This paper deals with the common practice of selecting pipeline valve diameters smaller than that of the pipeline itself. The most economic design in such a case dependent on both the valve diameter selected and the design of the reducers connecting the valve to the pipeline. The head loss through valves and reducers is discussed together with the capitalization of energy cost. Assuming a power penalty of R3 000/kW over the life of a pipeline, diagrams are presented from which the most economical valve installation may be designed. Three valve types are covered. A design example Illustrates the proposed procedure.
A pilot study on Comprehensive Traffic Observations (CTO) was carried out on a 600 km long route between Johannesburg and Durban from October 1983 to January 1985. Traffic was observed at seven CTO stations placed on different types of road comprising this route. Electronic observation equipment of the Traffic Engineertng Logger (TEL) type was used supplemented by, In one Instance, a Traffic Axle Weight Classifier (TAWC) for a more accurate estimation of axle load. The observations were carried out in week-long blocks, repeatedly, for 12 consecutive months, on a 24-hours a day basis. The pilot study concluded that CTO are capable of yielding accurate estimates of the average annual dally traffic.
Because they are difficult to sample and test in the laboratory, gravels are best tested in situ. Plate bearing tests are widely used to measure the modulus of solis and weak rocks and are also suitable for gravels. Equipment and test procedures have been developed to allow the rapid testing of gravels. The widespread use of trial holes and test pits for foundation investigations in Southern Africa provides the opportunity to perform these tests on a routine basis. The results of 175 plate bearing tests in gravels were analysed in the paper. The soli modulus was determined from each test using both a simplified elastic analysis and a rectangular hyperbola method. Relationships were presented between modulus and observed consistency, and also between plate bearing capacity and consistency.