[PSUBS-MAILIST] bow window

Sat Nov 15 20:53:50 EST 2014

I don’t know where ABS Rules and ASME PVHO start and stop but as I understand ABS would not give certification if the PVHO rules are not followed and in Section 7 It refers to windows should be made in accordance with ASME PVHO.  The reference to temperature is ASME PVHO-1-2007  Section 2 table 2-2.3.1-1 to 5.     I don’t know if there is a later version as 2007 is the only one I have.  My ABS Rules are only 2002. 

Chs,  Hugh

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Sean T. Stevrnson via Personal_Submersibles
Sent: Sunday, 16 November 2014 10:04 a.m.
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] bow window

The calculation shown is using the section of the ABS rules that deals specifically with spherical shell hull components. The usage factor eta is specified by ABS as 0.67 for this calculation, which means the maximum allowable working pressure (maximum possible test depth) would be 0.67 of the critical pressure (predicted failure or crush depth). Safety factors over and above this (operating depth or actual test depth vs. maximum allowable) are left to the designer's discretion.

In which section is that temperature dependence discussed?

Sean

On November 15, 2014 1:50:09 PM MST, Hugh Fulton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

For windows ABS still has very different safety factors for the different temperatures though. i.e. at 24 deg S.F. 6 at 38 deg S.F. 8 hence the query as to what you used for the 1.0 thick viewport for 500 ft test. 

The other thing I have always wanted to know is what temperature are the domes rated for that DW2000 uses and that the Perrys were designed for.   Hugh.

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Sean T. Stevrnson via Personal_Submersibles
Sent: Saturday, 15 November 2014 2:12 p.m.
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] bow window

Temperature doesn't really factor in to the calculations. Technically, seawater density is a function of both temperature and salinity (and very slight compressibility), but the user just enters an average value for density. Similarly, the shell material properties can be tweaked from the average values that are programmed in as defaults, to accommodate specific known material te! st values or just for increased conservatism. The calculations are assumed to be valid for any material within transition temperature limits, but no specific attempt is made to model creep in acrylic or toughness transitions in shell materials at extremely low or high temperatures. This software is just an implementation of the formulas presented in the ABS Rules. Simply put, if seawater is still liquid at your operating temperature, you're probably okay. The lack of perfect determinism at failure is why we h! ave safety factors.

Sean

On November 14, 2014 2:50:52 PM MST, Hugh Fulton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Sean,

That is a very s! exy programme you have there.  What temp do you have as standard for that calc?

Regards,  Hugh

From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Sean T. Stevenson via Personal_Submersibles
Sent: Friday, 14 November 2014 6:45 p.m.
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] bow window

On 2014-11-02 12:06, Vance Bradley via Personal_Submersibles wrote:

Cliff, I'm thinking full hull diameter, 36" or thereabouts.

Vance

Vance - I was running some hull calcs for Brian Cox, so I ran a calc for your 36" d! ome port just to see... Looks like you could get away with one inch thick material for a 500' test depth.  
Also - the calculator is designed for a full shell, so cut all the weight and buoyancy figures in half for a hemisphere.

Sean

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