An analysis is presented which describes and predicts the process of drainage of noxious liquid substances from piping arrangement consisted of horizontal and vertical pipe line in chemical tanker during the operation of air blowing. The process is modeled in three stages according to the location of the head of flowing single air slug in pipe line, that is,
stage 1: the head of slug locates in horizontal pipe,
stage 2: the head locates in vertical pipe,
stage 3: the head locates outside the outlet of pipe line.
Analytical expression is derived by taking into account the important factors in each stage.
The results predicted by the analysis in stage 1 and stage 2 are compared with experimental data obtained for various operational conditions using water and air as working fluid. Good agreement with experimantal data of pressure and the quantity of residue in horizontal pipe are shown.