Thank you, Bill, for making this crystal clear !
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-- Original Message --
From: "Bill Dube via EV"
To: ev@lists.evdl.org
Cc: "Bill Dube"
Sent: 10-Sep-21 19:04:37
Subject: [EVDL] Danger to public? (was: H2 tank expiration (was OT: fuel
cell mining truck)
"Fatigue" is the answer to your question.
When you repeatedly stress materials, minute flaws grow and result in failures.
Filling and emptying the pressure vessel results in a fatigue cycle, and will
eventually result in failure of a highly stressed part. You can bend a coat
hanger in half and it is fine, but you can't bend it repeatedly, as it will
break.
In the case of a pressure vessel, a failure can easily result in catastrophe.
Thus, periodic inspection is required, and retirement of cylinders is required
if large flaws are detected.
All sorts of "life safety" items are subjected to mandatory periodic inspection and
sometimes replacement at "end of predicted life" due to fatigue. For example, on
airplanes, you can only fly so many hours before you must replace the wing spars (main beams in the
wings) on specific airplanes. The cost will take your breath away, (millions per airplane) but it
is often less expensive than buying a new airplane.
The aim is to replace the "worn" part before it fails, instead of having it simply fail.
Having the wing part ways with an airplane in flight is the definition of a "life safety"
type event. Same as having a pressure vessel burst, especially one at high pressure full of H2.
As they say "Safety regulations are written in blood".
Bill D.
On 9/11/2021 10:01 AM, Peter Eckhoff via EV wrote:
What happens to Mirai tanks that have been refueled 300K to 500K
without a tank change? Do they pose a danger to the general driving
public?
Today, as an aside, I drove my Model 3 90 miles at 65 mph with the
equivalent of 3 adults in the car, AC running, and averaged over 5
miles per kwh. I was impressed since a Bolt I had owned averaged
about 3.9 miles/kwh under similar conditions.
On Fri, Sep 10, 2021 at 5:48 PM EVDL Administrator via EV
wrote:
On 10 Sep 2021 at 13:28, Bill Dube via EV wrote:
This replacement cost is another "nail in the coffin" of H2 fuel cell
vehicles. The cost of a battery replacement is less than the cost of
_mandatory_ H2 cylinder replacement.
Is it mandatory, though? It seems to be nothing more than a label inside
the fuel filler door with a date and a finger-wagging advisory, "Vehicles
with expired hydrogen tanks must not be driven or refueled until the
hydrogen tanks are replaced."
It seems as if everything is chipped and networked in cars these days.
You'd think that Toyota could have the body computer query the tanks, "Hey,
you guys expired yet?" before starting up, and refuse to go if they're past
their use-by dates. At least it could flip on a yellow warning light or
"service hydrogen tanks soon" message on the cabin display. If the manual
mentions that as a possible situation, I missed it.
Do FCVs require smog inspection? Would expired H2 tanks keep them from
being certified? I don't have a clue.
Without any consequences, the owner could just ignore the warning label, and
carry on with filling and driving the car.
David Roden, EVDL moderator & general lackey
To reach me, don't reply to this message; I won't get it. Use my
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