Even though you mentioned about red hotness the given value is not so alarming with respected to tube design temperature for H39WM material. Sometime the flame reflection on the tube surface will mislead as a hotspot.But in general in reformer tubes ,the hotspot color will be of black in nature. The possibility of getting hot spot may be due to the following reasons, 1)Catalyst facing EOR(End of run condition) 2)Powdering of catalyst at the particular pass tubes and possible increase of skin tempeature. 3)Tubes close to the burner. I would like to know the burner arrangement whether it is verticl or side mounted.In side mounted burners the hotspot problem is very high compared to top mounted burner due to its close promixity to the tubes but the heat distribution across the tube is very uniform.But in top mounted burner design the bottom most tube will get more heat than the tubes nearyby causing excess reaction at the bottom zone. As long as your skin temperature not exceeding the design value there is no concern about the tube life. regards,

Sastry Red hot profile for the full length of tube seen in 10 tubes (full length of tubes as described) indicates that inlet flow is uneven or catalyst dust (pressure drop across the ten tubes could be very high). Krish has suggested that this could be due to end of run for catalyst. With uneven flow (steam-naphtha) reformer tubes can run in some tubes with hot spot problems locally. With full length red hot spots, the problem appears more due to internal flow and also catalyst performance with high pressure drop across the particular set of tubes. Burner impingement (suggested by Debasis) may not happen for full length of tubes - whether side fired or top fired tube designs unless it is crumbling of catalyst with very high pressure drop across headers. Monitoring both inlet and out let header in the furnace will help you to know the difference in pressure drop across segments of tubes with hot spots of full length. Once you have evaluated the pressure drop and flow problem, and if the catalyst used is ? 2 years (i.e., quite likely nearing end of run - suggested by Krish), replacement action with planned shut down may be the best solution. If your tube skin temperature monitoring has been consistent (with thre shift basis for any normal operating reformer operation and with cross check independently by an Inspection group pyrometer) and if the temperature is within 890-920 deg cent then tube life may not be a great concern. If the tube skin temp recording is with errors and with high pressure drop in some segmented tubes, you have to evaluate carefully by NDT the tube (remnant life evaluation) by both NDT and in-situ metallography. Trust this will help you. C.V.Srinivasan Nishi Engineers Pvt Ltd India Aug 2, 2007 E-mail: nishi@vsnl.com >Hai, > >We have one Steam Naptha reformer in our Hydrohgen Unit. The >catalyst tubes are of H39WM Paralloy , 4", 12mm thk, 12.5m >length and 104 nos. > >The service life of these tubes is about 7 years so far. >Majority of these tubes were placed in Category C (10-30% >trasmittence) during the last Automated Ultrasonic >Scanning. > >The reformer is operated at 910deg.C witha designed temp. of >950deg.C > >We recently encountered that some of the tubes in one row >(about 10 tubes) became redhot over their full length. Skin >temperatures of these tubes recorded 890-920deg.C. > >I am looking for the following things for clarification: >1. Probable reasons for this redhotness of catalyst tubes >suddenly >2. Any metallurgical degradation/loss of strength by this >redhot condition >3. Is this the abnormal condition, considering the >continuous operation >4. Is it required that these tubes be monitored regularly, >if so what are things to be looked for apart from temp. > > >Regards, >Sastry