The dynamics of the triple gas-liquid-solid contact line is analysed for the
case where the gas is the saturated vapour corresponding to the liquid, like in
the vapour bubble in boiling. It is shown that even small superheating (with
respect to the saturation temperature) causes evaporation of the adsorption
liquid film and the true triple contact is established. It is shown that the
hydrodynamic contact line singularity cannot be relaxed with the Navier slip
condition under such circumstances. Augmented with the second derivative slip
condition is proposed to be applied. For the partial wetting conditions, a
non-stationary contact line problem where the contact line motion is caused by
evaporation or condensation is treated in the lubrication approximation in the
vicinity of the contact line. High heat fluxes in this region require the
transient heat conduction inside the heater to be accounted for. Two 2D
problems, those of drop retraction with no phase change and of drop evaporation
are solved and analysed as illustrations of the proposed approach