Re: CO2 Regulators Vs Bobbin Flowmeter?

["Suzy Jackson" <suzyj at bigpond_com>]

Adam Shaw wrote:

> He said that an adjustable regulator is probably not the best option for
> an aquarium, and what he has been doing for hydroponics people is to
> sell a pre-set regulator which brings the pressure down to around 250kPa

Whilst an adjustable regulator is not necessary, it does no harm, except of
course if you have small children or engineers that may fiddle with it.  On
my CO2 setup, I use a simple BOC fixed 200kPa regulator, that I bought at
the same time as I had the cylinder delivered.

> and then use a 'bobbin flow meter' after that
> to control the flow of gas. The flow meter has an adjustment range
> between 1-15L/min.

1 L/min strikes me as awfully high, unless of course you have a very large
tank.  On my 360 L tank, I bubble CO2 in at a rate of about 2 bubbles per
second, which comes out to something like 25ml/min.  (assuming 0.2ml
bubbles).

I use a Nupro metering valve, which I bought from NSW valve and fitting (the
local agents for Swagelock) along with the adapters to fit it to my
regulator, and to connect it to airline on the other side.  They aren't
particularly cheap (mine cost about AU$100) but they most certainly do the
job.

> He said that if it was
> necessary to have a smaller flow than that the flow meter could provide,
> then after the flow meter I could add a needle valve as well if I
> wished. He said that this system would be much more stable than using a
> plain adjustable regulator and needle valve combination.

The simple regulator - metering valve (AKA needle valve) is plenty stable
enough.  I have fiddled with mine maybe three times in the last year, and
two of those were on account of being an engineer.

We use flowmeters on nitrogen lines (to a desiccator cabinet) at work.  If
the ones you're talking about are similar to ours, then the rate of flow you
need for a fish tank is so low it wouldn't register on the flow gauge.

I have more details of my setup on my web page, at
http://www.suzyj.net/four_foot_technical.html  If you're in Sydney, you're
more than welcome to come over and have a look, as well.

Regards,

Suzy

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Suzy Jackson        suzyj at bigpond_com        http://www.suzyj.net