This blog was originally posted by Yokogawa.
The monitoring of safety instrumented systems (SIS) is becoming more relevant to organizations in today’s process industries. Most are actively gathering some form of measurement to record and assess safety system performance. However, is this information accurate, reliable and fully inclusive to have real certainty to monitor safety system performance?
Frequency is re-evaluated
With the release of the IEC 61511 2016 edition, one of the many changes included a much stronger focus on SIS performance measurement. Users must now have a recognized procedure for collecting data related to the demand rate and SIS reliability parameters. In addition, users must determine some periodic interval testing, with the frequency being re-evaluated based on various factors including historical test data, demand frequency, plant experience and hardware degradation.
This means that the process industries must re-evaluate their approach to the collection, measurement and analysis of their safety data. Without these measures, it is very difficult to see clearly how their SIS is performing against targets as defined in the safety requirements specification (SRS) throughout the lifecycle of the plant. By undertaking regular tests, checks and performance assessments, it is a more effective approach to identify potential problems and take the necessary corrective actions for safer operations.
Uncovering errors
Proof testing is a good example of why monitoring data is important. Proof testing is a periodic test, designed to reveal all ‘undetected or unrevealed’ failures that a safety device may be harboring, to prevent damage to business assets and reputation. Undertaking and performing these tests needs to be scheduled at intervals throughout the operational phase of the lifecycle, including after any maintenance or commissioning, or prior to planned preventative maintenance. In reality, proof testing in practice is challenging to plan, implement and maintain. The reasons why testing is not conducted as planned can be due to a number of factors. These can include an organizations size and its ability to deploy engineering resources in a timely manner, and a reduction in the number of competent and experienced technical personnel to administer and carry out these practices.
Producing and interpreting safety status reports is a time consuming and highly labor-intensive task, requiring individuals to convert raw safety data into more meaningful information. Software tools can maximize people’s time by automatically capturing data safety equipment performance that can be compared against reference information.
Improved Safety and Compliance
Other key safety related information related to performance includes analyzing trips or triggers, capturing frequency of demand, determining device transitions and travel times and SIF availability. These are just a few examples of key performance metrics that provide an indication of how well functional safety is being carried out, and pinpointing any areas of concern and non-conformance. Managing and maintaining this information throughout the lifespan of the system is more effective, and it can highlight errors and inaccuracies for improved plant safety and regulatory compliance.
A well-balanced approach to safety performance, which complies with safety regulations and can be easily maintained throughout the entire lifecycle at an affordable cost, is preferable for many organizations. An over-engineered SIS may exceed safety requirements, but may not be a cost effective solution. Similarly, an under-engineered SIS may be more cost-effective, but may compromise safety integrity.
Minimizing Risks
Safety related incidents and accidents could be significantly reduced and even prevented if a culture of process safety has a higher priority. Accidents like those in the Texas City Isomerization Explosion in 2005, or the Geismar Facility Explosion and Fire in 2013, show what can happen if there are program deficiencies and inadequate safety management processes in place. By carrying out regular SIS performance checks, potential serious problems are more easily identifiable and corrective actions can be taken before they become major issues.
The IEC 61511 committee has recognized that organizations may not be quite up to speed on their Operations and Maintenance (O&M) requirements, which is perhaps why the requirements have been further strengthened. If users are not up to the necessary standard on their O&M requirements, it may lead to future consequences and possible enforcement notifications from regulators.
‘Exaquantum Safety Function Monitoring’
Exaquantum Safety Function Monitoring is a safety performance monitoring solution that highlights and reports safety instrumented systems that have exceeded expected design targets to benchmark safety performance. The designed safety performance is compared against the actual operational safety function activity, to highlight issues, validate safety design, optimize test scheduling and help users improve safety and availability of the plant.