Inspecting and testing barrier integrity

Regular inspections and tests are necessary tools to ensure that such barriers as those discussed in Chapter 7 against fires and explosions are maintained. Legislation in Europe and the USA make it a responsibility of the employer to ensure that the barriers against major accidents involving chemical hazards are inspected regnlarly (Enropean Council, 1996 OSHA, 1994). The inspections have to be carried out by experts from the technical department of the plant or from a dedicated plant inspection department. 

Below is a list of typical equipment of a process plant that is subject to inspections  

The inspection or testing frequency has to be determined. Traditionally this has been based on manufacturer recommendations or on good engineering practice. A recent trend is to establish inspection intervals for individual types of equipment based on results of reliability analyses. Reliability data serve as necessary data inputs to such analyses. In order to establish a database on barrier reliabiUty, it is necessary to tag each piece of equipment and to record its inspection/test, repair and maintenance history. 

Inspection and testing procedures have to be documented for the different types of equipment and systems. It is important to ensure that overall barrier efficiency is tested. For gas alarms, for example, the complete loop has to be tested from the gas detector to the alarm presentation in the central control room. The results of each inspection/test have to be recorded, showing date, name of inspector, equipment tag number, description of inspection/test, results and actions. In cases where deficiencies are identified, the inspector has to evaluate whether they are of a nature requiring immediate shutdown and replacement of the failing unit. Less critical failure may wait for correction until the next scheduled revision stop. 

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