Our particle size analyser (a Micromeritics Saturn Digisizer II) is always thirsty. We feed it solutions from large, 25 litre jerry-cans (we used to use 10 litre jerry-cans, but we found the batch changes too frequent). Dust and dirt in the solutions is detrimental to the analysis, and we used to wrap the spout and tubes in cling-film to avoid contamination.
Using our new Velleman K8200, I recently 3-D printed these very simple dust caps to fit these cans, with holes tailored to the inlet and outlet tubes. This is a neater solution than cling-film.