Maximize tube life by using internal and external inspection devices

Authors


Abstract

Providing plant operator/owners the ability to substantially extend tube life in Steam Reformers is essential in maximizing use of capitol investments in Methanol, Hydrogen, and Ammonia plants. With price of Nickel at an all time high, a reformer tube can cost $20,000 USD installed in today's market. A plant needs to have data which will allow engineers to better manage these tubes to extend life expectancy beyond the typical 100,000 operating hours specified by the tube manufacturers.

Over the last +6 years well over 100 plants around the world have applied the LOTIS™ laser-based reformer tube testing technique to obtain invaluable information as it relates to steam reformer tube damage in its early stage as well as determine when a tube should be retired. Plant engineers have acknowledged the power of having such highly detailed 3-Dimensional images to better understand issues with fluegas maldistribution, flame impingement, refractory problems, etc. The one and only complaint is that the “internal” LOTIS™ could only be applied when catalyst was not inside the tube. This limited the inspections to 3–4 times over the course of the tube, which obviously left gaps in the inspection frequency requiring plants to relay on less accurate and less encompassing conventional inspection technologies.

Over the last few years development has been underway of an “external” LOTIS™ reformer tube inspection technology. During the developmental phase of this technology it has been globally applied within several steam reformers to provide confirmation to the validity of the data. Final release of this new “external” LOTIS™ reformer tube inspection method has now taken place. The newly release “external” devise will compliment the already industry accepted “internal” LOTIS™ laser reformer tube inspection process. Plant engineers now have the ability to collect tube condition data any time the plant is taken off line, regardless if catalyst is in the tube or not, to determine the presence and extent of Creep Strain damage. Because the “external” system employs numerous sensors, similar to that of the “internal” system, high-resolution 3-Dimensional, high-resolution color images are generated to continue with previously reformer tube management philosophy put in place with the original LOTIS™ internal laser-based technique.

During the design phase of the external crawler, top priority was given to the physical height of the crawler. Because >75% of creep strain damage in reformer tubes is located below the top of the tunnel or coffin region, it was essential that the crawler have the capability of traversing all the way to the bottom of the tunnel, up to the floor refractory. This low profile external crawler is now capable of covering ∼20% more of the tube's axial length than that of typical external. This is essential in maximizing the opportunity of detecting and quantifying creep strain within a tube which is filled with catalyst and does not have access to the interior bore.

The reformer tube management program now encompasses both internal and external inspection capabilities. A client will now have the ability to applying either internal or external technique depending upon the presence of catalyst or not. The intent of the newly external technique is not to replace the internal “LOTIS” technique; however it is intended to bridge the gap between internal inspection frequencies which can only be carried out during catalyst change outs. © 2005 American Institute of Chemical Engineers Process Saf Prog, 2005

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