EE - Forum Styles
fo

How Changes to Functional Safety Standards Can Optimize Fire and Gas Detection

When a major standard goes through an extensive revision, it can take some time for users to digest and begin applying the new rules. Such is the case right now with ANSI/ISA 84 for fire and gas systems.

 Design and implementation of large-scale safety systems of all types depends on standards to guide execution through all phases. Since people, equipment, and the environment depend on these systems, it is important employ the collective wisdom of standards committees. Those who work with fire & gas systems draw on ISA-TR84.00.07-2018, which recently went through a major revision. How users should interpret and apply these changes is the topic of an article in the December 2019 issue of Hydrocarbon Processing titled How Changes to Functional Safety Standards Can Optimize Fire and Gas Detection.

  The 2018 edition is the first update since this technical report was initially issued in 2010, so there are many revisions. Clearly it is not practical to cover the full extent of the revisions in a single article, so we simply hit some of the highlights, letting users decide what topics merit additional consideration.

 Engineers creating FGS-related safety functions and using the original 2010 technical report for guidance will now find substantial changes in the 2018 version. Most of these updates expand the range of acceptable technologies for various applications. They also add discussions on safety philosophy and offer practical guidance on implementation. These updates provide many more resources for assessing risk and configuring systems.

 The article takes a forest-and-trees approach, beginning with some of the more philosophical questions, as to when fire & gas system design should begin. The emphasis is on doing it earlier, while the plant is still being laid out, rather than starting later.

 Just as ANSI/ISA-84 emphasizes the concept of the safety instrumented system (SIS) lifecycle, the 2018 technical report drives designers to include the FGS design much earlier than in the larger SIS design process. This prevents looking at the completed plans and deciding how to configure the FGS to make it fit. The standard recognizes it is not enough to teach FGS designers simply how to perform a fire and gas hazard assessment, create a system and bolt it on. To be enduring, the lifecycle steps must be part of the FGS design process and integrated into every stage of a larger project for design, implementation and operation of a new plant, or an upgrade to an existing automation system.

 The new technical report acknowledges that new technologies have emerged, adding new options for system designers beyond those in the toolbox when the original standard was being compiled and reviewed.

 The technologies discussed in the 2010 technical report reflected the state of the art in the years just prior, basically 10 and more years ago. Since then, a broader and much improved range of sensor options has emerged, such as ultrasonic gas detectors. These can detect the sound made by a pressurized gas leak, providing immediate response rather than waiting for a gas cloud to accumulate to the point where it can be detected by conventional sensors. Most FGS implementations will need both technologies, but well-placed ultrasonic detectors can respond more quickly in critical applications.

 Emerson’s Rosemount Incus Ultrasonic Gas Leak Detector is exactly the kind of sensor suggested. The Incus is an advanced ultrasonic gas leak detection system utilizing four ultra-sensitive acoustic sensors, each of which constantly monitor wide areas for ultrasound generated from the release of pressurized gas. It’s ideal for monitoring well ventilated outdoor environments because it can withstand inclement weather, wind, and gas dilution or stratification—and cope with different leak directions.

 Users wanting to deploy such a sensor and apply other advances under the guidance of the standard will need to do a lot of study and work with appropriate experts, and Emerson can assist in these efforts.

 You can find more information like this and meet with other people looking at the same kinds of situations in the Emerson Exchange365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the Safety and Flame & Gas Groups and other specialty areas for suggestions and answers.