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Minimize Nat Gas Releases

Minimize Nat Gas Releases

RE: Minimize Nat Gas Releases

back in the 90's, i stuck my head in a compressor cylinder and smelled/heard the gas leak from the unit discharge valve. once repairs were made, i arranged a leak test using a plastic bag, cardboard box, and watch. although crude means/methods were used, the resultant leak value was $250k/year. this got the attention of the operators and other techs. eventually, they got a 2" daniels turbine meter w/ proper up/downstream pipe lengths and flexible hose to conduct a survey of other vents throughout the pipeline system. this little exercise opened up a lot of eyes into how much gas was venting to atmosphere. needless to say, valve maintenance activities picked up resulting in less gas loss. i would imagine there are other methods of monitoring gas leaks these days - ultrasound devices?

a matter to deal with is the gas loss during emergency blowdowns or pipeline blowdowns. a method used for pipelines is isolate the pipeline section and allow metering stations draw down the pipeline pressure. this takes time and having the pipeline down that length of time can impair pipeline capacity. another method i've also seen a portable 3-stage unit draw down the pipeline pressures, but this is an added expense and time-consuming task.

it'd be interesting to hear what operators do these days.

RE: Minimize Nat Gas Releases

I dont know a lot about detecting gas leaks, but I have heard of infrared detectors, sniffers, ionisation techniques. Its not difficult. Google equipped some of their Streetview vehicles in Boston and 14 other cities with sniffers of some kind a couple of years ago and came up with some astounding results. Something like 1 to 2 leaks per mile of gas distribution pipelines were found A major replacement program was begun shortly thereafter. Boston is not the only city affected. The problem is that the distribution companies were not taking it seriously, since the customer pays for losses, and they were prescribing ridiculously low budgets and using schedules extending 20yrs to "fix" that issue.

The data for all cities can be downloaded.
Birmingham, Boston, Burlington, Chicago, ConEd New York, Dallas, Indianapolis, Jacksonville,
Los Angeles, Mesa data, PSE&G New Jersey, Pittsburgh, Staten Island, Syracuse.

Simulation software is also used to model ideal flows and check against real-time SCADA input variables for evidence of leaks when pressures and flows between the two dont add up. They also keep a check on running totals at purchase and sales meters where even very small discrepancies can be detected oner many months.

As far as larger transmission pipelines, blowing down gas to atmosphere is the last thing that they want to do. Generally the line pressure is reduced to as low a pressure as possible through normal means during periods of low demand to make repairs. Any gas that can be evacuated by other means, usually portable compressors, are employed. Only the minimum amount of gas necessary is ultimately vented and displaced by N2, if needed. The vast majority of their gas losses are through antiquated equipment, valve packing, pneumatic control valves and the like. Most companies have been replacing as much of that as they could since the early 90s with electric operators when possible. Occasionally operational overpressure will trigger a blowdown vent, but that is not often and it is a hugh problem for the section manager to justify the lost gas to the VPOps. Losses must be explained in detail to the FEDs as well.

During the last four years, increases in gas field flaring were allowed, but I think that Presidential Order was rescinded on day #2, Jan 22. I think some fields are still doing this, but are attempting to comply ASAP.

RE: Minimize Nat Gas Releases

The UK started some of this 20 years ago replacing cast iron mains, some of which were laid in the 1800's or early 1900's for town gas. The safety regulator gave then 30 years to do it.

There's anecdotal evidence I've heard that said about that time that 10% of all gas metered into Wales ( pop about 3.2 millon) wasn't metered on the way out.

Also even if an operator found a pipe or junction and they didn't know where it went, if gas was still flowing in it they couldn't just shut it off.

Occasionally the iron pipes had completely rusted away and all you had was a hole in the earth....

The old style regulators driving valves could often be heard hissing away in remote enclosures. Not much leakage, but over the course of a year could certainly add up.

Pipeline blowdowns are pretty rare and yes, over the last 10-15 years at least, only the last dregs are free vented, the rest is sucked out and compressed into the downstream section. both from a commercial and environmental view point it makes much more sense now to conserve the gas and not just stick it up the stack.

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