Cleaning boiler tubes is mandatory for optimal boiler life. An acceptable regimen is annual cleaning; biannual for high-use units. Typically, large boilers are cleaned annually, small ones as needed.
Tube cleaning is performed by mechanically-driven brushes or scrapers sized accordingly for inside and outside tube diameters to loosen soot or ash. High-powered vacuums connected to the machines suck up the residue. For fire-tube boiler scale encrustation, rotary tube cleaning equipment is necessary. Equipment with powerful air motors drives flexible shafts fitted with various tools. The shafts are sheathed in water-tight casings which carry water to the cleaner tool, thereby cleaning and flushing tubes in one operation.
Boiler tube cleaning products include specialized brushes and heads for tube interiors and exteriors. Also available are hydraulic tube pullers, bleeder cleaners and leak detectors.
Proper heat transfer cannot be efficiently attained if fire-tubes are clogged with soot or ash. An accumulation of these contaminants acts as insulation, thus decreasing the rate of productivity on the boiler’s fire-side surfaces. Further, boiler tubes can become corroded due to soot’s inherent sulfur content. Built up over several years, soot accumulation can lead to complete boiler wear out.
Scale is another contributor to boiler inefficiency and wear out. If the solubility limits of calcium and magnesium are exceeded in the boiler’s water, scale deposits form. Unless the system’s water is properly treated, scale can thwart the operation of the safety-relief valves which guard against overpressure.
A range of routine tasks should be performed diligently. Amongst them: water treatment; efficiency testing; valve and filter checks; monitor boiler’s water level; inspect all controls, safety- indicator lights and alarms. Proactive testing and inspection prevents problems.
Efficiency testing is important economically. It gauges operating costs by tracking boiler performance. In measuring combustion efficiency, it helps foresee developing problems. Electronic testers can calculate net stack temperature and excess values including oxygen and carbon monoxide.
Chemical Tube Cleaners
Boiler chemical cleaning is for the water side of fire-tube boilers. Deposit removal from the tubes’ interior reduces tube failure. However, chemical cleaning is expensive. The process should only be employed when necessity dictates. Need is determined by sampling from high heat flux areas and analyzing for deposit loading on the inside of the water wall tube. Boiler cleaning chemicals for steam boilers include phosphates and polymers. For hot water boilers, sodium nitrite is preferred.