Dynamic Process Safety Management
CCPS Latin American Conference on Process Safety
9th Latin American Conference on Process Safety
Barrier Management and Protective Systems II
The process safety barrier management tools are almost completing a decade of existence, the solutions have become increasingly comprehensive, but there are still many doubts about the use of the tools, the main challenge being the implementation.
Knowing what has to be managed typically has a consensus, but the challenge is how to start and thus show that the tools really have a return on investment and results in the process safety barrier management.
This paper will present an implementation sequence with phases, each phase can present practical results.
Safety barriers can be divided into instrumented (intelligent) and non-instrumented (non-intelligent). The layers that use intelligent systems are easier to collect and manage data.
The preventive protection layers are typically intelligent, monitored by electronic systems and data networks, such as automatic control systems (PLCs and DCSs), Alarm Systems, Safety Instrumented Systems (SIS).
Non-intelligent systems tend to face up to a major transformation influenced by technologies such as IIOT, 5G, etc, but at this point the papper will consider that systems such as relief valves, dikes and other physical containments depend on monitoring by verification routines, with the physical presence of a human being. Still on human interactions, we can mention the training, operational procedures and administrative management tools that also make up the safety barriers system of an industrial unit.
At first look, it is common to have the impression that the initial activity of managing safety barriers consists of collecting data, transforming it into information and using it for maintenance activities. This method is very common when looking for patterns and data analysis of what is happening and trying to make predictions of the future, but in a safety system the activities consist of comparing the efficiency, availability and reliability of a layer with the definitions determined in the risk analyses. The management of safety layers could be considered as an auditing process against the definitions prior to the start of the operation or in its risk reviews.
In an audit it is necessary to know if all the relevant facts have been reported and dealt with, a typical example is the TRIPs analysis report, where the reasons for an unscheduled TRIP are identified, due to the large workload that this activity generates, normally only TRIPs that had a large financial loss or significant operational risk are treated.
TRIPs can generate very important information for a safety analysis, but it needs to be accompanied by a lot of information to make the analysis practical.
Concentrating TRIP information in a single analysis tool allows: ensuring that the data are in the same time base (saving the difficulties of time adjusting the occurrence of events) and collecting state information from other systems (adding informationâs such as state of deviations/by-pass, status of alarms and if they were acknowledged, conditions of process variables, diagnostics of instruments and actuators are organized in a sequence of events in the same time base). The results of this information should be used to verify if the cause is related to maintenance or operating procedures. TRIP data are also useful for future functional safety analysis as possible demand data from the occurrence of risk situations. The treatment of TRIPs is one of the items indicated in IEC 61511 to be managed. TRIPs management is considered the first step towards implementing safety barrier management, as the necessary data is already digitized, does not depend on the suitability of systems for collection and also does not need to be related to the definitions of protection layers, so, even if it is not auditable by the functional safety definitions, the user can manage important information.
The second step for the implementation of a safety barrier management tool is the management of SIFs (Safety Instrumented Functions), in this case IEC 61511 indicates some additional points for the TRIP analysis to be managed to maintain the life cycle of the safety loops. Data such as whether the by-pass time can interfere with safety and whether the periodicity of tests to evaluate hidden failures (proof-test) are being carried out in order to guarantee the desired integrity of the loop. When there is no online tool, typically the information you have is whether the system is compliant or non-compliant. With an online tool it is possible to present the value of integrity level degradation (SIL) for extending a by-pass or delaying a proof-test. A layer management tool in addition to these functions can cover all other managements indicated in IEC 61511.
The user at this stage will have a historical of SIS actions that will be valuable for future revisions of risk analysis, will have a performance report of SIS components, like the by-pass historical that will allow the elaboration of new strategies to minimize its use, among others.
The next steps refer to the alarm and mitigation layers. If we consider the Fire and Gas system (F&G) as intelligent, the implementation and benefits will be similar to the management of SIFs.
Passive and mechanical systems can have their data collected by patrol tools or by data from maintenance management systems.
The integration of all systems in a tool for monitoring safety barriers can allow users to have in real time the risk of each industrial unit, its causes and prediction of the duration of influences that reduce the availability of safety devices. It will also be able to generate its own database of device activation demands, among other benefits. Nowadays there are tools that meet all requirements for managing safety barriers for industries using IEC 61511.
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