Search results

This paper aims to examine the reliability of a cooling seawater pumping station which pumps seawater to refineries and petrochemical plants in Kuwait mainly for cooling purposes. Owing to the harsh operating climate and the lack of other alternative sources of water, high reliability of the pumping system is crucially important.

The reliability of a system can be considered from different views. The one taken in this study is to measure the reliability of the cooling seawater arriving to the consumer at the required pressure and flow rate while observing the operational constraints on the system. A reliability model has been developed and applied to the actual data from the pumping station.

The preliminary results indicate that the model could be a useful tool to assess the current condition of the system and to find ways of improving system reliability and availability.

The paper provides information of value to all concerned with relibility management.

This article will discuss corrosion and associated subjects as encountered at the two plants of The Dow Chemical Co., Freeport, Texas. This firm has an investment in this area in excess of $200 million (£71 million) and produces a variety of organic products, plastics, magnesium, bromine, chlorine and caustic soda as well as many related items. The plants are located about six miles apart on the coastal plain of the Gulf of Mexico where climatic, physiographical and industrial conditions are such that corrosion control is imperative to successful operation. This is the second of two articles; the first featured atmospheric corrosion and painting, and appeared in CORROSION TECHNOLOGY last month.

The purpose of the paper is to provide a method for selection of an optimum level of repair by replacement of an equipment based on its cost. In a ship where the engineer has a vast variety of equipment and systems to operate and maintain within limited time frames and availability of human resources, it is often difficult to disassemble a whole equipment to replace a faulty component. It is instead a lot easier to just replace the faulty equipment with whole new equipment. However, such a decision comes at an enormous capital cost. Therefore, the key question is, can we have a model to help us arrive at a decision on the correct level of carrying out repairs?

The paper uses a model based on cost and convolution of failure distributions of critical sub-components of an equipment. Necessary assumptions based on real life experience have been incorporated in the model.

The paper used an example of a particular type of motor driven sea water centrifugal pump which was commonly used in main engine sea water system, firefighting system, air conditioning system, etc. The pump had one of the highest failure rates in the ship (approximately one failure per 150 days) and the engineers found it cost and time effective to replace the entire pump on failure rather than carrying out replacement of the failed components. The model analyzed that the engineer’s hunch was not off the mark.

The implication of the work presented in the paper will be savings in maintenance cost and downtime due to optimal level of repairs on a multi-component equipment. The limitations of the work are assumption of independence of failures of components. This may not be true in all the cases. Further, opportunity based maintenance has also not been considered.

The originality of the paper lies in the presentation of a method for selection of an optimum level of maintenance for a multi-component equipment

The limited supply of fossil fuels, constant rise in the demand of energy and the importance of reducing greenhouse emissions have brought the adoption of renewable energy sources for generation of electrical power. One of these sources that has the potential to supply the world’s energy needs is the ocean. Currently, ocean in West African region is mostly utilized for the extraction of oil and gas from the continental shelf. However, this resource is depleting, and the adaptation of ocean energy could be of major importance. The purpose of this paper is to discuss the possibilities of ocean-based renewable energy (OBRE) and analyze the economic impact of adapting an ocean energy using a thermal gradient (OTEC) approach for energy generation.

The analysis is conducted from the perspective of cost, energy security and environmental protection.

This study shows that adapting ocean energy in the West Africa region can significantly produce the energy needed to match the rising energy demands for sustainable development of Nigeria. Although the transition toward using OBRE will incur high capital cost at the initial stage, eventually, it will lead to a cost-effective generation, transmission, environmental improvement and stable energy supply to match demand when compared with the conventional mode of generation in West Africa.

This study will be helpful in determining the feasibility, performance, issues and environmental effects related to the generation and transmission of OBRE in the West Africa region.

The study will contribute toward analysis of the opportunities for adopting renewable energy sources and increasing energy sustainability for the West Africa coast regions.

The Cathelco anti‐fouling and corrosion control system is now one of the most popular and widely specified systems for combatting the problem of marine fouling on ships.

Looks at the potential of water hydraulics as an alternative to more traditional systems and explains the advantages and disadvantages. Provides a number of examples of where water hydraulics is replacing other systems, in particular with the use of Nessie products. Also describes other areas where the use of water hydraulics is on the increase such as oil recovery, fire‐fighting, cheese making, abattoirs and sewerage service companies.

THERE ARE TWO main groups of alloys containing large amounts of copper and nickel used when maximum resistance to corrosion by sea‐water is required.

This paper aims to determine the optimum arrangement of a reverse osmosis system in two methods of plug and concentrate recycling.

To compare the optimum conditions of these two methods, a seawater reverse osmosis system was considered to produce fresh water at a rate of 4,000 m3/d for Mahyarkala city, located in north of Iran, for a period of 20 years. Using genetic algorithms and two-objective optimization method, the reverse osmosis system was designed.

The results showed that exergy efficiency in optimum condition for concentrate recycling and plug methods was 82.6 and 92.4 per cent, respectively. The optimizations results showed that concentrate recycling method, despite a 36 per cent reduction in the initial cost and a 2 per cent increase in maintenance expenses, provides 6 per cent higher recovery and 19.7 per cent less permeate concentration than two-stage plug method.

Optimization parameters include feed water pressure, the rate of water return from the brine for concentrate recycling system, type of SW membrane, feedwater flow rate and numbers of elements in each pressure vessel (PV). These parameters were also compared to each other in terms of recovery (R) and freshwater unit production cost. In addition, the exergy of all elements was analyzed by selecting the optimal mode of each system.

With the transition from supplying ships with direct current to alternating current, plus the increase in the number of electricity consumers within the coastline region, as well as with the construction of steel quays and docks and reinforced steel quays, the conditions have been created for the occurrence of wandering exchange currents in the sea. Corrosion due to these currents considerably exceeds all expectations. In this work, the rate of steel corrosion in synthetic sea‐water has been investigated in an alternating electric field. Electro‐chemical parameter measurements determining corrosion rate were performed on samples in sea‐water in an alternating current field and compared with the sample — applying a “blind test” — without an electric field. All measurements were performed at an electrolyte temperature of 20°C. Corrosion rate was investigated in dependence on the current density. The following factors were applied as measures of corrosion rate: specific concentration of Fe ions in the electrolyte and the change of potential of the steel electrode polarized within alternating electric field. Measurement results shown that in the sea‐water with an alternating electric field an increase in the corrosion of steel takes place, exceeding expected amounts. The change of steel potential in alternating current field is proportional to the corrosion rate and can be very simply applied for estimation of corrosion rate due to alternating currents.