Archives du mot-clef Failure analysis

Fatigue cracking of high pressure oil tube

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1-s2-0-s2213290213000321-gr1An article about a Case study of failure analysis published in « Case Studies in Engineering Failure Analysis« , July 2013.

A high pressure oil tube with nominal diameter 50.8 mm and nominal thickness 4 mm has prematurely failed with a longitudinal crack. The failure was detected after 11 months of operation. The tube is part of the hydraulic power unit of an off shore oil and gas platform. The maximum designed internal pressure was 20 MPa and the service temperature was 25 °C with no significant variation. In practice, the internal pressure varies from 16 to 20 MPa under operation, and shutdowns rarely occur.

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Fatigue Failure Analysis of Rim

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thikf9m1kxA new article published in the « International Research Journal of Engineering and Technology« , Aug-2016.

A Finite Element Method methodology is proposed for fatigue life and failure prediction of automotive steel wheel by the simulations of dynamic radial fatigue test (RFT). A short review of theoretical models, numerical simulation models were described in conjunction with bilinear elasto-plastic finite element stress analysis under wheel rotating loading.

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Sulfide stress corrosion cracking and hydrogen induced cracking

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A case study published in « Case Studies in Engineering Failure Analysis » on www.sciencedirect.com.

The wellhead flow control valve bodies which are the focal point of this failure case study were installed in some of the upstream facilities of Khangiran’s sour gas wells. These valve bodies have been operating satisfactorily for 3 years in wet H2S environment before some pits and cracks were detected in all of them during the periodical technical inspections. During investigation many cracks were observed on the inner surface of the valve body grown from the surface pits. The results indicate that flow control valve body failed due to combination of hydrogen induced corrosion cracking (HICC) and sulfide stress corrosion cracking (SSCC). According to HIC and SSC laboratory tests and also with regard to cost of engineering materials, it was evident that the best alternative for the valve body alloy is A217-WC9 cast Cr–Mo steel.

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An investigation of cracking causes in an outlet RTJ flange in ISOMAX unit

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2016-11-16_18h55_18A paper published in « Case Studies in Engineering Failure Analysis« , available on sciencedirect.com.

Corrosion has always been a problem in the petroleum refining and the petrochemical operations. The equipment of ISOMAX unit, such as reactors, furnace tubes, valves, and pipelines are frequently performed at high temperatures and high pressure condition. This working conditions, accelerates the failures due to corrosion. Therefore, heat- and corrosion-resistant alloys, e.g., austenitic stainless steels, have been widely used in this unit because of their excellent corrosion resistance, mechanical strength and toughness.

This paper describes failure analysis procedure of a cracked high pressure 321 SS RTJ flange in ISOMAX unit. In order to get conclusions related to crack propagation mechanisms of the flange, some investigations were done on the cracked flange that is mentioned in the body of the paper.

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Failure analysis of titanium alloy fasteners for aerospace applications

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2016-11-16_18h46_14A paper published in « Case Studies in Engineering Failure Analysis« , available on sciencedirect.com.

As a qualification of bolt for flight assembly, the bolt assembly has undergone proof pressure test at 2.4 MPa, Vibration test at frequency range of 20–100 Hz, ±3 db/oct for 120 s in both lateral and longitudinal directions and flight acceptance test. During routine visual inspection before electrical check, it was observed in one of the three fasteners that the head of the bolt had got sheared off from the shank portion of bolt. Further, a failure analysis was carried out on the failed bolt.

The objective of the study is metallurgical analysis of the failed bolt, fractography study to find out the root cause of the failure, and optimization of processing parameters for fastener manufacturing.

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Design and fabrication of Impact Die for Powder Metallurgy

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2016-11-16_17h43_25A paper publihed in « Materials Today: Proceedings », available online at www.sciencedirect.com

Die design is one of the most important steps in Powder Metallurgy process because the shape and attributes of the die will directly affect the final component. Die design has a number of steps and considerations to be made before fabrication. This project is an attempt to design and fabricate a die for cold compaction process used in the powder metallurgy process.

More at :  http://www.pmme.co.in/papers/EMT-388.pdf

Rolling element bearing failure analysis: A case study

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A paper published in « Case Studies in Engineering Failure Analysis« , january 2013

This paper addresses Rolling Contact Fatigue (RCF) occurs due to the result of cyclic stress developed during operation and mechanism that involve in fretting failure of rolling element bearing. As bearing raceways of non-rotating rolling element bearings exposed to vibration or sliding oscillation false Brinelling occurs. Bearing surface due to false Brinelling tends to damage within a short period, due to cavities created on the bearing raceway. Recommendation towards enhancement of bearing life is also suggested.

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Cracking of underground welded steel pipes caused by HAZ sensitization

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An article on case study, published in « Case Studies in Engineering Failure Analysis« , on january 2013.

Low alloy steel welded pipes buried in the ground were sent for failure analysis investigation. Failure of steel pipes was not caused by tensile ductile overload but resulted from low ductility fracture in the area of the weld, which also contains multiple intergranular secondary cracks. The failure is most probably attributed to intergranular cracking initiating from the outer surface in the weld heat affected zone and propagated through the wall thickness.

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Metallurgical investigation of different causes of center bursting led to wire breakage during production

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2016-11-03_09h22_22A case study published in « Case Studies in Engineering Failure Analysis« , on january 2013.

Central bursting cause problem as it is hard to detect by means of surface check. In this paper, three broken wires which failed during production were investigated. In first two wires breakage took place due to formation of hard and brittle phase. In third case failure took place due to inappropriate drawing operations.

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Analysis of corroded elbow section of carbon steel piping system of an oil–gas separator vessel

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An interessant case study published in « Case Studies in Engineering Failure Analysis« , on 09january 2013.

A pinhole in elbow section of oil piping system is formed by localized corrosion. The corrosion is found to result from sequential chlorination and sulfidation reactions : the chlorination results from hydrolysis of calcium chloride in the crude oil and the sulfidation results from hydrogen sulfide in the crude oil.

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