Boiler outages

To ensure optimum generating efficiency and minimize boiler outages and reductions in equipment life, a large number of operational functions must be both coordinated and tightly controlled. The use of... 

The run began on September 26, 1978 and terminated on November 2, 1978, for a total of 833 onstream hours (35 days). During the run, the scrubber was out of service for 48 hours due to a boiler outage caused by a tube leak, 5 hours for a scheduled inspection, and 8 hours for unscheduled outages to clean and repair the scrubber induced-draft fan damper. Excluding boiler outages and scheduled inspections, Run 932-2A operated with an onstream factor of 99.0 percent. As was typical of all long-term rims, the scrubber was more reliable than the boiler. 

The system was onstream for 1,688 hours. During the run, the scrubber was out of service for 78 hours due to equipment problems and 84 hours due to boiler outages. Excluding boiler outages, Run 917-1A operated with an onstream factor of 95.6 percent. 

Generating bank tubes have experienced corrosion adjacent to the mud drum in some recovery boilers. Thompson et al. [263] reported field and laboratory results. First, an in situ conductivity probe was used to determine when corrosive salts formed in the boiler at the mud drum/tube area. Then, erosion testing in the laboratory indicated that removal rates were insufficient to account for the tube wastage. Guzi [264] described an automated ultrasonic inspection procedin for use during boiler outages to detect near mud drum corrosion of generating tubes. 

In fossil fuel-fired WT boiler plants, boiler tube failure is perhaps the leading cause of forced outages, so identifying the chain of cause and effect is particularly important. 

Particularly critical areas for corrosive attack include economizer tube inlet headers, certain boiler tube areas, surface condenser tubes, and HP heaters. Problems occurring here may be related to EC or perhaps to the dissolution of copper or iron and its transport to some point elsewhere in the boiler system. If transported metal reaches certain critical areas (such as copper reaching turbine blades), very serious outages may occur. 

Insurance inspections and cleaning programs further add to the frequency at which a boiler may be out of service. During these outages and offline periods, the boiler metal waterside surfaces are especially susceptible to rapid corrosive attack and damage. Consequently, various protection protocols are employed to stave off this risk. The primary factors responsible for downtime corrosion are ... 

Wet lay-up programs are therefore used to protect standby boilers. These are essentially the same programs used to protect idle boilers that may be out of service for perhaps 30 days. (Boilers having outages of longer than 30-day periods generally are subjected to dry lay-up programs.)... 

Boilers having outages of longer than 30 days generally are subjected to dry lay-up programs on both the waterside and the fireside. Idle boilers and auxiliaries may be stored either open-and-dry or closed-and-dry. In both programs, the objective is to keep all waterside components completely dry. 

Heavy industrial boilers operating in continuous processes may be online for perhaps four or even five years before shutting down for maintenance and inspection. Here, correct boiler plant materials selection is critical, and the quality of the various utility support functions must be outstanding if forced outages are to be avoided. A heavy industrial or utility boiler that is unintentionally offline may cost 1 million a day in lost production or electricity generation. 

In a plant with a shaft-driven boiler feedwater pump, problems had historically occurred with failure of the bearing in the hydraulic coupling. There was no apparent cause, but throughout the 12-year life of the equipment, the failure occurred about once every 1 or 2 years and resulted in an outage of about 5 weeks. 

On November 14, 1993, a 600-foot concrete stack collapsed onto a coal-fired electric power plant killing one person and injuring four others. The incident occurred at a Texas Utilities plant near Mt. Pleasant, Texas while the facility was shut down for maintenance. Extensive damage occurred within the plant resulting in an extended outage. Destroyed in the incident were a 750 MW generator, a steam boiler, compressor, two... 

Another common problem is that particulate and soluble iron returns to the boiler by way of the condensate and feedwater. When water circulation is discontinued, these solids are much more likely to settle out on internal surfaces. Frequent outages increase the opportunity for these deposits to grow to the point where problems can result, since cleaning of the surfaces rarely takes place under these circumstances. 

A fourth important factor that increases outages and maintenance costs is the corrosive effects of alkali elements, especially sodium, which is associated with chlorine in certain coals. The specific damage to boilers by chlorine is not well known, but this mineral constituent clearly causes excessive rates of corrosion to coal handling equipment. 

It ran for 719 onstream hours (30 days) with no unscheduled outages. The scrubber was down once for a scheduled 3-hour inspection and again when the boiler came down for 135 hours to install a new station power transformer. 

Camera approach Directly observe the waterwall to find steam leaks and qualify them to determine whether or not the boiler can continue to operate until the scheduled outage, avoiding downtime that could cost hundreds of thousands of dollars. 

The steam-hydrocarbon reforming process is highly developed and will operate for months or even years without interruption, except for normal outages scheduled for boiler inspection, routine maintenance, and other attention which is placed on a definable schedule. The heat balance and utilization are well engineered ordinarily so that there is little waste, and what heat is unused on the furnace side of the reformer is subsequently recovered for use to generate steam. 

Furnace outages to remove accretions in the boiler and electrostatic precipitator... 

No power will ordinarily be drawn from the D-H Intertle line However, this power source can be manually switched to either bus at the 13 6 KV level Shis Intertle line can be used to siqpply power to the area during outages for maintenance reasons, e g, when the boiler Is shutdown, equipment on the B sub system can be powered from the D H Intertle line if desired for system main tenance or testing ... 

The standby boiler will be required during a reactor outage at steam generation rates up to its design capacity (575,000 pounds per hour). This steam will be required to drive the five pump drive turbines, the turbine generator, for deaeration of secondary loop makeup, for maintenance of mein a team header preeeure end for auxiliary eye tern uaee ... 

In this particular case, the boiler system may cause loss of production in the whole refinery in case of outage during winter time. Therefore the RAM analysis took into account the simulation for a specific range of time that in this case is winter time. 

During a recent outage, the boiler was inspected to determine whether the practice of cofiring caused any increase in slagging or fouling... 

A complete set of superheaters for a 100 MW combined heat and power boiler costs in excess of lm. The durability of superheaters is thus an important factor in determining the long-term production costs. Unplanned outages due to leaking superheaters are also very expensive. As well as causing corrosion problems, the build-up of deposits reduces the heat uptake to the superheaters which leads to lower efficiency. Consequently, ways are being sought to reduce superheater corrosion. 

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