4 FM quick reads on Boilers
1. Water Treatment Can Extend Boiler Life and Improve Energy Efficiency
Today's tip from Building Operating Management comes from James Piper, contributing editor for Building Operating Management and Maintenance Solutions magazines. Establish a water treatment program to ensure boiler efficiency and reliability.
Water treatment is one of the most important elements in any boiler maintenance program. Untreated boiler water contains contaminants that include dissolved minerals, gasses and particulates.
Dissolved minerals can result in the formation of scale on boilers' heat-transfer surfaces. Gasses can form corrosive compounds that attack surfaces. Suspended particulates can contribute to both problems.
Boiler scale forms when dissolved mineral salts in the water settle on heat-transfer surfaces. This scale acts as a layer of insulation, reducing the rate of heat transfer and the boiler's efficiency. Even a thin layer of scale can reduce efficiency by 10 percent or more. Scale also can result in localized overheating of a boiler tube. Uncorrected, this issue can lead to boiler tube failure, downtime and costly repairs.
Dissolved gasses, such as oxygen, can increase the boiler water's corrosiveness. As a result, metal surfaces in the boiler and heating system come under attack. If technicians do not correct the problem, the resulting corrosion can destroy metal surfaces, decreasing the service life of the boiler and system piping.
Water-treatment programs introduce limited quantities of certain chemicals that combine with impurities in the water and neutralize the impurities to keep them in suspension.
Facility managers should design and monitor water-treatment programs carefully. Using the wrong chemicals — or the wrong quantities — can damage the boiler or other system components. Monitoring is essential because changes in feedwater quality can require changes in the treatment program.
Water-treatment programs are most critical in steam systems. These systems have much higher requirements for make-up water, which contains contaminants that can damage boiler surfaces.
This has been a Building Operating Management Tip of the Day. Thanks for listening.
2. Boilers: Four Factors Shape Decision to Repair or Replace
Today's tip from Building Operating Management comes from James Piper, contributing editor for Building Operating Management and Maintenance Solutions magazines. Four factors can help a facility manager decide to repair or replace a boiler.
As with all building components, boilers have finite service lives. Even with ideal maintenance, they eventually require replacement. While a boiler's age is a major factor in determining whether to repair or replace a unit, it is not the only factor facility managers must consider.
No hard and fast rules exist for making this decision, but facility managers need to consider several important factors:
Age. As boilers age, maintenance costs gradually rise. Unless something serious goes wrong, replacement costs will always exceed repair costs. But the trend in maintenance costs is a more important factor. If these costs remain relatively constant, then repairing the boiler most likely is the better option. Consistently and rapidly increasing costs point toward replacement, as does difficulty in obtaining replacement parts.
History. Identical boilers operating in similar facilities often have widely different operating histories. Differences in set-up, operating practices, and maintenance often cause these variations. Operators and managers need to review the boiler's history to see if factors exist that suggest replacement is the better option.
Efficiency. New-generation boilers offer major increases in annual operating efficiency compared to boilers that are only 10 years old. Facility managers should consider the annual savings from replacement when evaluating options.
Configuration. Older systems with central boilers tended to include only one or two large boilers. That set-up often made it necessary to cycle one boiler to match part-load operating conditions. New-generation, centralized systems use several smaller, modular boilers, which allows operators to better match system capacity to facility needs, thus improving operating efficiency. Facility managers should review the historical building loads to see if a cost benefit exists for replacement with modular boilers.
This has been a Building Operating Management Tip of the Day. Thanks for listening.
3. Planning Pointers for Successful HVAC Retrofits
I'm Dan Hounsell, editor of Maintenance Solutions magazine. Today's topic is, planning for successful HVAC retrofits.
It is unusual for a retrofit project in an institutional or commercial facility to go off without a hitch. Schedules, equipment, materials, technicians and a host of other factors need to mesh almost precisely for that to occur. So when the project in question is the replacement of a major HVAC component that just happens to be embedded deep within a facility, success often is even more elusive.
That scenario is exactly what happened when St. Mary's Hospital in Madison, Wis., replaced its 25-year-old boiler in 2007. The project is a prime example of the role planning and preparation play in any project's success.
"I think it's a testament to the planning that we really didn't have surprises," says John Puckett, the hospital's director of plant services. "It was well thought out, well coordinated, well communicated. The staff was able to keep things running. We had contingency plans, but we didn't have to exercise them with the installation of the new boiler."
The department's role in the project went beyond technical issues.
Says Puckett, "Besides developing a close working relation with our contractor partners, communication strategies between the engineers and the staff, as well as our customers — those were the key elements of this department's role. We also had to maintain a consistent and reliable supply of all the associated systems and functions during the installation."
The old boiler's location deep inside the building created a host of challenges related to disconnecting and moving it to make way for the new boiler. That move took an entire week. Ensuring the hospital's utilities remained functional during the replacement process also created challenges.
Says Greg Hatzinger, the hospital's power plant supervisor, "It was a daily challenge, just simply because of where the boiler was located, just to keep services running and relocate feedwater and fuel lines — it was quite a challenge. It took a lot of coordination with the contractors to keep those going."
4. Three Boiler Control Upgrades Can Improve Energy Efficiency
Today's tip comes from James Piper, contributing editor for Building Operating Management and Maintenance Solutions magazines:
When specifying boiler controls it is important to understand that operating efficiency is only one consideration. The boiler control system must be able to meet the facility's peak heating load while operating efficiently under part-load conditions. Typical controls that facility managers should consider when upgrading existing boilers include the following:
1. Flue-gas trim. One of the best indicators of a boiler's combustion efficiency is the flue-gas composition. Trim controls constantly monitor the temperature and the chemical composition of the flue gas, making changes to the combustion controls to limit the quantity of excess air brought into the boiler. While all boilers require some excess air for complete combustion, natural-gas-fired boilers can operate effectively with as little as 3 percent excess air. Boiler efficiency increases approximately 1 percent for each 15 percent decrease in excess air provided to the boiler. With most boilers operating at 10 percent or more excess air, the annual energy savings from flue-gas trim controls is significant.
2. Automatic blowdown. To limit the quantity of deposits that can accumulate in a steam boiler, technicians can bleed off part of the boiler's water, typically on a continuous basis. The boiler wastes energy if the blowdown rate is too high, and the concentration of solids in the water becomes too high if the blowdown rate is too low. Automatic blowdown controls regulate the quantity of water that technicians bleed from the system based on the actual level of contaminants.
3. Sequencing. Many facilities operate more than one boiler at a time, depending on the load. This frequently results in more boiler capacity than is actually needed. Since the operating efficiency of a boiler is highest when it is operating at or near full load, this practice can waste a significant amount of energy. Automatic sequencing controls examine the load conditions and determine the boiler or combination of boilers that will meet that load most efficiently.
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