Failure Analyses

Failure Analysis: In-Situ Combustion Injector Well Tubing Failure

Severe plugging of in-situ combustion injector wells was found within 15 months of their commissioning in an on-land oil field in western India. Laboratory investigations were made to establish the cause and identify remedial measures. The tubing sections in the vicinity of the combustion front were exposed to an aggravated oxidation environment followed by moisture and oxygen intrusion through corrosion product. This triggered conversion of magnetite into porous, nonprotective hematite. The corrosion inhibitor treatment in the wet phase was found to be ineffective. A large amount of loosely bound corrosion product accumulated at the bottom of the hole during air/water injection. This plugged the well. Suitable well completion for the operating conditions was designed to prevent future failures.

Failure of an Air Inlet Header of a Secondary Reformer

Failures from the overheating of components may occur from short- or long-term exposure. Failures may cause plant shutdown, which in turn will have economic implications. Pipes that carry gases at high operating temperatures are susceptible to this type of failure. The more destructive ruptures occur at pipe metal operating temperatures well above the ASME oxidation limits of the material. This is typically above the eutectic transformation temperature for any selected alloy. This article presents the general aspects of overheating failures and a case study of a recent investigation of an air inlet header failure.

Role of Surface Finish in Fatigue Failure of Type 316L Stainless Steel Coil Tube

A Type 316L stainless steel (UNS S31603) coil tube used for dehydration of wet gas with tri-ethylene glycol cracked and failed after less than one year of service in a platform gas processing facility. The investigation revealed multiple fatigue cracks at a plastically deformed area on the coil external surface. Vibration of the coil tube during service caused the cracking.

Failure of a Column Reboiler in a MEG Recovery Unit

After only seven months of operation, a column reboiler in a mono-ethylene glycol recycling unit at a natural gas production plant failed because of localized corrosion on the portion of the tubes in the tube sheet. This attack was caused by abnormal clearance between the tubes and tube sheet, due to poor manufacturing quality, which allowed deposits to collect and initiate crevice corrosion.

Short-Term Overheating of Baffle Boiler Tubes

Several tubes in a baffle boiler experienced bending and one tube failed. Tests showed appreciable changes in hardness and microstructure on the failed tube. Failure occurred because of short-term overheating of the tube.

Formicary Corrosion of Cupronickel Tubing

The occurrence of formicary corrosion, or ant-nest corrosion, has been primarily reported throughout the heating, ventilation, and air-conditioning industry. Until now, the presence of formicary corrosion has been limited to refrigeration-grade copper (99.99% Cu). A failure investigation has attributed leaks in cupronickel tubing to formicary corrosion.

Rapid Failure of a Copper/Nickel Overhead Condenser Bundle

Rapid and unexpected failure of a CuNi bundle of a stabilizer overhead condenser occurred where an Al-brass bundle showed chemical resistance for more than 20 years. An investigation revealed that the intergranular attack/cracking of the cupronickel tubes was caused by attack of a wet hydrogen sulfide (H2S)- containing medium. Literature indicated that cupronickel is much more susceptible to attack by wet H2S than Al-brass. Cupronickel is unsuitable as tube material in overhead systems containing significant amounts of H2Sand ammonia (NH3).