Tuberculosis-diabetes mellitus bidirectional screening at a tertiary care centre, South India

Supported by the TB Union/MSF Course on Operational Researc

Remaining life assessment of service exposed reheater and superheater tubes in a boiler of a thermal power plant

This paper presents the high temperature tensile and the stress rupture properties of 150,000 hours service-exposed superheater and reheater tubes made of 2.25Cr-1 Mo steels in a 120 MW boiler of a thermal power plant. These were used to estimate the remaining life for safety. Experimentally determined yield strength and ultimate tensile strength as well as estimated 10,000 hours - 100000 hours rupture strength as obtained from experimental data in the temperature range of 793 to 853K exhibit a decreasing trend with increasing temperature. Microstructural study did not reveal any significant degradation in terms of creep cavities, cracks, graphitization etc. In general, analysis of tensile and stress rupture data reveal that the service exposed superheater and reheater tubes can remain in service for a length of more than ten years at the operating hoop stress level 40 MPa / 813K, provided no localised damage in the form of cracks or dents has been developed. It is recommended that a similar health check should be carried out after 50,000 hours of service exposure at 813K

Premature failure of a leaf spring due to improper materials processing

Failure analysis of a leaf spring which failed prematurely during service was carried out using optical and scanning electron microscopy, hardness and tensile testing, and residual stress evaluation by X-ray diffraction. Quench cracks, which are aligned normal to the length of the leaf, have been identified in shot peened and polished surfaces. These cracks have been attributed to an improper quenching process. It is established by theoretical analysis that the leaf thickness is smaller than the critical plate thickness required for this composition of steel, and that leads to an increase in quench severity. It appears that some of these quench cracks have propagated by a fatigue mode which is confirmed by the presence of beach marks on the fractures surface. Observation of intergranular cracking and the presence of FeS inclusions at the prior austenite rain boundaries implies that some sort of grain boundary embrittlement might have facilitated crack growth and led to failure. It has been suggested that quenching should be carried out by recommended procedures guided by the thickness of the component and chemical composition of the steel. Careful inspection of the surface after quenching must also be carried out to maintain quality assurance in order to avoid premature failure

Failure analysis of coal pulverizer mill shaft

Failure of a ball and race type coal pulverizer mill shaft has been analysed. It was found that the shaft, made of EN 25 steel, failed by fatigue. The fatigue cracks originated from the keyway area, unusually from the top edge. The presence of elongated manganese sulphide inclusions due to improper heat treatment had reduced the ductility and CVN toughness of the material, and thus made the material more prone to failure

Catalytic asymmetric epoxidation of unfunctionalised olefins using silica, LDH and resin-supported sulfonato-Mn(salen) complex

Sulfonated chiral Mn(salen) catalyst immobilised onto various supports such as silica, LDH and resin afforded remarkably higher rates and ees of up to 96% for the asymmetric epoxidation of unfunctionalised olefins. The LDH and resin supported (R,R)-1 catalysts were recovered quantitatively by simple filtration and reused for several times with consistent ees and insignificant loss of activity

Development of microalloyed steels and its design aspects Part I : Medium and low carbon micro-alloyed forging steels

The development in microalloyed forging steels (MAFS) has undergone a revolution during last four decades. The extent of carbon, manganese, silicon and one or more microalloying element significantly affects the microstructure of the transformation product and in turn its mechanical properties strength and toughness. The processing conditions too play an important role in determining the mechanical properties of the final component. Microalloyed forging steels have found potential application in critical auto components leading to hyper productivity and overall cost reduction