[PSUBS-MAILIST] air compensation

Tue Aug 1 19:02:40 EDT 2023

That said, sourcing your supply from a LP port of a SCUBA regulator should be sufficient. Off the shelf, most SCUBA 1st stages will deliver 120 - 160 psi over ambient to the LP ports, and are designed to provide sufficient flow at that pressure (once reduced to ambient pressure by SCUBA 2nd stages) to simultaneously support two divers at moderate workload.

Sean

-------- Original Message --------
On Aug. 1, 2023, 16:55, Sean T. Stevenson wrote:

> I think Alec was trying to point out that HP ports on SCUBA 1st stages are not designed to supply flow of any kind. Diver consumption only occurs via the LP ports. The HP ports are deadheaded in ordinary service, designed only to communicate a HP pressure signal to a SPG or transmitter. As such, on all modern SCUBA regulators, the supply orifice at the HP port and/or the mating fitting on a HP SCUBA SPG hose is nothing more than a pinhole, specifically designed to reduce gas loss in the event of a HP hose or downsteam equipment failure. Any downstream devices requiring a HP supply should source that supply directly from the HP storage or plumbing upstream of the SCUBA regulator, or from a different regulator designed to service HP flow, which SCUBA 1st stages are not.
>
> Sean
>
> -------- Original Message --------
> On Aug. 1, 2023, 16:41, Cliff Redus via Personal_Submersibles wrote:
>
>> My guess is there would be adequate flow rate. First stage scuba regulator has to pass enough air to supply demand of the largest diver. My guess is filling four MD 101 thrusters at the descent rate of a psub would be less than required for a diver. Easy enough to make a calculation. Sense the downstream pressure at the HP port orifice is way less than half the upstream tank pressure, the flow of air through the small orifice is in critical flow. As such a shock wave forms at the orifice and mass flow rate becomes independent of downstream pressure. It is a function of only upstream (tank) pressure and the orifice diameter.
>>
>> When I get a chance, I will make a quick calc and see what the rates are. Good to check this.
>>
>> Best
>>
>> On Tuesday, August 1, 2023 at 04:09:41 PM CDT, Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>> Hi Cliff,
>>
>> "The Tescom 44-4069 regulator would be a clean installation with just a single 1/4 SS tubing run from the HP port of the 1st stage regulator to the input port of Tescom 44-4069 regulator."
>>
>> There's a little problem with this plan, though easy to work around. The HP ports on regulators have a tiny orifice, in order to prevent rapid loss of air if a hose or SPG fails. These ports cannot provide the sort of flow you would want.
>>
>> Best,
>> Alec
>>
>> On Tue, Aug 1, 2023 at 12:17 PM Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>
>>> Sean, the specs do look good on this unit. To me the issue is going to be the cost. As background, the Parker regulator that Hugh, Alec and I have used for this application is the 364-02BSS/M1 Parker Watts Pneumatic Regulator.
>>>
>>> https://store.livhaven.com/r364-02bss-m1-watts-fluidair-pneumatic-regulator at $217.51. I purchased mine off ebay for a fraction of this.
>>>
>>> When I had the Parker 364-02BSS/M1 installed for pressure compensating for my four MK 101s, it was connected to the LP port from my AquaLung Titan balanced diaphragm first stage regulator. I had the Parker 364-02BSS/M1 adjusted to give about 2 psi over ambient. I had the first stage set to 50 psi over ambient water pressure. I use this for BIBBS and blowing the MBTs.
>>>
>>> The Tescom 44-4069 regulator would run directly off the HP air tank pressure then output go directly to thrusters. It would be interesting to compare the Cv's for both regulators to get a feel on how much air flow rate they can provide to the thrusters descending and venting when ascending.
>>>
>>> The Tescom 44-4069 regulator would be a clean installation with just a single 1/4 SS tubing run from the HP port of the 1st stage regulator to the input port of Tescom 44-4069 regulator. From the output port of the Tescom 44-4069 a single 1/4 SS tubing to a Swagelok Tee that branched off to two more "T"s to give four 1/4 SS tubing runs to the thrusters.
>>>
>>> We need to get a RFQ on one of these regulators. Do you have a preferred supplier?
>>>
>>> Cliff
>>>
>>> On Monday, July 31, 2023 at 09:47:29 PM CDT, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>>
>>> I would be inclined to use a Tescom 44-4069 regulator for this purpose. Not sure what these sell for.
>>>
>>> Sean
>>>
>>> -------- Original Message --------
>>> On Jul. 31, 2023, 20:37, Cliff Redus via Personal_Submersibles < personal_submersibles at psubs.org> wrote:
>>>
>>>>
>>>
>>> My original air competition for the R300 used the regulator that Hugh Fulton has on QSub. These are pricey new but you can get them used on eBay. I was operating all four of my Minn kotas 101 off this single regulator. It was a special ss pressure reducing/pressure releasing regulator. I had it installed on my last Florida dive which I went down about 100 ft . Unit worked fine. My first failure was on Flathead lake expedition in which one of my aft thrusters flooded. After that I switched to oil compensation. Alec is using same regular on his articulated arm and not the thrusters. He felt issue with the regulator was that the port for releasing pressure on ascent was too small. I believe he has addressed this by adding a pressure release valve or OP valve. He can elaborate more on his current strategy.
>>>
>>> Cliff
>>>
>>> Sent from my iPhone
>>>
>>>> On Jul 31, 2023, at 9:14 PM, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
>>>
>>>> John,
>>>> I am happy with both air & oil.
>>>> Am intending to fill my thrusters with oil, but have the oil pressurized off my air comp system. This will reduce air use to just whats in the lines.
>>>> My electric manipulator will be air compensated off the same unit. Putting oil in it adds another layer of complexity.
>>>> I think I need to put out a long video once I've finished this
>>>> air compensator.
>>>> From what I am hearing from Cliff, he didn't get enough air delivery from the single regulator he was using. However I thought this was the same unit that Alec is using & was now happy with.
>>>> Alan
>>>>
>>>> [Sent from Yahoo Mail on Android](https://mail.onelink.me/107872968?pid=nativeplacement&c=Global_Acquisition_YMktg_315_Internal_EmailSignature&af_sub1=Acquisition&af_sub2=Global_YMktg&af_sub3=&af_sub4=100000604&af_sub5=EmailSignature__Static_)
>>>>
>>>>> On Tue, 1 Aug 2023 at 1:29 pm, Jon Wallace via Personal_Submersibles
>>>>> <personal_submersibles at psubs.org> wrote:
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>>>>
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