Boiler Maintenance

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What does good boiler preventative maintenance include?

We have all been told that good boiler chemistry is essential to good boiler efficiency.

 

 

  • Soft water is a major component of good boiler chemistry:

Without it, boiler tubes will become contaminated with solids that prevent good heat exchange.

How much solids enter a boiler?


How damaging could one day of city water hardness be?

If a laundry is using 200 gallons of city water per minute with a water hardness of 20 grains: The total mass of hardness that should be removed if the facility were to run for 16 hours is:

Calculation:

200 GPM * 60 Minutes/hour * 16 hours * 20 Grains / 7,000 Grains per pound = 548.6 pounds

These 548 pounds of hardness (Calcium & Magnesium) would have a volume of approximately 50 gallons!

If your boiler is using 5% of your total water, then approximately 2.5 gallons of contamination could occur in one day of running hard. This is enough contaminate to cover the tubes in a 400 horsepower boiler with 0.002 of an inch of insulator!

Imagine using 5 gallons of 50% solids paint, per day, to coat your boiler tubes!

Calculation: (2.5 Gallons * 231 Cubic Inches / Gallon) / (400 BHP * 5 Square feet / BHP * 144 Square inches / Square foot) = 0.002 Inches.

Have you installed polishing softeners on your boiler, or are you relying on your primary softeners to handle the job? Polishing softeners on a cheap insurance policy! A two cubic foot system can be purchased for about $1800.00.

So, providing soft water, every day, is part of good boiler maintenance.


  • Feed water temperature:

Oxygen is about 6% soluble at 150 degrees Fahrenheit, and only 2% soluble at 210 degrees Fahrenheit. Less oxygen means less oxygen pitting. Also, less thermo shock will occur with higher feed water temperatures.

So, providing feed water at higher temperatures is part of good boiler maintenance.


  • Hot Spots:

Hot spots on a boiler tube are a tube failure in the making. One way to help reduce hot spots is the addition of turbulators. High stack-gas temperature indicates wasted heat that’s going right up the boiler stack. Turbulators can improve boiler efficiency, reducing stack-gas temperature. When turbulators are installed, carbon dioxide increases in the stack gases indicating more complete combustion; flame temperature increases indicate less excess air is being drawn into the boiler. Test conducted before and after the installation of turbulators, has shown repeatedly, that when installed, turbulators can cut heating costs. Turbulators help boilers last longer by eliminating hot and cool spots that cause thermal stress. Leading boiler manufacturers make turbulators available as a part of their original equipment package, proof that turbulators work.

So, turbulators are part of good boiler maintenance.


  • Mud Legs

Preventing dirt & scale from entering the boiler, Dirt pockets, (mud legs) provide a low-flow area where these contaminates can settle out of the steam and condensate stream. Dirt pockets must be cleaned out periodically and, therefore, should be part of a regularly scheduled maintenance program.

So, mud legs are part of good boiler maintenance.


  • Boiler blow down heat exchanger

No matter how hard you try to prevent it, solids will build up within the boiler!

So now you must bleed (blow down) these solids to an acceptable level. This involves losing valuable heat energy. Many boiler operators run the boiler at higher than recommended solids level to lessen the energy losses. To prevent this poor maintenance procedure, a simple surface blow down heat exchanger can be added.

So, the installation of a boiler blow down heat exchangers is part of good boiler maintenance.


  • Steam system design

If the steam & condensate system is a poor design, boiler performance will diminish.

Higher steam velocities, the speed of the steam flowing through the lines measured in feet per minute, will cause pipe erosion, increasing the contaminate levels within the boiler feed water. Steam velocity should be maintained between 6,000 and 12,000 fpm with a maximum of 15,000 fpm.

So, Steam system design is part of good boiler maintenance.


  • Stoichiometric ratio

Two key components of the boiler efficiency equation are the stoichiometric air/fuel ratio and the heat of combustion value for the fuel being burned. The stoichiometric ratio shows the exact amounts of air and fuel needed for a combustible to be completely consumed. The heat of combustion shows the amount of energy that would be released in such a perfect reaction.

Since our laundry boilers are operated in a variable load condition, controlling the excess air becomes a major component of boiler maintenance. If a boiler were to operate in a “rich” gas mixture condition, sooting will occur and unburned fuel gas will exit the stack. This could also lead to an uncontrolled fuel explosion. By definition, I assume, that if we allow the boiler to rapidly disseminate (explode) this would be poor boiler maintenance.

So, controlling the stoichiometric ratio is part of good boiler maintenance.


  • Additional boiler maintenance issues

Insulation maintenance

Burner adjustments

Added chemistry

Controlling boiler load variations

Combustion air filtering

Corrosion prevention

Fuel control

Fuel pre heating

Combustion air preheating

Safety valves (nearly 50% of the safety valves installed are done incorrectly, according to Factory Mutual)

Start up, shut down procedures

Boiler storage procedures

Water level controls

Exhaust stack pressure monitoring

Boiler grounding (boiler frame should be less than 5 ohms to earth)

Fire wall separation

Combustible material separation (not a good maintenance procedure to store gasoline within the boiler room, or to have the exhaust stack too close to a wood roof member)


Mike Burdine 1995

Mike Burdine 2008

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