Boilers can be dangerous if not inspected and maintained properly. Each year, countless accidents, breakdowns and unnecessary shutdowns occur among the approximately 43,000 industrial boilers in the chemical, food processing, paper, refining and primary metals industries throughout the United States.
Boiler breakdowns can cost thousands of dollars in equipment repairs as well as hundreds of thousands of dollars in property damage and business income losses. Boiler accidents also can cause loss of life and major structural damage to plants, facilities and equipment. When compared to a single instance of an unplanned plant shutdown, the cost of boiler inspection, maintenance and repairs is minor.
Proper boiler maintenance, servicing and inspection is not only a safety issue, it also can be a significant economic matter. Boiler downtime might force manufacturing plants to shut down plant operations and the production process, and every hour that production is stopped can cost hundreds of thousands of dollars.
No plant owner wants emergency shutdowns or equipment downtime, and the plant manager doesn’t want to be responsible if it occurs because boilers (or other equipment) weren’t serviced, inspected or maintained properly.
While boiler safety devices are designed to prevent dangerous conditions from turning into disasters, only proper boiler maintenance prevents the development of dangerous operating conditions in the first place. The only way the plant manager can be confident that control or safety devices are functioning properly is by regularly performing required maintenance, testing and inspection.
Regular inspection of boilers is the law, most often governed by the state, but in some cases governed by municipality and city. Boilers must be inspected by certified inspectors according to a mandated schedule. The day-to-day maintenance and service of boilers is the responsibility of plant engineers or plant managers. It’s important to remember that most problems don't occur suddenly. Instead, they develop slowly over a long period of time. So slowly, in fact, that the maintenance staff can grow accustomed to the change without realizing it has taken place.
Additionally, regular boiler inspections are important for optimal function and energy efficiency. Boilers are voracious energy users. Inefficient operation means wasted energy and increased operating costs.
Regular inspections also can extend the life of the vessel. As every plant owner and manager knows, industrial boilers are a major investment, costing upwards of $200,000.
Key boiler safety features
Boilers have a variety of safety features designed to prevent accidents and keep them functioning at optimal efficiency.
Safety valves are the primary safety feature on a boiler. Designed to relieve the pressure generated within the boiler if other systems fail, every steam and water-heating boiler must have at least one safety or safety relief valve of sufficient capacity to meet or exceed the maximum burner output.
The ability of a safety valve to perform its intended function properly can be affected by several things, including internal corrosion or restricted flow. Internal corrosion typically is the most common cause of “freezing” or binding of safety/relief valves. This is generally caused by slight leakage or “simmering” caused by an improperly seated valve disk and is a condition that must be corrected immediately. It’s never recommended that a boiler be operated too close to the safety valve setting because the set pressure can cause these valves to leak slightly, resulting in an internal corrosion buildup that eventually prevents the valve from operating.
Water level control and fuel cutoffs perform two separate functions, but sometimes are combined in one unit. They provide both a water level control function and a safety feature of a low-water fuel-cutoff device. It’s important to ensure that piping is open and free of scale or sludge buildup at all times. Properly installed piping uses cross tees to enable easy cleaning and inspection. Low-water fuel cutoffs should be checked periodically for proper operation. Because this test requires allowing the boiler water to go to the minimum safe operating level, qualified personnel should use extreme caution when doing this.
In addition to making these periodic tests of the low-water device, flush the float chamber on the water level control and the low-water fuel cutoff thoroughly to remove accumulated sediment. Both of these controls should be disassembled, cleaned and checked annually.
The water gauge glass on a boiler enables the operator to observe and verify visually the actual water level in the boiler. If not properly cleaned and maintained, the sight glass might show there is sufficient water when the boiler is actually operating in a low water condition. A stain or coating sometimes develops on the inside of the glass where it’s in contact with boiling water, and this stain can give the appearance of adequate water in the boiler, especially when the glass is either completely full or empty of water.