A Novel Nondestructive Technique for Detecting and Sizing Carburization Damage in Heater Tubes

By: Peter Conlin Wednesday, October 23, 2013

Materials Degradation and Corrosion

Fired Heaters come in many types and configurations: catalytic reformers, crude heaters, visbreakers, vacuum heaters, coker heaters, etc; and many are prone to carburization damage (i.e. residual carbon diffusing into the tube material, causing damage or even failure).

Many refineries today use delayed coking processes to upgrade their crude product. This process includes the use of fired heaters operating at high pressures and temperatures. In a carburizing environment this can lead to coke residue buildup at the tube ID followed by carbon diffusing into the tube wall, degrading the metallurgical structure of the tube.

Until recently, the only reliable method of testing for carburization damage was to cut out tube sections, test by metallurgical examination, then weld back in (and repeat as necessary until unaffected tubes are found); a slow and costly approach. Now, a relatively new nondestructive technique application, developed by Sonomatic, and in use worldwide, negates the need to repeatedly cut and weld tube sections to retrieve samples for metallurgical examination.

The technique uses ultrasound, or more specifically, a non-standard Time-of-Flight-Diffraction (TOFD) ultrasonic inspection method, to create thru-wall images of the tubes and identify the boundary between good (non-carburized) and bad (carburized) material. This technique is capable of detection and quantification of carburization damage in 2-9% Chrome alloy ferritic tubes.

This technique requires strict adherence to specific inspection protocols. The interface between carburized and non-carburized material can be missed if the controls are not followed. However when properly applied, the technique can detect the thru-wall extent of carburization to within 0.5mm, and has been verified with destructive testing and metallography in numerous trials.

The inspection results have been shown to fall well within the tolerances required for a critical assessment evaluation, and this technique is currently being used at refineries and process plants world-wide, providing accurate, reliable heater tube condition assessments.

Peter Conlin ISO 9712 Level 3

Click to Request Info

Tags: Corrosion, Piping, Ultrasonic Testing

About The Author

Peter Conlin

Contact:

Peter Conlin is employed by Becht's affiliate company, Sonomatic. Sonomatic is a worldwide organization offering ultrasonic imaging with advanced techniques using Sonomatic designed and constructed equipment. These include ToFD, Corrosion Mapping, CHIME, Microskip, Rapid Screening Techniques, EMAT, ROV deployable systems and Nautilus (subsea). Mr. Conlin has been involved with NDE since 1972 and specializes in the use of Advanced NDE techniques and the use of techniques for innovative applications such as locating / sizing carburization in heater tubes. He currently manages projects for Sonomatic regional bases which includes projects for the energy majors such as Shell, BP &, SSE. He serves as the QA and S,H,E, authority for Sonomatic with Lloyds Register and United Kingdom Accreditation Services, chairs the EEMUA INT group, formed and chaired the EEMUA WG for the production of the EEMUA RBI guidance document and sits on both CEN 121 & CEN 138 WG's for Ultrasonic Testing standards. He assisted with the introduction of the original BS7706 standard for Time of Flight Diffraction inspection and assisted BINDT in transitioning TOFD into the BS EN ISO 9712 3rd party personnel certification scheme. He produced the draft prEN ISO 16946 calibration block document for CEN 138 WG2 and is an active member of BINDT Central Management Committee and the EEMUA WG, introducing guidance documents for the use of NDT in industry. Mr. Conlin is a regular guest speaker for EEMUA, IMechE, and RCNDE on the use of NDT in industry and the responsibilities of each party.