[PSUBS-MAILIST] Heads Question

Mon Sep 18 09:34:33 EDT 2017

My preference has always been a double vee groove (so double bevel on the mating faces of both parts), such that the root pass occurs at the mid diameter. For the same open angle of weld preparation, a double vee will require significantly less weld deposition than will a bevel from inside or outside only, so you are minimizing the total heat input, and weld stress / shrinkage is somewhat evenly distributed since you are applying beads evenly to both sides. The only time I wouldn't bother with a double vee is if the shell thickness was so thin that the additional weld deposition is a non issue.

As with any CJP weld, prep, clean, set the gap, lay a strong root pass that appropriately fills the gap with good fusion to both sides, then back gouge the root (grind or air arc) from the opposite side to profile and expose the interface to verify fusion, and begin laying covering passes, alternating both inside / outside and staggering starts at different circumferential locations so that you don't dump too much heat into one place.

Sean

On September 18, 2017 5:56:43 AM MDT, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Alec,I like a bevel on both sides, and I also do a mig pass on the
>inside then grind outside as you do.  When your welding such light
>material, the external grind job is creating the same shape weld grove
>as if you started with a bevel on both sides.  Same difference really.
> The big difference is guys like Rick and Dan can do this all at ounce
>because they are professional welders.Hank
>On Sunday, September 17, 2017, 8:33:43 PM MDT, Alec Smyth via
>Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
> 
>Here's the method I used. The starting point is a bevel with the sharp
>end of course on the ID and the wide end of the wedge on the OD. An air
>gap of about 1/8" is left between the two parts.
>1) TIG weld the root pass, from the inside of the hull, plugging the
>air gap. 2) Grind with an angle grinder from the outside into the root
>pass. Use a 1/4" wheel on the angle grinder. You need to get a clean
>shiny U shaped channel, pure like-new metal, with no visible
>discontinuities whatsoever.3) Stick weld from the outside building up
>layers until meeting the plate thickness.
>Perhaps a double bevel would be needed for very thick material. The
>method I'm describing, I've used on material up to 1/2" with no
>problem.
>Dan, if I'm talking rubbish please set me straight!
>
>
>Best,
>Alec 
>
>On Sun, Sep 17, 2017 at 9:52 PM, Rick Patton via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>Definitely want to bevle both sides. If you don't, your wire/stick/Tig
>will short out way too soon becoming molten and not reaching the ID of
>the hull and you will have to do a lot of back gouging before reaching
>your first pass.Rick 
>On Sun, Sep 17, 2017 at 3:54 PM Brian Cox via Personal_Submersibles
><personal_submersibles at psubs. org> wrote:
>
>I have found that I get a better weld if both sides are beveled . Brian
>
>--- personal_submersibles at psubs. org wrote:
>
>From: Private via Personal_Submersibles <personal_submersibles at psubs.
>org>
>To: Personal Submersibles General Discussion
><personal_submersibles at psubs. org>
>Subject: Re: [PSUBS-MAILIST] Heads Question
>Date: Sat, 16 Sep 2017 19:30:01 -0400
>
>Hi David,
>Absolutely, you want it with the flange. Any impression otherwise was
>my "mind typo" that I was trying to clarify in the second email. If you
>can avoid beveling it yourself, however, it'll save quite a job. You
>only need one of the two edges beveled, either the head flange or the
>end of the cylinder it will mate to, and it doesn't matter which. Greg
>has a good point, but I suppose a key factor is whether you'll be
>welding yourself or contracting out. I learned to do my own, with an
>awful lot of help from Dan Lance.
>Best,
>Alec
>On Sep 16, 2017, at 12:50 PM, james cottrell via Personal_Submersibles
><personal_submersibles at psubs. org> wrote:
>
>
>Hi David,
>In my experience it was cheaper and faster to hire an ASME tank
>fabricator to produce a steel cylinder with the head (or heads) welded
>on. Mine came machine welded with an ASME code stamp. If your design
>will feature external frames, ask them for both heads welded on. If
>your design will feature internal frames (done later) ask them to weld
>one end only. This will be cheaper in the long run and better built.
>It's hard to beat pressure vessel code machine welding. Specify NO
>backing strips.
>Another tip- call it a "vacuum tank".
>Greg Cottrell
>
>From: David Colombo via Personal_Submersibles
><personal_submersibles at psubs. org>
>To: Personal Submersibles General Discussion
><personal_submersibles at psubs. org> 
> Sent: Saturday, September 16, 2017 12:20 PM
> Subject: Re: [PSUBS-MAILIST] Heads Question
>  
>Hi Alec, I just spoke with the company that Roberto mentioned here in
>California to place an order for dished head for the SeaQuestor. I will
>be using the 36"OD x .375 A516-70 steel what they call Elliptical 2:1
>Ratio ASME Code Type. It comes with a 2" flange which is really a 36"
>od ring shape as part of the forming. This would mate up to the 36"OD
>first hull section. I'm thinking that this would give me the best
>welding condition with two matched surfaces that I would bevel for full
>pen welding. I'm curious why not to have the flange?   My cost here is
>$480.00 + $96 to have it shipped to northern California from southern
>California. even though its only a nine hour drive one way, I think my
>time would be worth more than $5 hr to pick it up. LOL Unless of course
>its cheaper in Canada (Hank), I might make the trip and could serve as
>support crew for the Gamma. Any thoughts out there from fellow Psubers
>would be appreciated.
>
>Best Regards,
>David Colombo
>
>804 College Ave
>Santa Rosa, CA. 95404
>(707) 536-1424
>www.SeaQuestor.com
>
>
>On Fri, Sep 15, 2017 at 2:28 PM, Alec Smyth via Personal_Submersibles
><personal_submersibles at psubs. org> wrote:
>
>Ugh, mental typo. I meant "un-beveled" and "bevel them yourself", not
>"un-flanged" and "flange them yourself".
>!!!!!!!
>On Fri, Sep 15, 2017 at 5:25 PM, Alec Smyth <alecsmyth at gmail.com>
>wrote:
>
>Hi Roberto,
>I believe the short description for what you need is flanged, beveled,
>and code. You could get them unflanged, but it takes quite a while to
>make a flange with an angle grinder. The flanges if I recall are 2". Do
>set up a project page or something so we can follow progress!
>
>Best,
>Alec
>On Fri, Sep 15, 2017 at 5:07 PM, roberto alvarez via
>Personal_Submersibles <personal_submersibles at psubs.o rg> wrote:
>
>Hi, lost the plans cd for the k250, i am  interested in the  head
>selection, i found a seler in california and have flanged ,beveled
>,code, non code,
>Will apreciate your support in this ( until i found the plans cd )
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