Tubing is the most vulnerable component of a shell and tube heat exchanger. Its thin wall provides good heat transfer. However, there is little allowance for corrosion, erosion-corrosion, impingement erosion, vibration and other failure cause mechanisms which cause tube wall loss.

HES employs non-destructive examination (NDE) of tubes by electromagnetic and ultrasonic techniques to determine their condition. These include:

• Eddy Current Testing for non-ferromagnetic tube alloys.

• Axial Saturation eddy current testing for slightly magnetic tube alloys such as thin wall ferritic stainless steel.

• Radial saturation eddy current testing to obtain accurate tube degradation data of monel tube wall loss at support plates and baffles (fretting).

• Remote field and partial saturation eddy current testing of carbon steel tubing.

• Ultrasonic testing of thick wall carbon steel tubing such as those in petrochemical and process plant heat exchangers and feedwater heaters.

Since in-situ tube testing is as much an art as a science, the high degree of Heat Exchanger Systems (HES) test personnel training and experience is considered a key element required to obtain the accurate results necessary for predicting heat exchanger remaining life, particularly for heat exchangers in corrosive environments.

In addition to test personnel, HES's NDE services are supported by corporate heat exchanger and aqueous corrosion experts. Consequently, HES uses NDE techniques to determine defect type and severity and engineering analysis to assess problem cause(s).

While tube failures usually indicate the end approach of a heat exchanger's useful life, other components are also subject to failure. These include feedwater heater drain pipes and deaerator tanks. Failure of these components can be catastrophic. Therefore, HES maintains full capabilities in all NDE techniques to evaluate all heat exchangers and associated system components.

NDE identifies the nature, severity, and location of tube defects. This information, coupled with a knowledge of the materials in service plus the system design and operating experience often provides a sufficient basis for determine the failure mechanism. When it does not, heat exchanger tubes are frequently extracted to provide specimens for destructive root cause failure analysis which involves analysis by some of the following methods:

• Atomic absorption

• Metallurgical chemistry analysis

• Measurement of significant mechanical properties

• Microbiological/Biochemical Analyses

• Metallography

• X-ray diffraction

• Inductively coupled plasma spectroscopy

• Scanning auger microanalysis

• Electron spectroscopy for chemical analysis

• Infrared, organic carbon and biochemical analyses

Through the use of these analytical techniques, the causes of failures are identified in an unambiguous manner. Appropriate corrective actions can then be identified and a corrosion rate (remaining life) can be projected.

Reports are submitted in a concise manner.

For additional information call Robert J. Bell at (781) 337-9400 or email:  rjbell@heatexsys.com