Mention the term “BMS” (Burner Management System) to a group of process fired equipment users and you’ll likely hear these phrases in reply: “Physical separation”, “NFPA”, “FM guidelines”, “SIS” “SIL rating”. While these are legitimate statements that demonstrate flame safety understanding, you’re also likely to elicit more disparaging remarks to the tune of “necessary evil”, “the black box”, and “the reason we can’t run”. The latter terms are typically a result of poor application and design coupled with limited access and troubleshooting options available to operations. In this article, we’ll focus on the elements that differentiate a “bare bones” BMS (one that meets minimum functionality and not much else), to one that not only provides required flame safety, but that can also serve as a powerful ally in troubleshooting and maintaining top operational certainty. These four key measurements consistently make the difference between a “black box” approach to BMS and a true, partnering, integrated flame safety system.
Designing a superior BMS begins with a decision on hardware. Making the choice to use fit for purpose hardware (switches, relays, transmitters) is essential. Beginning with field devices, SIL (Safety Integrity Level) rated hardware ensures a greater level of reliability to the end user even if a system-wide SIL calculation is not necessarily the end goal. Using SIS (Safety Instrumentation System) hardware, as compared with cheaper, non-safety rated devices guarantees a more robust set of “eyes and ears” on the safety aspects of the combustion process. This also rings true with the choice of “logic solver” being selected. SIL-rated processors with appropriate internal redundancy is essential. Remember, operations should be spending time troubleshooting the burner’s combustion components, not faulty BMS field devices.
When a combustion process is running normally, the BMS should the invisible watchman. However, when a burner fault occurs, there should be no ambiguity to operations as to the culprit. Fault reporting is not a new concept, but failing to accurately capture the cause for a burner trip can be very frustrating. Often, a simple BMS will lump multiple causes for a burner trip under a “combustion failure” lamp on the panel or at best display a cryptic numeric code that must deciphered. Even at that, the displayed code may not represent the first-out cause of the trip. An effective BMS system must not only display trip causes in plainly understood language, but must hold the first-out cause so that the prime cause of the trip can quickly be remedied.
Clear communication of the burner light-off sequence is all about creating situational awareness to operations. There should be no doubt about where the BMS is in the light-off sequence, remaining purge times, field device positions (block valve positions. damper locations, etc.). Most importantly, any conditions preventing a normal light-off must be immediately captured and easily understandable by operations. Likewise, BMS programming must be transparent to the site engineering group. State-transition logic should be used to clearly show intended function and allow changes to be easily made by qualified personnel. “Spaghetti code” and hard to understand Boolean logic create ambiguity and are prone to mistakes when additional functionality is desired.
Providing full BMS integration into the burner CCS (Combustion Control System) platform provides a seamless flame safety and control experience to operations. Integration does not imply negating physical separation requirements, but rather making full use of the familiar DCS (Distributed Control System) environment. This means that graphical presentation, BMS field device status, alarm capturing, making use of BMS device data for process use, trending, are all easily accomplished without sacrificing required BMS autonomy. In short, operations have everything provided in one place with the power of native DCS functionality included.
The result of applying these measurements is a robust, highly intuitive BMS system that provides a wealth of information to operations. As stated previously, when a combustion process is running perfectly, the BMS should be in the background and monitoring only. However, when problems should arise, the difference between three minutes of quick troubleshooting and back online versus three hours of lost production can easily justify both the operational and economic decision to make the BMS an operational partner rather than an operational outsider.
Emerson Automation Solutions offers not only state-of-the art SIL-3 SIS hardware, but also possesses a wealth of global expertise across the full spectrum of industrial combustion flame safety systems applications. Reach out to any of our local business partners or contact me directly through EE365 to learn more.
Andrew J. Verdouw, P.E. | Professional Services Organization