New Facility Purge -- (Purge Oxygen with Fuel Gas)
New Facility Purge -- (Purge Oxygen with Fuel Gas)
(OP)
Specific Question: Is it safe to purge a new production facility of air using fuel gas?
Background Information
1. The facility is for oil production in a corrosive environment. Pipe is internally coated or stainless steel to address CO2 in the production stream.
2. CO2 is available for purge gas but would require a heater due to the high pressure and resulting freeze effect from dropping the pressure.
3. Nitrogen is an option for purge gas that comes at 4x the cost of fuel gas (accounting for the trucking and other fees)
4. Fuel gas is readily available and appears to be the cheapest solution.
5. Received some feedback/opinions on the operations recommendation to purge three times with fuel gas (pressure up to 100 psi and bleed down). I need help to validate these...
5A) Partial pressure of air would be too low to create an explosive mixture
5B) There is no ignition source. A static charge is not likely with fuel gas because of a lack of sufficient friction. Static charge would be "expected from an ethylene mixture that decomposes more in transport"??
5C) Pressure up and vent is better than a clearing purge due to the multiple branches and only two main vent stacks.
I would appreciate any experience to fill in the gaps? I have heard from a number of people that "it is common practice and not an issue". I personally need to improve my comfort factor with it.
Background Information
1. The facility is for oil production in a corrosive environment. Pipe is internally coated or stainless steel to address CO2 in the production stream.
2. CO2 is available for purge gas but would require a heater due to the high pressure and resulting freeze effect from dropping the pressure.
3. Nitrogen is an option for purge gas that comes at 4x the cost of fuel gas (accounting for the trucking and other fees)
4. Fuel gas is readily available and appears to be the cheapest solution.
5. Received some feedback/opinions on the operations recommendation to purge three times with fuel gas (pressure up to 100 psi and bleed down). I need help to validate these...
5A) Partial pressure of air would be too low to create an explosive mixture
5B) There is no ignition source. A static charge is not likely with fuel gas because of a lack of sufficient friction. Static charge would be "expected from an ethylene mixture that decomposes more in transport"??
5C) Pressure up and vent is better than a clearing purge due to the multiple branches and only two main vent stacks.
I would appreciate any experience to fill in the gaps? I have heard from a number of people that "it is common practice and not an issue". I personally need to improve my comfort factor with it.
Talk To Other Members
RE: New Facility Purge -- (Purge Oxygen with Fuel Gas)
HAZOP at www.curryhydrocarbons.ca
RE: New Facility Purge -- (Purge Oxygen with Fuel Gas)
RE: New Facility Purge -- (Purge Oxygen with Fuel Gas)
The Chemical Safety Board video
http:/
covers its investigation of the explosion. The first 8 minutes involve a heater maintenance case. The 2nd case in Middletown, Connecticut covers the power plant explosion resulting from the gas blow starts at 8:00 minutes into the video.
The board's conclusion is that gas blows are a "common but dangerous practice".
I suspect that the economic factors cited will determine which method is used. I just don't want to be nearby or on-site the day when a gas blow purge occurs.
RE: New Facility Purge -- (Purge Oxygen with Fuel Gas)
HAZOP at www.curryhydrocarbons.ca
RE: New Facility Purge -- (Purge Oxygen with Fuel Gas)
Now we have a new document nfpa 56 which expects people to look for aircraft in the area before purging, OVERKILLLLL.
Using nat gas is best, but we sometimes use a bottle of N2 between the air and nat gas, cheap insurance.