Ian Haynes "Industry best practice" for Reformer tube insepction is as follows: 1. Ultrasonic Through Wall transmission - sender and receiver probes - with a probe mounting holder suiting to the configuration of tube OD/I.D (i.e., wall thickness of tube being scanned). The key to success of UT scan prediction and confidence level in grading tube severity is in probe holder design to get maximum information from mid-wall to inner to outer fissures. Usually the innmer most - 3 mm and outer most 3 mm outer most wall thickness cannot be accurately scanned due to UT wave scatter in a centri-cast HP tube. Mid wall creep fissures - as mid wall fissures - due to hoop stress primarily - start from centre of wall thickness and proopagates from mid-wall to inner wall or outer wall or both depending on the firing the tube had seen over 9 years, the number of upset start ups and shut-downs the reformer furnace had seen in 9 years time (in your case). If short time flame impingement had occurred that would drastically reduce the tube life. 2. Based on the U.T Scan of the full length of tubes on the two fired sides of the tubes - with probe design design holder designed to suit the OD/ID + the pitch distance between the tubes - tube gradation is done based on the severity (classificiation of severity. This is based on the mid-wall to inner or outer creep fissure propogation. Usually there are seven grades of classification of severity from UT Scan fissure wall detection. 3. The severely classified tubes are then radiographed at select locations in the tubes where severity of creep fissures are higher. 3. Radiographic confimration of creep fissures will inform the grading for replacement. For Butt welds of tubes - only RT is the most accepted method by industry standard for reformer tube to confirm creep voids and creep fissures. Incidentally butt welds are rated at 80% of tube life if the tubes had been operated within design temperature conditions. 4. Some reformer furnace inspection companies do a magenetic permeability scan also along the full length of the tubes and also on welds. Magnetic permeability test is a successful method for pyrolytic furnaces in ethylene cracker but not good for hydrogen, steam-napatha, gas fired reformer tubes. 5. Some inspection companies and reformer operators do a video or optical scan of the inside surface from oxidation or bore carburization from inside of the tube. This requires complete empty of catalyst from tubes. 6. Essentially, industry practice today is UT through Scan (double probe scan) for mid wall fissures, grade the severity by UT scan, confirmatory RT of both tube and weld creep fissrues. This normally gives 90-95% level confidence to retire tubes with advanced creep fissures and plan for selective replacement. 7. For a hydrogen furnace - Foster Wheeler design - if the HP N 6 tubes had been fired within design conditions and with number of cyclic shut down/start ups have not been too drastic - you could expect good detection of mid-wall to inner or outer creep fissures. Both UT and RT scan of welds and tubes will give you enough information and confidence from retirement or select replacement and also for future inspection of the reformer furnace tubes. Trust this is of help to you C.V.Srinivasan Nishi Engineers Pvt Ltd India Oct 30,2005 E-mail:nishi@vsnl.com >I am looking for the "Industry Best Practice" with regards >to an Inspection Stratergy to detect tube >degradation due to 'creep damage' >The Reformer is a Foster Wheeler design and is used in >Hydrogen production. The heater has been in service for >9years with and unusually high number of shutdown-startup >cycles, as much as 15 in the first year of operation. >We did a H-Scan inspection 4 years ago when tubes were still >categorised as either Grade 1,2 or 3. >I am looking for the best recommended inspection method. > >Ian >Snr. Plt. Inspector >Trinidad.

In complement to other suggestions given you may consider Ultrasonic attenuation, eddy current, ultrasonic thickness, and diametrical measurement (UT Scan). Another reliable method for determining creep damage appears to be x-rays. X-ray will show the voids forming in the HK-40 that lead to creep damage. Regards Luis Marques