Compressor Newb

[GF99/99]

Hi Marsh,

Thanks for your reply. It was getting a bit lonely in this thread.

I bought those tanks in Sydney 21 years ago (new) and exported them to Africa in 1999. I am not sure if they would be any good now or not?

I agree with start small and keep it simple and will do that to kick off. But lots of logistical problems here. Its the 3rd world. Where I am on the lake is remote. We have one filling station in town and its often out of fuel. We have grid power but the grid is often down. We do have grid power most nights though and its cooler at night here (20 degrees C or so) so I was thinking it may be better to have some big tanks to fill at night then during the HOT.. (very HOT) to transfill to smaller tanks as I use them through out the day.

I have bought a new boat and 60HP outboard to dive from, bought the camera and underwater housing etc. Getting set to go....but then because of this forum remembered I have done nothing about figuring out AIR. So here I am.

I have a plot with waterfront to the lake. There is a small island offshore not to far away from me. I plan to blow bubbles in shallow water (10m) to hone my underwater photography skills before I go do the serious stuff in deeper water. I plan to do many many hours of blowing bubbles honing my skills. I will have to look up the dive tables again but I expect to get at least 2 x 1 hour dives per day in 10m of water. Plus my dive buddies who stay out on my perimeter on croc patrol need air too. So that's a lot of gas. Hence wondering if it makes sense to have a "bank" so that I only run a compressor at night to get longer life from filters (everything is imported here so everything hellish expensive) not to mention it being a lot easier/more convenient to "transfill" from a bank rather then start up a compressor every time I need to fill a few bottles.

I used to have 2 or 3 local divers diving with me (croc patrol) so we used to empty all 5 cylinders per day easily. There was a compressor locally back in the day but not now so have to figure it out for myself now.

While diving around the island close to is easy in terms of moving back and forth from home to the dive gorunds is easy its gets logistically difficult as I need to move further afield up the the lake (the lake is 700 Klms long and is very remote - its all in the bush). But I will deal with all that when I get to it.

I can get dive stuff from South Africa. There is a Bauer agent in JHB. So while its 3000 klms away from me to get to a service agent it is doable once a year.

Sorry to ask again but what is your budget?

No worries on the age of your tanks only hydro testing will determine if there good or not but most likely I'm sure there fine.

If your on a remote lake with grid power then I would suggest getting a gasoline or diesel driven compressor. You can fill in remote areas and you don't have to rely on grid power. If your looking to do 2 x 1hr dives a day then this is no problem for a basic small compressor. You would go for your dive then during your surface interval fill your tank then go for your second dive. Really I would not waste the money or time with setting up a huge air bank unless you have your heart set on it and your willing to spend the money. I personally have never set up an air bank nor do I know much about the but I understand the basic concept and for you the best bet would be to just make one your self out of several larger tanks then buy all the plumbing to connect them in series. Now if you really want to be able to fill 5 tanks with out having to start up your compressor and only off the air bank I think you would need a fairly substantial size air bank and your going to need 414 bar bulk tanks (I am assuming you will struggler to find these Zambia so most likely you will have to order them from the EU) and generaly these tanks are about USD $1,000 per tank not including shipping and import fees and you will need a couple of them in order to fill your tanks to 300 bar. The next option is to get 310 bar bulk tanks and once again I don't know how easy these will be to find in Zambia and with these you will only get 200bar fills maybe 250bar depending on how many you buy. Lastly your going to need a 414 bar compressor to refill your bulk storage tanks and a small one usually start at about USD $25,000. For maybe $10,000 you could probably get a 250 l/min gasoline or diesel drive compressor and just fill your tanks off that it would only tank about 20min to fill a tank to 300bar. And for half that price again maybe around $5,000 you could get a Bauer Junior II gasoline model.

Basically your looking at $30,000-$35,000 or more vs. $5,000 - $10,000 only to have the convivence of being able to fill you tanks up with out having to start up your compressor.

This is why I say its probably not worth it to setup and air bank. Just keep it simple and get a compressor and just fill your tanks off that. Best bet is to call up the Bauer dealer in SA and talk to them, they can inform you on what system is best for you needs.

 

[Angelo Farina]

I suppose that you are overthinking and oversizing everything. Start small, start simple.
If electricity comes and goes, better a compressor powered by gasoline or diesel fuel (depending on which one is easier to find and cheaper in your location). Banking compressed air is very expensive, dangerous and complex. Banking fuel is much simpler, cheap and safe.
Get a good used Bauer compressor, it will cost something as 5000-10000 USD, depending on conditions.
Here you see it new:
Bauer Mariner 320 Petrol dive compressor
That is well sized for filling 5 tanks of 15 liters each day. But do you really need to use 5 tanks every day?
How many divers are using them? How many dives per day for each diver? How long is the surface interval?
If you are the only diver, you can do with a much smaller compressor...
Then buy a number of fuel containers. And there you go...
Just pay attention that the exhaust of the engine does not get inside the air intake of the compressor.

 

[Miyaru]

I am in a tropical area so it is hot where I am and can be quite humid at certain times of the year.

This is going to be your main concern and I'd suggest you check that before deciding what to buy. Humidity is relatively high in the tropics, compared to colder climates. As a rough estimate: the air coming out of your compressor should be seven times drier than the air in the Sahara desert.

If the air is not dry enough, it causes a risk for steel tanks: rust. One of the reasons why dive operations in the tropics use aluminum tanks. The aluminum corrodes on the outside and forms a layer that stops further corrosion.

The compressor is responsible for separating all moisture. That's largely done by compression and the remaining humidity is taken out by a filter with Molecular Sieve, a white substance that is hungry for moisture and can 'ingest' 20% of it's own weight of water. Another filter element is Active Carbon, responsible for removing the oil smell from the air. But....AC has to remain totally dry to do it's job.

A small compressor like a Junior is not suited for long operations as it needs to cool down after filling one or two tanks. Add tropical temperatures to that, and it becomes even less attractive to choose this model.

Another thing to keep in mind with a compressor, is wear-and-tear and the required maintenance. A large filter will of course last longer than a small filter. For example a P41 Bauer filter could last 70 hours in a colder country, but only 30 hours in the tropics. How easy is it to get new filters, or the AC/MS to refill your own cartridges? Are cartridges refillable?

Every 500 hours, the valves in the cilinder heads need to be replaced. Because they simply wear down over time. Is a local tech available to perform that maintenance?
Every two years, oil should be replaced. It's not the usual engine oil, first because a compressor is not the same as a combustion engine, second because the oil must not have dangerous fumes that could contaminate air, because you're breathing it!
The compressor doesn't burn up the oil, but uses tiny amounts as water vapour needs something to condensate onto: oil. When you drain the condensate from the compressor, water comes out mixed with a tiny bit of compressor oil, looking like a white watery substance. Something to dispose of properly without dumping that into the environment! An automatic condensate drain will prolong the life of your compressor and filters. Draining should be done every 15 minutes, not every 15 years.

Compressor manufacturers make money by selling filter cartridges. Returning customers are good. If I buy a new P41 cartridge with Securus monitoring, it costs me around 138 euro. If I refill it myself, the filter materials cost me around 9 euro.

Another issue is lifetime (and the following is not backed by statistics, but my own opinion). I've seen too many dive centers around me struggle with compressor problems, each time costing thousands of euros for maintenance and replacements of moving parts. Back in the '60s, '70s and '80s, Bauer produced the K14 compressor, and that was a compressor built to last. Many of those are still around, some still operational after more than 20000 hours. It's my favourite and I have restored several of these models. I'm running a model from the '80s in the compressor room, and I have a '67 model with a gasoline engine as a mobile option for areas where there's no fill station nearby. Never any issue, just regular checks and of course timely filter changes.

 

[Angelo Farina]

I second the suggestion for the good old Bauer K14. I used them at Maldives in the eighties, they were the only lasting in that hot and humid climate.
All the normal maintenance was feasible easily by me. Just valve replacement required to send the unit back to the maintenance shop...

 

[Sub100]

Lots of great feed back on this - thanks to you all !

@Marsh - my budget is about 30-40K tops for a new machine. Dont want to go much beyond that.

It seems that the compressor is going to have to go back to a workshop to have valves changed out every 500 hours so it probably does not make sense to think of looking for a used unit in the USA and have it shipped to me (in a container with other stuff I need from the USA). Looks like its probably best to stick to South Africa and the chances of finding a used unit there is probably slim.

In my mis-understanding of "Banks" It seemed to me (for some reason) that it was beneficial to the compressor to do one long run to fill the bank. Also is it of benefit to only fill a bank to say 3000 PSI and use a booster to transfill to the actual dive tanks at a higher pressure thereby not exposing the compressor to those higher pressures with the result of less wear and tear on the compressor? I dont want a "bank" for the sake of having a bank - its only useful to me if it i someway provides a good benefit.

If it turns out its best to just stick to a compressor to fill dive bottles directly, does it matter to the life of the compressor if it is a petrol (gas) driven unit or diesel driven?

I will be diving with at least 2 guys as croc patrollers out on the flanks while I take photos and I need at least 2 dives a day for the 3 of us. I would like to get 4 days of diving a week for about 6 months of the year (I live about 1.5 Klms from the dive site so easy to do). What size compressor should I be aiming for? Is there any wisdom in oversizing the compressor so that it is not working too hard? Ie, a big compressor that only runs at 50% load ?

I was thinking of building out a compressor room in a 20ft container that is well insulated and fitted with aircon to lower the ambient temperature for filling tanks (or a bank). I suppose one could also install a dehumidifier as well in an installation like that. Would this help very much in extending the life of filters (remember I am in a very remote location thousands of kilometers from supplies). I am building out a workshop made up from containers regardless of a compressor setup so this is not a hard thing to add for me.

It doesn't matter what I go for it will have to be shipped in. None of this is available locally or in the country I am in. So whatever the specs are for tanks, or banks or a compressor does not matter - it will all have to be specc'd and sourced and imported.

I am reading about filters that can be refilled. This sounds interesting and is probably the way to go for me. Both for economy but also the logistical side of things. Can the refill material be bought in bulk and stored ? and if so how long can one store the refill material for? Where would I get this material?

Lots and lots of questions. Sorry for that. Still once we get a few basics down the curve will flatten out.

Thank you all for helping me out with this. When its up and running, come out for a dive !

 

[Angelo Farina]

Lots of great feed back on this - thanks to you all !

@Marsh - my budget is about 30-40K tops for a new machine. Dont want to go much beyond that.

It seems that the compressor is going to have to go back to a workshop to have valves changed out every 500 hours so it probably does not make sense to think of looking for a used unit in the USA and have it shipped to me (in a container with other stuff I need from the USA). Looks like its probably best to stick to South Africa and the chances of finding a used unit there is probably slim.

In my mis-understanding of "Banks" It seemed to me (for some reason) that it was beneficial to the compressor to do one long run to fill the bank. Also is it of benefit to only fill a bank to say 3000 PSI and use a booster to transfill to the actual dive tanks at a higher pressure thereby not exposing the compressor to those higher pressures with the result of less wear and tear on the compressor? I dont want a "bank" for the sake of having a bank - its only useful to me if it i someway provides a good benefit.

If it turns out its best to just stick to a compressor to fill dive bottles directly, does it matter to the life of the compressor if it is a petrol (gas) driven unit or diesel driven?

I will be diving with at least 2 guys as croc patrollers out on the flanks while I take photos and I need at least 2 dives a day for the 3 of us. I would like to get 4 days of diving a week for about 6 months of the year (I live about 1.5 Klms from the dive site so easy to do). What size compressor should I be aiming for? Is there any wisdom in oversizing the compressor so that it is not working too hard? Ie, a big compressor that only runs at 50% load ?

I was thinking of building out a compressor room in a 20ft container that is well insulated and fitted with aircon to lower the ambient temperature for filling tanks (or a bank). I suppose one could also install a dehumidifier as well in an installation like that. Would this help very much in extending the life of filters (remember I am in a very remote location thousands of kilometers from supplies). I am building out a workshop made up from containers regardless of a compressor setup so this is not a hard thing to add for me.

It doesn't matter what I go for it will have to be shipped in. None of this is available locally or in the country I am in. So whatever the specs are for tanks, or banks or a compressor does not matter - it will all have to be specc'd and sourced and imported.

I am reading about filters that can be refilled. This sounds interesting and is probably the way to go for me. Both for economy but also the logistical side of things. Can the refill material be bought in bulk and stored ? and if so how long can one store the refill material for? Where would I get this material?

Lots and lots of questions. Sorry for that. Still once we get a few basics down the curve will flatten out.

Thank you all for helping me out with this. When its up and running, come out for a dive !

3 divers, 2 dives per day: you need a set of at least 7, better 8 tanks. You already have 5, just buy other 2 or 3.
The Bauer compressor I linked in my previous post is just perfect for this workload, in a diving center they would use it 3 or 4 times more than you, so it will last you for decades, if you do a decent maintainance.
You absolutely do NOT need an air bank.
As you seem to have a lot of money to spend, buy the compressor new and you still have at least half of your budget free for other stuff...

 

[Angelo Farina]

Regarding compressor workload; the number of hours you need to run yhe compressor daily is simply given by the volume of air you and your buddies use every day. Assuming that each dive you use 2500 liters, it is 15000 liters per day for 6 dives.
That Bauer Mariner 230 compressor delivers 230 liters/minuto, so it will need to work just 15000/230=65 minutes every day. Nothing...
And it will take the same time filling an air bank or directly your cylinders.
What you probably will find handy is a multiple hose setup, allowing you to connect, say, up to 6 tanks simultaneously.
This way you attach all the used tanks of one day, start the compressor and wait that the filling is complete....

 

[Sub100]

Thanks for the input Angelo. Food for thought.

 

[Miyaru]

Most wear on a compressor is starting/stopping. If you can run it continuously in one long go, it's the best option. So that means filling all tanks in one go. The option that @Angelo Farina described:

Or if you have several decanting hoses, use DIN-T connectors to hook up all tanks:


If you fill only 1 tank with a compressor that can do 240+ liters per minute, the tank will be bloody hot after it's full and when you jump in the water, the pressure will be 20bar lower due to temperature drop (and gas compressibility factor). Topping the tanks up after cooling down is another start-stop cycle for the compressor!

Refillable cartidges: yes they do exist. The older blue plastic cartridges from Bauer are very easy to refill, but the newer P41 or P61 filters are one-time use. There are some refillable cartridges out there, but I had mine manufactured by a metal shop.

Material: Molecular Sieve, MS or 13X. You'll have to search for a local supplier. Characteristics:

Active Carbon should be easy to get. Pellet size for AC and MS: <1mm

 

[bakodiver391]

I'm in a similar position, running a Bauer K14 in a container within 7 degrees of the equator. It will take a BIG air conditioner to offset the heat generated by a compressor. I fill only in the early morning or in the evening and have a large fan in the doorway. I have to change filter elements twice as often as someone in a cold climate but that's just the cost of doing business. Changing valves is quite easy for someone who is mechanically inclined. It takes 1 special tool, and once you have had all the bolts and fittings apart and put food grade anti-sieze on them, it's easier next time. I only change valves when the performance degrades or interstage pressures are off, certainly more than 500 hours. Someone once said if your compressor is running within 10% of its' stated performance, don't mess with it.
To me it sounds like buying a diesel powered Bauer Mariner and enough tanks so you can fill at night and early morning would be your best bet.