An equation for plug motion has three factors. These are the pressure difference, the plug velocity, and the weight of plug. Plug motion depends largely on the first two factors.
When plugs move through an inclined pipe, the friction force increases somewhat. This increased friction force is based on the weight of the plug.
Also, a change in the transport apparatus, such as change in the length of pipeline, brings about a change in all friction forces.
In this report, the angle of the inclined pipe is changed between 0° and 20°, and the transport apparatus is partially changed. It is shown that plug motion depend on the partial change in these friction forces.

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