Annual Inspections

Another important maintenance task is the boiler's annual or biannual cleaning and inspection. Any accumulation of soot or ash on the boiler's fire-side surfaces reduces heat-transfer rates and decreases operating efficiency.

For example, even a barely visible accumulation of soot can reduce efficiency by up to 10 percent. If the soot accumulates for several years without a cleaning, it is common to find efficiency has declined by 20 percent or more.

Cleaning the boiler's water side is an important task. Large boilers typically require annual cleaning. Technicians should monitor smaller boilers, test them regularly, and clean them as needed.

Managers typically schedule annual cleanings to coordinate with the boiler's annual inspection, or in the case of heating boilers, at least one month before the start of the heating season. In addition to improving boiler efficiency, annual cleaning and inspection gives managers the opportunity to identify developing problems that otherwise might go undetected.

Even though today's generation of boilers is more efficient, more reliable, and safer than any previous generation, accidents still occur, and boilers still fail before they reach their rated service lives. Nearly two-thirds of boiler failures result directly from poor operating and maintenance practices, according to one estimate. Similarly, most unscheduled interruptions of services also are the result of poor operating and maintenance practices.

Good maintenance practices can go a long way to improving safety, but only as long as the maintenance program addresses specific safety measures.

Managers should start with the safety-relief valve, which represents the boiler's last line of defense against overpressure. Scale and other contaminants in the water system or plugged discharge lines can interfere with the valve's operation. Operators must test the safety-relief valves each time they start a boiler, and they must perform additional testing at intervals the manufacturer recommends.

Flame-safeguard controls also require regular testing. This control ensures the boiler lights, operates, and shuts down properly. Typical operation includes purging of combustible gasses from the boiler during start-up to reduce the risk of an explosion. The flame-safeguard control verifies all other safety interlocks are closed before ignition.

When the boiler shuts down, it initiates a purge cycle to eliminate combustible gasses. Depending on the size and type of boiler, technicians might need to inspect the flame-safeguard control daily or weekly.

Finally, the low-water cutoff control shuts down boilers in the event of a lost water supply, which can cause overheating and permanent damage. While the controls are reliable, components can fail, resulting in a false indication of the water level in the boiler. Again, depending on the size and type of boiler, operators might need to visually confirm each day that the boiler's water level is as indicated.

Operators must not simply assume that if the boiler's safety indicator lights and alarms are normal, everything is OK. Lights burn out, and alarm contacts can fail or be disconnected. Most operating panels include a test button for indicator lights and alarms. Operators need to use it regularly.

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