| HRSGs and boilers


In addition to periodic inspection of auxiliary boiler surfaces, the boiler burner should be inspected for any signs of component degradation or failure, control linkage/device changes, refractory degradation, buildup of debris on the combustion fan surfaces, filter cleanliness, and more. Observe the flame in the furnace through the rear sight port of the boiler to check for any marked changes in flame shape and colour.


Components out of adjustment or failures As with all mechanical equipment, burner and boiler related components will wear, linkages and control points will slip, and can fail over time. For example, fuel and air metering and control devices can work their way out of adjustment. Burner orifices and fuel delivery ports can wear, come loose, or fail completely. Other potential sources of degradation and failure include the flame retention diffuser and burner–boiler furnace refractory interface and tile liners. In addition to changes in stack temperature, often these sites of concern will result in abnormal flame geometry or colour and potentially incomplete combustion.


Much of the necessary inspection and maintenance work can be conducted by trained plant personnel. However, when it comes down to detailed inspection and maintenance of the burner itself as well as the fuel–air control and fuel delivery systems, these activities should be performed by experienced and authorised boiler-burner service agents.


Abnormal noise and vibrations While some level of vibration and sounds emanating from a boiler in operation is normal, excessive noise and vibrations are a warning sign that the boiler is no longer operating properly and is in need of attention. Boiler panting and pulsing, screeching and howling, visible and audible signs of excessive vibrations and shaking are a clear indication that something is awry. These objectionable events are clear indications that combustion quality has degraded, that issues may have arisen with stack breeching and/or draft control systems, or some other failure in the burner itself may have occurred.


When any of these situations occur, the boiler should be shut down and a service company should be contacted immediately. Very often, a simple tuning of the burner is all that is required. In other cases unfortunately, more dramatic maintenance and repair will be needed.


Leakage and corrosion Waterside corrosion of materials and leakage of steam or water onto the


Figure 3. Scale build-up in a boiler tube. (Picture courtesy Mike Sheppard of The Boiler Guy Says)


Figure 2. Boiler gross combustion efficiency as function of stack temperature and excess air


boiler room floor is a sure sign that your boiler


is in need of attention: ● Has fuel consumption increased without any significant change in load?


● Has there been a reduction in condensate return, and is there a need for more makeup water than usual? Are steam traps in good working condition?


● Is there heavy corrosion and pitting on boiler tubes and other waterside materials? Are weld joints failing?


● Is there water on the floor around the boiler? ● Is steam escaping from boiler access door or man-way gaskets?


These are sure signs that your boiler is in need of attention and possibly in need of water quality improvement.


Frequent alarms and abnormal shutdown


Boiler safety and control devices and systems typically range from flame monitoring to


controlling water level in the boiler. Depending on the level of safety designated for the given device, a fault trip in one of these devices will typically shut the unit down and possibly lock the unit out until the fault has been rectified. Low water is the most serious fault condition, followed by shutdowns and lockouts stemming from flame monitoring, high steam pressure or hot water temperature limits, etc.These faults may be indicated on a safety device itself, displayed on the boiler primary flame safety device (PFSD) or some other fault annunciation system – in the boiler room or at a remote location.


When these faults occur, an experienced and authorised service company should be notified immediately to investigate and rectify the problem. In-house personnel should not attempt to make combustion/flame adjustments or modifications, and under no circumstance should in-house personnel attempt to dismantle and clean primary safety devices such as low water cutoffs, over-pressure safety devices, etc.


Inability to satisfy demand over time Another sign that your boiler may need attention is the inability to satisfy plant requirements, even though peak demand hasn’t changed (Figure 5).


Low water temperature and/or steam pressure are other signs that attention is required.


Is it taking longer to reach pressure or temperature? Similar to rising stack temperature, this may be a sign that the boiler is scaling or sooting up, and its ability to transfer fuel energy to the boiler water is being impeded. It may be time for a good boiler cleaning, checking of steam and/or hot water delivery components, and more.


www.modernpowersystems.com | March 2026 | 19


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