INDUSTRIAL BOILER & MECHANICAL
Used Boiler Inventory

Typical Firetube Boiler Boil-out Procedure

 

It is recommended that your new firetube boiler be boiled-out before placing it into service. This may be done before or immediately following initial start-up. A proper boil-out will remove any grease or oil that may still be present in the waterside of the boiler as the result of boiler installation. A clean boiler waterside is one of the requirements of establishing and maintaining a stable waterside condition.

Manufacturers do not boil-out a new boiler. It is recommended that a qualified water treatment consultant in your area be contacted for a recommendation on a boil-out compound, which should include its own use procedure. In the absence of a boil-out procedure, many boiler manufacturers recommend the following.

  1. Isolate boiler from piping system (valve off).
     
  2. Remove safety valves from the boiler. A boiler safety valve tapping on the top of the boiler pressure vessel is often used as the opening to introduce the boil-out compound into the boiler. It will also serve as a vent to fill the boiler and operate it during boil-out.

    WARNING:
    ONLY QUALIFIED AND EXPERIENCED PERSONNEL SHOULD PERFORM A BOILER BOIL OUT. STEPS MUST BE TAKEN TO BE PROPERLY PROTECTED AGAINST THE HAZARDS OF HANDLING AND USING BOIL-OUT COMPOUNDS.

  3. Fill the boiler with clean, ambient temperature water. Allow sufficient room for the boil-out compound solution (generally diluted) and expansion of the water. The boiler will be boiled out to atmosphere.
     
  4. Start the boiler, following the appropriate start-up procedure included in this Manual. The boiler will be operated in the manual mode, low fire setting, for the duration of the boil-out Observe the open safety valve tapping, as the boiler is being warmed. Due to expansion, water will have to be drained from the boiler to prevent it from overflowing. Any number of blowdown valves can be used to drain the boiler during boil-out; however, follow the boil-out compound supplier's instructions on how to dispose the chemically treated boiler water. You might not be permitted use of a normal floor drain by environmental regulations.
     
  5. Continue to observe the open safety valve tapping on the top of the boiler. As the boiler water begins to boil, and then develop into a steady discharge of steam coming out of the open safety valve tapping, tum the boiler off. Wait until the steady stream of steam reduces to only traces of radiant steam, and then restart the boiler. Repeat this process as often as necessary for the duration of the boil-out.
     
  6. After the boiler has been allowed to cool down to normal hot water temperatures, drain the boiler     completely. Follow the boil-out compound supplier's instructions on how to dispose of the chemically treated boiler water. Refill the boiler completely with clean, hot water. Drain the boiler again.
     
  7. Remove all hand hole and manway covers from the boiler pressure vessel. Inspect the waterside of the boiler for cleanliness. Reinstall the hand hole and manway covers using new replacement gaskets.
     
  8. Reinstall the boiler safety valves on the boiler, including the discharge piping. Fill the boiler with clean, chemically treated water to its normal operating level. The boiler is now ready for initial start-up or to be placed into service.
     
    WARNING:
    HANDHOLE, MANWAY AND SMOKEBOX DOOR GASKETS MUST BE CHECKED FOR LEAKAGE FOLLOWING INITIAL OPERATION OF THE BOILER. THESE GASKETS MAY BEGIN TO LEAK DUE TO TEMPERATURE AND PRESSURE CHANGES AND EXPANSION OR CONTRACTION.
     

Recommended Water Quality for Firetube Boilers

 

Feed Water
pH 8.5-9.2 – Should be alkaline at all times.
Hardness Zero ppm
Silica Dictated by blowdown and maximum boiler residuals.
Total Dissolved Solids T.D.S. dictated by blowdown and maximum boiler residuals.
Dissolved Oxygen Should be reduced to less than 0.005cc/l by mechanical deaeration and the residual be controlled by addition of suitable oxygen scavengers – normally sodium sulfite.
Suspended Matter Zero
Oil & Grease Zero

 

Boiler Water
pH 10.5-11.5.
Alkalinity 700 ppm (max.)
Total Dissolved Solids Boilers sized 20,000 pph or less – 3500 ppm (max.)
Boilers sized larger than 20, 000 pph – 2500ppm (max.).
Phosphate Residual 50 ppm as PO4 (min.)
Dissolved Oxygen Zero
Suspended Matter Zero
If sodium sulfite is used for oxygen scavenging, maintain 25-50 ppm as Na2SO3.
Suspended Matter 50 ppm (max.)
Silica 12 ppm (max.)

 

This information is supplied as general guidance only and does not absolve the boiler owner from the responsibility of determining and maintaining water standards appropriate to the specific local water chemistry and specific boiler use.


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