Date: October 22/2020
Time: 7:30 a.m. to 5 p.m.
Location: NE 17-25-20 W4M
A blowdown is the act of releasing natural gas from the pipeline system so work can be done safely on the depressurized facilities. TC Energy employees will close the required valves to isolate the facilities and then open a blowdown valve to safely depressurize in a controlled manner. A loud roaring sound occurs when the natural gas is released, and in some cases a silencer can be used to minimize the noise.
The sound during a blowdown can be as loud as an airplane engine and may last up to 20 minutes or longer. As the flow of gas gradually slows down, the noise also lessens. The entire blowdown may last up to three hours. Wherever possible, TC Energy personnel employ silencers to minimize the noise during a blowdown.
After the natural gas is released, a funnel-shaped air expeller is placed on top of the blowdown valve opening, which draws any remaining gas out and makes it safe for activities such as welding.
Once maintenance is complete, work begins to safely bring the line back into service. Natural gas is sent back into the pipeline and, once it reaches pressure, the blowdown valve is opened once again to vent the atmospheric air. Once all the air is removed, the blowdown valve is closed. The line is then pressurized to its normal operating pressure.