[delraydella]

I hope they bought the extended warranty!

[Otto Nobedder]

I should have a new mass spec when I get there monday.

I posted solely because the forum is dead.

Steve S.

[Otto Nobedder]

Finally, now that the storm has passed, I was able to use the replacement mass-spec, and prove where my leak is.

Now, I'm waiting on detailed prints (sometime tue. I hope) for some guidance on where and how to open the outer vessel to access the defective weld. I know generally, as we've opened this area before on trailers from the same series, but I need enough access to remove the entire defective weld, as well as do a dye-pen to be sure the parent metal isn't compromised, as well.

Steve S.

[Otto Nobedder]

Turns out I only proved what my leak is near...

I actually put my finger on it today, for the first time. Once I confirm it tomorrow by repeating the test, I'll hit the spot with dye-pen and take a picture.

What an adventure finding that tiny-ass leak in over 1000 square feet of surface area.

Steve S.

[Otto Nobedder]

Either McMaster-Carr or UPS is a day behind due to Isaac, so I won't have the dye-penetrant 'til Monday, but here's the leak, as close as I can define it (+/- 3/4") with helium testing.

GEDC0429.JPG (198.82 KiB) Viewed 1905 times

GEDC0428.JPG (208.69 KiB) Viewed 1905 times

GEDC0430.JPG (195.54 KiB) Viewed 1905 times

[Otto Nobedder]

If you'll look below the tape in the first image, you'll notice a stress-riser line, the beginnings of a crack. That area is not leaking yet, but the leak would grow into this area.

The dark band is the HAZ of a flux-core weld on the outside of the vessel. It appears to have been done hotter than the WPS for the weld, as the metal is visibly distorted on the entire weld.

To repair this, I'll have to also open the outer vessel, as the crack most likely continues through the flux-core weld, and I'll have to work from both sides to eliminate the problem and get it through x-ray.

The bill on the complete repair could exceed $250,000.

Steve S.

[Otto Nobedder]

All right, I finally got the dye-penetrant today. It showed me a small row of almost microscopic porosity in the weld. It can't, on it's own, lead through the vessel, so the next step is to section out the rolled-angle stiffener, grind the welds clean, and start again in the same area. My assumtion (and you know how those things are ) is that the leak is where the visible weld and the HAZ from the weld below cross.

Here's the pic, though at this resolution it is difficult to see the line of porosity.

GEDC0431.JPG (180.38 KiB) Viewed 1723 times

Steve S.

[CraigLam]

Your welds are still better than mine, any day of the week.

[Otto Nobedder]

Thanks,

But that's not my weld. That's been there since 1978, if I recall the date of manufacture correctly. It took 34 years for it to start leaking, and it took me almost 3 weeks to find it.

Steve S.

[weldin mike 27]

Hey there,

How did they find out it was leaking in the first place? Cant have been much H coming out of such a small defect. She must be worth a few dollars to spend so much time and money on such an old trailer.

Mick

[Otto Nobedder]

Hi, Mick,

The trailer lost enough vacuum on the road that the outer vessel began to sweat... Think condensation on a glass of iced tea. They dispensed as much product to customers as they could, as quickly as they could, then the pressure rose within the inner vessel, and they had to vent the remainder. (Have to find a safe place to do that, or it's a HAZMAT emergency.)

In 1986 (the most recent build of this model I have info on), these cost $1.5M new, so they are willing to spend money on repair. With inflation, newer regulations, and increased labor costs, It would probably cost $3M to replace.

Steve S.

[Otto Nobedder]

This leak is challenging me. It is "travelling", meaning it is following a path created by other weldments in the vessel.

GEDC0436.JPG (191.58 KiB) Viewed 1707 times

You'll notice I've sectioned out a 6" length of angle iron from one of the hoops. Helium introduced to the end of the hoop, on the right, shows a leak. This means the leak is under the angle, between the two fillet welds that attach it to the vessel. To narrow this down, I have to stop-drill the angle to break the path between the fillets. I have so far shown that it is more than 12 inches from my starting point, but the leak rate was twice what it was before, and indication time was half, so I hope to find the leak is within the next 12 inches.

Steve S.

[weldin mike 27]

Hey,

Well thats some big coin. Well worth the repair it seems. Hope you track that sucker down. Thanks for the info.

Mick.

[Otto Nobedder]

FINALLY found it..

Here it is, with dye penetrant:

GEDC0443.JPG (195.36 KiB) Viewed 1702 times

The leak was 38 inches from where I detected it, as shown here:

GEDC0447.JPG (193.08 KiB) Viewed 1701 times

It was directly under the rolled-angle hoop, between the two fillets, and was likely a flaw original to the metal that was missed at x-ray because of the hoop of 4" X 2.5" angle welded directly over it. I finally located it by stop-drilling the angle at the weld every ten inches, cutting to the bottom of the angle at the drilled hole with a die grinder, and using a small flow of nitrogen to "interrupt" the helium I was testing with. Once I found a ten-inch section that tested positive, I halved it, and narrowed it to five inches. I sectioned that 5" out, ground and buffed to clean metal, and began testing small areas. Once I had a positive result, I hit it with the dye-penetrant, and there it was!

Now, they've decided to get engineering involved in deciding how to fix it, so I guess I'll be on another project for about a week.

Steve S.

[Otto Nobedder]

That "other project", by the way, is another inner leak!

[mArc]

Congrats, Steve!

For someone like myself, who's involved in a completely different part of the hydrogen chain, this has made for fascinating reading!

Mark

[Otto Nobedder]

Thanks, Mark,

I've been sharing this because I've been learning something every step along the way. At this stage in my career, I'm fascinated by what I still have left to learn. I actually enjoy discovering something I didn't know before.

[Otto Nobedder]

Hey, Mark,

You said you were involved in the "hydrogen chain". Are you in the "end-user" part? How are you involved?

Just curious... I'd like to know more about the end uses.

I know, for example, that a cell-phone company uses H2 for fuel-cells as backup power for their towers in Florida, and of course the obvious rocket-fuel use, but I don't know much about the other industries the use it.

Steve S.

[mArc]

Hi Steve,

Indeed, I'm involved in end-uses of hydrogen. I do research into catalysts for fuel cells, being devices that can, as you probably know, convert fuels (e.g. hydrogen or methanol) directly into electricity. The technology is not new in principle (the Apollo missions already used fuel cells), but there are many challenges that keep it from taking off seriously, e.g. low efficiency, high cost, long-term durability, etc.

BTW, I've seen one of those back-up fuel cells for cell-phone towers. Quite an intricate machine - essentially a massive UPS using hydrogen as energy reserve. And there's another challenge: a 50 liter cylinder of hydrogen at 180 bar only contains 750 g (1½ pounds) of hydrogen. It's an extremely light element, i.e. it has a low energy density. Of course, it can be liquefied, but that process takes a LOT of energy too!

Fuel cells can range from miniature (mW range) to industrial (100s of kW). Anything from portable power (e.g. laptop chargers) to automotive power sources, to remote sensing stations. It's a promising technology, but as I said, with its own challenges. Many of the catalysts are based on expensive Platinum Group Metals (PGMs), and much research is being done to find cheaper or more efficient alternatives, e.g. by using nano-technology, tailor-made alloys, etc. The electrolyte of a hydrogen fuel cell typically comes in the form of a specialized polymer membrane. Those are expensive too, and often not very efficient/conductive.

Another part of my research group is looking into hydrogen generation and storage.

So, that's a short peek into my "scene". Thanks for asking. By training, I'm a chemist (not pharmacist, but lab chemist) with a PhD.

[Edit: and by hobby, I'm a jack of all trades and master of absolutely none. Woodwork, mechanical and electrical home repairs, automotive DIY, music, piano tuning... - and lately, welding. ]

Cheers,
Mark

[Otto Nobedder]

Mark,

I'm rooting for your team!

I do have a good layman's knowledge (and some more advanced awareness) of fuel-cell research, and I look forward to the day this becomes a viable technology in the consumer market. You've pointed out the current weak links in the chain, from the energy-intensive production of usable fuels to the expensive nature of the raw materials and synthesized components of a typical fuel-cell.

I have a gut-feeling the answer to the fuel source may ultimately lie with biology. There are entire ecosystems along the deep-ocean rifts where the basis of the food chain is microorganisms that process H2S and heat, in the absense of solar power. This planet has no shortage of H2S...

As to the advanced materials for the fuel cells, I can't even begin to speculate... CHM201 was as far as I went with it in school.

Steve S.

[Otto Nobedder]

I finally got an answer from engineering...

It was exactly what I expected, and was planning; Today I started opening the outer vessel where the leak is. I'll be sectioning out a 12" square (okay, with the corners rounded) of the outer vessel, and peeling back the insulation in layers to reach the "outside" of the inner vessel so this crack can be welded and back-welded. I'll have pictures, of course.

I hope they feel the engineer made his paycheck, by recommending what I was planning to do anyway...

Steve S.

[delraydella]

What do you figure will be the total cost of this repair?

[Otto Nobedder]

Steve,

I was originally estimating $250K USD. I've advanced that to about $300K, with the (wise) decision to enter the outer vessel to back-weld the repair.

I have significant structure to remove (and re-install or replace) to enter the outer vessel at the repair.

Steve S.

[delraydella]

Can I assume that the repair is still cheaper than a new trailer?

[Otto Nobedder]

Can I assume that the repair is still cheaper than a new trailer?

Significantly. (This may have been asked earlier in the thread... It sounds familiar.) The cost for a new one in 1986 (The most recent build info I have) was $1.5M

26 years of inflation, new regulations, etc, I'd expect the replacement cost to be $3M.

Versus $300K in repair, it's a bargain. Their engineers have been very cooperative with the way I think it should be done, so the board has been easy to get work-order approvals from.

Steve S.