You are here:
Home
»
Systems

Burner Management Systems

What is a Burner Management System (BMS)?

A Burner Management System, often abbreviated as BMS, is a safety system used to assure safe startup, operation and shut down of process burners. A process burner being a mechanical device that mixes fuel and air and when this mixture is ignited provides a platform for combustion. Therefore a burner management system will be used in the petrochemical, power generation, and chemical industries where boilers, furnaces, incinerators and industrial burners are used.

In broad terms, a BMS safety system will:
- Inhibit startup until safe conditions are met
- Automate ignition and purging activities
- Control and monitor burners to detect unsafe operating conditions and shutdown if unsafe conditions exist
- Safely shutdown burners
- Provide operators with vital status information
A more detailed description of what a BMS does is provided below.

What does a Burner Management System do?

Not all Burner Management Systems are identical, therefore there is no definitive answer to the question "What does a BMS do?". However, the following captures the main functions common to most BMS systems:

Start-up Sequence

When the system is initiated, the BMS goes through a predefined startup sequence. It performs a gas tightness test on the safety shutdown valves in the pilot fuel, and main fuel supply lines, and checks various safety parameters and interlocks to ensure that it’s safe to proceed with ignition. It will inhibit startup when the conditions are not met.

Pre-Purge

Before igniting the burner, the BMS initiates a pre-purge cycle, during which it purges the combustion chamber of any potentially explosive gases or residual fuel. This ensures a safe starting environment. It will prevent firing unless a satisfactory purge has first been completed.

Ignition

Once the pre-purge is complete and conditions are safe, the BMS initiates the ignition sequence. This involves setting the air damper to the ignition position, powering the ignition transformer and opening the pilot valve(s) to start the combustion process and obtain a pilot flame.

Flame Detection

As soon as the burner ignites, the BMS monitors the flame using flame sensors or detectors. It continuously checks for the presence and stability of the flame. When the sensors don’t detect the flame or detect unsafe operating conditions, the BMS signals the actuators to stop the flow of fuel to the burners, to inhibit the flames.

Burner Operation

The BMS modulates the burner’s fuel valve and air supply damper to maintain the desired temperature, pressure, or other process parameters. It may adjust the fuel to air ratio to optimise combustion efficiency.

Safety Monitoring

Throughout operation, the BMS continually monitors various safety parameters, such as flame stability, fuel pressure, combustion air flow, exhaust gas temperature, and excess oxygen levels. If any parameter deviates from safe limits, the BMS can take corrective actions, such as shutting down the burner. It will provide component condition feedback to the operator and, if so equipped, to the plant control systems and/or data loggers.

Shutdown Sequence

When the operation needs to stop, either due to a scheduled process end or a safety issue, the BMS initiates a shutdown sequence. This includes reducing fuel and air supply, extinguishing the flame, and ensuring a safe cool-down period.

Post-Purge

After the burner is extinguished, the BMS initiates a post-purge cycle to remove any remaining combustion gases from the system.

Other things a BMS may do

Cold Start Thermal Shock Protection. To limit mechanical stress due to thermal differences on burner components and refractory linings some BMS systems slowly increase the burner firing rate on a cold start.

Components of a Burner Management System

Typical BMS Components

A Burner Management System (BMS) is composed of various components that work together to ensure the safe and efficient operation of industrial burners. Many of these components will have a Safety Integrity Rating of 2 or 3.

The key components of a BMS are listed below:

Control Unit The brains of a BMS are in the BMS Control Unit. This is the Central processing unit that executes the control logic and sequences for the burner. Two types are common, namely; Programmable Logic Controllers (PLC), and Microprocessor based Controllers. The later is an alternative to PLCs, and these controllers handle the same tasks but with embedded software.

Human-Machine Interface (HMI) The HMI provides a user-friendly interface for operators to monitor and control the burner system. This usually employs touchscreen displays with visual interfaces that show real time data, alarms, and status of the burner system.

Sensors and Transducers A variety of sensors, transducers and transmitters are used. These are all connected to the Control Unit, and include:
- Temperature Sensors to measure the temperature of the flame, furnace, or boiler. The temperature sensor selection will depend on where it is located in the burner system.
- Pressure Sensors to monitor various pressures within the burner system, e.g. fuel gas pressure, combustion chamber pressure.
- Flame Detectors to detect the presence of a flame. Flame prescence is continually monitored.
- Oxygen Sensors to measure oxygen levels to ensure optimal combustion.

Safety Interlocks Various safety interlocks are ensured through the use of Shutoff Valves and Limit Switches. The shutoff valves will automatically close to stop the fuel supply in case of unsafe conditions, and the Limit Switches ensure components are in the correct position before allowing start up to begin.

Ignition System The ignition system comprises Spark Generators and Igniters. The Spark Generators provide the necessary spark to ignite the fuel-air mixture. The spark is provided in the Igniters. These are devices that initiate the combustion process.

Fuel Supply System Fuel pumps deliver the fuel to the burner at the required pressure and fuel control valves regulate the flow of fuel to the burner.

Air Supply System Blowers/Fans provide the necessary air for combustion, and Dampers control the amount of air entering the burner.

Combustion Control System comprises Fuel to Air Ratio Controllers. These maintain the optimal fuel-to-air ratio for efficient combustion by adjusting the fuel and air supply based on load demand.

Network Interfaces allow integration with other control systems such as Distributed Control Systems (DCS) or Supervisory Control and Data Acquisition (SCADA) systems.

BMS Compliance Standards

Various standards apply to many components within a burner management system. These include:
API 538 – applies to industrial burners, in general refinery and petrochemical services. It was written by manufacturers and users of industrial boilers to supplement rather than duplicate the requirements of NFPA 85. API 538 specifies requirements and gives recommendations for the design, operation, maintenance, and troubleshooting of industrial boilers. It covers waterside control, combustion control, BMS, feedwater preparation, steam purity, emissions, etc.
API 556 – the standard addresses instrumentation, control, and protective systems for gas-fired heaters used in the refining industry. As it is specific to refinery process heaters, it is widely used by the refining industry, although local jurisdictions may also bring additional requirements. It was written by specialists covering the fields of fired equipment, instrumentation, control, and protective functions. It integrates the operating experience and incident history of major refiners to reduce the overall risk exposure to equipment and personnel. For each hazard scenario, API 556 provides recommendations on design, control system constraints/overrides, operator response to alarms, and protective functions to ensure satisfactory mitigation of the process hazard. Except for a few prescriptive “shalls”, the user may choose between solutions of different levels of sophistication and cost, which all mitigate hazards but provide different availability levels.
AS 3814 – this code outlines the minimum safety requirements for gas-fired industrial and commercial appliances in Australia. Among all codes and standards for industrial fired equipment, this standard is known for its complexity, making compliance challenging.
CSA B149.3 – specifies requirements for fuel-related components in their assembly on appliances in Canada. It applies to a wide array of applications that require gas-fired equipment.
EN 746-2 – specifies safety requirements for industrial furnaces and heating equipment, outlining hazards, safety measures, and compliance with European Directives. EN 746-2 applies to various fired equipment in industries like cement, lime, ceramic, iron and steel, glass, waste incineration, drying, refining, chemical, and petrochemical. Due to equipment diversity, applying generic requirements may be challenging or costly.
IEC 60730-2-5 – refers to construction and performance requirements for electronic devices in automatic Burner Control Systems. Adherence to this standard is often the quickest path to compliance for gas-fired appliance controls. It serves as a recognised benchmark for product design and testing. Note that compliance requirements vary by region. While following IEC 60730-2-5 aids compliance, additional requirements may apply.
ISO 13577-2 – applies to fired equipment in the same process industries as EN 746-2. This standard is global, with specific requirements for Europe, USA, and Japan in its annexes. It outlines safety requirements for people and property during commissioning, startup, operation, shutdown, maintenance, dismantling, and in case of malfunctions.
NFPA 85 – applies to gas, liquid, and solid fuel boilers with a heat release over 3.7 MW. This code addresses combustion system hazards, design, installation, operation, maintenance procedures, and training. It includes combustion and draft control equipment, safety interlocks, alarms, trips, and other controls for safe operation.
NFPA 86 – applies to thermal oxidizers, incinerators, ovens, dryers, and specialist furnaces. Excludes process heaters in the chemical and petroleum industry. Designed per API 560 and API 566.
NFPA 87 – applies to thermal and process fluid heaters. It does not apply to process heaters used in the chemical and petroleum industry and is designed in accordance with API 560 and API 556.