Hp gas compressor, diving air

Robg71

Robg71

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Ok, please feel free to take the mick, as i should know all about them, but the small ones are lots smaller than the equipment I use at work, and a 1 tonne v4 compair compressor may be a bit overkill for what i have in mind. but do any of you chaps have hp gas compressors on your boats.
I am looking at Bauer, or coltri. Somewhere in the six to ten cfm range. 300bar, and electric....

Have you got one....
Whats your thoughts on it....

Not worried about the filtration side, i can deal with that, but does require ability for a remote intake.

Cheers :)
 
Robg71 said:
Ok, please feel free to take the mick, as i should know all about them, but the small ones are lots smaller than the equipment I use at work, and a 1 tonne v4 compair compressor may be a bit overkill for what i have in mind. but do any of you chaps have hp gas compressors on your boats.
I am looking at Bauer, or coltri. Somewhere in the six to ten cfm range. 300bar, and electric....

Have you got one....
Whats your thoughts on it....

Not worried about the filtration side, i can deal with that, but does require ability for a remote intake.

Cheers :)
Click to expand...
My brother has the Coltri (among many other compressors) and I'm about to order the s/s one for Match2. I'm a useless amateur diver so don't listen to me but my bro is a very serious diver for 25 years and knows his stuff. He says Bauer is obviously higher build quality but when you are trying to save space the Coltri wins and is perfectly acceptable quality. It has a generally good reputation among divers as the one to buy when you want small size and generally does what it says on the tin
 
Thats what im looking for. Many thanks J.
Recommendations from a user is better than any dealer,

Im looking at the mch 11em. Looks like a good compromise between size, weight and compressor capacity.....

Not sure about useless amateur, if you come back, no bends all safe and sound, and enjoy it....
Too many people push too far beyond there own limits needlessly...
 
Robg71 said:
Thats what im looking for. Many thanks J.
Recommendations from a user is better than any dealer,

Im looking at the mch 11em. Looks like a good compromise between size, weight and compressor capacity.....

Not sure about useless amateur, if you come back, no bends all safe and sound, and enjoy it....
Too many people push too far beyond there own limits needlessly...
Click to expand...

Ah ok. You're looking at something a bit bigger than their mini mini job. The one people buy for uber space saving on boats is the MCH 6 series. I'm planning on this one for Match 2 http://www.coltrisub.it/COMPRESSORS/PORTABLE/ENG/ELECTRIC/MCH6_EM_INOX/mch6_em_inox.htm

The one my brother has and reports favourably on is the petrol engine version of MCH 6 but the compressor part is, to state the obvious, the same whether you buy petrol or electric. He uses it as back up or when he is on other peoples boats, because he has a much bigger Bauer and airbank on board his own boat (which will finally be in the Med next year, meaning a full dive workshop on the quay for all of us gin palace boaters hurrah)

The MCH6 is properly compact - 41kilos. Fills a 10 litre bottle to 225 bar in half an hour or so which I can live with bearing in mind its compact dimensions. For cleaning the props and stuff I only use a 5 litre bottle and try not to breathe too much haha! The Coltri is therefore filling the bottle as fast as I'm using it, kinda thing, when you're on holiday and not in a hurry
 
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Robg71 said:
Im looking at the mch 11em.
Click to expand...
Geez, it shows that you're used to some serious stuff! :)
That's a pretty substantial bit of kit, for onboard usage (if I'm correct in guessing that it's what you have in mind).
Did you consider the genset required?
Just for your reference/information, my boat was originally equipped with a MCH 6, also electric.
But the first owner removed it, because it made the genset struggle at start up...

PS for jfm: I've just seen your last post, no worries, I'm sure your huge gensets will be more than able to cope with that!
I was just mentioning that because I remember to have checked the nominal current requirements on their website at that time, and it was way lower than the genset.
But they didn't publish the startup requirements, IIRC.
 
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The stuff we use are compair 54 series. Rated 300bar and around 60cfm. Fills a scuba bottle in not very long... And not recommended..... They get a bit warm :(

I am hoping the invertor system will take up any startup current shortfall, thats what they say it will do. Hence trying to get specs etc to figure out how much current I can play with.
I certainly dont want a bigger compressor, and will drop down in size if I really need to, but hope not. Its all linked with trying to spec the genset and electrics....

Mch 8 has a 3kw motor.
The 11 has a 4kw.
Probably identical in every other respect....
 
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The other thing to consider mapism is that nowadays VFDs are so cheap you can easily install a "soft start" one to reduce the current spike on motor start up, or you can use one to create 3-phase and then buy a 3-phase compressor, which has less current spike on start up
I know Rob you are a serious diver (understatement!) but surely the Coltri MCH 6 (10 lire bottle in 30mins) is enough for recreational use on your own boat? You can get the autostop function and leave the thing running the day before the dive, or whatever. In fact even 2x MCH6 would be lighter than one of the big compressors!
 
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Actually,it probably would be. Does yours annoy you when running. Or do you not hear it.
Noise was and is my main gripe. Hence bigger is on for less time. (Albeit... May be louder as well)
The other issue is running them to 300 bar, as the smaller ones in the past I know have struggled to cope with that. Most compressors will give you fill times to 200, but they know full well, that the thermal efficiency drops quite a lot when running up to 300 bar, hence takes longer per se...

I dont do anything daft when scuba diving, as generally on my own,but I do like the extra gas at 300 bar wether i use it or not. I dont go out looking for records, quite happy just getting my toes wet at 20 to 30 meters max....If there is food to find down there Im happy...

Do you have any startup current figures, as i couldnt find any.
 
Robg71 said:
Do you have any startup current figures, as i couldnt find any.
Click to expand...

It's at the bottom of the page. For the MCH 6:

Information for onboard use with electric generator:
Starting load ampere: *42 A **87 A
Generator power at starting (without pressure): 4 KVA

The 87A is for 110V version, so you're looking at 42A.
 
I dont have mine yet so cannot comment on noise but it will be in the engine room with door shut so I'm very confident there will be no annoying noise

Agreed 300bar is nice to have but asks more of the compressor. TBH I'm perfectly happy filling to 225 or so becuase I'm totally a recreational diver and 30m is the max depth I want to go to (had to laugh at your "getting toes wet :D))

No I do not have start up data sorry, and there isn't much on website. Happy to report back later when I get the thing. Start up spike will depend on various things including wear levels on the unit and temperature of the metalwork at start up, I suppose, so manufacturers will be reluctnat to quote figures. But with VFDs at say £200 surely this aint ever gonna be a problem that you wont be able to fix
 
jfm said:
I dont have mine yet so cannot comment on noise but it will be in the engine room with door shut so I'm very confident there will be no annoying noise

Agreed 300bar is nice to have but asks more of the compressor. TBH I'm perfectly happy filling to 225 or so becuase I'm totally a recreational diver and 30m is the max depth I want to go to (had to laugh at your "getting toes wet :D))

No I do not have start up data sorry, and there isn't much on website. Happy to report back later when I get the thing. Start up spike will depend on various things including wear levels on the unit and temperature of the metalwork at start up, I suppose, so manufacturers will be reluctnat to quote figures. But with VFDs at say £200 surely this aint ever gonna be a problem that you wont be able to fix
Click to expand...


Glad to keep you amused :)

Have you got anywhere else to keep your compressor? Im sure you have done your maths, but another cubby hole somewhere cooler and pipe in a remote air intake will be better for your compressor and your lungs....
 
Nick_H said:
It's at the bottom of the page. For the MCH 6:

Information for onboard use with electric generator:
Starting load ampere: *42 A **87 A
Generator power at starting (without pressure): 4 KVA

The 87A is for 110V version, so you're looking at 42A.
Click to expand...

Now you mention that Nick I remeber seeing it a while ago. I'm a bit baffled by the numbers and do not see how a 4kva genset (nominally a bit less than 20 amps) is going to deal with 42amps, unless Coltri is relying on the genset having a very slow breaker
 
Robg71 said:
Glad to keep you amused :)

Have you got anywhere else to keep your compressor? Im sure you have done your maths, but another cubby hole somewhere cooler and pipe in a remote air intake will be better for your compressor and your lungs....
Click to expand...
I can get cool air to its cooling fins in the engine room, using existing fans installed during build as a customisation. And yes I'll definitely have a remote intake to pull air from outside
 
jfm said:
Now you mention that Nick I remeber seeing it a while ago. I'm a bit baffled by the numbers and do not see how a 4kva genset (nominally a bit less than 20 amps) is going to deal with 42amps, unless Coltri is relying on the genset having a very slow breaker
Click to expand...

The breakers take time to trip, depending on the degree of overload & on the breaker curve, if say 10x the rating, they will trip within a few tenths of second, 100x the rating, within a few mS.

The amount of starting load the set will take depends more on the rotating mass (flywheel effect) than the power of the prime mover.

Of course your suggestion of a VFD solves all those problems !
 
starfire said:
The breakers take time to trip, depending on the degree of overload & on the breaker curve, if say 10x the rating, they will trip within a few tenths of second, 100x the rating, within a few mS.

The amount of starting load the set will take depends more on the rotating mass (flywheel effect) than the power of the prime mover.

Of course your suggestion of a VFD solves all those problems !
Click to expand...
Thanks, and I see your logic/laws of physics. As I said above, coltri are relying on there being a trip delay in the breaker

For Coltri to claim a 4kw genset will be ok with a 4kva genset involves them making an assumption/guess as to the curve of the breaker. Someone who just so happens to have a 4kva genset that is fitted with a "conservatively" curved (ie trip-happy) breaker might be disappointed when their £2k compressor just keeps tripping the thing!
 
Robg71 said:
Compair are pretty much industry standard these days. Hamworthy have started going bang as they get older, (personally think its bad maintenance) so were replaced by compair
Click to expand...

Aye, it just delivers the goods; not sure which model it is, but it's 3 phase electric and it's in a man-portable cage like little generators come in measuring perhaps 400x400x700mm.
 
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