Over-Firing: Causes, Prevention and Remedies
Over-firing is one of the most common problems faced by furnace operators. If neglected, over-firing can cause serious damage to both the furnace and its associated equipment, leading to increased downtime and costly repairs.
When a furnace is overfired, it essentially means that the fuel being burned is too hot or is being burned at too high a rate. This excess heat energy is transferred to the equipment being heated, causing it to reach temperatures beyond the recommended range for that particular piece of equipment. The resultant extra heat can not only damage the furnace itself, but also the material being processed and the production system in general.
The most common causes of over-firing are:
• An insufficient combustion air supply (the air needed to complete the combustion process), resulting in excess fuel burning and a higher temperature in the combustion gases being produced.
• An inadequate exhaust system, resulting in the furnace not being able to cope with the level of heat being produced by the combustion process.
• An improper fuel-air ratio (the ratio of fuel to air), resulting in too much fuel being burned, leading to an excessive heat output.
• A malfunctioning control system, resulting in the wrong inputs being used to regulate the temperature of the furnace.
• Human error, resulting from the operators not properly understanding how to set up the furnace to operate properly.
Fortunately, over-firing can be prevented by following the correct operating and maintenance procedures. Firstly, operators must be properly trained to understand how to safely operate and maintain the furnace. They should be aware of the correct fuel-air ratio, combustion air supply and exhaust system, and be able to adjust these parameters as needed to ensure that the temperatures produced are within the desired range.
Regulating devices, such as temperature sensors and flow meters, should also be regularly monitored and calibrated to ensure they are operating within their specified tolerances. This will allow the control system to apply the right inputs and regulate the internal temperature of the furnace appropriately.
Finally, regular maintenance, such as cleaning and replacing filters, must be carried out to ensure the furnace is in good operating condition. This will help to prevent excess heat from being generated, which is key to avoiding over-firing.
In the event that a furnace does become over-fired, action should be taken to cool the equipment down as quickly and safely as possible. This can include turning off the fuel supply, reducing the combustion air, increasing the exhaust flow, and using fans or water sprays. Once the temperature of the equipment has been lowered to a safe level, the underlying cause of the over-firing can then be identified and rectified.
In conclusion, over-firing is an issue which can cause serious damage to furnaces and associated equipment, as well as lead to additional downtime and costly repairs. To prevent this, operators and maintenance personnel must be fully trained and knowledgeable in how to safely and correctly set up the furnace and keep it in good condition. If an over-firing does occur, steps must be taken to quickly cool the furnace or equipment down and identify and rectify the cause.
