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All anti‐corrosive coatings have a common role of protecting the substrate to which they are applied.

COMING OUT firmly against a Government scheme for splitting jobs in their sectors is the Council of Civil Service Unions. They say that “The net effect of job‐splitting would be to create a number of part‐time posts from existing full‐time ones which will be seen as an unacceptable dilution of full‐time posts.”

Summary The properties of coal tar systems and the mechanical requirements of pipeline protections before and after installation of the pipelines are defined. Correct specification related to the particular service conditions and adequate inspection are of paramount importance. With correct selection of primer, grade of coal tar enamel and glass reinforcements coal tar based systems are providing the most reliable protection under almost all service conditions.

Coal‐tar and asphalt‐base coatings have been the major protective coatings used on pipelines for nearly half a century. The coal‐tar coatings are the only ones recognised for use as a lining and coating for water‐lines, but in oil and gas systems both types are being used. The coal‐tar hot‐applied coatings have dominated even this field. It is estimated that, since the war, the amount of the two types of hot‐applied coatings used in the Western hemisphere has varied between 200,000 and 350,000 tons p.a. and the percentage of hot‐applied asphalts used has varied between 10 and 30%.

This paper aims to the transportation of high concentration slurry through pipelines that will require thorough understanding of physical and rheological properties of slurry, as well as its hydraulic flow behavior. In spite of several contributions by the previous researchers, there is still a need to enrich the current understanding of hydraulic conveying through pipeline at various flow parameters. The pilot plant loop tests, particularly at high concentrations, are tedious, time-consuming and complex in nature. Therefore, in the current research the prediction methodology for slurry pipeline design based on rheological model of the slurry is used for calculation of pressure drop and other design parameters.

It has been established that slurry rheology plays important role in the prediction of pressure drop for laminar and turbulent flow of commercial slurries through pipeline. In the current research fly ash slurry at high concentration is chosen for rheological analysis. The effect of particle size and solid concentration is experimentally tested over the rheological behavior of slurry and based on the rheological data a correlation is developed for calculation of pressure drop in slurry pipeline.

The present study strongly supports the analytical approach of pressure drop prediction based on the rheological parameters obtained from the bench scale tests. The rheological properties are strongly influenced by particle size distribution (PSD), shear rate and solid mass concentration of the slurry samples. Pressure drop along the pipeline is highly influenced by flow velocity and solid concentration. The presence of coarser particles in the slurry samples also leads to high pressure drop along the pipeline. As the concentration of solid increase the shear stress and shear viscosity increase cause higher pressure drop.

The transportation of slurry in the pipeline is very complex as there are lot of factors that affect the flow behavior of slurry in pipelines. From the vast study of literature it is found that flow behavior of slurry changes with the change in parameters such as solids concentration, flow velocity, PSD, chemical additives and so on. Therefore, the accurate prediction of hydraulic parameter is very difficult. Different slurry samples behave differently depending upon their physical and rheological characteristics. So it is required to study each slurry samples individually that is time-consuming and costly.

Nowadays in the world, long distance slurry pipelines are used for the transportation of highly concentration slurries. Many researchers have carried out an experiment in the design aspects of hydraulic transportation system. Rheological characteristics of slurry also play crucial role in determining important parameters of hydraulic conveying such as head loss in commercial slurry pipeline. The current research is useful for the prediction of pressure drop based on rheological behavior of fly ash slurry at various solid concentrations. The current research is helpful for finding the effect of solid concentration and flow velocity on the flow behavior of slurry.

Slurry pipeline transportation has advantages over rail and road transportation because of low energy consumption, economical, less maintenance and eco-friendly nature. Presently majority of the thermal power plants in India and other parts of the world dispose of coal ash at low concentration (20 per cent by weight) to ash ponds using the slurry pipeline. Transporting solids in slurry pipelines at higher concentrations will require a thorough knowledge of pressure drop. In the current research a rheological model is proposed for prediction of pressure drop in the slurry pipeline, which is useful for optimization of flow parameters.

All the experimental work is done on fly ash slurry samples collect from the Jharli thermal power plant from Haryana State of India. Bench scale tests are performed in the water resource laboratory of IIT Delhi for physical and rheological analysis of slurry. It has been shown in the results that up to solid concentration of 50 per cent by mass all the samples behave as non-Newtonian and follows a Herschel–Bulkley model with shear thickening behavior. In the present research all the result outcomes are unique and original and does not copied from anywhere.

Transportation of solids by slurry pipeline is a rapidly growing field. The pipelines, in the process of transportation undergo severe deterioration externally as well as internally. Corrosion‐erosion, metal damage caused by the combined action of electrocemical corrosion and mechanical erosion, has been studied extensively. In hydraulic transportation of sand, internal wear is caused by combined action of corrosion, associated with the corrosive water, the flow velocity and abrasion due to geometry of the solid particles on the interior pipe wall. Corrosion in slurry pipeline is generally due to the presence of dissolved oxygen in the slurry. The control of corrosion wear in a coal slurry pipeline is reported by Bomberger. The corrosion study by Postlethwaite and Tinkler showed that the presence of solids in commercial concentration increases the rate of corrosion in pipelines. The most common erosion occurred generally is the scratching or grooving of the pipe by the slurry particles. An erosion‐corrosion study in pilot plant slurry transportation in pipeline carrying wide range of water borne solids such as coal, iron ore and sand have shown that the presence of solids increases the chemical corrosion rate, apart from any accompanying erosion. It was also observed that due to severe corrosion‐erosion problem in pipeline, even a pinhole in such a line would be enlarged gradually in a matter of minutes by the out flow of high pressure abrasive slurry. Jacues and Neil had given an account of the causes, control and the economics of internal corrosion of slurry pipelines Zabell et. al. had studied the effect of bacteria using six different processes on corrosion of iron and the steel water pipes. The copper pipe line had been specially studied by Fischer and few others in various environments.

Introduction It is well appreciated that the primary purpose of an external coating on a pipeline is of course to prevent corrosion and the coating system should possess appropriate physical and chemical properties which allow this function to be fulfilled. There are, however, additional mechanical requirements of a coating system if the material is to be effective during handling, construction, testing and operation and it is within the context of these latter requirements that current interest in external coatings has arisen.

The design of optimum pipe and duct networks with available procedures is difficult, if not impossible. A more efficient procedure that will automatically produce the optimum design is required. Such a procedure is presented in this article. The design is formulated as a constrained nonlinear optimization problem. This problem is solved using a unique numerical optimization algorithm. The solution entails the calculation of the cross sectional dimensions of the ducts and pipes so that the life cycle cost of the network is minimized. The topology equations are derived using graph theory thereby allowing complex networks with loops to be designed numerically. A duct network consisting of a fan and 35 duct sections is designed according to certain specifications. Using the proposed procedure optimum designs were obtained within seconds on a 33 MHz 486 micro‐computer. The procedure was further applied to the optimization of a coal pipeline. It is shown that the optimized solution will cost 14% ($8 million) less than the previous design with conventional design techniques.