Organizations across many industries require the safe and successful operation of fired equipment to run critical processes. Often, this necessitates an essential safety function typically provided by a burner management system (BMS). While safety requirements usually are known, many organizations do not consider the extent to which the BMS can impact plant availability and production performance.
Updating and optimizing BMS implementations can actively support reliable production operation to help the plant achieve its best business results. Conducting a field study, considering built-for-purpose safety and simplifying system logic — each discussed in detail below — will ensure these types of projects proceed as planned.
What is the BMS?
The BMS — also referred to as a flame-safety system — is a safety element of combustion control found on nearly every combustion process. It manages safe light-off and startup of the combustion unit and then continues to monitor the process for unsafe conditions.
If something unsafe is detected by the BMS system, it initiates a process trip. The BMS must perform its job well or the safety and availability of the combustion process will be affected. The BMS usually consists of more than just the safety logic controller; it also includes sensing and actuating devices.
Understanding Needs and Opportunities with a Field Survey
Often, a legacy BMS can be difficult for site operations and maintenance personnel to manage. Many systems were put in place decades ago using older standards, and they were installed at the lowest cost and with minimum functionality. Documentation often is limited and not up to date with changes and patches made over the years.
One of the first steps any organization should take when updating a BMS for improved safety and operation is to perform a comprehensive field survey and code-compliance audit of all aspects of the combustion process and safety system. Whether an organization performs the field survey with internal personnel or works with another company, performing a detailed review is necessary to document required changes. The survey and audit process identify present standards and codes along with the changes necessary to support the best reliability and troubleshooting ability.
Older implementations often do not fully meet current codes and recommended practices because standards and best methods likely have changed over time. Legacy system installations may be grandfathered, or exempt from a new law or regulation. When a BMS project is completed or new systems are brought online, however, owners often are required to bring combustion safety up to present standards.
Fortunately, the changes driven by code updates normally are relatively modest and bring some operating benefit. In a system that has not been updated for years, it is common to find missing sensors, installed equipment that is not listed for safety service or vent pipelines that are not sized sufficiently.
A site survey can identify code-compliance issues. It also can point out ways to make the safety system more reliable and the combustion process easier to troubleshoot. For example, in legacy and OEM installations, it has been common to wire multiple sensing devices in series to the logic controller. Hence, when there is a trip or difficulty lighting-off, the BMS does not know exactly which device is the cause of the problem. Switches also have been used in the past for high and low pressure interlocks instead of more reliable and capable transmitters.
Often, the field survey will identify wiring and device modifications, allowing the new BMS to provide a higher degree of operating functionality. The organization should rely on its most experienced engineers or a trusted partner to help ensure that all infrastructure is properly scoped.
Fired units like this industrial heater depend on reliable burner management systems for safe and efficient light-off and startup. After ignition, the burner management system continues to monitor the heater for any aberrations.
Built-for-Purpose Safety Hardware and Integration
Standards and best practices for flame safety are quickly moving toward the recommended use of control hardware that is safety integrity level (SIL) capable. Using controllers that are SIL capable is not mandated for every BMS installation today, but the movement is in this direction. It is likely prudent to “future proof” new installations by installing built-for-purpose safety equipment.
SIL-capable controllers may be marginally more expensive, but this capital cost increase usually is offset with lower lifecycle costs for the combustion control platform. Organizations using non-SIL-rated systems often are required to perform more engineering and logic configuration to ensure required safety functionality. In some circumstances, a plant may also need to add additional devices to prove BMS performance. This additional equipment increases upfront costs as well as required maintenance over its lifecycle, adding to total cost of ownership.
SIL-rated components have been tested thoroughly to function properly in their intended setting. They often have a higher rated mean time between failures than non-SIL-rated equipment. This leads to less maintenance and a lower likelihood of production outages due to repairs. These savings quickly add up and, ultimately, result in SIL components adding little to no extra lifecycle cost.
Many organizations also are finding value in using integrated safety and automation systems such as an integrated control and safety system (ICSS). An ICSS maintains the required physical separation between safety and other process control functions within a single architecture.
The same user interface and engineering environment are used to access both the safety and the basic controls. Cybersecurity is improved because the organization only needs to defend one set of equipment. In addition, operator training is simplified because personnel do not need to be trained on two different systems.
Integrated control and safety systems maintain required physical separation between safety and process control while minimizing the footprint for easier operation and maintenance.
Simplifying System Logic
Legacy BMS implementations often limit operating availability and performance. The components and functionality of older systems may make them difficult to use and troubleshoot. Nuisance trips are common issue. Poor functionality can be due to the way field devices are wired, the complexity of the installed logic or the limited diagnostic information available to operations and maintenance personnel.
As organizations update BMS installations, many are moving away from the legacy ladder logic or Boolean approach traditionally used for safety programming. Modern BMS logic configurations now are being done with sequence- and state-based functions that simplify the design, development and maintenance of the safety logic.
The sequence approach to burner management configuration divides safety logic into separate sequences for the combustion unit. These sequences are further broken down into discrete steps, each with clear definition of the inputs and actions required to move from one step to another.
The sequence configuration method supports a user interface that clearly presents the state of the combustion process. If an operator is trying to light off a boiler and the sequence is held up because the forced draft damper is not at purge position, that cause will be clearly displayed on the operator’s workstation. The operator then can use that information to immediately resolve the problem, without the delays caused by searching for the issue. Once the purge permissives are met, the sequence advances as normal.
Sequence-based logic helps direct operations and maintenance to the source of any problems with a clear presentation of the sequence state, permissive status and the root cause behind any trips. Operators and maintenance personnel can perform their tasks more efficiently, and they gain more confidence to make safe, correct decisions when the system is not responding as expected.
A Modern BMS Enables Operational Success
Legacy BMS implementations often suffer trips and component failure issues. These problems become even more frustrating when they are difficult to troubleshoot and challenging to eliminate. A site using systems with such problems often can still protect plant personnel and equipment reasonably well, but the process interruptions resulting from sub-optimal functionality will have an impact on availability, productivity and cost.
Modernizing the BMS is an important step toward improving safety and availability, which in turn plays a significant role in improving business results. Safety-rated systems and modern, intuitive logic simplify the process. A modern BMS with the appropriate sensor and actuator components will manage the safe light-off, startup and shutdown of combustion equipment — and it will clearly communicates the process steps and faults to the people responsible for process operation. This results into fewer, shorter unplanned outages and a high return on investment over the lifecycle of the updated BMS solution.