SA-6 Compressor Balanced Stage Pressures and Temperatures With Other Considerations

[iain/hsm]

As I see things our "To Do" list for the SA-6 from suggestions so far is as follows

1. Build up a standard test bed unit and data log the nominal running performance temperature and pressures
2. Rip off the belt guard and see any improvement (consider alternative design)
3. Rip off the front grill cover and add the biggest fan we can get both in Europe and USA and test again. (Consider modified design)
4. Discuss engineering design modifications and material changes for the over 3000 to 5000 psi range applications and severe duty cycle use
5. Discuss material changes and modifications for Nitrox applications ( tested to say 50%)
6. Discuss technique to lower the 1st stage discharge temperature
7. Discuss RTD fittings and placement on the SA-6 (Remote Temperature Device)

Please add to the list and feel free to add questions. Iain

 

[tbone1004]

@iain/hsm fair enough on the fan, but one of the units is going to be 230vac in, so may just have to get different fans.

The priority for me would certainly be #4. Our common banks are 4500psi, so the ability to cycle between 3000-4500psi and be continuous duty rated for filling banks would be incredible.
50% would just make banking that storage bottle easier, but less of a priority for me

 

[RayfromTX]

8. Discuss material changes and modifications for Trimix applications (what would be the maximum helium content in a practical, reasonable build?)

a guy can dream can't he?

 

[tbone1004]

@RayfromTX that's going to be a combination of heat buildup as addressed with RTD's, and how much blow-by you can accept since that is not an insignificant amount when you get into high He contents.... I know plenty of guys that blend 21/35 in the SA6 at full speed.

 

[RayfromTX]

21/35 is plenty but I was looking for a gas for 100 meters since I'm wishing.

 

[NAM001]

Now I really like this, way off topic I know but such an important consideration.
But I have again one question as I'm not sure if we are all talking about the same thing or if the Anglofiles on the forum understand the term "sweet spot" or you lot understand what us lot think of balancing a compressor

I have heard before on the forum this term "balancing" or the compressor being "balanced" and never got around to asking before I'm just not sure what we all mean by the term "balanced" or if we even fully understand the term
Maybe we should use the term balancing just for describing mechanical vibration reduction
and the term "Pressure Balancing" for what your describing above the "Sweet Spot"

If so the "Pressure balancing" on your SA-6 design is 3000psig or 207 bar.

But the mechanical balancing is adustable by the counter weight length at the front end (fan side)
and at the back end (driven pulley) by adjusting the PCD position of the three 19mm weight balancing holes
Or by using a standard industrial SPZ twin groove pulley and adding another counter weight at the back end
in the opposing face to the front one (upside down) The crankshaft has a drilling at the back end pulley side for this purpose.

It was not my intent to go of content but to voice concerns with the idea of slowing any compressor and reducing the BPR settings to facilitate a low current startup.

 

[T Mogle]

Hi folks,

I find your debate interesting. I have been a yacht owner for a long time. Current yacht for the last ten years a 42” sailing yacht. Sailing short-handed with my wife, where I have just taken up diving. Following your discussions regarding air compressors have been interesting. As a yacht owner got a few comments:
- On a boat of this size you will not change the electrical system from 12v to 24v or stuff like that.
Too expensive to make the change. You will maintain and upgrade what you got. Rewire – yes, replace – yes, upgrade – yes. But convert from 12v to 24v madness. Too expensive, most likely everything will need to be replaced.
- I got Rolls AMG batteries, 2x 240 for service and 1x Rolls 80 for starting.
This battery bank is considered to be plentiful on 42 feet boat. We got plans to add 1x Rolls 240 as a separate battery for two el winches. At present is just an item on our wish list.
- How do we charge the batteries?
I think this debate should focus on the air compressor, and forget how the energy is generated. Using a solar panel setup, as discussed is irrelevant. The air compressor will take power from the battery bank. The batteries need to be charged one way or another. How that is done is more or less irrelevant. One a yacht like mine you will change the batteries several ways often at the same time. I am currently charging batteries using a) running the engine and using the alternator b) running the Sea & Watt Hydrogenerator POD 600. A separate prop under the water generating electricity at all times. When sailing at average 7 knots, it produces 50 amps. c) Shore power when in marinas.
On other boats, it is common to have Soar panels (we find them too ugly), wind turbines (find them too noisy), Diesel generator (On my wish list, but planning to spend the money on diving gear).
- What is using power onboard?
Every yacht is different. Most people would say that the fridge uses most. On our boat it is a) the fridge. b) Our watermaker produces 50-60 litre per hour. I usually run the watermaker for one hour every day. c) The autopilot. In the autopilot, hydraulics could use a good amount of power. d) Navigation systems, lights. e) The windless. Got a 1500w windless, when it runs it eats power.
- Then a few comments on your air compression discussion:
We plan to have four tanks onboard and need to fill them. No plans for more guests, so no need for a fast air filling station. I am looking for an air compressor that goes on electricity. 12v or 220v. We permanently got 220v onboard for TV, laptops, hair dryers and other crap. This is completely wired into the boat, automatically controlled by our Struder el system. The scuba tanks need to be filled very ad-hoc. We dive, then we give the tanks a top-up. If it takes a long time to fill the tanks, I have no problem with that. The air-compressor need to be very easy to run. I got lots of other systems with higher priority on board that need my attention. I am technical (when I need to be) I have no spare time to maintain and run an air compressor. Yearly service, ok, other it must be plug-and-play and easy to use. Attention required will be minimal. It will be permanently installed somewhere. Space is limited, so smaller is better. Very impressed by the pictures posted, I expected a bigger unit. My plan is a permanent installation in the lazarette, with a high powered hose from the air compressor to the cockpit. When filling, the compressor is located down below, out of the way, in a noise protected area, with a pre-fitted high powered hose to the cockpit just a few feet away. It saves me from moving the tanks around when they need filling.

Just a few comments from an ocean sailor and upcoming diver.

 

[tbone1004]

@T Mogle I think you meant for that post to be in the original thread this spun out of for the first part of your comments.
As far as a compressor that will do what you need/want it to do, the Rix SA3 or SA6 would be a good option for you. They can be mounted in any orientation and are pretty robust little units. Bauer makes units for marine use as well but then you have to deal with oil and more robust filtration.

 

[rjack321]

@RayfromTX that's going to be a combination of heat buildup as addressed with RTD's, and how much blow-by you can accept since that is not an insignificant amount when you get into high He contents.... I know plenty of guys that blend 21/35 in the SA6 at full speed.

I noticed earlier you were planning on banking argon (98% via separation but basically argon). Were you planning on pumping this through your Rix? Argon and a Rix do not play well together. The heat of compression burned up a friend's SA-6 trying to pump argon. Personally with the development of decent heated undergarments I don't see the value of even using argon.

 

[tbone1004]

@rjack321 was that directed at me or @RayfromTX ? I don't believe in argon and have no intention of banking it.