Field Engineering Services: Boiler Performance Analysis

 

B&W's field engineers can help you ensure your boiler is performing at its highest possible level of efficiency. Anything less than that can be detrimental to your equipment and to your bottom line.

Our performance-enhancing services include:

Circulation Analysis
One of the most complex boiler upgrades involves modifying the water circulation system. Poor circulation often leads to tube failures throughout the boiler circuits that are exposed to hot flue gas. These failures can result from insufficient cooling, poor water distribution, flow instability, inadequate drum internals, or internal corrosion and deposits.

B&W has the experience to solve tough circulation problems on all types of utility, industrial and recovery boilers. Our highly trained and experienced engineers are experts in determining the exact causes of circulation problems and finding the right solutions.

Consultation
If you are concerned a problem may exist but are not sure where to begin looking, a local service representative can conduct an inspection to identify probable areas of boiler problems. For general evaluation, our on-line (in operation) examinations consist of efficiency tests, external inspections, expansion and structural inspections, valve leak detection, combustion tuning, air flow and flue gas flow distribution measurements, computer flow modeling, air flow meter calibrations and combustion control tuning.

System testing and calibration
Once a performance deficiency has been identified, it is important to follow up with corrective steps. Additional tests may be required to pinpoint the problem(s). Often, several factors contribute to the overall efficiency loss, so each system must be isolated and checked separately. Combustion control calibration, primary instrument element failures, loose linkages and instrument drift, which aren't always obvious, may be causing problems. Our service engineers are trained to quickly and efficiently identify system performance problems.

Engineering studies
Before renovating or replacing your old boiler, you should know that improved designs and new materials can make your unit perform better than ever. The first step in identifying areas for improvement is an engineering study, in which the current base line operating condition is evaluated and modern technology is applied. Increased capacities can often be achieved without any loss in reliability.

Tube failure analysis
The single, most dominant cause of boiler forced outages is pressure part failure. This usually is a result of hot side tube failures, but could relate to header cracks, drum cracks, cold side tube failures, valve failures or the failure of drum/header internals. Once our field engineers determine the root cause of the failure, corrective procedures can be identified to eliminate the chance for repeat failures.

Reliability studies
Studies of your unit's reliability can be conducted to evaluate:

  • the pressure vessel with a thorough inspection and a detailed non-destructive examination of the tubes and headers (also called a condition assessment report)
  • the condition and operability of the fuel handling equipment. This may include the fuel preparation equipment, such as pulverizers; the fuel delivery equipment, such as piping and burner lines; and the burners themselves
  • the air and flue gas conveying means, including the air supply (forced draft fans), air heater, windbox, boiler passes, induced draft fan(s) and out to the stack
  • controls
  • feedwater supply and boiler water treatment
  • safety valves

Efficiency evaluations
Boiler efficiency is easy to lose, but hard to get back, mainly because the losses are in little slip streams, spread throughout the boiler system. A few of the more common causes of efficency reductions are: high levels of incomplete combustion (carbon monoxide, CO), unburned carbon (UBC), loss on ignition (LOI, a test that measures UBC in ash), dry gas loss (excess air going up the stack), moisture losses (water or hydrogen coming in with the fuel and air), high exit gas temperature (heat not absorbed in the boiler), steam leaks and thermal radiation.

Efficiency enhancements
Performance and efficiency improvements are not always limited to just the boiler. The application of the steam is just as important. A 50 degree (Fahrenheit) shortfall in main steam temperature (or reheat steam temperature) may be critical to a process, or may have a significant impact on the turbine's efficiency. When rebuilding your boiler, it is also important to consider cogeneration. It is very beneficial to incorporate thermal waste gases as inputs to the boiler, or to use extraction steam for process and institutional thermal loads. The addition of a gas turbine to a cold windbox boiler system can add significantly to the overall plant efficiency.

Air and gas flow studies and modeling
Excessive pressure drop, flow stratifications, turbulence and poor distribution are some of the causes of poor boiler performance. Once flow imbalance is identified, the characteristics can be programmed into a computer for the generation of a model for the quick and efficient evaluation and placement of turning vanes, flow balancing restrictors, and baffle plates. Improved distribution and streamed line flow can reduce pockets of unburned carbon and reduce erosion, as well as reduce fan power and excess air requirements.

Air heater inspection
The air heater, which exchanges heat from the exhaust gases to the incoming fresh air, is an important heat trap on most boilers. However, because it may operate close to the acid dew point of the exhaust flue gas (which causes corrosion), and because there is usually a high pressure differential between the flue gas and the air sides (which allows excessive air leakage to flow out the stack), proper maintenance of the air heater is critical. Inspection of the air heater can only take place when the unit is out of service; therefore, it is important to quickly evaluate the maintenance requirements and carry out the necessary repairs. Our air heater specialists can help you make a prompt evaluation.

For more information, please contact us.

Field Engineering Services

 
 

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