is far too low in order to make a statistical statement. However, every single event may provide valuable information regarding hazards assessed incorrectly up to now and regarding the design of protective measures. In this regard, these events shall continue to serve as an important source of information when developing rules and when designing technical and organisational protective measures.