1:46:44 break ends, meeting resumes

What surprises me here is that there isn't a downstream pressure sensor directly built into the regulator itself. If there had been - and even if it was set to a slightly higher pressure to allow for flow losses - then having a single remote-sensing line connected to the wrong pipe would not have led to a catastrophic overpressure event. This is just common sense, and there are similar pressure regulators (albeit of lower flow capacity) fitted to every portable gas bottle in use. Similarly, I would expect the flow rate to be regulated as well as the pressure. An unexpected jump in flow rate seems likely to indicate a serious gas leak and should logically trigger a shutdown of that valve, along with an alert that such a shutdown has occurred and a telemetry log of the event. …of course, *now* I see that this is addressed in the second half of the meeting.

@Live.Vibe.Lasers

4 жыл бұрын

if the sensing lines are sensing the low pressure system far from the regulator...isn't there pressure drop on the sensing line itself that needs to be taken into account? how does that work in physics? Higher pressure has proportionally lower pressure drop than low pressure if all else is equal? Is this considered hydrodynamics?

@Kromaatikse

4 жыл бұрын

@@Live.Vibe.Lasers Pressure *drop* is the product of flow rate and resistance to flow, much like resistance in an electrical circuit, in which V=IR in Ohm's Law. Sensing lines are designed to have no flow in them (under normal conditions) so the pressure at both ends is the same. You sometimes see something similar in electronics, when the point at which voltage has to be regulated or sensed is remote - there may be additional thin sense wires, not carrying current.

@Tadesan

2 жыл бұрын

Yes absolutely! With a small bit of intelligent forethought, cleverness, and simple sensors, most systems can be made very safe and effective. People simply quit before it comes to that level of excellence.

burst disc and automatic flare of low pressure system?

My question is. From an emergency point of view. Does the utility company have outside regulators with shut off on the exterior of the home where this is involved?

@Kromaatikse

4 жыл бұрын

I'm pretty sure there is a shut-off valve per home served, adjacent to the supply meter. That valve is intended to permit piping work to be carried out inside the home. However, using them to mitigate an overpressure event would require operating several thousand valves, which is impractical in an emergency of this type. The most serious damage was initiated within a few minutes of the event, when the high-pressure gas reached appliances which couldn't withstand it.

@BienvenidoEspinal

4 жыл бұрын

Since this is a low pressure system there wouldn't be a need for regulators outside of each home. Had the system been high pressure than each home would've been fitted with a service regulator to cut the pressure down to low pressure. The service regulator does have automatic pressure relief in the case of overpressure of the customers piping.

@boby115

4 жыл бұрын

@@BienvenidoEspinal you are correct. This was a low pressure system ,there would have been no Regulators installed at any of the gas meter sets. The Meters would have been located inside the structures with one shut off valve being at the meter and the other at the curb inside a valve box requiring something called a Street Key to turn off the gas.This incident was caused by poor procedure training and inexperienced employees performing work on something they did not have full knowledge of. A good analogy would be a doctor trained in bypass surgery but never went to medical school to learn the function of the whole body. This incident would have never happened with proper procedure training like we have at the gas utility in St Louis, Missouri. We use monitoring gauges any time a gas main is by pasted . The gauge points would be set up Downstream, Upstream and if we felt the need one at the repair point ( by pass). We would constantly monitor these gauges noting any changes in pressure and taking immediate corrective action. By Columbia Gas and it's contractor not using $60 worth of gauges it cost a man his life, numerous injuries & 1 billion dollars. My experience comes from 35 years at the gas company in St Louis, Missouri. I am now retired and consult from time to time on gas incidents such as this one.

@Tocsin-Bang

4 жыл бұрын

In the UK there is a shut-off valve external to each property, plus typically a street valve. Inside the property there is a second valve, in addition to a pressure controlled shut-off.

@boby115

4 жыл бұрын

@@Tocsin-Bang , this was an extremely old system. In no way should you think this system is current technology in the United States. Columbia Gas was just in the process of maintaining some old infrastructure do to leaks on the old system. These neighborhoods were on schedule for full replacement in time. I can assure you the modern systems we install today in the United States are state-of-the-art ( excessive flow valves, polyethylene plastic services & mains on any pressure below 100 psi. ,Coated steel mains and services with any pressures 100 psi & above, when possible we try to locate all gas meters outside of structures, all Regulators installed meet today's highest standards, gas meters installed today are considered smart meters with Spike meter reading systems connected to our computer systems to alert us if any one of our customers has a usage over normal). A good analogy of your statement would be the cars in the UK have airbags and anti-lock brakes and you compare it to a 1930 Model A Ford in the United States; that would not be a fair comparison.

They were hot.....do you have anything Bruce ?

Wow Jennifer Homenndy lost a lot of weight, she looks great

@geoffbuck6865

4 жыл бұрын

Cindy Tepper: I think JH is very glamorous, but she scares me rigid - those eyes are so piercing!!!

@Tadesan

2 жыл бұрын

She’s so powerful! Love her.

I love the mission of the NTSB...but geez, seems like a snobbish group.

@twothreebravo

3 жыл бұрын

Really? They seem pretty easy going to me.