Question

Write the procedure for steam purging

Answer 1

PROCEDURE FOR STEAM PURGING:

Steam-out is a steam purging process to remove either hydrocarbons, prior to vessel opening for maintenance and inspection OR to remove air in the vessel prior to start-up.

> Steam free of condensate is introduced into the column/vessel at the bottom and allowed to flow through to the top vent into the atmosphere, sweeping out the air /hydrocarbons to atmosphere.

> Gradually the vessel gets heated up and the resulting condensate is drained at the bottom.

>Only after the vessel is pressurized (slightly above atmospheric pressure), the vent is opened as it may suck air into the vessel otherwise, which may lead to an explosive mixture in case the vessel holds hydrocarbons.

>Again at the end of steaming ( checked by hydrocarbons OR Oxygen in vented Steam), the vent is closed first in case of start-up and the vessel filled with an inert gas like Nitrogen to take the place of steam.

> In case of shut-down, the vent is left open and air is allowed to enter the vessel prior to opening of manholes.

>Also sometimes, the vent is closed for leak testing with pressurized steam at its saturation temperature.

[If you are steaming a column and the condenser is adequate for steam out, then it is usually a simple matter to condense and collect the condensate without steaming to the air. In other cases it may be be possible to clear other pieces of equipment (feed heaters and lines, etc) into the process with steam.

Unfortunately to design a system to capture steam out vapors is not always practical (or safe). For enviromentally sensitive applications you can hire companies to use oxidizing chemicals or other methods. Each application requires its own consideration, but steaming out to the atmosphere will likely remain a workhorse for clearing equipment for most of your career.]