Once we get to the place where we can agree that fluids and gases are “stored energy” and that those “stored energies” have to be bled/drained to achieve a Zero Energy State (ZES), we can then discuss the potential hazards these necessary actions can create. I have written a lot about using 1/4 turn ball valves as energy isolation devices and that once they are closed and locked, we now have a stored energy situation on the other side. We must provide a means to bleed/drain off the stored energy.
When the energy source is just plant air or water, we can bleed/drain the stored air/water pressure into the working space without creating serious hazards. However, when the gas or fluid we are dealing with is a hazardous material, bleeding or draining the gas/fluid into the occupied space, we could create a hazardous working environment.
For example:
Natural Gas is a common flammable gas that many businesses use for boiler and heater fuel. NG comes with two (2) hazards that must be controlled:
1) flammable, and
2) pressure
Closing the isolation valve will isolate the NG flow, but after the valve, the NG will be a form of “stored energy.” To achieve a ZES, we have to bleed off the NG.
Consider the following…
How much gas will be bled from the piping? As NG is flammable and lighter than air, where and how we bleed it off our system matters.
Nitrogen and Carbon Dioxide are simple asphyxiants. Bleeding them off into the working space could, depending on the volume of gas being bled off, create a hazardous atmosphere (e.g., lowering O2 levels)
Ammonia and Chlorine are extremely hazardous substances, and bleeding them into the working space could create a hazardous environment.
So, bleeding off “stored energy” when that stored energy has the potential to create a hazardous condition will necessitate that our specific energy control procedures will need to cover the means and methods of how to SAFELY drain/bleed these hazardous materials to a “safe location.” We may need to include a PPE Hazard Assessment, hose/tubing to be used, and even some media that can act as a scrubbing media to safely control/contain/neutralize/absorb the hazardous material.