Aidy Ali

Bio: Aidy Ali is an academic researcher. The author has an hindex of 1, co-authored 1 publication(s) receiving 2 citation(s).

Investigation of torsional fatigue failure of a centrifugal pump shaft

Abstract: Shafts of centrifugal pumps are both load bearing and power transmitting component which are usually composed of martensitic stainless steel. In this paper, an attempt is made to manifest how minute deviations from the standard dimensions of the keyway of a shaft leads to the occurrence of premature torsional fatigue along the keyway seat. Microstructural characterization via optical microscope, SEM and EDS further revealed faulty heat treatment of the material that resulted in inferior mechanical properties which assisted in the accelerated crack propagation and ultimate failure of the shaft within 2.5 years of service leading to a shutdown of blast furnace for approximately 10 h. Comparative material analysis was carried out on samples of shaft from other pumps in service (which has not failed) to manifest that proper heat treatment of the shaft material can bring about desired mechanical properties of component and procrastinate the failure.

Estimation of Digital Substation Reliability Indices

Abstract: The paper deals with the problem of improving the reliability of digital power supply facilities, namely digital substations. The goal of the study is to identify factors of a negative impact on the digital substation reliability indices. Based on the influencing factors analysis, technical measures for increasing reliability indexes are proposed. Based on the basic principles of the classical theory of reliability a numerical estimate of the probability of failure-free operation for the main equipment digital substation was made taken as an example the real digital substation switchgear 220 kV. Detailed equivalent circuits are given to ensure the reliability of the main units of digital substations. The numerical values of the reliability indices of the main elements are given in tabular form. The digital substation blocks with low reliability indices, as well as the most vulnerable elements of equivalent circuitry of its nodes, are identified. It was revealed that a large number of secondary circuits used in digital measuring instruments and interface devices negatively affect the reliability of digital substation units. Recommendations on maintaining the required level of reliability of power supply are given.