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

[Rick Patton via Personal_Submersibles]

Hank, what is the max limit of your scuba depth gauge and what kind is it?

On Tue, Nov 21, 2023 at 4:19 AM hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> I have onboard sonar to establish depth from bottom. I have just added a
> scuba depth gauge outside my dome that I really like.   The DW is kinda
> tight inside, so the gauge outside is real nice to look at.
> Hank
>
> Sent from my iPhone
>
> On Nov 21, 2023, at 6:27 AM, 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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