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Re: [PSUBS-MAILIST] Design depth



Jon, Alan, et al,
 
I think there is some inconsistency in definitions due to the different sources.  ABS defines Design Depth as:
 
"The depth in meters (feet) of water (seawater or fresh water) equivalent to the maximum pressure for which the underwater unit is designed and approved to operate, measured to the lowest part of the unit."
 
That sounds a lot like operating depth, but still leaves me with some questions as to exactly what they mean.  I could take that to refer to either the 300' or the 600' in my example, but it seems to make more sense for it to be referring to the 300 feet.  I have understood the Design Depth in navy terms to mean the maximum depth which the hull could withstand with only a slight margin before failure.
 
ABS defines Rated Depth as:
 
"The depth in meters or feet of water (seawater or fresh water) equivalent to the pressure for which the underwater unit has been operationally tested in the presence of the Surveyor, measured to the lowest part of the unit. The rated depth may not exceed the design depth."  Note the last sentence.
 
I think it would be good to get ALL the depth definitions very clear according to ABS and cease any reference to navy standards since the same term could mean very different things depending on whose definition is being alluded to.  It's not something that is going to be sufficiently addressed tonight.  Let's take time to get it right and contact whomever we might need to if that should become necessary in order to understand each of the terms being used to define the subject term.
 
Section 3.1 ABS states:
 
After out-of-roundness measurements have been taken, all externally-pressurized pressure hulls are to be externally hydrostatically proof tested in the presence of the Surveyor to a pressure equivalent to a depth of 1.25 times the design depth for two cycles. Pressure hulls designed for both internal and external pressure are also to be subjected to an internal hydrostatic pressure test in accordance with Part 4, Chapter 4 of the Steel Vessel Rules. Acrylic components are to be tested in accordance with Section 7 of these Rules.
 
Until later,
Jim
 
In a message dated 12/9/2010 10:50:48 P.M. Central Standard Time, jonw@psubs.org writes:
Jim,

You are correct.  Just note however that ABS certification (section 3.5 in same Underwater Vehicles document) requires a manned test to design depth so they appear to be stricter than the US Navy standard.

Jon


On 12/9/2010 11:43 PM, JimToddPsub@aol.com wrote:
Jon,
 
Correct me if I'm wrong, but I think we're talking about two different things, one of which I did not reference.  I was referring to sea tests of a manned vessel when I referred to the US navy standard of 2/3 of design depth.
 
I think you were referring to the hull pressure test (unmanned) which often is conducted in a pressure chamber.  It's been a couple of months since I've reviewed that and I'm now a bit fuzzy on it.  At that time I was able to locate several facilities with the capability to test my hull including measuring compression.  I also took a cursory look at the effect of temperature on the hull.
 
Thanks for the correction.