Optimal Maintenance Policy for Second-Hand Equipments under Uncertainty

This chapter addresses a maintenance optimization problem for re-manufactured equipments that will be reintroduced into the market as second-hand equipments. The main difference of this work and the previous literature on the maintenance optimization of second-hand equipments is the influence of the uncertainties due to the indirect obsolescence concept. The uncertainty is herein about the spare parts availability to perform some maintenance actions on equipment due to technology vanishing. The maintenance policy involves in fact a minimal repair at failure and a preventive repair after some operating period. To deal with this shortcoming, the life cycle of technology or spare parts availability is defined and modeled as a random variable whose lifetimes distribution is well known and Weibull distributed. Accordingly, an optimal maintenance policy is discussed and derived for such equipment in order to overcome the uncertainty on reparation action. Moreover, experiments are then conducted and different life cycle of technologies are evaluated according to their obsolescence processes (accidental or progressive vanishing) on the optimal operating condition.

Identification of Optimal Operating Condition of Six Bus System Based on Reliability Evaluation

Practical Transmission system interconnecting Ramagundam Thermal power plant, Kotagudam thermal power plant and Nagarjunasagar hydal power plant with Hyderabad, Karnool and Gooty load points is considered for present study. This six bus ring system is a part of the Telangana state transmission system. Reliability indices of the system for variable load at Hyderabad load bus are obtained. Based on the reliability indices the optimal operating condition of the system is identified. Operating the system at identified optimal operating point will nullify the installation of redundant components and adequacy improving components. Generation outage transmission outage and generation cum transmission outages are the possible contingencies which can occur during the operation of the considered practical composite power system. Telangana state transmission system is simulated for different possible contingencies with Power system simulation for Engineering software tool. Load point and system reliability indices evaluated for twelve different contingency cases. Referring to load point and system reliability indices, optimal operating point of ring system evaluated. Present study will indicate the load magnitude, upper boundary of load magnitude corresponding to reliable operation of the system.

The Optimization of Ozonolysis Reaction For Synthesis of Biopolyol From Used Palm Cooking Oil

Biopolyol is a raw material for synthesis of polyurethanes which is used as thermoset and thermoplastic materials, adhesives, rigid or non-rigid foams and also for coating. The utilization of waste edible oil as feedstock for synthesis of biopolyol has attracted some researchers. However, there is little attention focused on the application of ozone technology for synthesis of biopolyol from used cooking oil through ozonolysis reaction. Response surface methodology was performed to determine the optimal operating condition in the synthesis of biopolyol using ozone and sorbitol as a hydroxyl group source. The influence of input variables such as temperature, reaction time, molar ratio of oil to sorbitol and ozone concentration on hydroxyl value quantified was studied. The optimal condition was determined by high amount of hydroxyl value resulted from response surface method which used the experimental data. The ozonolysis reaction was conducted in a batch reactor equipped with agitator, tube sparger, thermocouple, reflux condenser and potassium iodide trap. Central composite design with four independent variables and one response variable was performed to determine the influence of independent variables on output variable of hydroxyl value of biopolyol. The hydroxyl value of polyol is a quadratic function of molar ratio of oil to methanol and a linear function of reaction temperature. The optimal operating condition was achieved at a temperature of 25℃, a reaction time of 5 hours, molar ratio of used cooking oil to sorbitol is 1:7 and ozone concentration about 4.8%.Keywords: Ozonolysis; Biopolyol; Hydroxyl value; Used cooking oil; Palm oil