[PSUBS-MAILIST] Vanguard class sub (UK) unintended depth excursion

Tue Nov 21 10:35:56 EST 2023

I run an external analog outside the dome as well as the (2) sidescan units
for depth to bottom, one set with a min setting alarm as max depth alarm
when on the surface to determine if I'm in a safe dive area.
David

On Tue, Nov 21, 2023, 6:23 AM Jon Wallace via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> The O2 and CO2 electronic sensors I use can be calibrated in open air.  Of
> course that requires that the sensors can be removed from the vessel and
> taken to an open area, which mine can.  In situ, you'd have to use a test
> gas of known purity which would be another tank to drag around.  Pressure
> transducer testing could be done with just a scuba tank as the supply gas.
>
> If a vessel is diving in water shallower than it's rated depth would a
> pressure transducer verification still be critical?
>
> Jon
>
>
>
> On Tuesday, November 21, 2023 at 08:29:05 AM EST, Sean T. Stevenson via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
> I wasn't thinking of verification at depth, but rather verification of the
> transducer(s) / gauges prior to the dive, as distinct from a full
> calibration.
>
> Having, for example, a process connection on the vessel that would allow
> you to tie in a pressure source and a reference gauge, and doing a quick
> two-point verification of the gauge readings at 20% and 80% of nominal
> range - all before getting wet.
>
> Incidentally, here is the ABS language on the subject. It seems that
> redundant systems are
>
> "
> 13.3 Monitoring Equipment (2007) Life support instrumentation systems,
> including power supplies, are to be provided in duplicate or an alternative
> means of measurement is to be provided. Changes in temperature, humidity
> and total pressure are not to affect the accuracy of measurements.
> Electronic life support instrumentation is to incorporate provisions for
> calibration. Internal pressure is to be monitored using a mechanical type
> instrument in addition to any other type of pressure indicating instrument.
> "
>
> Sean
>
> -------- Original Message --------
> On Nov. 21, 2023, 06:00, Al Secor via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
>
>
> That would only add the danger of entanglement.  I would add a pressure
> gauge (analog) in series of the digital sensor
> or scuba depth gauge mounted outside in view of the pilot.
>
> Al
>
>
> On Tue, Nov 21, 2023 at 7:24 AM Jon Wallace via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> As Dan mentioned, for psubbers, not diving in water deeper than your sub's
> capability is good advice and we have this concept codified in the PSUBS
> operating guidelines section 4.1.2 paragraph 2.  Using multiple sensors for
> either backup or a weighted result between them is also a good idea except
> could be an expensive option given the price of some sensors.  A pressure
> transducer of mediocre accuracy for example is going to be in the $150 each
> range.
>
> What kind of protocol for verification of a single sensor would be
> effective?  The only thing I can think of for depth would be tying a marked
> rope to the vessel and comparing the pilot's observation to surface
> observation.
>
> Jon
>
>
> On Monday, November 20, 2023 at 11:57:50 AM EST, Sean T. Stevenson via
> Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>
>
> Just read an article about an incident with a British Vanguard Class
> submarine that had an incident where it went far too deep, apparently as a
> result of faulty instrumentation. Engineers became aware of the sub's depth
> when they observed some backup depth instrument(s) and rectified the
> situation before it became a castastrophe.
>
> Just wanted to prompt some discussion here, because PSubs don't
> necessarily employ robust backup systems, and at minimum, we should
> endeavour to ensure that all critical instrumentation is periodically
> calibrated to some reference standard to ensure accuracy, and also
> periodically verified in order to have some mechanism in place to detect
> malfunctioning instruments.
>
> Backup instrumentation is a great method to achieve the latter (instrument
> verification), but comparing the primary and backup instruments needs to be
> part of SOPs. Where backups don't exist, some means of functional
> verification should at least be employed, if not per dive, then perhaps per
> trip?
>
> This was a military sub that was almost lost because of an easily
> avoidable problem.
>
> FWIW.
>
> Sean
>
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