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Ponton C.,Massachusetts Institute of Technology | Ponton C.,Woods Hole Oceanographic Institution | Giosan L.,Woods Hole Oceanographic Institution | Eglinton T.I.,Woods Hole Oceanographic Institution | And 5 more authors.
Geophysical Research Letters | Year: 2012

Spanning a latitudinal range typical for deserts, the Indian peninsula is fertile instead and sustains over a billion people through monsoonal rains. Despite the strong link between climate and society, our knowledge of the long-term monsoon variability is incomplete over the Indian subcontinent. Here we reconstruct the Holocene paleoclimate in the core monsoon zone (CMZ) of the Indian peninsula using a sediment core recovered offshore from the mouth of Godavari River. Carbon isotopes of sedimentary leaf waxes provide an integrated and regionally extensive record of the flora in the CMZ and document a gradual increase in aridity-adapted vegetation from ∼4,000 until 1,700 years ago followed by the persistence of aridity-adapted plants after that. The oxygen isotopic composition of planktonic foraminifer Globigerinoides ruber detects unprecedented high salinity events in the Bay of Bengal over the last 3,000 years, and especially after 1,700 years ago, which suggest that the CMZ aridification intensified in the late Holocene through a series of sub-millennial dry episodes. Cultural changes occurred across the Indian subcontinent as the climate became more arid after ∼4,000 years. Sedentary agriculture took hold in the drying central and south India, while the urban Harappan civilization collapsed in the already arid Indus basin. The establishment of a more variable hydroclimate over the last ca. 1,700 years may have led to the rapid proliferation of water-conservation technology in south India. Copyright 2012 by the American Geophysical Union.

Srivastava S.K.,Institute of Engineering and Ocean Technology | Srivastava S.K.,Oil and Natural Gas Corporation | Kumar B.,Institute of Engineering and Ocean Technology | Kumar B.,Oil and Natural Gas Corporation | And 2 more authors.
Materials Performance | Year: 2010

A failure investigation was conducted to determine the cause and mechanism of a seam weld rupture of a 14-inch diameter API 5LX-46 electric resistance welding oil pipeline. Detailed laboratory investigations, including visual inspection, thickness measurement, elemental composition analysis, metallographic investigation, inclusion rating, hardness testing, tensile strength evaluation, fractography through scanning electron microscopy (SEM), were done to identify the causes and mechanism of the failure. A dye penetration test (DPT) was conducted over the entire sample, and no significant indications of surface cracks were observed. The prepared sample of the HAZ was etched with 2% Nital to reveal its microstructure. The sample exhibited banded ferrite and pearlite microstructure, typical of rolled carbon steel products with a large number of elongated and spherical inclusions/stringers. Visual inspection revealed that the opening of the failure had a smooth surface on either side of the edge without inward or outward bulging.

Bhat S.,Institute of Engineering and Ocean Technology | Kumar B.,Institute of Engineering and Ocean Technology | Baishya D.,Institute of Engineering and Ocean Technology | Katarki M.V.,Institute of Engineering and Ocean Technology
Materials Performance | Year: 2011

Some of the suitable construction materials for acid gas pipelines and injection wells are discussed. The severe corrosiveness of the acid gas has been assessed and suitable materials of construction (MOC) have been identified for equipment and piping for injection and handling of acid gas injection (AGI). AGI involves compression of the gas from the sweetening process and injection into a suitable underground formation and is essentially a zero emission process. The corrosion severity has been evaluated by considering the partial pressure of CO 2, H 2S, the temperature, and liquid water wetting conditions. Investigations have revealed that carbon steel (CS) can he used as the MOC for acid gas pipelines and injection wells.

Bhat S.,Institute of Engineering and Ocean Technology | Kumar B.,Institute of Engineering and Ocean Technology | Prasad S.R.,Institute of Engineering and Ocean Technology | Katarki M.V.,Institute of Engineering and Ocean Technology
Materials Performance | Year: 2011

The factors that led to the failure of a new 8-in pipeline from group gathering station to central tank farm within eight months after commissioning in one of the oil and gas fields of western India are presented. On-site inspection revealed little external corrosion, but significant internal corrosion was found, especially in the 5 to 7 o'clock area. The nodules of corrosion product were observed at the 6 o'clock position along a portion of the pipeline, but away from the leak area. Sulfate-reducing bacteria (SRB) count in water samples collected at the source of the pipeline was determined by a Bactaslyde BS-115 test kit and totaled 100,000 per 100 mL. The results showed that intermittent flow, stagnation, and operating conditions of the pipeline facilitated a localized pitting rate of 3.2 mm/y. The actual pitting failure occurred in less than a year. The prevention of microbe deposition, attachment, and colony growth by regular pigging is a major method to mitigate the corrosion.

Mahanta R.,Institute of Engineering and Ocean technology | Ghanekar R.K.,Institute of Engineering and Ocean technology | Kumar A.,Institute of Engineering and Ocean technology
Frontiers in Offshore Geotechnics III - Proceedings of the 3rd International Symposium on Frontiers in Offshore Geotechnics, ISFOG 2015 | Year: 2015

Out of the 4 (four) widely accepted CPT-based pile capacity methods for offshore driven piles, for two of the methods – ICP and UWA methods – modifications have been suggested by researchers for application on calcareous sands. Unit shaft friction of piles driven through predominantly calcareous sand zones have been examined for 4 (four) piles which met refusal at 2 (two) sites in western Indian offshore. Values from “modified” CPT-based methods were compared with results of CAPWAP analysis. Study on the sites shows that ‘modified ICP’ and ‘modified UWA’ methods predict local shaft friction values that are generally lower compared to those obtained from CAPWAP analysis. Interestingly, the average unit shaft frictions over the length of the piles in sand predicted by individual CPT-based methods allowed by API (2007) for siliceous sands, are within about 30% of the values derived from CAPWAP. © 2015 Taylor and Francis Group, London.

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