Practical Use of Gas Booster with Argon and O2 Question

Hi,

I have been researching gas boosters for a while now and I do have a practical question for those experienced.

Example Setup:

- 160cuft Supply tank of Argon (psi) : I would use this for my small 6cuft psi Argon Tanks

- 300 cuft supply tank of O2 (psi) : This supply tank is Meant for Deco Bottle filling

( <= 40% blending would be handled by a separate O2 supply tank connecting into a Nitrox Stick).


My question is that if I am going to want to boost my Argon fills and then turn around and want to do O2 fills (75% to 100%) how do I do this and keep all of those nasty hydrocarbons out? I can't imagine O2 cleaning your booster between argon and o2 fills every time would be the solution nor is buying two boosters. ???

How are you handling this? And does this make sense

Thanks! There are a number of people using their boosters for helium, oxygen and argon and they happily swap between the three gasses. Argon is very clean from a supply cylinder as it is generally used for welding and any impurities will cause the welder to run poorly. The major issue with Argon is having it mixed into your breathing gas due to any gas which remains in the lines and then gets pumped into scuba tanks by mistake. You can avoid this by purging your booster and panel with clean air - basically blowing some air from your banks through the booster and the panel - depending on your specific set up and configuration. Basically, if you just bleed the booster, the argon will still remain in there at 1ATA, so you need to push it out by putting another gas in its place. You could use oxygen, air or helium to do this too and just let the first 5 or 6 strokes blow out the bleed screw on your panel or booster outlet - again, this depends if you are boosting back through your panel or just directly from supply cylinders to scuba cylinders.

Personally, I don't run argon through my panel or my booster, but that is more because the water temperature in Australia is never low enough to need argon in my drysuit. Air is fine for suit inflation here as it generally doesn't get under 50 deg 'F (9 deg 'C).

As far as oxygen cleaning goes, I subscribe to the train of thought that one needs to be careful with oxygen and that gas velocity is the largest single contributor to an oxygen fire. Clean your booster and boost slowly, one cycle every 2 to 4 seconds for me with oxygen. Now having said that, if you have oil and high pressure oxygen, those two alone are not enough to cause ignition, but by introducing gas velocity, you have all the ingredients needed for a nice little mushroom cloud within your booster. You can't take the oxygen out of the mix, you can take the oil/hydrocarbons out by oxygen cleaning and you can minimize the velocity by boosting slowly - two out of three ain't bad, one out of three (a dirty booster pumping oxygen slowly) is not so good.

Hopefully this helps you somewhat.

I'm seeking some advice for something that should be pretty simple. I have a tendency to over-complicate, but here goes:

Background info:
I've got a project in which a water treatment plant receives water at an average rate of 1 MGD, with a max rate of 3 MGD. After standard chlorination math I've found that the chlorination system will need to be able to feed a maximum of 125 PPD. However, the plant currently has a chlorinator rated for 250 PPD. For conservative reasons I've decided to ensure that the chlorine ejector has enough supply pressure and flow to output 250 PPD, even though it really only seems like 125 PPD is sufficient.

The system has a booster pump which withdraws a water supply from the incoming water main (conveying 1-3 MGD), boosts across the ejector, and injects in the water supply main at a point downstream from the withdrawal point. I have determined that the pressure at the injection point is approximately 46 ft (20 psi). The 1" solution line from the ejector assembly to the injection point is approximately 85' with several bends and fittings.

Problem:
It's my understanding that the backpressure seen on the ejector depends on the system flow (injection point pressure + headloss from injection point to ejector). Obviously you can't calculate the headloss without knowing the system flow. So that leads me to selecting a pump. The chlorinator companies don't really dabble in booster pumps. They just say you need a particular flow and head, and I have yet to find an example online where this is gone over in detail.

I plotted the system head curve looking from the pump discharge to the injection point. I assumed that the static head condition over the pump is essentially zero (technically slightly negative), since it's taking water from a pipe under pressure and discharging it right back into that pipe. So the system head is literally controlled by friction losses. So I started plugging in flows and heads along my developed system curve to see which would be me the proper combination of ejector backpressure and supply pressure/flow. Since the system head curve will only show me the head instantaneously at the booster pump, I had to factor in flow and headlosses to the ejector inlet.

My question is, am I overcomplicating this? Or does this seem like a reasonable way to design?  https://files.engineering.com/getfile.aspx?folder=e5d7-2b8c-4a0e-afd6-7cac1fc9&file=_CHLO_Bull__reprint.pdf
The injector performance is from the manufacturer. Yes there is a large pressure drop across the ejector.

250 lbs per day chlorine = 4.7 kg/hr.

Using the chart for EJ- Ejector. 30 psi (2.07 bar) = backpressure. The chart gives a 4.5 bar (65psi) inlet pressure and 105 lpm (27.7 gpm) flow.

You are taking water from the pipe at 20 psi. (your page shows 55 psi?). The pump boosts the pressure from 20 psi to 95 psi (20 + 65 + 10). The ejector has s pressure drop of 65 psi. That leaves 30 psi on the discharge side of the ejector.

I assume you have 7 psi head loss in the discharge piping after the ejector. That would leave you with the pressure in the bypass line of 23 psi which is then discharging into the main line which has a pressure of 20 psi.

Confirm with the manufacturer that the EJ- Ejector is the correct ejector size for 250 lbs/day.