The prediction of pressure drop is important to pipeline design and it is often necessary to use data from one pipeline size to predict what will happen in another pipeline size. This paper looks at the effect of two different products when scaling for diameter in vertical pipelines. Data has been measured for cement and flour in two bore sizes. A means of modelling has been established to allow prediction of the operation of a pipeline of one bore size, from trials on another bore size in vertical sections. The model used to correlate pipeline diameter with pressure gradient data in vertical pneumatic conveying pipelines will be discussed along with the general data trends for the two materials.