Stator vanes (cast from a Cu-Mn-Al alloy) in a hydraulic dynamometer used in a steam-turbine test facility were severely eroded. The dynamometer was designed to absorb up to 51 MW (69,000 hp) at 3670 rpm, and constituted an extrapolation of previous design practices and experience. Its stator was subject to severe erosion after relatively short operating times and initially required replacement after each test program. Although up to 60 cu cm (3.7 cu in.) of material was being lost from each vane, it only reduced the power-absorption capacity by a small amount. Analysis supported the conclusion that the damage was due to liquid erosion, but it could not be firmly established whether it was caused by cavitation or by liquid impact. Recommendations included making a material substitution (to Mo-13Cr-4Ni stainless steel) and doing a redesign to reduce susceptibility to erosion as well as erosion-producing conditions.

Rotor blades in the compressor section of a J79 engine had failed. Optical, stereoscopic, microhardness testing, and SEM examinations were conducted to determine the cause. The blades were made of STS403 and were used uncoated. They were damaged over an extensive area, from the 15th through the 17th compressor stages, as were stator vanes and casing sections. The fractured surface of the 17th blade showed multiple origins along with secondary cracking and extensive propagation that preceded separation. The metallographic analysis of the microstructure suggested work hardening. Based on the results, the cause of the fractured blade was high-amplitude fatigue due to severe stall. After normal engine usage of five months, the blade fractured sending fragments throughout the combustion and turbine sections.

The failure of HP turbine blades in a low bypass turbofan engine was analyzed to determine the root cause. Forensic and metallurgical investigations were conducted on all failed blades as well as failed downstream components. It was found that one of the blades fractured in the dovetail region, causing extensive damage throughout the turbine. Remedial measures were suggested to prevent such failures in the future.

The assignment of financial liability for turbine blade failures in steam turbines rests on the ability to determine the damage mechanism or mechanisms responsible for the failure. A discussion is presented outlining various items to look for in a post-turbine blade failure investigation. The discussion centers around the question of how to determine whether the failure was a fatigue induced failure, occurring in accordance with normal life cycle estimates, or whether outside influences could have initiated or hastened the failure.

Erosion of solid surfaces can be brought about solely by liquids in two ways: from damage induced by formation and subsequent collapse of voids or cavities within the liquid, and from high-velocity impacts between a solid surface and liquid droplets. The former process is called cavitation erosion and the latter is liquid-droplet erosion. This article emphasizes on manifestations of damage and ways to minimize or repair these types of liquid impact damage, with illustrations.

Numerous flaws were detected in a steam turbine rotor during a scheduled inspection and maintenance outage. A fracture-mechanics-based analysis of the flaws showed that the rotor could not be safely returned to service. Material, samples from the bore were analyzed to evaluate the actual mechanical properties and to determine the metallurgical cause of the observed indications. Samples were examined in a scanning electron microscope and subjected to chemical analysis and several mechanical property tests, including tensile, Charpy V-notch impact, and fracture toughness. The material was found to be a typical Cr-Mo-V steel, and it met the property requirements. No evidence of temper embrittlement was found. The analyses showed that the observed flaws were present in the original forging and attributed them to lack of ingot consolidation. A series of actions, including overboring of the rotor to remove indications close to the surface and revision of starting procedures, were implemented to extend the remaining life of the rotor and ensure its fitness for continued service.

This article briefly introduces the concepts of failure analysis and root cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It reviews four fundamental categories of physical root causes, namely, design deficiencies, material defects, manufacturing/installation defects, and service life anomalies, with examples. The article describes several common charting methods that may be useful in performing an RCA. It also discusses other failure analysis tools, including review of all sources of input and information, people interviews, laboratory investigations, stress analysis, and fracture mechanics analysis. The article concludes with information on the categories of failure and failure prevention.

This article briefly introduces the concepts of failure analysis, including root-cause analysis (RCA), and the role of failure analysis as a general engineering tool for enhancing product quality and failure prevention. It initially provides definitions of failure on several different levels, followed by a discussion on the role of failure analysis and the appreciation of quality assurance and user expectations. Systematic analysis of equipment failures reveals physical root causes that fall into one of four fundamental categories: design, manufacturing/installation, service, and material, which are discussed in the following sections along with examples. The tools available for failure analysis are then covered. Further, the article describes the categories of mode of failure: distortion or undesired deformation, fracture, corrosion, and wear. It provides information on the processes involved in RCA and the charting methods that may be useful in RCA and ends with a description of various factors associated with failure prevention.

Vibration analysis can be used in solving both rotating and nonrotating equipment problems. This paper presents case histories that, over a span of approximately 25 years, used vibration analysis to troubleshoot a wide range of problems.