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#308482 - 09/14/18 03:40 AM ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame
NW Ponderer Offline
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Carpal Tunnel

Registered: 09/09/11
Posts: 16454
‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame. This is a major event. I admit, my first thought was that this was a "test run" for an infrastructure attack. shocked
Quote:
An expert in natural gas distribution says “over-pressurization” may be to blame for the more than 70 gas-related fires and explosions in Lawrence, Andover and North Andover Thursday night.

Mark McDonald, president of the New England Gas Workers Association (NEGWA), says that a failure in the primary and secondary pressure regulators along the gas distribution lines may have caused the explosions that ignited more than 70 homes across those three towns.
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#308484 - 09/14/18 04:01 AM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: NW Ponderer]
Greger Offline

Pooh-Bah

Registered: 11/24/06
Posts: 14490
Loc: Florida
'at's worse than a feckin Sharknado. Jeeex. Gas is scary but it seldom fails.

A few years ago we had a nearby Blue Rhino gas plant explode. 53000 20 pound tanks of propane. It lit up the sky.
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#308486 - 09/14/18 06:55 AM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: NW Ponderer]
pondering_it_all Offline
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Registered: 02/27/06
Posts: 8162
Loc: North San Diego County
The nice thing about electricity: We assume it's dangerous so we put fuses and breakers at every possible point. Over-voltage on a distribution line would immediately blow a big honking fuse, and everybody downstream would be fine. We design the infrastructure so it can take lightening hits with minimal damage.

You don't think about it, but all the transformers along the way are power-limiting devices too. So too much voltage will blow a transformer.

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#308510 - 09/15/18 07:44 PM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: pondering_it_all]
Jeffery J. Haas Online   sick


Pooh-Bah

Registered: 08/03/04
Posts: 13505
Loc: Whittier, California
Originally Posted By: pondering_it_all
The nice thing about electricity: We assume it's dangerous so we put fuses and breakers at every possible point. Over-voltage on a distribution line would immediately blow a big honking fuse, and everybody downstream would be fine. We design the infrastructure so it can take lightening hits with minimal damage.

You don't think about it, but all the transformers along the way are power-limiting devices too. So too much voltage will blow a transformer.


There was "a failure in the primary and secondary pressure regulators along the gas distribution lines"...the regulators ARE the so called "fuses" except instead of "opening" the circuit they close the circuit.
The electrical equivalent would be a protection diode, which short circuits if DC polarity is reversed, and the resulting short circuit is supposed to blow a fuse or trip a circuit breaker, thus protecting the circuit board components from being fried.

A primary or secondary gas pressure regulator in a residential pipeline system is indeed a "big honking" unit, and federal regulations require they be inspected (and replaced) at regular intervals. It is awfully difficult to imagine BOTH a primary AND secondary regulator for an entire city infrastructure failing so badly for no apparent reason.
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#308512 - 09/15/18 08:51 PM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: NW Ponderer]
pondering_it_all Offline
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Registered: 02/27/06
Posts: 8162
Loc: North San Diego County
And I don't see any reason they would be controlled online, they operate at fixed pressures. So they could not be hacked. You might want shut-off valves to be controlled remotely or even automatically if something goes wrong. But that would just let hackers shut off the gas, not change the pressure settings. Maybe it was a cascading failure: The high pressure one failed and the resulting high pressure in the line blew out a lower pressure regulator downstream.

The big question is: If regulators fail open, why would you not include over-pressure sensors and automatic shutoff valves in the line?

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#308513 - 09/15/18 10:53 PM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: NW Ponderer]
logtroll Offline
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Registered: 04/26/10
Posts: 8935
Loc: New Mexico (not old Mexico)
Something's definitely fishy about this. What pressure regulators do is regulate pressure. That happens multiple times in a gas distribution system with incremental stepping down from the source (over 1000 psi), into smaller branch lines, again into smaller branch lines, finally down to less than 10 psi at a residence. As mentioned above, regulators are designed to close as pressure rises, though there may be some inlet pressure that could"blow" the valve. But the ultimate safety device is a pop-off vent that will relieve pressure somewhere besides inside the house.

If I had to guess, I'd say that some unscrupulous contractor saved some money on safety valves while some crooked or incompetent inspector stood by - then years later some gas company workers screwed up and over-pressurized the feeder lines and the ultimate system failure happened in those homes.
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#308514 - 09/15/18 11:03 PM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: logtroll]
logtroll Offline
veteran

Registered: 04/26/10
Posts: 8935
Loc: New Mexico (not old Mexico)
Could have been a batch of faulty valves, too, that were never stressed until now.

Apologies to the imaginary sleazy contractor and crooked inspector... blush
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#308517 - 09/16/18 05:52 PM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: logtroll]
pondering_it_all Offline
veteran

Registered: 02/27/06
Posts: 8162
Loc: North San Diego County
Quote:
If I had to guess, I'd say that some unscrupulous contractor saved some money on safety valves while some crooked or incompetent inspector stood by


Well, this is Boston we're talking about.

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#308538 - 09/17/18 04:42 AM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: NW Ponderer]
pdx rick Offline
Member
Carpal Tunnel

Registered: 05/09/05
Posts: 41100
Loc: Puget Sound, WA


What I find odd is that the explosions were random in which houses where blown apart. Hmm
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#308543 - 09/17/18 07:57 AM Re: ‘Unprecedented’: Natural gas expert says ‘over-pressurization’ may be to blame [Re: NW Ponderer]
pondering_it_all Offline
veteran

Registered: 02/27/06
Posts: 8162
Loc: North San Diego County
Not odd: When you stress stuff like gas regulators in parallel, some are going to fail at lower pressure than others. As soon as enough fail, the pressure in the line goes down and the rest of the regulators then don't fail.

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