Uncovering hidden operational risks
02 April 2014
As long as production runs according to plan, possible risks often remain undiscovered until an unexpected event triggers an incident. HAZOP studies can help uncover these hidden risks and take preventive and systematic actions to improve safety. Rainer Semmler, TÜV SÜD Chemie Service, discusses what might happen if workflows in the process are interrupted.
Although safety levels in Germany are relatively high, the registration of reportable incidents still occurs. In the majority of cases, these incidents are triggered by unexpected events and unusual situations which initiate a severe chain of events – often aided by complex production processes, chemical substances and hazardous materials.
In standard operation, these risks and hazards often remain undetected. However, in combination with human error even simple technical defects can cause these risks and hazards to come to light.
Frequently, the causes are not directly related to the production process, so that they are not covered by conventional risk analyses. Planning mistakes in the conversion and modernisation of plants and systems, for example, involve considerable risks if materials have not been processed correctly. Similarly negligence while using a welding device or cutting torch may trigger a chain of events. Accidents involving operating equipment or vehicles can cause incidents of considerable scale in unfavourable conditions. If these cases coincide with ineffective safety solutions, the matter must often be solved by the emergency services and incident specialists.
An increasing number of companies rely on hazard and operability studies (HAZOP) for identifying safety issues and risks. The procedure basically involves a facilitated technical discussion. Internal and external specialists systematically analyse potential weaknesses in workflows and production processes and quantify the possible consequences. This well-structured approach enables owners and operators to uncover operational and process-related risks and develop possible strategies and countermeasures.
The study leader should be an impartial, experienced and technically adept facilitator. Possible scenarios should be created to represent deviations from the desired target conditions for discussion by an expert group. To ensure that all possible aspects are taken into consideration, the individual systems and sub-systems are analysed and questions posed. What happens in the case of critical changes in parameters such as temperature, pressure, flow rate or the mixing ratio of fluids and substances? What events may this cause? Analysis of the processes considers technological and organisational risks, but also possible human error and external influences such as extreme weather conditions, transport accidents and acts of sabotage on the company premises, and even faults in automation and control systems.
Subsequently, the experts take a closer look at the chains of events and determine possible damage and effects. Depending on the probability of occurrence (from unlikely to certain) and the consequences of damage (negligible to catastrophic) each event can be assigned to a damage category. The systematic approach facilitates the prioritisation of measures and impartial assessment of risks, illustrating the actual need for action.
An expert but independent recorder documents the arguments, comments and results in a record. They supply the basis for developing adequate technological or organisational solutions and safety mechanisms. Systems used to fill a tank with acid, for example, can be equipped with a pH control system to avoid confusion between products when filling the tank. Another option lies in equipping systems with an emergency off switch. Possible organisational solutions include shorter maintenance intervals or introduction of the principle of dual control.
Comprehensive documentation also helps later on during the design, planning, modification and modernisation of plants and in the induction of new members of staff. In addition, service providers, sub-contractors and assemblers obtain reliable and solid information about the risks involved on site caused by flying sparks during welding or accidental mixing of hazardous substances. The documentation not only provides a detailed overview of current plant safety, but also helps owners and operators to review the state of the art in safety which is required by law, and compare it to the safety systems realised in the company. In addition, it may also positively affect approval procedures (e.g. in accordance with the German Air Pollution Control Act, BImSchG) and insurance terms.
No two companies are the same. Given this, the technical know-how of the participants and the study leader selected are of critical importance for the efficiency and effectiveness of the HAZOP procedure. Depending on the degree of complexity, a HAZOP team ideally comprises between six and ten experts. The study leader plays a special role. They must systematise and structure the team meetings, develop useful scenarios and guide the participants to new solutions. Further systematic methods, such as failure mode and effect analysis (FMEA), event tree analysis (ETA) or fault tree analysis (FTA) complete the approach.
Working with internal experts, the study leaders and experts of TÜV SÜD Chemie Service reliably identify process-related weaknesses in companies. The well-structured but still open procedure of HAZOP analysis is therefore suitable for comprehensive risk prevention. To keep safety solutions up to date, the procedure should be repeated at regular intervals. This results in permanent and efficient enhancement of safety levels, prevents damage and operational failure and supplies a reliable information basis for the necessary investments.
The HAZOP procedure at a glance
•Which hazards does the plant basically involve? Qualify risks.
•What may cause hazards to become severe? Determine the causes.
•What consequences for people, operation and the environment must be expected? Assess impacts.
•Which measures can limit the consequences to a minimum? Develop counter-actions.
The employees of the company develop answers to these safety-related questions in multidisciplinary rounds. Instructions by an external expert and experienced study leader are of key importance in this context.
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