This article, which is published in two parts, describes research that focuses on the analysis – through an experimental study – of the sealing behaviour of a non-contact dynamic sealing device known as a viscoseal (or sometimes called a helical groove seal). Despite its reliability and its advantageous characteristics, compared with other types of sealing devices, the viscoseal is still under-researched because of its complex characteristics. The experimental apparatus used in this work is equipped with two different test cells. This first, made from acrylic glass, is transparent and is used for the visualisation of the liquid–air interface within the viscoseal. The second cell, used for pressure measurement, is composed of bronze. The experimental results are compared with numerical results obtained using the Reynolds model and also with computational fluid dynamics code. The first instalment, which appears here, includes a general introduction and covers the experimental set-up and relevant references. Part II will be published in the September issue.