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Hi Jon, I'm not one to throw out the baby with the bath water, sort speak. The PVHO, ABS, and other standards have been put together with many thousands of hours of hard work, calculations and testing. What I see Stachiw doing there was part of the push pull aspect that is required to develop a standard. Whether it makes it better, or worse, it's part of the process. Unless one is required to go by a particular standard to be able to have there sub function in a particular way, for a particular purpose, we are able to choose what rules, if any we choose to use. For many of use we are lucky we don't have to have are subs ABS classed or we would be forced to watch from the sidelines. For me I choose to use PVHO, and ABS as a tool, not a bible, and if I find other data that is different then PVHO or ABS from sources like Stachiw, Moorhouse, Nuytten, or the like, I will go with the one that I find to have the most convincing data. What entails a perfect safety record? I know of a 48 passenger ABS, PVHO certified tourist sub, that a local friend of mine was a key part of building in Seattle , called the Voyager that used to operated in Hawaii, that had a hydrogen explosion on it, that seriously injured two of the crew that came into the sub in the morning to get it ready for the day, after charging the batteries over night. There was a problem with the battery bank venting system and the hydrogen built up under the floor plates enough that when the static spark set it off from the two men walking around inside, the explosion a cured, and the floor lifted up so fast it injured the men. There is a chance the company didn't report it or that sub might of been required to got through a complete over haul. Regards, Szybowski > Date: Fri, 24 Jul 2009 14:29:41 -0400 > From: jonw@psubs.org > To: personal_submersibles@psubs.org > Subject: Re: [PSUBS-MAILIST] Service Life vs. Design Life of Acrylic Windows > > Considering Stachiw was Chairman of the subcommittee on viewports for > the PVHO standard, I wouldn't take such a black/white view of the > standards. Stachiw also wrote in his book: > > "It is worth remembering, that since its inception in 1977, the Standard has > maintained a perfect safety record over -14.5 to 20,000 psi pressure > range in hundreds of different manned and unmanned applications. It would, > therefore, be foolhardy to ignore the guidelines for acrylic window > installations in pressure vessels for human occupancy presented by the > standard." > > You have to remember that Stachiw's work was not primarily targeted for > small personal submersibles but rather, for large research vessels, > aquariums, and military applications. His differentiation between > design life and service life in the text you provided was not, I think, > intended as a damnation of PVHO regarding that topic but instead, a > practical look that other factors may be considered. Specifically, he > asserted that "in service inspection" and testing was required to make a > determination one way or the other from the "design" life of viewports. > > The conclusion one should draw from this then, is that if you have the > resources to properly inspect and test your viewports as required by > PVHO-2, then you may be able to justify deviation from the standard one > way or the other. However, for most psubbers this likely will not be > applicable, or perhaps practical. > > To put this in perspective, 10,000 cycles on a psub viewport is one > dive, every day, for 27 years and 3 months. I don't know any psubbers > that spend that much time in their submarine. That means a psubber is > more likely to hit the 10 year time limit rather than the 10,000 cycle > service limit, regarding design life of viewports. So the only question > remaining then, is how much do you trust your viewports after a decade > of time has passed? Has it been sitting in a temperature controlled > museum? Or in a dusty garage with lots of other junk? > > Jon > > > Brent Hartwig wrote: > > *Below Dr. Stachiw describes his professional opinion on what he has > > calculated and tested verses what the PVHO standard has adopted. When > > I see data from experts like this, I have further reason to not wish > > to follow every thing that ABS and PVHO currently considers to be best > > practice. Another case in point is when Paul Moorhouse was building > > Alicia, and ABS required him to use a scaled down tanker prop shaft. > > He found that to be massive over kill and it added a lot of weight in > > the stern he didn't need there. Plus the extra cost of the larger parts.* > > > > > ************************************************************************ > ************************************************************************ > ************************************************************************ > The personal submersibles mailing list complies with the US Federal > CAN-SPAM Act of 2003. 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