Natural gas safety

ScottC1

After the disaster that occurred in Massachusetts recently involving explosions in homes due to system over pressurization, is there a mechanism that can be added to home system that would prevent this from happening? I live in Maine and want to switch to Natural gas but have safety concerns.

pecmsg

That’s like asking for protection from over voltage situations. Can it happen yes but the checks should be in place to prevent situations like that from even coming close!

Intplm.

Can't always protect from bad work ethic? or incompetence or ?
What happened in Mass. isn't a common problem. It's good to be safe but many have all the protections that are available from their utility.
And what @pecmsg said.

EBEBRATT-Ed

You certainly could install a gas pressure relief valve on your main gas line and pipe the vent to a safe location.....but not a remote location. If it leaks you want to know.

GBart

The concept is that natural gas to residential is never supplied over 14” w.c. (0.5 PSIG) but most residential units state that the inlet pressure should be 5-7"wc, etc.

There has been industry argument over whether or not residential should require regulators with OPD ( over pressurization devices) which vent to the atmosphere. Commercial units have these because pressure inside the building lines going to the units can exceed .5PSIG.

The technology exists, it's just not used in residential, and the vent has to be outside. see attachment

http://www.follinflo-controls.com/PDFs/Tech.Sheets/Reg_Opp.pdf

Jamie Hall

Dunno. Maybe it's just me, but if I were a gas company about the last thing I'd want is the liability of a pressure relief valve with a vent to anywhere in a residential setting.

On the other hand, is there such a thing as an overpressure shutoff valve which shuts and stays shut when an overpressure on the upstream side is experienced? That would do it if it were outside somewhere...

Tim McElwain

Simple answer is an excess flow valve buried in the ground with the service coming into the house or building. If the flow exceeds the designed load in the house it slams shut and must be reset by a professional from the gas company. They have them on Propane delivery Bobtails in case of a drive away while filling. It immediately shuts of the flow and has to be resent.

EBEBRATT-Ed

They have "excess flow valves" on commercial natural gas jobs around here.

I would have no issue with a PRV relieving gas to the outside of a building.

The alternative is what happened in The Merimack Valley last Fall.

I would rather see excess pressure relived outside than have the excess pressure in the building.

Put excess pressure inside the building and it reaches the flame things go boom. Or it blows the regulator and leaks through the diaphragm and the gas is inside the house if the regulator can contain it

GBart

Jamie Hall said:

Dunno. Maybe it's just me, but if I were a gas company about the last thing I'd want is the liability of a pressure relief valve with a vent to anywhere in a residential setting.

On the other hand, is there such a thing as an overpressure shutoff valve which shuts and stays shut when an overpressure on the upstream side is experienced? That would do it if it were outside somewhere...

They are vented outside, the gas co meter/regulators vent right out of themselves, right outside your house, NG rises when it leaks..........now LP would be an issue but we don't LP doing an entire town/city from central piping.

ScottC1

This is all very helpful input. Thank you for taking the time to comment. Sounds like I should have a discussion with my gas company, voice my concerns and see what they recommend. It is invaluable to have these insights before having that discussion.

Intplm.

@IamNotLost thanks for sharing. These events are always a reminder to have the greatest respect for gas and gas installations.
Recently in RI (not a explosion) . The one in Mass. a few months ago and there is one that happened in Ct. Near Farmington in the mid to late ninetys that leveled what I think was a condo complex. Never saw a report as to what caused that one.
I'm wondering why the causes always seem to take so darn long to be released? As in the video you shared.

Lance

While one might think a pressure reducing control could prevent this, it cannot. A proper solution would be a relief valve designed to handle the volume of gas on the pipe size at that pressure. Of course lighter than air gas would have to be vented above the building. Codes may not be written for the homes, but this is how the gas pump stations are protected. I have seen gas blow off at high pressure, noisy and dangerous. Any spark, static or otherwise would make a torch. And radiant heat will be hot. Think oil well fire! Still it might be an option. Might cost a lot too.
We live with danger we know not from where or when every day.
Even overpressure water has its dangers.

Leonard

YIKES.....NYLON bolts!!!!
Can't afford stainless steel?

(From 1-st link , 3 posts up)

JUGHNE

Perhaps the coefficient of expansion and contraction more closely matches the rest of the "plastic" materials than SS might?

mikeg2015

We had a regulator freeze up and was supplying a full 2psi to the regulators on gas furnaces in 2 apartments. The regulator in one unit “locked up” and wouldn’t even open. the other furnace was running over fired. Not sure what pressure it took to blow up lines in a home. I would think the regulator at the meter would lock up and beyond that the regulator on the appliance would lock up. It does make a good argument for threaded black pipe instead of CSST or trac pipe, since threaded black pipe can probably handle 100psi+ without failing.

Tim McElwain

It depends on the gas system. Older systems that did not have redundant gas valves are typically the ones that will allow higher pressures to be experienced on burners. That was why in 1979 redundant (dual seated) gas valves were mandated on all new equipment produced after 1979. Example an older Honeywell valve would be a model V800A a redundant would be a VR8300A. The "R" tells you it is redundant.

Most in line gas regulators (newer valves the regulator is built into the gas valve) used on older equipment were designed to lock up at 14" W.C. roughly a 1/2 pound of pressure. I have however found that some versions were better than others in fulfilling that function.

Most utility regulators installed ahead of the gas meter will with excessive pressure have the internal relief activate and the gas would be released through the vent on the regulator. They typically do not lock up like propane regulators do.

Jamie Hall

"I'm wondering why the causes always seem to take so darn long to be released? " -- @Intplm. It's because it takes a long time, and a lot of research -- both in the initial field investigations and in later reviews and often laboratory testing -- to determine all of the factors that may have led to the problem. The investigators -- such as the NTSB in the US or TSB in Canada -- aren't just interested in the proximate cause, nor are they even slightly interested in assigning blame (in fact, their reports cannot be used in a court of law). They want to know all the factors which led up to -- and often things that followed -- and understand them, so that safety can be improved.

It has been said -- and it is true -- that the drastic improvements in safety in aviation and the rail industry are "written in blood", and it's true. By learning what went wrong we can learn how to prevent it in the future, or at least try. It's notable that the highway industry -- particularly passenger vehicles -- usually have no such investigations; just lawyers pointing fingers.

Intplm.

Very well put @Jamie Hall . You have explained this well as many explainations before. Thank you.