A severe catastrophic rupture failure occurred in a spool pipe made of titanium (ASTM B337 grade 2) in an oxidation reactor of the Purified Terephthalic Acid (PTA) production plant. The titanium spool pipe was connected directly to the hot air inlet nozzle of the oxidation reactor - operated at 215 °C and 365.5 psi in a hot air media. The reactor contained para-xylene, acetic acid, a catalyst (Br-, Co++, and Mn++); this mixture was continuously stirred to achieve the PTA formation reaction. A failure analysis investigation was carried out to identify the root-cause of the problem. The investigation revealed that the spool pipe was damaged because of an unexpected rapid overheating of the titanium spool which likely occurred at the start-up of the process due to an explosive exothermic reaction. Remedial measures were proposed to avert the reoccurrence of similar failure in the future.

Subject
Discoloration, Terephthalic acid, Materials, Piping, Reactors, Mechanical failure, Overheating, Color, Acetic acid, Titanium, Deposit corrosion, Damage, Oxidation
Keywords:
titanium, spool pipe, thin-lip rupture, rapid overheating, Purified Terephthalic Acid (PTA)
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2004
Association for Materials Protection and Performance (AMPP)
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