[PSUBS-MAILIST] Terminating a conical transition
Sean T. Stevenson via Personal_Submersibles
personal_submersibles at psubs.org
Sat May 3 10:27:49 EDT 2014
Or a single eccentric conical section?
Sean
On May 3, 2014 8:03:36 AM MDT, via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>Joe,
>
>
>It seems like an expensive and complex assembly for what you get. Why
>not close the aft segment in a simpler way and fair the stern to the
>shape you prefer? A hemisphere with an extended shaft housing to put
>the prop where you want it, for instance.
>
>
>Vance
>
>
>
>-----Original Message-----
>From: Joe Perkel via Personal_Submersibles
><personal_submersibles at psubs.org>
>To: Personal Submersibles General Discussion
><personal_submersibles at psubs.org>
>Sent: Sat, May 3, 2014 8:17 am
>Subject: Re: [PSUBS-MAILIST] Terminating a conical transition
>
>
>
>Sean,
>
>
>Yes, a bolted flange with O ring.
>
>
>I've attached an image of what's on my mind. This hull is 36" OD,
>cylinder length is 120". Anything bigger in diameter, simply gets way
>to big and bulky for handling.
>
>
>I'm thinking at this size, I must bolt at least two hull sections
>together for outfitting and maintenance, and the cones can be
>un-stiffened or perhaps only at the joints.
>
>
>Joe
>
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>
>
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>
>On Friday, May 2, 2014 9:50 PM, Sean T. Stevenson via
>Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
>
>Each cone section in that case is considered alone, so if you were
>using stiffeners, you would need a heavy stiffener at every joint.
>Depending on the size, it may be simpler to use unstiffened geometry
>for such an assembly.
>The rules do not address bolting pressure hull sections together, but I
>don't see why you couldn't, provided you meet the requirements in terms
>of the stress analysis under the maximum combined loading conditions,
>which are prescribed in the ABS rules. Might require some FEA to be
>sure. You're thinking an O-ring groove seal? Or other arrangement? I
>think an ASME code compliant flange would be a good place to start, but
>I would make sure that the cross-sectional area of each half of the
>flange considered individually met the requirements of a heavy
>stiffener per ABS, at a minimum material location (bolt hole). I would
>also be inclined to use SuperBolts for the connection.
>http://www.nord-lock.com/superbolt/multi-jackbolt-tensioners/
>Sean
>
>
>
>
>On May 2, 2014 6:03:21 PM MDT, Joe Perkel via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>
>Sean,
>
>Would the heavy stiffener rule apply equally to several cone segments
>stepping down at different angles?
>
>Also, do ASME pipe flange specifications translate equally to bolted
>pressure hull sections? Have I missed a section somewhere on bolted
>cylindrical sections?
>
>Very helpful Sean thank you!
>
>Joe
>
>Sent from Yahoo Mail for iPad
>
>
>
>
>
>
>
>From: Sean T.
>Stevenson via Personal_Submersibles <personal_submersibles at psubs.org>;
>
>To: Personal
>Submersibles General Discussion <personal_submersibles at psubs.org>;
>
>Subject: Re:
>[PSUBS-MAILIST] Terminating a conical transition
>
>Sent: Fri, May
>2, 2014 11:45:11 PM
>
>
>
>
>
>2:1 semi-elliptical heads are usually fabricated with some length of
>straight flange (tangential cylindrical section) beyond the axis of the
>ellipse. Hemispherical heads may or may not have a straight flange
>section, but in either case are permissible to use adjacent to conical
>sections, provided all other requirements are met. For stiffened cones,
>you must have stiffeners meeting the "heavy stiffener" criteria at both
>ends, as close as practicable to the cone-to-cylinder and cone-to-head
>transitions. For unstiffened cones, the length L_c used in overall
>buckling calculations must be the total length between the next heavy
>stiffener to either side of the entire compartment length, or between
>the 40% of head depth points if otherwise unbounded. Cone to head
>welds are done in the same manner as cone to cylinder welds, and if
>your head is supplied w! ith aflange, it is the same thing.
>Sean
>
>
>
>
>On May 2, 2014 2:48:52 PM MDT, Joe Perkel via Personal_Submersibles
><personal_submersibles at psubs.org> wrote:
>
>
>I have spotted the ABS diagrams and specifications for re-enforcement
>and butt welds at conical to cylinder transitions. I am somewhat
>unclear however as to terminating at the head.
>
>
>For example, the diagrams in the 2014 ABS underwater vehicles and
>hyperbaric chamber publication shows conical transitions either
>bordered by a cylinder at either end, or simply open at the small
>end???
>
>
>I want to terminate the small end of a conical transition directly to a
>small diameter hemi-head without another straight section, but I am
>unclear as to whether or not that is acceptable in practice.
>
>
>Joe
>
>
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>
>
>
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