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Re: [PSUBS-MAILIST] Re: Mig welding a sub




Ian,
 
I'm going to annotate your post with my replies in red
 
James Long
Owner/Designer
Lil Brother LLC (Instrument Division)
----- Original Message -----
From: "irox" <irox@ix.netcom.com>
To: <personal_submersibles@psubs.org>
Sent: Wednesday, July 25, 2007 4:25 PM
Subject: Re: [PSUBS-MAILIST] Re: Mig welding a sub


Ah, I think understand what you are talking about.  Your talking
about not needing the same inspection/process for creating 200feet
operational depth sub vs creating a 1000feet operational depth sub?
Apologies if I'm not reading your emails correctly.
 
Yes....that is why I'm trying to say, that the construction is critical, but not as such as a deeper depth rating. It's ok, I some times do not construct my emails correctly to relay the message I'm trying to get across. Hopefully I'll do better with my sub.  :-)


If you take into account safety factors, then the two hulls
can come out similar.  Also, if you are skimping on inspection, then
over engineering isn't a bad idea (i.e. using a material thicker
compared to the relative operation depth than a full inspected
sub would use compared to it's operation depth).
 
I tend to agree, to a point. I don't see it as skimping on inspection. You can test some welds before actually building the sub. I just don't know if I would x-ray every pressure hull weld. That would be a huge expense. There are problems associated with over engineering also. If the pressure hull gets to a point of penetration problems, you can end up with a bigger problem than lack of inspection.

For safety factors, I'm think of the time for action after you
cross your operational depth (due to some sort of problem).  With
a 25% safety factor in 1000foot operation depth sub, you have the
time taken to travel 250feet to react to the problem.  But in a
200foot operation depth sub, 25% only gives you 50feet to react,
if you want to same amount of time to react, you need a 150% safety
factor.  So combine the safety factor with some over engineering
since you are not full inspecting/x-raying the welds, and you end
up with similar pressure hulls.
 
This is an operational problem.....not a safety factor problem. I would never take a sub to a location (submerged) that would exceed the maximum design rating (with ofcourse safety built in). This is a standard safety area. If you can't exceed the submersible depth, nothing can go wrong. If you operate a sub submerged with a pressure rating of 250 ft. in 500 ft. waters you are asking for disaster. My take on this, if you are building a sub with a max depth of 250 ft. the theoretical crush depth should be 500 ft. but I would never operate it in waters over 250 ft. submerged.
 
I know some one is going to say that is impossible......I didn't say I would never operate the sub in 500 ft. waters, I just would never dive in 500 ft water. If the sub starts to sink while in transit (the passage through water deeper than 250 ft.) I would get out, because I'll be on the surface.
 
But we should consider, I probably wouldn't have my welds tested by x-ray. I'm just not going to that length. I don't knock anyone who does, I just don't see it necessary for me to have piece of mind.


At least this would be my (current) thinking/approach.
 
I believe we are in agreement.
 
I tend to do things my way, and so far (with all the things I've done) it hasn't failed me yet. I hope (while knocking on wood) I do not become a statistic that someone reads about.

James

-----Original Message-----
>From: Lil Brother LLC <
lil_brother_llc@bellsouth.net>
>Sent: Jul 25, 2007 4:22 PM
>To:
personal_submersibles@psubs.org
>Subject: Re: [PSUBS-MAILIST] Re: Mig welding a sub
>
>Ian,
>
>There wouldn't be a difference, if you are brave enough to use a thin
>material to go to 1000 ft. It would be a waste to use a 1000 ft. material
>(thickness wise) to only go to 200 ft.
>
>The equipment necessary to weld (properly) a hull 1/2 inch thick can easily
>weld a hull 3/16 think, but the opposite is not true.
>
>I'm not just discussing the seam, but the equipment, diligence, and
>inspection required for the seam to be proper. It is more difficult to weld
>a 1/2 piece of material proper than a 3/16 piece.
>
>James Long
>Owner/Designer
>Lil Brother LLC (Instrument Division)
>----- Original Message -----
>From: "irox" <
irox@ix.netcom.com>
>To: <
personal_submersibles@psubs.org>
>Sent: Wednesday, July 25, 2007 2:51 PM
>Subject: Re: [PSUBS-MAILIST] Re: Mig welding a sub
>
>
>
>Then, what is the difference between a seam welded for a
>200feet dive depth and 1000feet dive depth for the same
>thickness material?
>
>I don't think there is a difference.
>
>Ian.
>
>-----Original Message-----
>>From: Lil Brother LLC <
lil_brother_llc@bellsouth.net>
>>Sent: Jul 25, 2007 3:16 PM
>>To:
personal_submersibles@psubs.org
>>Subject: Re: [PSUBS-MAILIST] Re: Mig welding a sub
>>
>>Ian,
>>
>>As I understand it...the material thickness plays a major part of the
>>welding process. The thickness makes a major difference.
>>
>>James Long
>>Owner/Designer
>>Lil Brother LLC (Instrument Division)
>>----- Original Message -----
>>From: "irox" <
irox@ix.netcom.com>
>>To: <
personal_submersibles@psubs.org>
>>Sent: Wednesday, July 25, 2007 2:05 PM
>>Subject: Re: [PSUBS-MAILIST] Re: Mig welding a sub
>>
>>
>>
>>What's the difference between the seams?  From what I've read there
>>would be no difference other than the matterial/thicknesses being
>>connected.
>>
>>Ian.
>>
>>-----Original Message-----
>>>From: Lil Brother LLC <
lil_brother_llc@bellsouth.net>
>>>Sent: Jul 25, 2007 2:21 PM
>>>To:
personal_submersibles@psubs.org
>>>Subject: Re: [PSUBS-MAILIST] Re: Mig welding a sub
>>>
>>>Dan,
>>>
>>>I somehow missed this message.....
>>>
>>>I have a question........Wouldn't submerged series arc be the best method
>>>to seal a pressure vessel? It's totally one bead, has similar penetration
>>>to stick, and is easily controlled.
>>>
>>>Although I'm not sure who would have a rig that could weld a round vessel,
>>>I'm sure it could be done.
>>>
>>>I agree a backhoe bucket weld wouldn't do the trick, but also on the other
>>>hand the seam to seal a vessel designed to go 1000 feet, is not the same
>>>seam as a vessel only designed to go to 200. The variables are totally
>>>different.
>>>
>>>James Long
>>>Owner/Designer
>>>Lil Brother LLC (Instrument Division)
>>>  ----- Original Message -----
>>>  From: james kocourek
>>>  To:
personal_submersibles@psubs.org
>>>  Sent: Wednesday, July 25, 2007 5:51 AM
>>>  Subject: Re: [PSUBS-MAILIST] Re: Mig welding a sub
>>>
>>>
>>>  Hi Dan,
>>>  I appreciate your input. I have done failure testing prior to welding on
>>> my sub with exceptional success. I think that some of the time flux core
>>> gets a bad rap because of the fact that the little buzz boxes use flux
>>> core. Mine is a 350 amp mig computer controlled pulse welder as speced by
>>> both lincoln tech specialists and my coach, an extremely experienced and
>>> active pressure vessel welder.
>>>
>>>  I concure that one cannot be too cautious.
>>>
>>>  I am interested in talking with you more at the convention about this
>>> subject and appreciate your feedback.
>>>
>>>  Rest assured that I did considerable homework prior to choosing the
>>> method that I am using now.
>>>
>>>  Thanks again & Best Regards,
>>>
>>>  Jim Kocourek
>>>    ----- Original Message -----
>>>    From: Daniel Lance
>>>    To:
personal_submersibles@psubs.org
>>>    Sent: Tuesday, July 24, 2007 7:50 PM
>>>    Subject: [PSUBS-MAILIST] Re: Mig welding a sub
>>>
>>>
>>>
>>>    James
>>>    I believe it would be in your best interest to strive for  the highest
>>> possible weld integrity for the pressure hull of your submarine. A weld
>>> procedure that is acceptable for a backhoe bucket isn't necessarily
>>> adequate for Pressure Vessel Quality work.  Typical Quality Control
>>> standards for PVQ require full penetration X-ray quality welds to acheive
>>> 100 % of the strength required for such a demanding applicaton. While
>>> there are many welding processes available to the average person, ( mig,
>>> tig, stick). Some are better suited than others in a given situation
>>> depending on a particular individuals skill and experience level.  As an
>>> example , I have seen "side bend" Mig weld tests performed by highly
>>> skilled  welders with ten's of thousands of hours of welding experience
>>> split apart in the weld bead zone. Mig has a tendency to exhibit very
>>> shallow penetration in certain circumstances. The trick is to know WHA! T
>>> circumstances. If you are going to perform your own welding I!
>>  would recommend that you do what industry does. Take a weldor
>>qualification test in the weld process and welding procedure you intend to
>>implement in your build project. Get a copy of  "The Procedure Handbook of
>>Arc Welding" by the Lincoln Electric Co. of Cleveland Ohio. This an
>>excellent reference book with a chapter devoted to weldor qualification
>>tests. If you have a hydraulic press in your shop you can perform your own
>>tests.  If you plan to hire someone to do the welding for you insist that
>>they pass an approved  test administered by a qualified laboratory. Rework
>>is expensive , do it right the first time. And of course,......what is your
>>life worth?....... someone who says they can do it or someone who can prove
>>that they can do it.
>>>    Happy sub building,
>>>
>>>    Daniel Lance
>>>   
lanceind@earthlink.net
>>>
>>>
>>
>>
>>
>>
>>
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