A boiler assessment is needed to gather information about the unit’s erosion history, fuel and ash, cavity and pressure part design and unit operation.

To understand the contribution of gas flow to the erosion problem, a cold air velocity test is done in the unit at ambient conditions. Analysis of this data should indicate where high flow regions exist, and when coupled with the unit assessment information should indicate the best location for flow modification devices.

Recommendations for selection and placement of flow/erosion control devices is determined next. These devices are used to redistribute fly ash and reduce local flow in areas with serious erosion levels. Conceptual drawings are made to document placement and type of controls.

Following installation of the controls, a second test should be performed to measure the changes in gas flow. This would help identify the adequacy of the controls and provide data for estimating the change in erosion rates. If needed, modifications to the flow controls could be performed before returning to normal operation.

The conduct of this program can be done in a staged approach with the test and assessment done during one outage and the installation during a different outage - NORMAL TRACK. It can also be done during one extended outage - FAST TRACK. This requires a predesign (by DRENNEN ENGINEERING, INC.) with materials purchase and fabrication by the utility before the outage. The CAVT is performed at the beginning of the outage and the flow control recommendations modified if required. The installation proceeds during the outage with the follow-up CAVT performed after the installation of the controls. If modifications are required, they can be made with materials on hand or postponed until the next outage.

At the initiation of an erosion control program at your site, detailed information about your unit would be requested as described above. The next step would be a site visit to conduct the inspection and air flow test. Check the Cold Air Velocity Test section for details of this task.