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Anyone working on solutions that work on 12VDC and facilities without compressed air?
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Ron,
Have looked into it but have not purchased anything, yet. ?There are oil-less compressors available that are called airbrush compressors. ?They are sometimes used for airbrushing cakes (food products) and are oil-less. ?Most are small and best would be to use one with a tank. ?Typical prices are ~$100. ?There is a few available that are 12vdc but are considerable more money. ?Might be better off using a standard one with an inverter. ?Have not investigated any more than checking what is available that might work. Marc Al WA9ZCO |
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Dr. Flywheel
Thanks for the?suggestion. I am more interested?in low energy consumption?and question whether compressed?air is really necessary?for "surge ventilator" operation. The common BVM ("AMBU" bag) squeezer solution that we see all over the place seems to take care of many aspects of providing air supply and safety features. However, supply supply chain problems may be disrupted and these devices may not be readily available, as we have seen shortages of many medical?supplies. For the?sake of this issue, I am also taking out of the picture the sensors and control parts of the system, which I am working on separately, with other groups.I am trying to focus only on the air supply system (without added assuming?that oxygen can be added). I experimented?with different pressurizing systems, the most promising seems to be air mattress inhalators. They seem to be much more efficient than blowers or fans, due to the very simple bellows design. Such inflating devices are rather cheap and may not be as scarce as medical supplies are. I am mostly interested to know if anyone out there has better solution to providing pressurized air at the levels needed to ventilate a person under surge conditions. If no alternatives are available, I will commit to improving my compressed air supply system, using the mattress inflators. Note that in spite of the use of an external air source (as I suggest) this does not preclude a hybrid solution, as an in-line AMBU type BVM can still be utilized for its valve and mask parts. --Ron N7FTZ On Thu, Apr 9, 2020 at 1:15 PM MA <wa9zco@...> wrote: Ron, |
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Ron Power options were discussed several days ago. ? Arv _._ On Thu, Apr 9, 2020 at 1:56 PM Dr. Flywheel <Dr.Flywheel@...> wrote:
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ICU and ARDS especially is always going to be complex business needing oxygen and electricity and moderate supply of highly trained staff and associated consumables. I think its important to remember these parallel requirements. In any hospital environment where they don't have access to oxygen, compressed medical compressed air, and reasonably reliable electricity, then I don't think any pandemic ventilators will save anybody. I guess I'm saying that I don't see any benefit from doing a design for a pandemic ARDS ventilator that does not assume these basics (although we can assume that they all be scarce). To be clear, I think people in these extremely impoverished situations deserve help too - just not in the form of ventilators. Erich Schulz,?mbbs, mba, fanzca 0410 277 408 On Fri, 10 Apr 2020 at 08:12, Arv Evans <arvid.evans@...> wrote:
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Dr. Flywheel
I my experiments, bellows type air pumps have the best chance of producing the volumes and pressures necessary?to drive a? "surge ventilator" and they can be ganged if necessary?to increase capacity. However, at this?moment, I continue to experiment further with the actual drive mechanisms that operate the bellows. A dumb cam may work fine with limited dynamic of pressure build profile; however I am waiting for a screw drive to arrive to see if I can use a stepper motor to provide more control over pump "squeeze" profile. The solution must still be able to work from 12 VDC field power. Regardless, I continue to collaborate with Erich Shultz on engineering specifications that assume availability?of regular electrical power, oxygen, and compressed air within a standard hospital environment. --Ron N7FTZ On Thu, Apr 9, 2020 at 5:46 PM MA <wa9zco@...> wrote: Ron, |
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There are two brands of blower I am aware of used in CPAP and ventilators but when I asked one of them last week they have 10 - 12 month lead times and have told me they already have orders for over 1 million units.
they can supply ample flow and pressure to run two patients but we won¡¯t be getting any stock from that playing field even if we offered cash or naked women. can I ask the gentleman who tried axial fans in series , which models did you use and were the joints sealed with gaskets to prevent leakage ? i didn¡¯t yet find any single axial flow fans that give more than 2 cmH2O so you would need need at least 3 of them just to get in the lower spectrum of functionality? |
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On Fri, Apr 10, 2020 at 10:38 AM, <sydneygold888@...> wrote:
Sydney, I used surplus fans and they were screwed together and tape/sealed to the pipe reducer assembly. ?Used two different models connected in series and neither produced adequate pressure to be effective, not even close to where it needs to be. ?Could not even pilot the Orbit valve. ?Only tried this because I had the parts on hand. can I ask the gentleman who tried axial fans in series , which models did you use and were the joints sealed with gaskets to prevent leakage ?Picture enclosed. Marc Al WA9ZCO |
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Dr. Flywheel
For those of you who insist on using small electrical fans for providing pressurized air to a "surge ventilator", I suggest to look into the use of "ducted fan" hobby parts. I tested a few of them; however, the negative side is that they are noisy and only good for providing a source of pressurized air with fixed dynamics. This may not be a negative factor for your design, so by all means, you are welcome to try. On the?positive side: ducted?fans are much more optimized to yield pressurized?air at reasonably high volume. They are typically used to power model?airplanes by providing through-fuselage air thrust. They are also very compact. Unit prices are between $15-80, depending on size. As I mentioned?earlier, for now I am sticking by the bellows type of pump, utilizing air mattress?inflating foot pumps and focus on improved airflow dynamics. Here is an example of a ducted fan, available from hobby stores: See:? All the?best. --Ron N7FTZ On Fri, Apr 10, 2020 at 9:07 AM MA <wa9zco@...> wrote: On Fri, Apr 10, 2020 at 10:38 AM, <sydneygold888@...> wrote: |
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On Fri, Apr 10, 2020 at 09:07 AM, MA wrote:
Could not even pilot the Orbit valve.The turbine blowers and fans probingly don't apply to high pressure compressed air source ventilators. They are more in line with the needs of the low pressure air source ventilators.? But for those of us looking at low pressure source ventilator design, your fan data is valuable.? By the way, it seems many of the air mattress blower type inflators can produce more than the 55 mbar that is the pressure specified for the max output pressure of the Medtronic ventilator. (A low pressure source turbine design.) If air mattress inflators were used, multiple in parallel would provide redundancy to make up for the likely less robust design of these blowers.? Speaking of low pressure designs, a way to mix oxygen into the air seems to be needed for any design to be useful. Possibly just rapidity pulsing a solenoid valve base on calculations bases on air flow. Like the fuel injection on your car.? Tom, wb6b |
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Has anybody looked at Scuba Tanks as a regulated air source? _._ On Fri, Apr 10, 2020 at 3:59 PM Tom, wb6b <wb6b@...> wrote: On Fri, Apr 10, 2020 at 09:07 AM, MA wrote: |
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On Fri, Apr 10, 2020 at 03:09 PM, Arv Evans wrote:
Scuba Tanks as a regulated air sourceHmmm... I've got two of those sitting in my garage, as well as first stage regulators. Maybe many other folks do, also. Probably need to live near the coastlines to find places to fill them to the required 3000 (and more) PSI of filtered air. Tom, wb6b |
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I am working on my version of the control which has in addition to the 12V controlled inspiration valve a triac AC switch to cycle a vacuum cleaner for pressureozed flow. Ashtar posted a video of his system running a vacuum cleaner, but his relay burned out.
I don't know if my system will ever see the light of day or not at this point due to liability concerns.? It may just be exported .? As the owner of Ten Tec I have pick and place machines, etc, but it appears that to build these I would have to spend thousands of dollars for parts and once again I would have to sell them for a premium price in order to afford the liability.?Also?I will not be able to release my design as open source due to the liability issue and also?due to investing tens of thousands of dollars of my own money to build a number of them. ?I'm not certain why I was not listed asa developer or pulled under the UCF liability.? I guess design for manufacture isn't important.? I'm not sure how much I can actually continue on this. But to answer your suggestion think about using a 12V leaf blower or the motor from a cordless dust buster. There are lots of options for improvisation ?because the pressure is relatively low.? You can slow down a DC motor with simple voltage regulator but be careful to address what happens in a failure mode.? 73 Mike N8WFF |
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Tom , the Medtronics uses a Blower from AirFan ( France ) , they put out 86 millibar ( 87 cm / H2o ) aka 34 in/H2o at 100 Litres / minute.
Ventilators need only 4 - 20 cm H2o? but the AirFans and other brands of high pressure pumps are expensive? and as i mentioned above , their lead time is over 10 months. If using a bellows style with DC servo drive motor we could get infinite output curves with the right software. |
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ARDS ventilators should really be capable of delivering tidal volumes against 30cmH2O (and arguably 40 for brief periods, such as "recruiting"). It's my impression that power won't be and issue with this (UF) design, but will be with other designs (especially turbine designs). I'm feeling in my bones (having looked at numerous projects now) that control and regulation and sensing are likely to be greater pain points overall. Erich Schulz,?mbbs, mba, fanzca 0410 277 408 On Sat, 11 Apr 2020 at 13:54, <sydneygold888@...> wrote: Tom , the Medtronics uses a Blower from AirFan ( France ) , they put out 86 millibar ( 87 cm / H2o ) aka 34 in/H2o at 100 Litres / minute. |
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It will take a lot of refills if continuously breathing from scuba tanks for weeks on end.
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I'd guess a couple hours per tank for each patient. Not cheap energy-wise to compress air to 2000 psi for no good reason. The regulators are interesting, simple and reliable enough, mostly. Jerry, KE7ER On Fri, Apr 10, 2020 at 03:32 PM, Tom, wb6b wrote:
On Fri, Apr 10, 2020 at 03:09 PM, Arv Evans wrote: |
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On Fri, Apr 10, 2020 at 08:54 PM, <sydneygold888@...> wrote:
If using a bellows style with DC servo drive motor we could get infinite output curves with the right software.Good point. From my layman's (but hopefully improving) view that is a good way to go. There is an interesting "museum" of photos of old ventilators. Bellows were ?one of the main designs. Seems like the Bird ventilator was an early departure from that, using a nozzle blowing compressed oxygen into a venturi to suck in air to mix with the compressed O2 gas flow. Timing and control done by air circuits. In many ways that design is more amazing the current designs that can rely on a microprocessor to do the heavy lifting. In my case I'm leaning towards a design that optionally could use one "low pressure" air source (bellows, turbine, bellows or blower air mattress inflators, industrial strength turbine pumps) to power multiple ventilators. So I'm looking at an easy to build, possibility disposable, valve(s) controlled by an RC servo. Also it seems the two port designs are universal, have many accessories designed to work within that system, and have evolved to handle the real world of sick patients driving messy substances into the system.? Many creative designs have been proposed to help in they crisis. Even if many don't make it out of the gate immediately, maybe we will see many of these designs developing into innovative, smaller, simpler to use, more cost effective machines that will make it into the mainstream in the future. ? Tom, wb6b |
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Let me know if have any drawings Tom Erich Schulz,?mbbs, mba, fanzca 0410 277 408 On Sat, 11 Apr 2020 at 14:53, Tom, wb6b <wb6b@...> wrote: On Fri, Apr 10, 2020 at 08:54 PM, <sydneygold888@...> wrote: |
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On Fri, Apr 10, 2020 at 09:40 PM, Jerry Gaffke wrote:
It will take a lot of refillsTrue. Scuba tanks may only be viable as a backup when power is out or transport. Fire stations may be able to fill the tanks, especially if some of the firefighters are scuba divers and have a fill adaptor. I wonder what the logistics of that would be. I suppose if the compressed air in the hospital was a weak link in a power outage (along with all the other equipment that must be kept running), then a battery backup on the ventilator would be moot.? Tom, wb6b |
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