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Re: [PSUBS-MAILIST] Welding Revisited
Dan,
You said the magic words:
"Most psubers won't spend the money to x-ray
their welds , but would'nt you like to know they would pass a test if you
did one ?"
I don't care who the person is, how good they are, there is a possibility of
the weld failing x-ray inspection. If that were not the case, the U. S. Navy
wouldn't x-ray every weld on a sub.
Just because a highly qualified welder is diligent and does his best, does
not mean he will not make a mistake. He is human after all.
You couldn't actually tell if the weld would pass an x-ray unless it is
actually performed. Granted the welder will be very careful about his work,
a third person is always less concerned with your safety than you are. This
is just a fact of human nature.
"If your hull fails at 200 hundred feet you will be just as dead
as if it failed at 900 feet."
The statistics would say that you are mistaken. The human body (if not
crushed) would be far more likely to survive the pressurization(even
rapidly) at 200 feet, but is extremely unlikely to survive at 900.
James Long
Owner/Designer
Lil Brother LLC (Instrument Division)
----- Original Message -----
From: "Daniel Lance" <lanceind@earthlink.net>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, July 25, 2007 8:04 PM
Subject: RE: [PSUBS-MAILIST] Welding Revisited
James,
If you tell a welder his welds are going to be x-rayed when the job is
completed there is a tendency for that person to be more diligent in his
work.
X-ray "quality"welding as it applies to Pressure Vessel Quality work means
a bare minimum of porosity, slag inclusions, undercut etc. and no tolerance
for lack of complete penetration and/ or non fusion in the root pass. A
submarine pressure hull must be built to PVQ standards to acheive 100% of
the hull integrity needed for its intended purpose.Setting the "bar" high
for selecting a weld process, procedure or weldor is whats necessary for
such a demanding application. Most psubers won't spend the money to x-ray
their welds , but would'nt you like to know they would pass a test if you
did one ? If your hull fails at 200 hundred feet you will be just as dead
as if it failed at 900 feet.
Dan Lance
> [Original Message]
> From: Lil Brother LLC <lil_brother_llc@bellsouth.net>
> To: <personal_submersibles@psubs.org>
> Date: 7/25/2007 12:45:47 AM
> Subject: [PSUBS-MAILIST] Welding Revisited
>
> Ok,
>
> We have discussed welding and the methods involved.
>
> Shouldn't we also discuss the situations that pertain to each type and
the
> critical requirement for each?
>
> I know that a professional welder knows what he is talking about, but I
> think x-ray on welds that will never pass regular scuba diving depths is
a
> little extreme on the side of safety.
>
> I'm not knocking safety at all, I tend to lean to the safe side of
> everything. But there is a point to overkill when it comes to safety
> measures.
>
> I agree, if you are going to depths of 600 -1000 feet, I would definitely
> have the most certified welder available, and have the welds tested by
> x-ray.
>
> But I don't see the need to go to that measure if the sub is only going
to a
> max depth of 200 ft. I do see the need of the welds being proper,
airtight
> and strong.
>
> But I'm a realist, so I can handle the opinions from whoever disagrees
with
> me.
>
> James Long
> Owner/Designer
> Lil Brother LLC (Instrument Division)
>
>
>
>
>
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603-529-1100
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