How do you calculate how much your shielding gas is costing you per minute? If I
have an M sized tank of C25 (capacity 125) and I'm running it 20 cubic feet per
minute at 20 psi, how many minutes will that flow?

Is there a primer somewhere online or in a book that breaks this down?

Grant Erwin

Ignoramus20878 wrote:

Is that 20 cubic feet per MINUTE or per HOUR?

Ah. I think I'm beginning to see where I was led astray. If it's CFH, and the
tank is rated in cubic feet then the math is trivial. Thanks.

GWE

I think that a simple division would suggest that at 20 cfH, it would
last for 125/20 hours, or approximately 6 hours (note that also some
gas will be left in the tank). You divide the fill cost by 6 (hours)
and then by 60 (min/hr) to get the cost per minute.

Say your fill cost is $48.

Cost per minute = 48/(125/20)/60 = 12.8 cents per minute or $7.68 per hour.

i

Is there a primer somewhere online or in a book that breaks this down?

Grant Erwin

"Grant Erwin" wrote: (clip) I'm running it 20 cubic feet per minute at 20
psi, (clip)
^^^^^^^^^^^^^^
The part I don't get is the "20 psi" part.

On Tue, 29 Nov 2005 21:46:53 GMT, "Leo Lichtman"
wrote:


"Grant Erwin" wrote: (clip) I'm running it 20 cubic feet per minute at 20
psi, (clip)
^^^^^^^^^^^^^^
The part I don't get is the "20 psi" part.

It doesn't matter. The psi. All that matters is flow per time. All the
pressure does is push the gas out through an orifice.
ERS

Eric R Snow wrote:

On Tue, 29 Nov 2005 21:46:53 GMT, "Leo Lichtman"
wrote:



"Grant Erwin" wrote: (clip) I'm running it 20 cubic feet per minute at 20
psi, (clip)
^^^^^^^^^^^^^^
The part I don't get is the "20 psi" part.



It doesn't matter. The psi. All that matters is flow per time. All the
pressure does is push the gas out through an orifice.
ERS


Actually, it may matter. The flowmeters are calibrated for one gas,
at one pressure. If this is a one-piece, non-adjustable TIG regulator,
the flowmeter is probably calibrated for Argon or CO2 at the regulator
pressure. In the most general case, flowmeters are calibrated at STP,
so if the system is at 20 PSI gauge pressure, that is 2.3 Atmospheres,
and so the flowmeter will read somewhat low.

But, assuming the flowmeter was calibrated at this pressure, for this
gas, then PSI makes no difference in the gas consumption.

Jon

Grant Erwin wrote:

How do you calculate how much your shielding gas is costing you per minute? If I
have an M sized tank of C25 (capacity 125) and I'm running it 20 cubic feet per
minute at 20 psi, how many minutes will that flow?

Is there a primer somewhere online or in a book that breaks this down?

Grant Erwin

Connect a running time meter to the gas on contactor relay of your mig
welder and read it when the bottle runs dry. Divide the cost of the
gas cylinder by the number of minutes recorded on the timer.

John

Eric R Snow wrote:

On Tue, 29 Nov 2005 21:46:53 GMT, "Leo Lichtman"
wrote:


"Grant Erwin" wrote: (clip) I'm running it 20 cubic feet per minute at 20
psi, (clip)
^^^^^^^^^^^^^^
The part I don't get is the "20 psi" part.

It doesn't matter. The psi. All that matters is flow per time. All the
pressure does is push the gas out through an orifice.
ERS

You have to convert the numbers to volume of gas at standard pressure to
come up with a valid answer.

John

Grant Erwin wrote:

Ignoramus20878 wrote:

Is that 20 cubic feet per MINUTE or per HOUR?


Ah. I think I'm beginning to see where I was led astray. If it's CFH,
and the tank is rated in cubic feet then the math is trivial. Thanks.

GWE

I think that a simple division would suggest that at 20 cfH, it would
last for 125/20 hours, or approximately 6 hours (note that also some
gas will be left in the tank). You divide the fill cost by 6 (hours)
and then by 60 (min/hr) to get the cost per minute.

Say your fill cost is $48.
Cost per minute = 48/(125/20)/60 = 12.8 cents per minute or $7.68 per
hour.
i

Is there a primer somewhere online or in a book that breaks this down?

Grant Erwin




Is the tank pressure higher that the regulator pressure? If the tank is
100 PSI
and the regulator is set for 20 PSI then 1 cf in the tank will be 5 cf
after the regulator.

When the tank pressure drops the expansion will also drop. So the
calculation is not trivial.

Bill K7NOM

Are you still figuring the bid on that 3'x3' cube project? How did that
work out??

"Grant Erwin" wrote in message
...
How do you calculate how much your shielding gas is costing you per
minute? If I have an M sized tank of C25 (capacity 125) and I'm running it
20 cubic feet per minute at 20 psi, how many minutes will that flow?

Is there a primer somewhere online or in a book that breaks this down?

Grant Erwin

Emmo wrote:

Are you still figuring the bid on that 3'x3' cube project? How did that
work out??

The project wasn't actually a 3x3' cube. I just posed that as an ubersimple
design that anyone could comprehend with no drawings, to learn how you guys do
bidding. I figured it one way, then I figured the number of inches of weld and
cost it out the other way, they were within about 2%. I didn't get the job but
it wasn't because of my numbers, I couldn't store the customer's jig long-term
since my shop is in my house and my shop is too small so it would have to sit
outside, and in the town where I live this would result in losing my business
license.

I did learn a lot by bidding the job, though.

Grant

I'm pretty sure you could plug me into a regulator and i would be good
fer a few beads.
I'll even supply the oxygen
you bring the dune buggy frame

Try to find a man named Don Holder.
not the same person Don Smith in Michigan. very brilliant men with a
rich history.
Kalamazoo area
we grew up together and they are way smarter than I
Good friends of mine
Both are welding genies and have won many awards for their prowess
behind the Tig and stick.

Try to find a man named Don Holder.
not the same person Don Smith in Michigan. very brilliant men with a
rich history.
Kalamazoo area
we grew up together and they are way smarter than I
Good friends of mine
Both are welding genies and have won many awards for their prowess
behind the Tig and stick.

On Tue, 29 Nov 2005 21:46:53 GMT, "Leo Lichtman"
wrote:


"Grant Erwin" wrote: (clip) I'm running it 20 cubic feet per minute at 20
psi, (clip)
^^^^^^^^^^^^^^
The part I don't get is the "20 psi" part.


It's inconsequential for low pressure like 20 PSI. Ig's responses
were right, except that the delivery PSI will determine how much gas
gets left unused in the bottle. If "full" is about 2150 PSIG
(146.3 bar) 20 PSIG (1.36 bar) is better than 99% depleted.

Ignoramus20878 wrote:

On Wed, 30 Nov 2005 01:17:45 GMT, Bill Janssen wrote:



Is the tank pressure higher that the regulator pressure? If the tank is
100 PSI
and the regulator is set for 20 PSI then 1 cf in the tank will be 5 cf
after the regulator.

When the tank pressure drops the expansion will also drop. So the
calculation is not trivial.



the cubic feet capacity of the tank refers to quantity of uncompressed
gas at atmospheric pressure. I have a 300 c.f. tank, but it does not
occupy 300 ft of space (equivalent to 10 refrigerators). It only
occupies perhaps 5 cf or so.

i


Thanks for the correction. After I posted It accured to me that the
capacity as I stated would require
a large tank.

So I stand corrected (informed).

Bill K7NOM

In article ,
says...


Eric R Snow wrote:

On Tue, 29 Nov 2005 21:46:53 GMT, "Leo Lichtman"
wrote:



"Grant Erwin" wrote: (clip) I'm running it 20 cubic feet per minute at 20
psi, (clip)
^^^^^^^^^^^^^^
The part I don't get is the "20 psi" part.



It doesn't matter. The psi. All that matters is flow per time. All the
pressure does is push the gas out through an orifice.
ERS


Actually, it may matter. The flowmeters are calibrated for one gas,
at one pressure. If this is a one-piece, non-adjustable TIG regulator,
the flowmeter is probably calibrated for Argon or CO2 at the regulator
pressure. In the most general case, flowmeters are calibrated at STP,
so if the system is at 20 PSI gauge pressure, that is 2.3 Atmospheres,
and so the flowmeter will read somewhat low.

If this is the usual rotameter (ball in a tapered tube
floweter), the accuracy will be affected by downstream
pressure, but is relatively insensitive to the regulator
setting. In other words, backpressure due to restrictions
between the flowmeter and atmosphere will affect accuracy
more than the pressure at the inlet to the needle valve,
which is upstream from the flowmeter.

Ned Simmons

On Tue, 29 Nov 2005 12:49:31 -0800, Grant Erwin
wrote:

How do you calculate how much your shielding gas is costing you per minute?

Take the bottle hire charges, divide by 365x24x60

Prices round here, the gas itself is free 8-(

On Tue, 29 Nov 2005 13:22:30 -0800, Grant Erwin
wrote:

Ignoramus20878 wrote:

Is that 20 cubic feet per MINUTE or per HOUR?

Ah. I think I'm beginning to see where I was led astray. If it's CFH, and the
tank is rated in cubic feet then the math is trivial. Thanks.

GWE

Its indeed in CFM/H

Gunner, who pays $18USD + $3 for a 135 CF tank of Argon OR C25


I think that a simple division would suggest that at 20 cfH, it would
last for 125/20 hours, or approximately 6 hours (note that also some
gas will be left in the tank). You divide the fill cost by 6 (hours)
and then by 60 (min/hr) to get the cost per minute.

Say your fill cost is $48.

Cost per minute = 48/(125/20)/60 = 12.8 cents per minute or $7.68 per hour.

i

Is there a primer somewhere online or in a book that breaks this down?

Grant Erwin




"Pax Americana is a philosophy. Hardly an empire.
Making sure other people play nice and dont kill each other (and us)
off in job lots is hardly empire building, particularly when you give
them self determination under "play nice" rules.

Think of it as having your older brother knock the **** out of you
for torturing the cat." Gunner