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dogsridewith
14th Sep 2018, 14:24
https://www.theguardian.com/us-news/2018/sep/13/massachusetts-gas-explosions

Sixty to one hundred homes in different neighborhoods north-west of Boston simultaneously caught fire and/or exploded, w/ one person killed by a falling chimney.

Individual buildings exploding due to gas leaks seem to make national news here a couple times a year, but this is obviously something different--a gas line pressure spike was mentioned. Also that it might take days or weeks to determine the cause. But it shouldn't take long to reveal whether the distribution pressure regulators were old...or new web-connected devices, which opens possibilities such as Iranian retaliation for their problems w/ centrifuges controlled by internet-connected computers?

(note: this story is not on the USA-Guardian's home page. The following one is, and is #3 on most-viewed--"Rat in a hot pot wipes millions off Chinese restaurant chain's value.")

CloudHound
14th Sep 2018, 22:30
Cheers!!!!!!!

Um... lifting...
14th Sep 2018, 22:57
A number of neighborhoods are under mandatory evacuation and have had their electricity cut off. I know a few people who this has impacted directly.

Gas utility personnel and firefighters have been manually turning off gas valves at the pipeline source. The only silver lining is that it's not February.

tdracer
14th Sep 2018, 23:27
(note: this story is not on the USA-Guardian's home page. The following one is, and is #3 on most-viewed--"Rat in a hot pot wipes millions off Chinese restaurant chain's value.")
I think you need to find a new news home page. It was the lead story last night on att.net ...

lomapaseo
15th Sep 2018, 01:08
What I've heard from elsewhere is that someone managed to connect a high-pressure line to a low-pressure network with no regulator in between. Net result is a whole load of appliances failed and if they're really unlucky, a few ruptured underground pipes too.

I don't see much liklihood in underground pipes going bad from an overpressure. Much more lilkely that the end point on a line such as a jet nozzle where the pressure drops and the gas expands is the problem area.

Very large flame front or it snuffs itself out and fills the house with the excess gas.

There probably are some safe guards in the houses good for 95% reliability but the other 5% would match what's in the initial reports

EEngr
15th Sep 2018, 02:07
The mis-connection sounds plausible. Back in the 'old days', gas systems had a system-wide regulator which dropped an entire neighborhood's delivery pressure to a fraction of a pound (typically measured in inches of water column). Newer systems, like my neighborhood, distribute gas at 50 psi (or more) to regulators located at each house meter. Some news reports mentioned Boston being in the midst of a system upgrade. It's possible that they overlooked some houses for the installation of regulated meters before stepping the pressure up in the distribution line.

dogsridewith
15th Sep 2018, 03:55
Thanks for insights preceding main-stream news.

This event is interesting in Pennsylvania where property owners are expressing safety and environmental concerns over a big new cross-state Sunoco gas line(s) to get fracking product to the Atlantic Ocean for shipping overseas. (One rural lady w/ a couple acres impacted did demonstrator stuff that may have included the live-in-trees-to-be-removed sort of thing...her charging papers said she put out bait to lure in dangerous animals to scare pipeline workers. Construction was shut down for awhile by authorities due to quality issues.)

Why is USA sending finite fuel resources overseas when importing same was the greatest trade-balance problem not so long ago?

tdracer
15th Sep 2018, 04:37
Why is USA sending finite fuel resources overseas when importing same was the greatest trade-balance problem not so long ago?
Thanks to fracking, the USA is producing a surplus of natural gas. Since storing the stuff isn't trivial, they are looking to export it. While some wells produce mainly natural gas, most produce a mixture of petroleum and gas - so shutting off the well isn't an option if they want the oil.
At current trends (increasing petroleum production and decreasing demand) the USA could well be a net oil exporter within a few years. The USA already exports some oil to ease distribution - where the oil is produced is not generally where it's needed, so it's cheaper to export some of the domestic oil in some areas and import it in others than to try and distribute all the domestic oil for domestic use.

dogsridewith
15th Sep 2018, 12:09
Thanks for expressing that reason well. But then I say "Hook...me...up." (and run fiber-optic internet/phone/TV cable, and a super-potable drinking water supply in the same trench) We installed electric and phone lines in every home and business in a big country w/ a low average population density, and many or most all got sewer, TV and gas. (Utilities installation is stalled generally, w/ one of my own state governors installing free internet through-out Philadelphia--biggest city and his political origin--then signing a bill making illegal any municipal installation of internet.)

I get the politics of coal miner and mine owner politics, but long term it would make sense to conserve that stable and useful fuel, and burn the gas here...as clean-coal combustion and robot-mining technology progresses.

I'm in a rural area w/o fast internet and w/cell-phone dead areas, but could literally watch three tubes of trans-atlantic fiber-optic being installed by horizontal drilling during the Obama economy-stimulation era. Natural gas is moving closer...to within 15 miles or so.

tescoapp
15th Sep 2018, 17:58
If someone has connected a 99 psi to the domestic local supply which is normally 2 psi then the whole network is screwed.

Supply pipes will be well into the plastic range more than likely fast fracture split as well. All regulators that were attached to it will need to be replaced. Every house will have one take 2 psi down to 1/3 PIS.

There is going to be pockets of gas underground everywhere.

The trunk pipelines in the USA, the routing, the design codes they use and the operation of them are a different issue entirely. A lot of them its seems to be "it will be someone else's problem" to sort the obvious outcome out in 10-15 years time. BTW they are at 500 to 1500 PSI.

You can say at least its not Feb I would be extremely surprised if they have sorted it by this time next year. If I was living there I would be getting 3-4 bottles of gas delivered and replacing them as they are used up keeping a couple as backup all the time. Basements etc I would be installing gas detector alarms even if not connected. The stuff is going to be working its way out for months.

lomapaseo
16th Sep 2018, 00:54
If someone has connected a 99 psi to the domestic local supply which is normally 2 psi then the whole network is screwed.

just what pipe size and factor of safety are you assuming

dogsridewith
16th Sep 2018, 13:51
Prior comment on "pressure spike" has turned to zero content regarding cause by major network TV. Headline is NTSB predicting up to 2 years for a final report. News reports that most or all are now allowed to return to homes. Zero content on ability to use gas appliances therein, inspecting them, or times involved.

dogsridewith
16th Sep 2018, 13:55
If someone has connected a 99 psi to the domestic local supply which is normally 2 psi then the whole network is screwed.

Supply pipes will be well into the plastic range more than likely fast fracture split as well. All regulators that were attached to it will need to be replaced. Every house will have one take 2 psi down to 1/3 PIS.

There is going to be pockets of gas underground everywhere.

The trunk pipelines in the USA, the routing, the design codes they use and the operation of them are a different issue entirely. A lot of them its seems to be "it will be someone else's problem" to sort the obvious outcome out in 10-15 years time. BTW they are at 500 to 1500 PSI.

You can say at least its not Feb I would be extremely surprised if they have sorted it by this time next year. If I was living there I would be getting 3-4 bottles of gas delivered and replacing them as they are used up keeping a couple as backup all the time. Basements etc I would be installing gas detector alarms even if not connected. The stuff is going to be working its way out for months.

What about all the gas appliances and gas plumbing in these homes?

Is bottled natural gas a common thing? Propane is a common bottle gas here, and appliances need re-jetting to convert from natural gas.

tescoapp
16th Sep 2018, 14:29
Will be for local safety officers to decide.

I would say if your inlet regulator/gas meter has survived then it will be ok. But the supply pipe may have split further up the line and I would be worried about gas working its way out along the pipe into where the pipe enters the building.

If it's been blown off they will likely disconnect and pressure test and if no leaks deem it ok. My family in the building I would take it a bit further than that but I doubt they will unless legally forced to .

Don't have a clue what's available in the usa. Search for bottled methane. It's got a lower calorific content. The bottles are 4 times heavier than propane.

Search for CNG bottle

Turbine D
16th Sep 2018, 15:35
Original Quote by lomapaseo
I don't see much liklihood in underground pipes going bad from an overpressure. Much more lilkely that the end point on a line such as a jet nozzle where the pressure drops and the gas expands is the problem area.
Leakage is dependent on various factors and overpressure is one of them. First and foremost, about half the underground pipes in the Boston area are among the oldest in the US, well over 50 years old and are made of cast iron which isn't exactly corrosion proof as it ages. An assumption alway is that the lengths of pipes are welded together, but that isn't necessarily the case. Many are joined by coupling devises. Our neighborhood in Ohio is 50 years old and when the gas lines were installed coupling was the preferred pipe joining method. Today nearly all of the couplings have required replacement due to leakage along with some of the pipes that showed signs of corrosion. Especially in the wintertime on a cold night with no wind, you could walk around the neighborhood and get a whiff of natural gas in various locations. The utility company is quite responsive in making repairs when potential leak problems are reported.

Another consideration is how the gas line enters the home or business. When we lived in New Jersey, the gas meter was in the basement of our home and the pipeline entered directly underground into the basement. In Ohio in our residential area, all the gas meters are external and above ground. It is a good safety feature.

RatherBeFlying
16th Sep 2018, 17:32
The gas main in my older Toronto neighborhood was huge. They had to dig down to it when I installed gas furnaces, previously electric wallet suckers.

With that volume, I would imagine that it would take a while for a regulator failure to overpressure a local distribution network. Someone was sleeping at the switch.

tescoapp
16th Sep 2018, 20:59
just what pipe size and factor of safety are you assuming


Basically anything that's covered by ASME B31. The domestic supply will be covered by ANSI Z223 now if its new.

Piping codes are a bit funny because the stresses you get out the code are not actual stresses, there is also a presumption that the pipe is going to work harden with plastic ratcheting.

I mostly worked with ASME 31.7

The safety factor with these codes is very hard to define because they were created in the 1935's before fatigue, critical crack intensity creep and plastic ratcheting was understood.

I can only presume that everything will be in code for a 5 PSI system which would be normal because there is not much point going for less as that's the max domestic regulators can usually handle.

But in any case the code does not cover this situation which is a dynamic blast of pressure.

A normal safety factor for 5 PSI would be x1.3 so pressure 6.5 PSI, the stuff I used to do was 1.75 so would be 8.75PSI. The codes would then have other safety factors built in and also a corrosion factor over life span.

99PSI is more than 10 times the safety factor for ASME 31.7.

Because the flow would be high velocity with no restriction initially the flow would mean dynamic mass effects would be encountered so when it hits regulators they will take fractions of seconds to fail and release it will send shockwaves back up the supply which will then create pressure boosts.
The whole system will never get anywhere near 99PSI things will have started failing when the end point got over 8-10 PSI what transient pressures you would have got in the supply pipes I haven't got a clue. I doubt very much anyone else has a clue either. You have a whole network now that been massively over loaded well outside design codes you have zero clue what state all the components are in.

When we test pipes and components we normally do it hydrostatically. Ie fill the object up with water then put a very little bit of compressed air in at safe high point and bring it up to the test pressure and then go through the proofing cycles to work harden it. If something fails, because water is deemed incompressible (you can compress it but its not much) then the amount of energy in the system is only in the small volume of gas that you have injected. There is a bang when it lets loose and the pressure quickly drops, there will be structural elastic energy released as well but not much work occurs and things won't be imparted with much kinetic.

Some pillock agreed to do a live pressure test (ie no water) and did the numbers and built up a system test with about 4m3 of gas involved. They didn't do the calc's on every spool and flange. And they certainly didn't do the calc on the inlet flange with valve assembly hanging 90 degs to its normal orientation. due to high volume its was going to take ages to pump the gas in. High volume compressor could do up to 50 bar so went with that. For the last 20 bar he decided to use a high pressure bank at 100 bar. Threw the handle for the last 20 bar and bang.. At the dead end on the system the pressure got to 60bar the last pressure reading at the inlet was 120 bar. 80kg of flange and valve exited the workshop through the roof heading out across Aberdeen bay straight towards the what I now know as the approach for Aberdeen Airport. I worked it out that there was over 80 MJ's of energy in the system approximately 20kg of TNT. I also worked out that the lump of metal made about 3000ft and splashed down nearer Stonehaven to Aberdeen.

I am sure the fluidologists can give you some numbers of the pressure peaks in the system. They will be well outside any design codes or even add a bit on for mum safety factors.

well over 50 years old and are made of cast iron which isn't exactly corrosion proof as it ages

Brittle as hell as well. Just think what happens when you smack one with a hammer.

With that volume, I would imagine that it would take a while for a regulator failure to overpressure a local distribution network


Depends on how much supply is on the other side, bigger the pipe the higher the velocity of the gas which means more dynamic momentum effects.

As some people seem to think better in electricity terms. Just think what would happen and what you would have to check/replace if someone managed to put 1100 Volts into the domestic electricity supply. And if at any point you think a fuse would protect that.... remember there are no equivalent of fuses in domestic gas supplies.

dogsridewith
17th Sep 2018, 02:07
Wow. If you're interested in a bit of consulting or, to use a new expression, "side hustle," send that post and your resume to the utility named on the area's gas bills. And to NTSB (if I got that right as the investigating government entity.) Seriously.

tescoapp
17th Sep 2018, 06:14
nah there are a lot more qualified people in this stuff out there than me.

This is first year mechanical engineering stuff.

This will be in the hands of lawyers now. And they will each have huge pools of "experts" with collectively hundreds of letters after their names. It will end up with a pentangle or more of interested parties with 2-3 insurance company's involved as well. It doesn't sit well with my engineering ethics either.

Just go and have a search what is happening to the Miami Bridge investigation to see why no pilot in their right mind would want to go anywhere near it. Its not like a bit of project engineering work on the side with a defined goal at the end.

If your mind works in a certain engineering way its fairly easy to envisage what will have happened and how things will have evolved. Putting it into hard numbers will take years with a certain amount of WAG estimates.

If you want side hustle invest in a load of piping gear and hole digging plant there is going to be a load of pipelaying needing to be done. Buy a load of methane domestic detectors CO and fire detectors and set up a service for installing safety alarms in peoples buildings. Drill and some screws and a few tubes of no nails and your good to go.

tescoapp
17th Sep 2018, 06:56
BTW the chat round the engineering circles is they were doing work on the main high pressure supply regulators (which there are a couple) after this there is meant to be over pressure protection down stream of. Its basically a rupture plate backup and valve linked to a venting stack. The main high pressure supply is at over 60 bar huge diameter of pipe and colossal volume.

If the pressure relief system didn't work or it didn't have enough capacity hasn't been released. It seems its a cascade of failures more than likely dating back years.

belfrybat
17th Sep 2018, 23:09
Were there no pressure sensors and switches to trigger alarms and protections?

tescoapp
18th Sep 2018, 15:30
Of course there were. Just like there was in Chernobyl.