Recommendations for portable compressors requested

[iain/hsm]

From my perspective it's not all bad news, it only sounds like it to begin with.

But $4000 is much too short you need at least double that IMHO

First off my take is that your a commercial operation, therefore you have both responsibility and liability. Air purity quality is paramount but the downside is the size of this vessels generator and if of sufficient spare power to drive a 5BHP 4Kw electric driven compressor. (even with a soft start)

From experience a 30 footer with a Yammer generator will only just be big enough to boil a kettle and turn on lights. So your faced with the possibility of using a petrol (gas) engine or using the PTO shaft from the main engine.

Personally I would loose the will to live pumping up 6 divers tanks four times a day with the noise alone from a petrol engine, coupled with fuel usage and pollution.

The fuel use and fuel storage also would have to be worked out later, but you can forget the 4.2 cfm Max-Air and also the small 3 cfm Rix SA-3 both are too small.

The Rix SA-6 is one of the few portable compressors man enough for continuous operation but with the Honda GX240 petrol engine its consuming 2.2 litres an hour of fuel and the integral fuel tank volume on the Honda is only 5.3 litres,

Say with 2.5 hours of running before refuelling, and doing that on a rolling deck with a hot engine, needs concentration LOL ?

But 2.5 hours running on the Rix SA-6 will produce 825 cfm. As each cylinder is around say 70 cfm per fill. So giving you around 12 fills per tank load of fuel.

Your requirement for 6 divers four fills a day is double the Honda GX 240 fuel tank capacity so I would consider removing the engine mounted fuel tank and using a outboard motor type 5 gallon fuel tank with say a 6 foot OMC fuel line and fit a small fuel lift pump to the Honda and a small engineering modification to the block.

Now you have 6 gallons around 22 litres of fuel safely stored and secured remote from the hot compressor and enough fuel for around 50 fills

Incidentally for small 32 footer you could also consider using the main engine PTO shaft option on the vessel. The 1500RPM of the Rix SA-6 is a match and being oil free we have even mounted them upside down in the engine bay, (separator orientation considered) Diesel fuel use is a consideration you need around 4Kw of power to run the compressor but worth exploring the options.

The other main consideration using a petrol engine for this length of time each day is the exhaust pollution. Both the compressor air intake position needs careful consideration to both its location, diameter material and type as well as CO considerations and alarms in each of the the cabins and below deck spaces.

Filter options to follow. Iain

 

[Fishpie]

You'll need a of minimum 5kw and a soft start to run a SA6.
The 50' sailboat I spend half my time on has a permanently installed Rix SA6 and with everything else turned off the 5kw Northern Lights generator is just man enough to start up the compressor.

For the petrol option a detachable 6 gal outboard tank can easily be plumbed in instead of the integrated Honda tank......Rix even makes a model with a Subaru Robin engine that comes with no fuel tank ready with OB barb and vacuum fuel pump.

 

[tbone1004]

The rixes that I've seen/used have only ever had the option to plug in a standard 5 gallon marine fuel tank, but mounting one to a PTO is a damn good idea since the frame can be oriented whatever way you want. It certainly doesn't know which way is up. I'm pming with the OP now since my Rix is currently apart and I'm waiting on a few parts to get it back to run.

 

[iain/hsm]

You'll need a of minimum 5kw and a soft start to run a SA6.
The 50' sailboat I spend half my time on has a permanently installed Rix SA6 and with everything else turned off the 5kw Northern Lights generator is just man enough to start up the compressor.

For the petrol option a detachable 6 gal outboard tank can easily be plumbed in instead of the integrated Honda tank......Rix even makes a model with a Subaru Robin engine that comes with no fuel tank ready with OB barb and vacuum fuel pump.

On the generator front I guess we need to nail the difference between KvA from Kw

I had assumed the OP had a typical small marine rated 5 KvA generator so with a 0.8 power factor reduction for the motor giving the 4 Kw I quoted.

Now maybe off topic but I would rate Northern Lights as one of the best small generators around and critically they are rated Kw and not KvA

Kw is short for Kilo Watts and is different than KvA, Kilo Volt Amps

Further depending on model choice a 5Kw Northern Lights unit will be rated running at 1800 RPM and not like the Italian junk that quotes performance in the higher KvA units and omits to inform you its also at 3600RPM

However on the Rix SA-6 compressor front you really also need to know exactly what the compressor draws at full load and pressure and in terms of Kw or BHP it is not just the size of motor or engine supplied or fitted with the sale.

We supply a 5.5 BHP 4Kw 3 phase electric as it only $20 more than the 5 HP

But on a petrol frame the Honda 8 BHP is preferred due to efficiency losses and again not much difference in price, also the centre lines of the drive shafts line up better.

The Subaru is OK and IMHO just a rework from the earlier Wisconsin Robin Engine and before that the Telydyne 7 hp. But for petrol engines rule of thumb is always go at least 2HP above an electric motor size.

The SA-6 needs exactly 4.87 BHP (3.63 Kw) to compress 5.5 SCFM to 5000psi with a 70 Deg F inlet temperature. As the OP filling requirement is at a lower pressure I'm guessing at 3000 psi the reduction in required power draw is commensuratenand considerably less again if starting off load. Iain Middlebrook

 

[divezonescuba]

We helped a friend buy a Rix 6 from Rix directly. It was just a little less than 10K with the automatic pressure cutoff switch and a few other accessories. In discussions with Rix, the 6 cannot be used with a nitrox stick for continuous blending.

 

[tbone1004]

Rix officially says it can't be, but most people use them with sticks daily, as long as you keep the o2 percentage down it's fine. They don't like helium being run through them, tend to get a little toasty when you do that though.