corrosion products and is often wrongly called scale.
The exteriors of all boiler drums and headers should be inspected for signs of corrosion under the insulation. Rusty streaks or signs of corrosion on or around the edges of the covering, the drum pads, or the tubes indicate possible corrosion of the drum and should be investigated immediately. If machinery or piping is installed over the boiler, water may drip down on the boiler and work its way under the insulation. In such installations, the boiler drum coverings must be removed, and the exterior of the drum must be inspected carefully.
All corrosion-resisting steel plates such as baffle plates, seal plates, superheater support plates, steam drum protection plates, and so forth, must be carefully inspected whenever firesides are opened. These steel plates are subject to damage from overheating, particularly if clogged gas passages interfere with the designed flow of combustion gases and allow extremely hot gases to flow over the plates. Since failure of these parts could have extremely serious consequences, the plates should be inspected at every opportunity and should be renewed when necessary.
The uptakes and smoke pipes are examined according to a maintenance system. Check the uptake expansion joints to be sure they are not clogged with soot. Look for ruptures and for loose reinforcing ribs or Z-bar stiffeners. Check the rain gutters to see that they are not plugged with soot. Check the top of the economizer to see if it is clean.
Following the hydrostatic test, the boiler should be fired and brought up to operating pressure and temperature. All automatically and manually operated control devices provided for control of steam and water pressure, hot-water temperature, combustion, and boiler water level should be inspected and caused to function under operating conditions. All associated valves and piping, pressure- and temperature-indicating devices, metering and recording devices, and all boiler auxiliaries should be inspected under operating conditions. All safety valves and water- pressure relief valves should be made to function from overpressure.
Inspections and tests may be made with the main steam or hot-water distribution valves closed or open as necessary to fire the boiler and operate it under normal operating conditions. Testing the function of automatically or manually controlled devices and apparatus that may interfere with distribution requirements should be one with main steam or hot-water distribution valves closed, as applicable.
The purpose of these inspections and tests is to discover any inefficient operation or maintenance of the boiler or its auxiliaries that may be evidenced under operating conditions. All deficiencies requiring adjustment, repair, or replacement, and all conditions indicating excessive operating costs and maintenance costs should be reported.
The operation of all firing equipment, including oil burners, gas burners, fuel injectors, fuel igniters, coal stokers and feeders, and other such equipment provided to introduce fuel into the boiler furnace and ignite the fuel, should be inspected for any deficiency that may be evidenced under operating conditions. In particular, igniters and burners should be checked to ensure that burner protrusion, angle, setting, and so forth, is such that light off and operation are as effective as possible.
Inspect the operation of combustion controls, steam pressure controls, water temperature controls, and feedwater controls. Assure that the ability of the combustion control and steam pressure control to maintain proper steam pressure (or water temperature in high- temperature water installations) and air-fuel ratio is demonstrated throughout the capacity range of the boiler. Air-fuel ratio should be checked by CO2 or O2 measuring devices. On smaller boilers the appearance of the fire may be used as a guide for inspection of air-fuel ratio. Check fullyContinue Reading