Modular Burner Management – a modern approach
Published: 26 June, 2018
Modern Burner Management Systems need to be flexible, scalable and cost effective. As applications become more complex the demands on Burner Management controllers increase. Low-NOx burner technology and the popularity of biogas, off-gas, syngas and other exotic fuels require Burner Management controllers to offer the flexibility to enable users to configure them to meet contemporary application needs. PWE reports.
A Burner Management System performs several duties. The primary function is to ensure the burner can start-up safely and reliably. During operation it is essential that any fault that could cause a hazardous situation is detected immediately and the burner is shut down in a controlled and safe manner. Fault conditions such as loss of flame or air pressure are directly associated with the burner, but external faults, such high process pressure and temperature, also need to be monitored and reacted to accordingly.
Primary faults, such as loss of flame or air pressure need to shut the burner down and should generate a lock-out condition requiring the cause of the fault be investigated, corrective action taken if necessary, and a manual reset be made before the burner can restart.
Secondary faults, such as gas minimum pressure, can be treated differently. These faults can stop the burner and initiate an alarm condition but when the alarm condition clears the burner can be allowed to be started up automatically without the need for operator intervention.
Burner systems and design varies dramatically from simple single stage burners with ionisation flame detection through to complex large burners firing two or more fuels with sophisticated flame scanners that can discriminate one flame from another or a flame from background radiation.
In the past, four channel outputs were enough to meet most burner applications. An output channel is defined as a hard-wired control output capable of positioning a servo motor or a variable speed drive for a motor, usually driving a fan but sometimes an oil pump. For more complex burner systems it is not uncommon for there to be a requirement for six or seven channel outputs. Examples of these are:
• Secondary air fan (main combustion air)
• Secondary air damper
• Primary air damper
• Oil valve servo motor
• Gas valve servo motor
• Flue gas recirculation damper
• Burner sleeve
• Oil pump
• Atomising cup speed
For electronic Burner Management Systems the convention is to be able to group all the channel outputs, often called ‘drives’, that are used to fire a particular fuel (or mixture of fuels) into ‘profiles’ or ‘curvesets’. Depending on the complexity of the controller one, two, four, eight or sixteen curvesets can be assigned. The concept behind curvesets is to allow the drives associated with fuel groups to be grouped together and programmed to be positioned for safe repeatable start-up and shutdown, and to be moved together in ratio as the burner is modulated from low-fire to high-fire. Before electronic Burner Management was developed mechanical cams and linkages were used to move control valves and dampers in ratio through the firing range. These mechanical linkages are still used but do not offer the flexibility of electronic systems, suffer from wear that results in backlash and hysteresis and are easily tampered with.
Modern electronic systems enable drives to be individually adjusted allowing oxygen trim and CO Control to be applied, both of which can significantly improve efficiency, reduce fuel usage and associated emissions.
One example of this is LAMTEC’s new Combustion Management System (CMS), which is a contemporary modular burner manager that offers complete flexibility to meet almost all burner applications. For applications that cannot be addressed using standard configurations and parameterisation, the CMS offers the opportunity for experienced customers to freely programme non-safety critical functions using CODESYS soft PLC IEC 61131-3 development software.
Mick Barstow, LAMTEC’s export business development manager, says that at the heart of the CMS system is the (MCC) Burner Module; this is where the processors are located and has the I/O for the control of a basic burner. Additional modules are used to build the CMS into a full Burner Management System and include:
• TPS Modules – each controls one or two three-point step servomotors with potentiometer feedback
• VS Modules – allow control of 4-20mA devices with 4-20mA feedback – typically a VSD but could be pneumatic actuator
o (TPS and VS modules can be combined to provide up to 10 channel drive outputs)
• SDI Modules– Safety Digital Inputs (up to 60 inputs available)
• SDO Modules– Safety Digital Output (up to 41 outputs available)
• SAI Modules – Safety Analog Input (9 failsafe or 18 non-failsafe inputs available)
• VS Modules can be assigned for Analog Outputs
• Fieldbus – interfacing to a number of standard Fieldbus protocols including Profibus DP and ProfiNet. Modbus TCP is included as standard on the MCC.
There is a choice of HMIs from a low-cost keypad through to a number of high-resolution touchscreens.
When combined with LAMTEC’s wide range of flame scanners and in-situ zirconia oxygen and COe probes/analysers, the CMS provides a full combustion management solution that meets all relevant safety standards, addresses almost all combustion applications and helps reduce fuel usage, costs and emissions.
Barstow says that the CMS is compatible with existing LAMTEC System Bus (LSB) devices and is fully scalable allowing additional functions, such as VSD fan control, oxygen trim and CO Control, to be added as and when required.
The CMS complements the successful BT300 BurnerTronic range of Burner Management controllers, designed for smaller packaged burners, and brings LAMTEC’s product range completely up-to-date.
For further information please visit: www.lamtec.de