Burner maintenance is vital for optimal combustion and also to avoid excessive generation of pollution (CO, NOX, CO2 emissions).
Failure to carry this out can lead to process problems such as poor product quality, increased gas consumption, furnace insulation damage, and unexpected interruption to operations.
Preventive maintenance of your burners is the most efficient way to avoid these unforeseen events and to operate at your maximum capacity.
Factors you should review during maintenance
Below, we share the most common burner problems and what you should review in each case:
1. Unstable flames
- Keep an eye on flame shape and burner conditions.
- Check that the combustion block is not damaged.
- Check the appropriate values for working pressures on each burner via the appropriate charts or manuals.
- Make sure there’s no loss of air pressure due to clogged air filters (turbo blower).
- Note that leaks in the air pipelines can occur when the burner does not have enough pressure; over time the flexible sleeves can show evidence of wear and leaks.
- Check the gas pressures are at the appropriate values and that the gas filter is clean to avoid pressure drop, which will affect flow.
- Check regulator diaphragms; over time they may deteriorate and cause equipment failure.
- Correct the air control valve settings, adjusting minimum and maximum flow required.
- Check that the ratio regulator lines are not plugged or leaking.
- Monitor internal pressure control where dampers are present.
- Address hot spots on furnace walls caused by damage to the insulation.
- Look for leaks caused by damage to bench and car seals.
2. Inefficient burning of fuel
- Review recommended air and gas pressures and flows in burner manuals.
- Check neither burner block nor flame stabilizer is damaged.
- Check the air tubes or burner nozzles.
3. Poor product quality
- Check the combustion air/gas mixture and ensure it is appropriate for the current process; it is not always stoichiometric but in some special cases it can be oxidizing or reducing.
- Check for air infiltration due to poor adjustment or control of internal pressure.
- Check for air infiltration due to degraded insulation (door seals, benches, cars, etc).
- See if there might be poor temperature control or damaged thermocouples – false contact in thermocouple wire.
- Correctly tune the PID temperature controller.
4. Damage to insulation
- Note that when the flame is poorly adjusted it can cause damage if it is longer than normal and touches the insulation.
- Correctly adjust the air/gas ratio; check the burner nozzle or refractory block.
- Check that the refractory block surround is sealed correctly and that there are no leaks. This is a very common failure and can damage the furnace casing and the burner if not addressed in time.
5. Burners that go out
- Set the correct air/fuel ratio.
- Check that the burner setting is within the burner turndown range.
- Ensure that all burner parts are free from damage (nozzle, tubes, block).
- Check that the flame detector signal is within design parameters.
6. Safety measures
- Review safety tolerances, low air pressure, high gas pressure, low gas pressure, air flow switch, etc.
- Adjustment to relief valves: check that this is in the correct range to act before high pressure damages your equipment.
- Ensure that the flame detector functions correctly.
- Check that the safety valves are closing correctly; they are checked with the help of tightness tests (Paragraph A.126.96.36.199 of NFPA 86 – Latest Edition for the leak test procedure).
- Adjust fittings and actuators with control valves.
- Ensure that the ignition purge sequence has a sufficient length of time to assure at least five changes of air in the furnace.
- Check motor starters have overcurrent protection.
- Monitor lighting and adjustment of the pilot.
- Ensure that the spark plug and ignition cable are in good condition.
- Check that the firing sequence is correct, in accordance with NFPA 86.
- Review the sequence programming of the PLC.
7. Burners not lighting
- Adjust the burner’s low fire setting.
- Check on the pilot or spark plug calibration.
- Confirm there’s presence of a good spark in the spark plug.
- Make sure the main valves aren’t closed.
- Check burner damage from degraded parts.
- Check that the flame detector is working properly.
- Failure of safety interlock in ignition sequence.
- Check for ignition sequence errors.
How can Nutec Bickley help you?
- On-site service policies: we schedule visits for preventive maintenance according to the specific needs of each operation.
- Equipment review and testing: aimed at detecting items that are damaged or that need to be replaced.
- Equipment calibration: air/fuel ratio, safety sequences, pressure switches, control valve settings, actuators.
- Component safety upgrades: to ensure NFPA 86 compliance.
- Training of personnel in charge of furnace operation or maintenance.
- Flue gas measurement: O2, CO, CO2, NOX.
- Spare parts: from the most well-known brands such as Fives North American, Kromschröder, Dungs, Siemens, Fisher, Honeywell, ASCO, DELTA, Elektrogas, etc.
- Surveys: we check temperature uniformity and correct operation.
- Industry 4.0: evaluation and real-time monitoring of burner signal status.
The maintenance of burners is a vital function since it affects the performance of the furnace’s other components, so we advise you to carry out reviews on a four-monthly basis, depending on the use and performance of your furnace.
At Nutec Bickley we are specialists in customized systems. Contact our qualified consultants to learn more about all the solutions we have available for you.
Author: Hilario Zavala – Combustion and Control Technical Consultant