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

Wed Nov 22 13:10:02 EST 2023

Thanks Hank
Rick

On Wed, Nov 22, 2023 at 6:59 AM hank pronk via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:

> The one I have on for now is 160 feet
> Hank
>
>
> Sent from my iPhone
>
> On Nov 21, 2023, at 11:34 AM, Rick Patton via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
>
> 
> 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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>>
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