Protecting Sweet Pipeline from back flow when tying into Sour
Protecting Sweet Pipeline from back flow when tying into Sour
(OP)
It has been standard practice at our company to use two check valves on a sweet pipeline when tying into a sour pipeline in order to protect against back flow. I've been looking through all the codes I can get my hands on to find this as a requirement but can't find it written anywhere explicitly.
Does anyone know a code which would explicitly state the need for this double check valve to protect against back flow?
I've talked with the ERCB and they stated that they only required one unless the tie-in was specifically for the purpose of blending (at which point other regulations come in) but everyone here seems certain a code calls for two.
Does anyone know a code which would explicitly state the need for this double check valve to protect against back flow?
I've talked with the ERCB and they stated that they only required one unless the tie-in was specifically for the purpose of blending (at which point other regulations come in) but everyone here seems certain a code calls for two.





RE: Protecting Sweet Pipeline from back flow when tying into Sour
Let your acquaintances be many, but your advisors one in a thousand' ... Book of Ecclesiasticus
RE: Protecting Sweet Pipeline from back flow when tying into Sour
For safety-critical spec breaks, this seemed like the most cost effective way to be able to verify integrity in a place with no access to electricity or pressurized gas (the line was produced water). Without the means (and procedures, and schedule) to test the check valves there is no way I'd sign off on it being a spec break.
David
RE: Protecting Sweet Pipeline from back flow when tying into Sour
I assumed this would atleast be would in a some set of recommended practices like API.
RE: Protecting Sweet Pipeline from back flow when tying into Sour
RE: Protecting Sweet Pipeline from back flow when tying into Sour
While I don't want a building to fill up with sweet gas, I REALLY don't want it to fill up with sour gas. Either one would kill folks (either from an oxygen deficient atmosphere or from poison gas).
I was thinking that I have significantly more stringent design criteria for a sour pipeline than for a sweet pipeline. If I can provide a spec break between the two lines, then I can build the sweet line to the sweet spec and the sour line to the sour spec. Spec breaks are by definition safety critical.
David
RE: Protecting Sweet Pipeline from back flow when tying into Sour
Could be a wall thickness pressure safety issue over time, if you don't address a significant corrosion potential by one method or another.
It might be a product-material compatibility issue, if you chose your materials poorly.
Breathing 100% oxygen, or closing a 2" valve might be a safety issue too. Neither of those addressed by design codes either.
In any case, don't look for the two check requirement in the design codes. You won't find it.
Let your acquaintances be many, but your advisors one in a thousand' ... Book of Ecclesiasticus