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Leveraging the Annual Boiler Shutdown for Safety and Efficiency

Tip Sheet: April 2013

Key Facts

  • An average boiler consumes more than four times its initial cost every year
  • Most boiler occurrences are either due to poor maintenance or a failure in the low water cutoff control
  • When the boiler is open, look for evidence of scaling or corrosion and check the refractory for cracks

During the annual boiler shutdown, inspect all the equipment in the boiler room.

  
  

The average boiler consumes more than four times its initial cost every year of use. That’s why it is important to look for ways to increase a boiler’s efficiency during its annual shutdown. If the boiler is shut down in the proper way and appropriate action is taken, the boiler not only operates more efficiently and reliably, it also continues to run safely.   

  
In 2002, Hartford Boiler inspectors completed a 10-year analysis to determine what was causing boiler occurrences, or explosions. What they discovered was that poor maintenance was primarily a factor, due to the improper training of boiler operators, or there was a failure in the low water cutoff control, which caused the boiler to disengage from its foundation, resulting in property damage as well as serious bodily injury, even death.   

     

During the annual boiler shutdown, inspect all the equipment in the boiler room. Walk around the boiler before you even look inside. Look at the external piping, the valving, the feed system, pumps and pump seals. Listen for any bearing or cavitation noise. Check the alignment of pumps and motor assemblies, as well as the water softener. Check the brine tank for salt and brine water levels.  

     

Next, properly shut down the boiler and secure it. Once the boiler is open, look for evidence of scaling or corrosion. Evaluate the condition of the gaskets and replace any that are dried out, brittle or cracked. Check the refractory for cracks. Small cracks that are less than 1/8” will seal themselves when the boiler is under fire. Cracks in the door more than 1/8” must be patched. Otherwise, further deterioration will occur, and the entire door may have to be replaced.  

     

Check the throat tile and furnace liner and look for cracking or missing chunks. The throat tile insulates, and also shapes, aiding combustion. The furnace liner protects the furnace from the extreme temperatures in front of the burner. It is very important that these are not compromised. If there are cracks or large chunks missing, repair them. Otherwise, you will have to replace the entire throat tile or liner in the future.  

     

Check the burner drawer assembly and burner housing. Look at the burner housing for evidence of any cracking or warping where there has been excessive heat applied. Every burner has a baffle or diffuser. If you see any cracking, bending or deformation of the diffuser, replace these parts. They cannot be repaired. These parts must be intact in order to achieve the proper mixing of fuel and air. Sometimes, the air damper blades get distorted or the bearings wear. They must move freely with no binding. Any evidence of a problem needs to be addressed immediately.  

   

The next thing to consider, as far as the burner is concerned, is the scanner. Make sure there is no evidence of cracking or clouding of it. The scanner tube and eye must be in excellent condition to pick up the flame signal. Also, look closely at the pilot tube. The pilot spark electrode is contained within it and must be clean and properly gapped to avoid nuisance failures. If the electrode is corroded, burned or lacking the proper space between the tip of the electrode rod and inner pilot tube, it will not have sufficient intensity to ignite. If you are having pilot problems, this could be the cause.  

     

When you are ready to close the boiler, follow the manufacturer’s procedures. Sometimes, a manufacturer recommends that you begin to adjust the bolting according to a certain rotation. Seal it the way they suggest and torque it accordingly.  

     

Next, take a close look at the controls. Check the wiring of the pressure controls to see if they are brittle or there is any evidence of overheating. Note the color of the mercury in the switches. If it is caramelized or brown, replace the control. Today, there are combination controls available from Honeywell and other manufacturers that do not contain mercury.  

     

In a single-point positioning system, check the linkages for wear and slippage. If they are present, and not corrected, they will cause unreliable air/fuel ratio control throughout the modulating range. This is extremely wasteful of fuel and can increase boiler maintenance due to sooting. Consider replacing the single-point positioning system with parallel positioning, which takes stretch, hysteresis and wear out of the equation. With parallel positioning, and depending on the amount of modulation, you’ll be saving 1/2 - 2% in fuel costs compared to a single-point positioning system.  

     

Next, closely examine the low water cutoff. It is the most important safety control on the boiler; however, historically operators have not given it the attention it deserves. Recognizing that many boiler occurrences result from a failure in the low water cutoff control, today’s design engineers are creating advanced controls to detect potential low water problems early. One such control is the Level Master, available from Cleaver-Brooks.  

     

 Lastly, when the inspection is over, direct your attention to the burner management and combustion controls. Are they old and outdated? If they are, consider upgrading where it makes sense. Consider a PLC-based platform that incorporates a burner management and combustion control system(s). These platforms are expandable to include parallel positioning, O2 trim, draft control, etc. They include powerful communications for indicating operating parameters, historic data gathering, trending and alarms.  


In the final analysis, it is critical that an annual boiler shutdown be a part of your standard operating procedures, and that your technician is trained to perform a thorough inspection, or consult an authorized boiler representative.