Now showing 1 - 5 of 5
No Thumbnail Available
Publication

Root cause analysis on manufacturing defects in brass oxygen valves

2023-05-01 , Wan Mohd Haqqi Wan Ahmad , Shaiful Rizam Shamsudin , Salleh S.H.M. , Mohd Rafi Adzman , 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.

No Thumbnail Available
Publication

Modeling and Simulation of Metal Oxide Surge Arresters Models by using ATPDraw Software

2023-01-01 , Mohd Rafi Adzman , Ting K.X. , Shaiful Rizam Shamsudin , 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.

No Thumbnail Available
Publication

Failure investigation and analysis of locally manufactured turbine blade

2023-05-01 , Mahalaksmi Gunasilan , Shaiful Rizam Shamsudin , Rajaselan Wardan , Aleena Ramlee , Wan Mohd Haqqi Wan Ahmad , Mohd Rafi Adzman

This study aims to identify the root cause of a turbine blade failure after only 36 hours of operation and recommends measures to prevent future failures. The analysis involved four samples, including an OEM sample, three fabricated samples with cracks and parts, including a kept sample for failure analysis. Microstructural analysis using Villella's reagent as an etchant, surface morphology, and micro-elemental analysis were conducted using the benchtop SEM & EDS. The hardness of the samples was tested using the Rockwell (HRC) method. The failed blade was made of AISI 422 grade stainless steel. It failed due to chipping that initiated cracks when it was tightly fastened, facilitated by internal stress and intermetallic particles in the microstructure. Instead of turbine blades made of hardened steel, the material was found to be slightly ductile and highly prone to compression before breaking when over-tightened during assembly. Inadequate heat treatment practices caused varied microstructural patterns, including the presence of intermetallic particles and significant hardness differences between the fabricated and OEM samples, leading to internal stress. In order to prevent future failures, there is a requirement to improve quality control measures during the fabrication process, particularly in the aspect of heat treatment practices.Thorough testing and analysis of the material microstructure may also be necessary to identify and eliminate potential sources of internal stress and intermetallic particles. Proper installation and fastening of turbine blades, regular inspection, and maintenance can also help identify early signs of failure and prevent catastrophic failures from occurring.

No Thumbnail Available
Publication

Effect on Current Density on Zero Charge Corrosion Protection of Pure Mg in 3.5% NaCl Solution

2021-11-12 , Gunasilan M. , Shaiful Rizam Shamsudin , Mohd Rafi Adzman , Salleh S.H.M. , Sanusi M.S. , Ahmad W.M.H.W.

The cathodic protection uses two-electrode polarization, which requires large currents and substantial voltages. Efforts are being made to identify possibilities for improvements by developing zero-charge corrosion protection techniques. Studies were performed to determine the zero-charges potential effect by analyzing corrosion signs on reactive metal samples such as pure Mg. Mg samples were fed by current/voltage pulses for 120 hours, with specified pulse parameters and varied Ecorr- offsets, ranging from +2 to -218 mV. The volumetric hydrogen gas collection technique is used to determine the hydrogen evolution rate. Surface observation is carried out by stereomicroscope to determine the presence of corrosion signs on the sample surface. Overall, all current densities and hydrogen evolution rates had very low readings on the studied Ecor offset parameters. Mg samples fed with pulses at -1800 and -1900 mV vs SCE revealed zero charge potential effects since their surface was clean and showed no indications of corrosion even after being exposed to the corrosive solution for 120 hours. Thus, corrosion protection is successfully done and meets the Epzc condition.

No Thumbnail Available
Publication

Influence of flow accelerated corrosion on corrosion protection of mild steel in 3.5% NaCl solution

2024-03-07 , Mahalaksmi Gunasilan , Shaiful Rizam Shamsudin , Mohd Rafi Adzman , Siti Hawa Mohamed Salleh , 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.