Here's an interesting additional read, about a 54 year old pipeline that blew 12 years ago:

https://www.ntsb.gov/investigations/accidentreport...

I've read a number of NTSB reports; and, while I may not always agree with the findings, they do come across as clearly written and well presented. Especially compared to almost any other report on almost any subject.



spsalso

Prior thread - thread815-456392: Kentucky Explosion Enbridge's Texas Eastern Line

From the NTSB report summary:
Safety issues identified in this report include nonconservative assumptions used to calculate the potential impact radius, incomplete evaluation of the risks caused by a change of gas flow direction, limitations in data analysis related to in-line inspection tool usage, incomplete assessment of threats and threat interactions, and missed opportunities in training and requalification practices. Three
recommendations are made to Enbridge Inc., and three recommendations are made to the Pipeline and Hazardous Materials Safety Administration.

The pipeline had unidentified material problems that were visible in a reanalysis of 2011 smart pig data. Keeping old stuff safe requires more than the legal minimum of care.

It took me quite a while to work out how flow direction change impacted CP, but basically it ended up close to the compressor station and increased in temperature, causing the rather ancient coating to fail more than before and needing some big jumps in applied voltage. Hydrogen emission from presumably a coating defect at the hard spot then resulted in cracking and eventual failure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

LittleInch

This is one of the ancient cross-country pipelines being considered for injection and transport of the new green hydrogen.

Sixty year old coatings are failing, 1958 "hard spots" which are currently unacceptable in API pipe are endemic .

What do you think of these future plans ?

MJCronin
Sr. Process Engineer

MJC,

I've often been amazed at how thin and ancient some of the gas transmission pipes are in the US.

I wouldn't put Hydrogen, even at a few percent, in any of them. Hydrogen is interesting stuff and I really don't think a lot of existing lines are going to be suitable. You will though only find out a few years later as the cracking issue takes time.

But if you do and then 5 years later all these pipelines start springing leaks / rupturing you're going to be in trouble.

Hydrogen also has an annoying tendency to go BANG and not a fireball which is not widely appreciated at the moment.

It also catches fire / explodes with something like static electricity - 10% of the energy you need to make methane catch fire and a huge flammable range

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

I believe hydrogen only goes BANG when it's mixed with oxygen.

Unmixed, it burns. See Hindenburg. Exceedingly well. See Hindenburg.

I saw this demonstrated using soap bubbles: blow one with H2, quick burn--blow one with H2 and O2, BANG. Amusing, on a small scale.


spsalso

Ha,

The flames in the Hindenburg were coming out of very low pressure gas bags and were probably on fire from the word go. As soon as hydrogen comes out of the pipe it is mixing as it comes out with very high velocity. The hydrogen in the Hindenburg would have burned from the point of contact with the air and actually created a huge fireball above the air ship.

And the flammable range of hydrogen to air is about 4 to 75%.

So yes Pure 100% H2 burns if you can prevent it mixing. but once it's out of the pipe you can't stop it mixing. And given it's low density it mixes very well.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

MJCronin,

On using old pipelines for green H2, I refer to an old Project Engineer's rule of thumb passed down over the years, "it only costs a little extra to use used equipment". In this case though, it may cost much more than a "little extra" when future property and life loss is included.

This is more than a little scary.

Good Luck,
Latexman

Latexman, if it weren't for used equipment, I wouldn't get anything new at my site.

- Andrew

SuperSalad,

Oh my, I do know how that is. My current company seems to specialize in buying old existing plants/businesses. So I see a lot of operating equipment in their 2nd/3rd/4th . . . life. There's always a challenge!

Good Luck,
Latexman

Thank You LittleInch ... I appreciate your comments

.... and yes, I have an agenda....

I am a member of several groups that advocate the "reuse" of the cross country Natural Gas Pipelines for green hydrogen transport

I was aware that MBAs operate most of the pipelines at maximum design pressures and, after sixty years, not much is left of them...

Repeatedly I was criticised as an "old man without vision" and how could I be all "sciency" and that "somebody will think of something"

All unrealistic and deeply psychotic Horseshiit in my opinion ...

Sir, your comments, opinion and experiences confirm my technical assesment of the pipeline industry and doubles my resolve

MJCronin
Sr. Process Engineer

When the memphis I-40 bridge failed a few years ago, it was discovered that the welding procedures of 50 yrs ago did not adequately protect against hydrogen damage during the welding process. One may wonder if that same issue applies to the longitudinally seam welded gas pipelines that are yet being used.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

Because a lot of the issues with hydrogen are about cracking and accelerated crack growth plus hardness issues, the failures won't be immediate, but likely to be 5 to 10 years after gas starts flowing.

Stress Corrosion Cracking was a big issue in the 1960's and more recently Canadian pipelines were rupturing regularly from 1985 to 1995

So re use of lines of this sort of vintage are going to be an issue, but long after the people who decide have left....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

The Horror of "hard spots" in 60 year old piping systems, pushed to the absolute limit ..


https://www.wtvq.com/closer-look-fallout-of-2019-p...

"According to the NTSB report, Enbridge hired a company to test for hard spots in the Lincoln County area in April 2011. They calculated that there were 16 hard spots in a 19-mile segment between compressor sites....

Enbridge also rated the threat of hard spots in the specific segment that ruptured as 1.53 out of 10, with zero being a non-risk.

After the explosion, the NTSB directed Enbridge to measure again for hard spots. This time, with eight years newer equipment, the company found 441 hard spots along the same 19 miles.

The third party Enbridge hired said this was due to advances in technology.

The deadly rupture occurred at an overlap of two hard spots.

“These companies say that in-line inspection is just as good as bringing it out of the ground and looking at it. But we keep seeing these ruptures after in-line inspection,” Bill Caram, director of the Pipeline Safety Trust, said.



MJCronin
Sr. Process Engineer

16-441 Quite a difference.
Test runs should always be done when evaluating new technology.
If they supplied a few lengths of pipe with known hard spot locations and pulled the device through, they might have discovered it only found 4% of the defects.

Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

I see this all of the time in heat exchanger tube testing.
Don't do an ID ECT or UT if you are not prepared to extract tubes and verify the results.
Otherwise you are just believing in smoke.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

Re the hydrogen mixed versus unmixed...

I, along with a few other engineers, used to run some science shows for elementary students. My part of the educational program was the "Fire" section. I ended that section by poking three balloons with a candle taped to the end of a yardstick. The first was filled with helium and put the candle out when popped. The second balloon was filled with pure hydrogen. When popped, this gave off a nice fireball with a mild noise.

The third balloon I filled with a stochiometric mixture of H2 and O2. This balloon detonated, letting out quite a shockwave and deafening boom.

So H2 definitely goes BOOM when pre-mixed with O2. However, a pipeline leak will have H2 shooting out at a high velocity. Flame propagation speed of H2 is only 1.5-3 m/s (I see various values for this), meaning a leaking pipeline will generate a constant flame if ignited.

The problem, of course, comes from the initial ignition. If the leak doesn't end up self-igniting, you certainly have a situation where an explosion will happen.

For those of us in different disciplines, can I assume a hard spot is an area where the pipe material has hardened and become embrittled?

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. - http://xkcd.com/319/

Basically yes. Usually occurring during manufacture after being quenched or uneven heat treatment during plate rolling. And yes, it cracks much more easily.

Hydrogen comes from the cathodic protection at a coating failure reacting with water.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.