co2 pipw work flows

In my opinion, The smaller the pipe you can run would be better (cost efficient wise) as long as a larger volume is not needed at the end, so the 1/4 pipe would be most cost efficient basically. but also stainless steel would be the safest bet for less problems in the long run, but would be higher cost yet last longest. :)

Dear chrishamlett:

...

There are design requriements that may or may not apply based on low temperature design. What is the wall thickness and material of the 1/4" now?

Increasing the surface area of the piping increases heat loss to ambient. Increasing the diameter also serves to slow the velocity down, requiring that the flow stay in this now-warmer environment longer.

Personally, I'd hire a consultant. Someone that can keep your company out of litigation. If you don't, then I'd recommend you have your customer do it.

David A. Smith

Let's get a feel for this question by dealing with one that you may be more familiar with. If I run an electric hedge trimmer from a 25 ft electric extension, how would I choose a 100 ft extension lead?

The very first question you would probably ask is "What current does the hedge-trimmer take? Then, " how thick are the wires in the 25 ft extension?"

Given these data, you could probably deduce that if the voltage drop with the short extension was satisfactory, you would need about four times the wire cross-section in a 100 ft extension. Perhaps less than that even.

Now your actual question: we have the pressure, the temperature, but not the maximum flow rate desired. This is a problem. If the flow is negligible (unlikely, because you are selling them a bigger tank) then you could run 1/4 inch pipe all the way.

OK, lets suppose that you don't want to increase the head loss (pressure drop) due to steady flow over the longer route by more than

Old pipe: length X V^2 / 0.25 New pipe:

This amounts to reducing the flow velocity to one half its former value, giving 1/4 the head loss per unit length. This slower flow speed for equal flow rate needs a pipe diameter about root( 2) X 1/4 inch so a 1/2 inch pipe has got a chance!

This setup has the potential for causing a nasty accident - if a truck runs into it etc., etc. Are you fitting a flow snubber?

If you were in the US you might be well-advised to pay for an engineer's design. A lawyer for the plaintifs could search on the name "IGC company", for example. If he found your note on this group, he would be home and dry for a big payout!

Good Luck

Brian Whatcott Altus OK

Brian thanks for the reply, at present the customer uses the liquid out of a 200 ltr vessel which is 8 mtr a way from the job he uses 4 to

regards Chris

Well let's see: Torricelli found that the flow speed from a hole was the same as the speed that a particle would travel if dropped from the same height as the 'head' i.e. pressure. that is, V = sqrt( 2.g.H) H is head, g = 9,81 m/s/s

The pressure you give is 300 psi. Liquid CO2 has a density of

But the nozzle diameter is 1/8 inch or 3.2 mm so its area is pi D^2/4 = 7.9E-6 m^2 and the flow rate is 72.2 X 7.9E-6 m^2 / s = 0.000570 cu meters/sec

Let's cross check: how long would a 200 liter tank last, if I got these numbers right?

That's remarkably fast. Perhaps we had better model the pipe length as more than just an 1/8 in diameter hole.

In this case, instead of Torricelli's relation for exit speed, we use a variation V = sqrt(2.g.H / (1 + K) ) where K is a loss coefficient K = 4 f L / D where L = pipe length, D is pipe diam f is a friction factor say 0.008

K = 4 x 0.008 x 0.3 / 0.0032 = 3

Hmmmm... that halves the maximum flow - still goes pretty fast, uh?

In other words, just working out the maximum flow out of 12 inches of a 1/8 in diameter pipe overstates the maximum rate the customer uses.

Oh well...

Brian Whatcott Altus OK