# Needle Valve ?



## stagfest (Dec 11, 2006)

Hi,

I have a problem with my sodastream Co2 canister that's attached to a Harris 601 regulator and adaptor. When I first switch the gas on I can get 2bps consistantly. After afew hours it drops down to 1bps then it just stops. I have a feeling that because the regulator isn't fully open its restricting the flow of co2?? So if I were to put a needle valve on i could fully open the reg and let the needle valve control the flow of gas. What do you all thing?

So if the above is correct see below...

I am in desperate need of a needle valve. I just can't seem to get consistant results with just the Harris 601 Regulator. Could someone please point me in the right direction. I'm in Australia BTW.

-Cheers Merv-


----------



## orlando (Feb 14, 2007)

Is there a solenoid?


----------



## stagfest (Dec 11, 2006)

No there isn't. Just a regulator...


----------



## furballi (Feb 2, 2007)

You'll need a high-quality needle valve in ADDITION to the regulator. Set the regulator around 10 to 15 psig, then add a needle valve. A quality but cheap needle valve is the Fabco NV-55. This should suffice for 99.99% of the users. If you have more $ to burn, then go with the straight brass Ideal valve with the 1/32" orifice (-1-).

Approximate cost in US is $15 for NV-55, and $75 for Ideal 52 series -1-.

http://www.fabco-air.com/distributors.html#OUTSIDE

http://www.idealvalve.com/brassvalves.htm

McMaster Carr has the ideal valve

http://www.mcmaster.com/


----------



## yoink (Aug 31, 2005)

I find a higher working pressure makes the needle valves a little more accurate and consistent. I use about 25-30 psi.


----------



## freydo (Jan 7, 2006)

yoink said:


> I find a higher working pressure makes the needle valves a little more accurate and consistent. I use about 25-30 psi.


i agree. i set my psi to around 35 and then adjust the bpm with my needle valves. you do have to keep in mind that when you initially set your pressurized co2 system up, you will notice that the psi drops from where you first set it. but this is normal, at least for me. but you will need a needle valve for the fine tuning.

you can also check out Rex Grigg's site for needle valves: CO2 Stuff For Sale


----------



## furballi (Feb 2, 2007)

The amount of inlet pressure required to achieve the desired mass flow rate of CO2 across the needle valve is dependent on several major variables:

1. Length and diameter of CO2 tubing on the outlet side of the needle valve. Longer length and smaller diameter translate to higher resistance.

2. Depth of water column (hydrostatic pressure). Add 0.432 psi/foot of resistance for fresh water, and 0.445 psi/foot for salt water.

3. Quality of the needle valve. A high quality needle valve should be able to go from BUBBLE TIGHT to FULL OPEN in a linear fashion. Look at the graph of the valve's flow rate vs number of turns. It should be straight, not curved (parabolic).

A needle valve works on the principle of pressure differential across an orifice. If there is excessive downstream resistance at the outlet side of the needle valve, then one must increase the inlet pressure to obtain acceptable regulation. In general, keep the length of the tubing going from the needle valve to the aquarium as short as possible. Also introduce CO2 near the surface of the water column to minimize the hydrostatic pressure. 

A properly configured rig should not present more than 3 psi of downstream resistance. Since all high quality needle valves are rated for 10 psi inlet pressure, the ideal regulated pressure is 10 psi, PLUS the 3 psi of downstream resistance.

There are those who believe that one must purchase an expensive regulator to achieve stable regulated flow. This is true only for high mass flow rate of CO2. With the much slower mass flowrate found in planted tank, the inlet pressure should remain constant.


----------

