Materials Selection & Design

Using Industrial Computerized Tomography for Corrosion Investigation

Industrial computerized tomography (ICT) was used to investigate the corrosion failure of a chlorine condenser tube, shell, and welding. The ICT analysis indicated that corrosion was most serious where the tube and shell were welded together. This work also showed that ICT can be a valuable tool in corrosion analysis because it can detect gaps or interstices, and quantify their size, shape, and position.

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).

Pipeline Restoration at a Generating Station Using Chemical Grout

A gravity-flow water inlet line had developed many ruptures and cracks, leading to appreciable groundwater inflow. Contaminants brought in by the groundwater increased the cost of treating the water for station use. The problem was solved by injecting chemical grout to the exterior side of the pipe.

Centrifugally Cast Fiberglass-Reinforced Polymer Mortar Pipe for a Large-Diameter Interceptor Sewer

This article discusses one city’s approach to preserving the integrity of its infrastructure through the use of corrosion-resistant piping systems. Technological developments in centrifugally cast fiberglass pipes have provided installation advantages and lifelong benefits to municipalities.

Recent Fiberglass-Reinforced Plastic Applications: Radome and Hybrid Bridge System

This article describes two case histories: construction and installation of a fiberglass-reinforced plastic (FRP) radome and the design, construction, and utilization of composite FRP/concrete bridge beams. The shape, structural requirements, and radar transmission requirements of the radome are discussed, as are the design, fabrication, and testing of the composite beams.

Enhancing Asset Value Through Corrosion Management

The relative value of an aging asset depends on many parameters, among which are production rate/ continuity and integrity management (IM) costs. Reducing unplanned shutdowns and IM costs can maintain or even improve the relative asset value. This article describes—using data collected over a five-year period—how having asset corrosion management and risk-based inspection systems in place may achieve the above.

Stress Corrosion Cracking of Various Alloys—Part 1

Stress corrosion cracking (SCC) can lead to rapid and catastrophic failure in many different metals and alloys. Failures often occur with little or no prior warning. A systematic approach is needed to evaluate any failure and identify its cause. The case histories in this article illustrate features that are commonly evident in various materials that experience SCC.

Stress Corrosion Cracking of Various Alloys—Part 2

Stress corrosion cracking (SCC) can lead to rapid and catastrophic failure. Failures often occur with little or no prior warning. A systematic approach is needed to evaluate any failure and identify its cause. This article continues the case histories begun in Part 1 and illustrate common features evident in SCC.

Developing Welding Procedures for Sour Service

Controlling the hardness of the weld heat-affected zone (HAZ) in sour service is essential to help prevent sulfide stress cracking. It is important to evaluate HAZ properties when developing welding procedures. The behavior of specific alloys during welding presents roadblocks to HAZ hardness control. Two cases are presented to show that weld thermal simulation is an efficient tool for developing welding procedures for sour service.

Investigating Polyethylene-Encased Ductile Iron Pipelines

This article presents several case histories where ductile iron (DI) pipeline sections have been investigated to ascertain the corrosion control benefits of polyethylene (PE) encasement. The procedures and results of the investigations are evaluated and discussed. These investigations demonstrate the overall effectiveness of PE encasement as a corrosion control system for DI pipe.