A comparison is made between the pressure distributions in identical brass and nylon pipe-lines conveying polystyrene powder, showing that electrostatic charging of the solid particles has a negligible effect on highspeed, gas-solids pipe flow. A theory is presented for the prediction of the electrostatic charging rate of the solid particles. It is predicted and confirmed experimentally that the current to earth from electrically isolated sections of the brass pipe and from aluminium foil wrapped on a length of the nylon pipe varies linearly with the solids loading.

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The introduction of a small transverse opening or cross-bore into the wall of a cylindrical pressure vessel is sometimes necessary. Under static conditions such a cross-bore may have little effect on the bursting pressure of a plain cylinder, but under cyclic stress conditions, the fatigue life of the vessel is severely reduced. If the cross-bore axis is offset from the radial centre-line of the cylinder, then the fatigue life of such a vessel is shown to be substantially greater than that of a similar vessel containing a radial cross-bore.

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This paper presents an experimental and theoretical study of the design and performance of inertia air filters, with particular reference to rail traction duty. Using a specially constructed test rig, performance testing of commercially available filters was carried out over a wide range of operating conditions. Subsequently, a more fundamental study of some design variables was carried out in a small-scale test rig. The testing was supported by a theoretical approach using a digital computer model of the inertia filtration process. The results of the work indicate that the inertia filter is suited to high-volume, low pressure drop applications. However, operational difficulties, owing to dust build-up occurring within the filter and variations of bleed ratio, may be encountered. The theoretical model was shown to reproduce all the major operating characteristics of the filters measured in the test programme, and to respond to design changes in a similar way to that indicated by earlier published work. A hypothesis of the mechanism of separation is proposed, and it is suggested that the performance of new filter layouts can be examined at the design stage. Supporting work describes the selection, measurement, and production of a suitable range of polydisperse solids for the test programme.