2400 Longhorn Industrial Drive, New Braunfels, Texas 78130Ph: (830)629-8080 Fax: (830)629-6899 email: info@myej.net

Copyright © 2001 Senior Flexonics Pathway.

NEWS RELEASE

The lines connecting the reactors on the ABB LummusCrest Catofin unit used in MTBE production operate at12000 to 13000 F. These lines vary from 18" to 84" diam-eter and are externally insulated, insuring that the pipewall operates at close to the media temperature. Theclose proximity of the reactors and the large line sizesrequires the use of dozens of expansion joints on a typi-cal Catofin unit to handle thermal growth of the pipingand reactors. Vibrations caused by changing processconditions in the lines add intensity to the harsh operat-ing environment.

The expansion joints at the Super Octanos MTBE facil-ity in Venezuela were built by a respected Europeanmanufacturer u sing conventional hot wall design prin-ciples. The expansion joints had single ply reinforcedbellows designed to operate at the media temperature.This meant that the bellows would be operating at tem-peratures where creep strength was the limitation ondesign.

After experiencing several bellows failures, the SuperOctanos facility purchased an upgraded design for 2-36"slotted hinged expansion joints, 1-36" gimbal and 2-18"gimbal expansion joints. The detail design specificationwas provided by Refinery Technology, Inc., a Houstonbased engineering consultant that was hired by SuperOctanos to review the piping design of the Catofin unit.The final design approved by RTI included many featuresthat have been promoted by Senior Flexonics Pathwayforhigh temperature expansion joints in recent years.

The replacement expansion joints were designed withinternally insulated bellows to insure that the bellowswould operate below 8000 F There is little information onfatigue characteristics of bellows operating in the creeprange (above 8000 F). Keeping the bellows operatingtemperature below 8000 F insured that the bellows wouldhave a cycle life that could be accurately predicted byindustry design standards.

SENIOR FLEXONICS PATHWAY BUILDS IMPROVED DESIGN

NR 49

MTBE EXPANSION JOINTS FOR SUPER OCTANOS

2-36” slotted hinge expansion joints with hydrostatic testplates in place. Expansion joints will be installed as amatched pair with a long center spool between them tohandle a large lateral offset and several inches of axialmovement.

36” gimbal expansion joint designed for 42 psigat 1300 deg. F. Bellows are internally insulatedto recude the bellows operating temperature.

The bellows were two ply testable construction so that afailure of the inner ply could be recognized and moni-tored without causing an emergency. Because the bel-lows were designed to operate at a temperature wherethe bellows material strength was limited by ultimatetensile strength instead of creep strength, the bellowsdid not require any external reinforcement. Without rein-forcing rings the entire exterior of the bellows were avail-able for future field inspections and the bellows wereless complicated to manufacture.

On the new hinge and gimbal expansion joints, the re-straint hardware transferring pressure thrust forces fromthe hinges to the pipe shell were constructed with a float-ing ring design. Conventional design would incorporatethe use of a fixed ring or fixed double rings welded di-rectly to the pipe shell. Fixed ring design on high tem-perature applications causes a very high stress in the

pipe shell that can result in cracking of the pipe shellover long periods of operation. The floating ring designeliminates this possible failure mode. Based upon thevery favorable experience Senior Flexonics Pathwayhashad with the above design features on FCC power recov-ery systems and other high temperature services, thesereplacement expansion joints should last the life of theCatofin unit.

To inquire about expansion joints for MTBE service orother critical applications, contact Senior Flexonics Path-way, 2400 Longhorn Industrial Drive, New Braunfels,Texas 78130.

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Close up of ply testable connection on the38” gimbal expansion joint. Note that thefragile testable connection from the bellowsis terminated at a plate for protection. Athreaded pressure indicating device can beattached in the field without damaging thetestable connection.

Close up of floating doublering design used to transferpressure thrust forces from thehingesto the pipe shell. Thepressure thrust forces areresisted by pads that keep thedouble rings in placelongitudinally. However, thepipe can grow radially insideof the double rings withoutbeing pinched or loacallystrained.