Prediction of discharge rate from pressurized vessel blowdown through sheared pipe



It is a common industrial practice to store chemicals in large vessels. For emergency response management, prediction of the impacted area due to the dispersion of a chemical accidentally released from a vessel is crucial. Therefore, accurate estimation of the release rate and condition of the flowing stream is warranted.

Based on this need, a general purpose quasi-steady model is developed which can calculate the discharge rate from a tank-pipe system (rupture in the tank or shearing of an attached pipe). The tank may contain gas, vapor, saturated or sub cooled liquid (under its own vapor pressure or padding pressure). The model output includes the history of the tank variables i.e., pressure, temperature, mass content, liquid level as well as the transient outflow of chemicals from a rupture or pipe as a function of momentary tank thermodynamics condition. The results of the model for the case of two phase flow through a pipe are validated against experimental data. Charts are provided which show the effect of the pipe length and the padding pressure on the discharge of the tank content.