Process for operating a plasma arc torch

摘要

A process for operating a plasma arc torch on shut down includes decreasing current to the electrode from its initial operational value Io to a lesser intermediate value Im in a ramping function between times t1 and t2. Gas pressure within the plasma gas chamber is controlled between times t1 and t2 so that the gas pressure decreases from its operational value Po to a lesser intermediate value Pm substantially concurrently with the decreasing of current between times t1 and t2 and at a controlled rate such that plasma gas flow rate through the nozzle is maintained at least about its operational level Fo or greater between times t1 and t2. At time t2, current is shut off to the electrode.