Mohd Amin Abd Majid

Simulation model for natural gas transmission pipeline network system

Abstract This paper focuses on developing a simulation model for the analysis of transmission pipeline network system (TPNS) with detailed characteristics of compressor stations. Compressor station is the key element in the TPNS since it provides energy to keep the gas moving. The simulation model is used to create a system that simulates TPNS with different configurations to get pressure and flow parameters. The mathematical formulations for the TPNS simulation were derived from the principles of flow of fluid through pipe, mass balance and compressor characteristics. In order to determine the unknown pressure and flow parameters, a visual C++ code was developed based on Newton–Raphson solution technique. Using the parameters obtained, the model evaluates the energy consumption for various configurations in order to guide for the selection of optimal TPNS. Results from the evaluations of the model with the existing TPNS and comparison with the existing approaches showed that the developed simulation model enabled to determine the operational parameters with less than 10 iterations. Hence, the simulation model could assist in decisions regarding the design and operations of the TPNS.

Power and Thermal Efficiency Study of Offshore Gas Turbines under Various Ambient Temperatures

Gas turbines offer a reduced weight and compact solution for installation on offshore platforms and floating facilities. The purpose of this study is to examine the influence of various parameters on offshore gas turbines performance. Operating measurements of a 23MW gas turbine installed at an offshore oil and gas plant in east of Peninsular Malaysia was used for model verification and evaluation. The results showed that the gas turbine performance improvements involve the study of a wide range of different parameters including ambient temperature, compression ratio, fuel-air ratio and operating load. These achieved relations will help in appropriate assessment of offshore gas turbines thermal efficiency.

Semi-Quantitative Risk Assessment Matrix for Rotating Equipment

In petrochemical, power generation, oil and gas industries and in variety of other sectors rotating equipments are in use to fulfill production requirements. Failure of rotating equipment, especially in such industries can result to risk related issues. A well implemented rotating equipment risk assessment strategy is most needed to achieve desired plant availability and efficiency. In this research semi-quantitative risk assessment approach is proposed to evaluate the risk of rotating equipment and categorize their associated failure risks. Borda ranking is adopted to evaluate the risk in order to minimize risk ties which exist in risk matrix. Compressor is taken as case study to show the applicability of the proposed method for rotating equipment. It was observed that risks of selected failure modes of gas turbine compressor fall in the categories of serious and medium levels based on risk matrix. Rotor bend distortion, blade failure or inlet guide vane failures needed more attention for treatment based on Borda ranking.

Reliability Analysis for Parallel-Serial Robots in Automotive Assembly Plant: A Case Study

Robot arrangement in the automotive assembly plant in manufacturing environment consists of series and parallel configurations. Robot subsystems at painting lines were configured in series configuration while overall system was configured in parallel. Interruption of operations due to breakdown at both subsystems during operation would affect the production throughput. The robots’ breakdown data for each subsystem were acquired for reliability analysis of parallel-serial configuration of robots. This study is to analyze the serial subsystems robot reliability compared to reliability of robots in overall system in parallel-serial configuration. The seven years actual breakdown data were acquired from the automotive painting plant. By using the reliability block diagram (RBD) method, at the 5000 operating hours, the two subsystems at the painting lines were evaluated. Reliability of the two subsystems are 0.029 and 0.119 respectively. While the overall parallel-serial system has the reliability of 0.145. It is proven that the parallel-serial reliability of the system is better compared to series configuration of the subsystems. With parallel-serial system, the production line would not be interrupted during the corrective or preventive maintenance worked.

Effect of Post Weld Heat Treatment on Weld Hardness Quality of P91 Welded Pipes

Quality of a weld produced is generally evaluated by different parameters such as weld size, bead geometry, deposition rate, hardness and strength. A common problem that has been faced at the construction sites is to obtain a good welded joint having the required strength with minimal detrimental residual stresses to avoid any premature cracking due to high variation of hardness. In order to address this issue and to attain good weld quality, this study has been made to comprehend the effect of the post weld heat treatment on P91 material welds produced by TIG welding. Findings from the studies indicate that the PWHT has significant influence on the weld hardness of Alloy Steel-A335 P91 pipes. It is eminent that during cooling, after welding of P91, quenched martensite was formed in the HAZ that results in an increased hardness to an undesirable level of more than 250HB. PWHT at temperature of 760°C for 2 hours has good influence on mechanical properties as the hardness decreases and turns out to be uniformly distributed. If the PWHT is correctly carried out, the hardness of parent metals, heat affected zones and weld metal can be brought into the required limits to avoid any premature cracking due to high variation of hardness.

Analogical Approach for Optimizing Natural Gas Transmission Pipeline Network System

The increase in demand for natural gas in different sectors attracted different scholars in optimizing the operation and configurations of natural gas pipeline network (NGPN) systems. Even though there have been reports regarding the attempts of solutions for optimizing NGPN problems, the issues of NGPN regarding energy minimizations are not fully address yet. This paper proposed robust solution for NGPN system energy consumption minimization at compressor stations based on analogical approach. The analogies between NGPN system and inventory model were observed and applied in the analysis of steady state NGPN system. The proposed technique is based on the inventory model to find optimal operations for natural gas pipeline network system. The method for the determination of the optimal pressures was efficient and handled the non-linearity that occurs on both objective and the constraint equations. Results on a gunbarrel NGPN showed the proposed method assisted in determining the discharge and suction pressures to minimized energy consumption at compressor stations.