Increasing the volume of an elastomer seal through the action of the hydraulic fluid.The height of the swelling is different, depending on the seal materials. For example, polyamide swells strongly in water by approximately 10% or NBR in naphthene-based oils, but very little in paraffin-basedmineral oils..
The swelling behaviour of seals must be considered, as this increases the sealing friction and therefore its wear. Predictions regarding the swelling of seals are possible using the sealing compatibility index (DVI)).