Best Practices for Industrial Boiler Maintenance
March 10, 2014
Boilers play a crucial role in keeping refineries and plants running; they also represent a significant capital investment for the company that owns them. Keeping industrial boilers properly maintained and running smoothly is extremely important.
Maintain the Fuel System
The regular maintenance and upkeep of the boiler’s fuel system is one of the most important boiler maintenance practices. An efficient fuel system is important both for the boiler’s overall health as well as for keeping fuel costs down. The entire fuel system should be checked and undergo routine inspection, in addition to periodically cleaning the burner.
Check and Clean the Water Gauge Glass
The water gauge glass should be checked periodically by the boiler operator to visually ensure that there is adequate water in the boiler. Over time the glass can become stained and cloudy, making it difficult to get an accurate reading or giving the impression that the boiler has more or less water than it actually does. During periods when the boiler is turned off, such as during a turnaround, it is important to clean, and if necessary, completely replace the water gauge glass. The piping leading to the water gauge should also be cleaned and inspected to ensure that a false water level is not being given.
Clean Piping and Float Chamber for Water Level Control
The water level control feature on a boiler plays the critical role of enabling the operator to set the water level. In order to work properly it is important that the piping be clear of sludge and sediment. Additionally the float chamber should be flushed to ensure that there isn't any sediment buildup.
Check Fuel Cutoff
The fuel cutoff feature is often combined with the water level control into a single unit. The fuel cutoff is designed to automatically cut off the fuel if the water level drops too low making it an extremely important safety feature. A qualified technician should test this function to ensure that it is working properly. Both the water level control and fuel cutoff should be disassembled, cleaned, and checked on a yearly basis.
Check Safety Valves for Corrosion
Safety valves are one of the primary safety features on boilers. All boilers must contain at least one safety valve that has a sufficient capacity to meet or exceed the maximum output of the burner. So if other systems fail, the safety valve can release the pressure. To properly work, the safety valves must be free of corrosion. Internal corrosion is typically the result of a slight leakage, or "simmering," that comes from an improper seating of the valve disk. This problem must be corrected immediately and internal corrosion of the safety valve should be carefully prevented.
Monitor Stack Temperature Gauge Readings
A stack temperature gauge is usually installed on the boiler to detect the temperature of the flue gas leaving the boiler. Stack temperature gauge readings should be closely monitored because high readings often indicate that the tubes are developing a soot or scale buildup or that the baffling inside the boiler might have burned through or deteriorated, thereby allowing some of the hot gas to bypass the heat transfer surfaces. It is estimated that for every 40°F increase in stack temperature around 1% of a boiler's thermal efficiency is lost.
Check and Maintain the Condensate Recovery System
The condensate recovery system collects condensate from the steam traps and reuses it as feedwater. This is an important function that lowers boiler operating costs. The condensate is usually around 160°F - 200°F, much higher than the typical 80°F or lower water temperature of fresh utility water. In turn, the boiler does not have to work as hard to heat the condensate. Checking and maintaining the condensate recovery system is an important tool for keeping operating costs down.
Check and Maintain the Water Treatment System
The water treatment system is used to filter out impurities present in untreated water. If allowed to remain, these impurities can cause corrosion or sediment buildup, which reduce the boiler's efficiency and necessitate more frequent blowdowns. By keeping the water treatment system in good health the boiler's efficiency is maintained and fewer blowdowns are needed.
Analyze and Optimize Air-to-Fuel Ratio
The air-to-fuel ratio refers to the amount of oxygen to fuel being used during combustion. Establishing and maintaining the optimal ratio is very important for the boiler's efficiency. Too much air uses excess energy by being needlessly heated. By contrast, too little air results in an incomplete fuel burning...wasting fuel and causing soot, smoke, and carbon monoxide. The ratio can be measured and optimized by analyzing flue gas and using a computer-based distributed control system (DCS) that will automatically control fuel and oxygen levels as needed.
Clean the Boiler Heat Transfer Surfaces
Soot build up on the boiler heat transfer surfaces can act as an insulator and reduce the efficiency of the heat transfer between the combustion gas and steam generation, thereby diminishing the function of the heat transfer system. Regularly cleaning of these surfaces should be a part of routine maintenance practices. This is generally done by executing maintenance on the soot blower system.
Minimize Heat Loss
Heat loss is the enemy of boiler efficiency. To minimize heat loss an economizer can be installed to recover heat waste from the stack. This heat can then be redirected to the boiler feedwater and used for preheating.
Keep and Review Boiler Logs
A boiler log is a record of the boiler's operation, maintenance, and testing. Boiler logs keep a record for knowing when it is time to perform routine maintenance and tests and also for tracking changes in the boiler's operating conditions over time. The changes can be indicative of a problem or general loss of efficiency and without a written detailed account these subtle, gradual changes might otherwise go unnoticed. Thus a very important part of good boiler maintenance practices is keeping and regularly reviewing the boiler log.
The best practices for industrial boiler maintenance listed here should go a long way toward helping companies keep their industrial boilers in optimum shape for as long as possible. It is important to follow all safety regulations and to have experience with the particular industrial boiler in use. Whenever problems are detected they should quickly and proactively be corrected before they can escalate. STI Group offers comprehensive industrial boiler services from fabrication, repair and maintenance, retrofits, and turnarounds.