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3 results on '"Al-Owaisi, S."'

1. Development of an improved structural integrity assessment methodology for pressurised pipes containing defects

Author

Al Owaisi, S. S.

Subjects
620.1, TJ Mechanical engineering and machinery
Abstract

Metal loss due to corrosion is a serious threat to the integrity of pressurised oil and gas transmission pipes. Pipe metal loss defects are found in either single form or in groups (clusters). One of the critical situations arises when two or more defects are spaced close enough to act as a single lengthier defect, causing major impact on the pressure containing capacity of a pipe and leading to rupture rather than localised leak at the centre of defects. There have been many studies conducted to determine the distance needed for defects to interact leading to a failure pressure lower than that when the defects are treated as single and not interacting. Despite such efforts, there is no universally agreed defect interaction rule and pipe operators around the world have various rules to pick and choose from. In this work, the effects of defect shapes and orientations on closely spaced defects are tested experimentally and further analysed using finite element analysis. Burst pressures of commonly used ductile steel pipes in the oil and gas industries, namely X52 and X60, are measured under internal pressure loading. The pipes were machined with circular and curved boxed defects at different orientations to simulate actual metal loss defects. The burst pressure results were compared with those obtained using existing analytical methods. Comparison of the results showed conservatism in the existing analytical methods which may potentially lead to unnecessary plant shutdowns and pipe repairs. A failure criterion for both single and interacting defects was proposed and validated numerically using the experimental data obtained in this research work. The numerical results when using the proposed failure criterion showed that defect shapes and orientations have a great influence on the failure pressure of pipes containing interacting defects. A simplified mathematical model based on the parametric results and relevant to the cases studied is proposed with the objective of reducing the known conservatism in the existing pipe standards when it comes to the assessment of defect interaction.

Published
2016

2. Fruit Flies and their Management in Oman: Research Experience since 2003.

Author

Al-Wahaibi, A., Al-Raeesi, A., Al-Ansari, S., AlSaadi, W., Al-Rawahi, S., Al-Issai, M., Al-Kiyumi, A., Al-Alawi, A., Al-Owaisi, S., Al-Maqbali, H., and Al-Abdali, M.

Subjects
FRUIT flies, WATERMELONS, CULTIVATED plants, PHEROMONE traps, FRUIT culture, WILD plants, BEAUVERIA bassiana, GREENHOUSE plants
Abstract

Fruit fly species in Oman were investigated via sampling of fruits from cultivated and wild plants and hanging traps. A total of 13 species of tephritids were identified using morphological and molecular techniques. Three unidentified species could be new to science. Moreover, 2-3 species of braconid parasitoids and one figitid species, mostly associated with fruit fly infested Ziziphus fruits, were collected. A new lure for female fruit flies, consisting of a combination of urea and watermelon seeds, exhibited effectiveness on par with commercial lures such as torula yeast and Ceratrap. In terms of physical barriers, row covers significantly reduced zucchini fruit damage even when applied as a wall around the planting line. An experiment, involving combining growing melon in the greenhouse with a honeybee hive for flower pollination, proved successful in producing a large number of undamaged fruits. In terms of biological control, we managed to set up a system for rearing of major pestiferous fruit fly species and their parasitoids. We currently have two active cultures of Bactrocera zonata and B. dorsalis, and one active culture of Diachasmimorpha longicaudata (DL), a braconid parasitoid imported from Kenya. We hope in the future to produce large numbers of DL wasps for augmentative release in Oman. Fruit fly cultures have served as stock for testing plant extracts as repellents against female B. zonata and B. dorsalis and for testing Beauveria bassiana formulations for control of adults and larvae of B. zonata. Studies of Fruit fly population dynamics and height of flight have shown that yellow sticky traps, set at different heights from 0.5 to 3.5 m, captured significantly more males than females. Additionally, most fruit flies were captured at 2m and lower. The population of male B. dorsalis in ME traps was highest from April to June, and lowest from November to January. Conversely, the population of male B. zonata in ME traps peaked from September to December, and dropped to its lowest levels from April to July. [ABSTRACT FROM AUTHOR]

Published
2023

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