FEEDWATER HEATERS INSPECTION
Tube failures in feedwater heaters are another major cause of forced outages in a fossil power plant. Inspection of HP feedwater Heaters produces one of the highest cost benefits of any NDT
inspection in a power plant. The most common tube materials in feedwater heaters are carbon steel, stainless steel, brass and copper-nickel alloys. OD
erosion is the most common type of damage in carbon steel tubes.
The tubing in the feedwater heaters should be periodically inspected to determine its condition. Depending on the rate of degradation, an inspection interval of 3 to 6 years is recommended. Selection of tubes for inspection is the key to an effective feedwater heater inspection. In addition to regular inspections, inspection after a tube failure is highly recommended. A tube failure is an indication of damage and impending tube failures.
Conventional eddy current is applied for non-ferromagnetic materials. Remote Field Eddy current is quite effective for inspection of carbon steel tubing. In addition to remote field, ultrasonic IRIS techniques can be applied for inspection. While the IRIS techniques are more accurate, it is slow compared to the remote field eddy current technique. In general Remote field is used for the normal inspection and IRIS is utilized for verification.