Now showing 1 - 10 of 14
  • Publication
    Modeling and Simulation of Metal Oxide Surge Arresters Models by using ATPDraw Software
    ( 2023-01-01) ;
    Ting K.X.
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    ;
    Gunasilan M.
    Lightning is a natural phenomenon that occurs quite often, especially in Malaysia. Lightning is very dangerous as the voltage of the lightning is very high which can affect human daily living by damaging the electrical and electronic components. Thus, the study of lightning surges is essential in order to coordinate insulation to the electric power system. The function of the surge protection device (SPD) is to divert the surge current from the distribution line. This paper performed a comparison performance of simplified modeling of metal oxide surge arrester (MOSA). The typical models of the surge protection devices (SPDs) such as the IEEE and Pinceti model were modeled and simulated using the ATPDraw software and the performance of those model were studied with several manufacturer surge arresters. The MATLAB software was used to obtain the results on the impulse voltage signal of the SPDs. Both models' performances are being investigated, and MATLAB has been used to examine the voltage data. According to the findings, the IEEE model is more effective for usage as a lightning arrester in MV networks.
  • Publication
    Incoloy 800HT weldolet integrity in hot collector replica testing insights
    ( 2024-12) ;
    Ku Adri Azhan Ku Mohamad
    ;
    Junaidi Che Halim
    ;
    In this paper, the integrity assessment of Primary Reformer’s hot collector weldolet in the fertilizer plant was conducted. It aims to discuss the findings of the relevant weldolet weldments which include dye penetrant test ultrasonic test, in-situ field metallography (replication), hardness measurements and rectification measures. The first step of the steam reforming process takes place in the Primary Reformer, where preheated hydrocarbon and steam mixture is passed downwards through vertical tubes containing catalyst. The hot gas that exited from the catalyst tubes is termed reformed gas and will enter two headers, namely hot and cold collectors. From then, the reformed gas will transform into raw ammonia synthesis gas after undergoing several processes. The facility was commissioned in 2006 and is still in operation. During the Plant Turnaround in 2022, the Primary Reformer’s hot collector weldolet component is categorised as high nickel content material, commercially known as Incoloy 800HT, was detected with circumferential crack at several locations. The operating temperature of the weldolet is 8110C. The observed damage mechanism of the crack was “Aged Phenomenon”. However, at four locations of the weldments, further dye penetrant test (DPT) and metallurgical testing using replica test had observed sigma phase microstructure which is related to sigma phase embrittlement (SPE) without any creep cavity observed. Finally, both occurrences were reported and reviewed.
  • Publication
    Influence of flow accelerated corrosion on corrosion protection of mild steel in 3.5% NaCl solution
    ( 2024-03-07)
    Mahalaksmi Gunasilan
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    ; ; ;
    Wan Mohd Haqqi Wan Ahmad
    ;
    Mohamad K.A.A.K.
    Mild steel is a primary material used to construct ships and other maritime structures. Corrosion protection systems are sometimes ineffective in aqueous mediums subjected to movement, flow, waves, and even turbulence under unpredictable conditions. This study aims to ascertain the influence of flow velocity on mild steel corrosion in the aqueous medium. The mild steel samples are immersed in a 3.5% sodium chloride (NaCl) solution for five days. They were protected against corrosion using an impressed current cathodic protection (ICCP) system. The flow velocity is increased to 200-800 rpm, while the stationary flow is also examined as a control. Data on the metal's potential and current density were collected, and the surface morphology was analyzed using a stereomicroscope. Corrosion protection occurs exclusively in stationary flow, whereas corrosion occurs in solutions flowing at a most studied velocity. Metals show corrosion severity levels ranging from 200 to 600 rpm with increasing current consumption and metal potential. At 800 rpm, the metal surface appears to begin passivating, reducing the current consumption and potential. The flow velocity accelerates corrosion, yet at the high-speed stream, the corrosion is slowed because the steel surface becomes passive and assists the corrosion protection.
  • Publication
    Root cause analysis on manufacturing defects in brass oxygen valves
    ( 2023-05-01)
    Wan Mohd Haqqi Wan Ahmad
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    ;
    Salleh S.H.M.
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    ;
    Rajaselan Wardan
    ;
    Mahalaksmi Gunasilan
    Brass valves are widely used in oxygen gas cylinder systems to regulate pressure and ensure safe operation. The production methods for brass valves include hot forging (700 °C), stress-relieving (300 °C), shot blasting, machining, and selective chrome plating on the external surface. Pneumatic testing at 400 bar has detected more than 10 % of the product production was found to have signs of leakage, and the most severe was when there were visible hairline cracks on the inner wall. Therefore, several tests to investigate valve failure were conducted to identify the root cause of the failure using a series of microscopic methods on the failed sample as well as the as-received brass billet. The study found that hairline cracks in brass valves were most likely caused by internal dross originating from the billet that was not properly removed during the casting process. The presence of dross in the billet manufacturing stage was identified as the primary reason for valve failure. Hot forging and other manufacturing techniques were found to be insufficient to eliminate the formation of dross, leading to a deterioration in the mechanical properties of the valves. In order to overcome this issue, flux can be added to the molten brass to help remove impurities and reduce the formation of dross. As a result, the mechanical properties of the final product deteriorated even though it had gone through the forging process.
  • Publication
    The efficiency of Zero Charge Corrosion Protection on pure Mg by Planned Interval Test
    ( 2020-11-24) ;
    Sanusi M.S.
    ;
    Wardan R.
    ;
    Azmi Rahmat
    ;
    The concept of zero charge potential (Epzc) is manipulated to eliminates the effect of the electric double layer in order to mitigate the corrosion reactions through the zero-charge corrosion protection (ZCCP) method. The efficiency of the ZCCP method was examined by planned intervals test on pure Mg metal in 3.5% NaCl solution. The test results showed that the tendency of both liquid corrosiveness and metal corrodibility are decreased from -1562.7mm/yr (Eocp) to -98.2mm/yr (Epzc). ZCCP technique was succeeded by corrosion protection efficiency of pure Mg which was recorded between 93 to 96% in 3.5%) NaCl solution.
  • Publication
    Effects of different pH of 3.5% NaCl solution on steel under zero charge corrosion protection technique
    ( 2021-11-12)
    Wardan R.
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    ;
    Sampasivam T.
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    Mohd Fitri M.W.
    ;
    Yati M.S.D.
    The study is carried out to understand the new corrosion protection technique, non-polarization concept, using current/voltage pulses to achieve a potential of zero charges (Epzc) of the metal-solution interface. As a result, a cost-saving and ecological method has been proposed as a new anti-corrosion method. In the methodology, U-bend samples are immersed in a 3.5% NaCl solution with different pH values. The readings prove the occurrence of electrochemical reaction, absence of charges, and the effect of Epzc. An examination on the ZCCP on low-carbon steel in 3.5% NaCl solution was analyze for 120 hours days. This study is carried out to understand the concept of corrosion behaviour and a new corrosion protection technique which applies non-polarization concept. A U-bend mild steel is used to corrosion effect in various pH values under zero charge protection. Samples were then immersed in 3.5% NaCl solution with different pH values. Electrochemical behaviour of steel sample in 3.5% NaCl solution was analysed by means of Tafel extrapolation. It was found that Ecorr and icorr recorded dissimilar readings at different pH values. As Ecorr rises, icorr drops from pH 6 to pH 9, hence corrosion rate also decreases from pH 6 to pH 9. Zero charge corrosion protection (ZCCP) technique is used to study the efficiency of corrosion protection method in different pH values. Readings of alternating current (IAC) and direct voltage (VDC) are recorded throughout the ZCCP experiment. These readings prove the occurrence of electrochemical reaction, absence of charges and the effect of Epzc.
  • Publication
    Corrosion behaviour of mild steel : insights from tafel extrapolation analysis in flowing 3.5% NaCl solutions and soil with diverse resistivity levels
    ( 2024-12)
    Mahalaksmi Gunasilan
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    ; ; ;
    Wan Mohd Haqqi Wan Ahmad
    The corrosion behaviour of AISI 1006 steel in diverse environmental conditions were comprehensively investigated to offer valuable insights into corrosion mitigation strategies for critical infrastructure protection. This study employed an optical emission spectrometer, pH measurements, soil resistivity assessment, and Tafel extrapolation conducted with a potentiostat. The study encompassed stagnant and flowing 3.5% NaCl solutions, with flow velocities ranging from 0 to 12 km/h, and considered soil corrosiveness based on soil resistivity. In stagnant 3.5% NaCl solutions, minimal corrosion was observed due to limited oxygen availability, resulting in a 6.634 x 10¯3 mm/year corrosion rate. A noteworthy trend was evident in flowing 3.5% NaCl solutions, with corrosion rates peaking at 9 km/h (11.918 x 10¯3 mm/year) and subsequently decreasing at 12 km/h (10.423 x 10¯3 mm/year). This intriguing pattern may be attributed to the potential formation of a protective oxide layer at higher flow velocities, likely due to increased dissolved oxygen and mass transport. The soil's corrosiveness significantly influenced corrosion rates, with lower-resistivity soils exhibiting heightened corrosion rates. In very mildly corrosive soil, AISI 1006 steel displayed a corrosion rate of 2.818 x 10¯4 mm/year. The corrosion rate increased as soil corrosiveness intensified, reaching its peak of 6.319 x 10¯4 mm/year in severely corrosive soil. Extremely corrosive soil led to a corrosion rate of 8.033 x 10¯4 mm/year, as improved soil conductivity accelerated ion transfer and electron flow, ultimately expediting corrosionrelated electrochemical reactions. This study enhances the understanding of AISI 1006 steel corrosion in varying conditions, providing critical data for corrosion control in structures and assets, emphasising the need for tailored prevention measures.
  • Publication
    Effect of porosity and water absorption on compressive strength of fly ash based geopolymer and OPC paste
    (IOP Publishing, 2020)
    SitiAisyah Razak
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    ;
    The fly ash based geopolymer is a promising binder by activation of fly ash with an alkaline activating solution. The fly ash based geopolymer prepared was characterized by several methods. The experimental result, studies effect of the porosity and water absorption on compressive strength of fly ash based geopolymer and Ordinary Portland Cement paste for comparison. The porosity studies were determined using the Brunauer, Emmett and Teller method included nitrogen adsorption / desorption plots. Then followed by water absorption and compressive strength tested at 7 and 28 days curing time. The result shows that the porosity of fly ash based geopolymer paste was in the lower surface area, pore volume and pore size compared to Ordinary Portland Cement paste. The small pore size of the fly ash based geopolymer had a significant proportion of a micropores whilst Ordinary Portland Cement paste pores were mostly mesopores. The highest compressive strength of fly ash-based geopolymer can be achieved up to 76.723 MPa at 28 days when less of pore size and water absorption. Therefore, the paste based on geopolymeric materials is a better durability and high resistance to aggressive environment compared Ordinary Portland Cement paste.
  • Publication
    Effect of Pulse Frequencies on Low Carbon Steel in 3.5 wt% NaCl Solution under Zero Charge Corrosion Protection
    ( 2020-11-24)
    Wardan R.
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    ;
    Sanusi M.S.
    ;
    Mohd Fitri M. W.
    Zero charge corrosion protection (ZCCP) is an alternative to the existing cathodic protection methods. It applies a current/voltage pulse with a certain particular frequency to attain a potential of zero charge (Epzc) on the electrode-electrolyte interface. A study on the pulse frequencies of ZCCP system on low-carbon steel in 3.5 % NaCl Na solution was carried out for 14 days. The pulse frequencies are varied from 4, 20, 50 and 100 Hz. The ability of these frequencies in protecting samples is determined by means of corrosion rate based on weight loss analysis and surface morphology. Experimental observations indicate that low carbon steel corrosion protection is strongly influenced by changes in pulse frequency. Corrosion rates were found to gradually decrease as pulse frequency increased from 4, 20 to 50 Hz, nevertheless at higher frequencies (100 Hz), corrosion protection was observed to be less effective where the corrosion rate dramatically grew up. The surface morphology of the steel surface is smooth and protected at a pulse frequency of 50 Hz. This indicates that the current / voltage pulse of ZCCP system only requires 50 Hz which is equivalent to a standard AC power frequency applied in most countries including Malaysia.
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  • Publication
    Effect physical and mechanical properties of fly ash-based geopolymers on corrosion reinforcement bar: A review
    (AIP Publishing, 2020)
    Siti Aisyah Abd Razak
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    ;
    A major concern for any society with reinforced concrete structures is steel corrosion. Much effort has been made to minimize corrosion damages in new structures and develop corrosion protection of existing structures. The physical and mechanical of fly ash-based geopolymer are enhanced with a few factors that influence its high performance than Ordinary Portland Cement concrete in many aspects such as compressive strength, workability, exposure to aggressive environment and high temperature. This review paper focus on effect of physical and mechanical properties of fly ash based geopolymer paste on the corrosion reinforcement bar. The geopolymerization process in geopolymer paste can improve the properties of fly ash-based geopolymers. Hence, the physical and mechanical properties is important the stability and contribute high compressive strength of geopolymer and improve the corrosion resistance of reinforcement bar.
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