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Can anyone help me on determining the flow rate of argon?

Can anyone help me on determining the flow rate of argon?

Can anyone help me on determining the flow rate of argon?

(OP)
I am an intern at a steel mill. I very new to this, so bear with me. I currently have a project to size a flowmeter. I know the pressure upstream is around 200psig, this is coming from and Airliquide vessel outside the plant. Down stream we have a pressure regulator and it is regulated down to 80 psig. The headlosses for the system will take forever to determine. The temperature leaving the vessel is -20 degrees F and I am not sure what the temp is at the regulator. Please any help would be greatly appreciated.

RE: Can anyone help me on determining the flow rate of argon?

Constant enthalpy?
Heat gain/loss from piping to 80 psig regulator depends on flow rate, ambient temp, insulation, etc.

Look at http://webbook.nist.gov/chemistry/fluid/  for argon thermo physical properties.  

I assume you want the temp of gas downstream of the 80 psig regulator.

Determine the process, look up the thermo physical properties.

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Actually I need the flow rate. Sorry for the confusion. I am trying to determine the max and min flow rates for the application. I believe the temperature of the gas is 70 degree F, because the pipe goes underground.

RE: Can anyone help me on determining the flow rate of argon?

All you need to find out is what range of flowrates you want to measure and where you will have room to put in a flow meter, in the 200 psi line or in the 80 psi line.

You will also need to determine how accurate you need the flowrate measurement.  A rough flowrate can be determined from a simple orifice plate, for +/- 0.5% you'll need a proper flow meter of some type of which there are several types to chose from, a meter tube with a machined orifice fitting or a turbine meter, or you could use a coriolis meter.  You should have a straight place about equal to 20 x the pipe diameter to install a proper metering device.

You may be able to get an idea of the average flowrates by finding out how many times they are filling the tank and divide by the hours of operation, then apply some "factors".

If you still can't estimate the hi and lo flow rates, make a rough estimate of the lengths of pipe of various pipe diameters going from the vessel to the regulator, measure the temp at the tank and regulator and repost the answer here, or send me an e-mail if you like.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

Do you have a level instrument or, better yet, a level recorder on the argon tank?  If you have a recorder or data achive, use that to determine minimum, average, and maximum usage rates.  If the tank vents off vapor to control it's pressure and temperature you'll have to figure that out too.

Good luck,
Latexman

RE: Can anyone help me on determining the flow rate of argon?

Another suggestion for guesstimating flow rate:

How often do is your argon delivered and in what quantity?

Divide the volume of delivered product by the number of minutes/hours between deliveries for a guesstimate.
Modify that by whether the argon is used continuously, like a continuous bleed into an atmosphere furnace, or unevenly in batches.

I've had similar situations, where the flow rates were total unknowns.

What I did was install a set of orifice flange unions, and a valved bypass on the straightest run of pipe I could find.  I got a multivariable DP transmitter which takes a temperature reading from an RTD in addition to knowing the DP and static AP upstream of the orifice (I use Honeywell SMV, Rosemount makes one, too.)   Rather than install a
thermowell and RTD for just a flowrate test, I configure the meter for a fixed gas temperature and buy 3 orifice plates sized to beta 0.75, 0.5 & 0.3 for the pipe diameter at the working pressure of the line.  

Then I'd install the 0.75 plate and check flow rate.  If the flow was down in the noise region, I'd go to bypass, swap to the 0.5 plate, and see what it looked like.   If low on the 0.5 plate, I go to 0.3.   

My assumption (not always valid) is that someone sized the pipe to maintain some reasonable flow rate, so I have a fair chance of hitting a readable flow somewhere over a range of 0.3 - 0.75 beta for a given pipe size.

I've done this 4 times so far and it's worked OK 3 times.  The one time it didn't the flow rate was pitifully small for a 2" line, so I rigged a section of pipe with 3/4" line and got a reasonable flow rate from the 3/4" line.  

I don't leave the multivariable in the line because it's a test tool.  It's been replaced with 3 different flow meters: a rotameter, a vortex meter and a turbine meter, depending on service, but each of those flowmeters needs a flow range to be sized correctly.

Clamp-on ultrasonics might now be useable on gases, but when I did my projects, I couldn't hire anyone to measure gas flows with clamp-ons.  Technology has likely changed over 5 years.

Dan

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Well, I need the flow rate going to the purging system. This is the 80 psi end of the regulator. There is at least 100 yard(estimate) of piping and who know how many bends. There is also a elevation change of about one story, so lets say 20 ft. The temp leaving the vaporizer, right before going underground, is -20 degree F below ambient. I believe the temp at the regulator is ambient temperature. The flow rate at the outside regulator is 480000 scfh. This flow rate is teed off and slit into two seperate piping system. I am assuming the flow rate is 24000 scfh for each line.

RE: Can anyone help me on determining the flow rate of argon?

That is a very big tank.  Are you sure about the 480,000 scfh?  Since regulators do not indicate flow I assume that you are basing the flow rate statement on changes in tank level?  Correct?

StoneCold

RE: Can anyone help me on determining the flow rate of argon?

As stated in a previous thread on orifice metering, the volumetric flow is simply the stream velocity times the area of the bore of the pipeline.  You can use the Bernoulli Equation to determine velocity of the fluid in the pipeline as a function of pressure drop.

Without getting heavy handed, you can make the assumption that the flow is isentalphic and not compressed.  It has been correctly pointed out from Zapster's comment on isenthalpic flow that in the absence of throttling, heat loss is neglegable.  Other assumptions are that the pipeline is perfectly level (no potential gradient), frictional losses are low (ideal fluid), efficient exit condition (unity for velocity coefficient) and isentropic flow (reversable).  Then:

P1/rho1 + 1/2 v1^2 = P2/rho2 + 1/2 v2^2

set v1 = 0 (vessel very much larger than pipeline; this means the surface drop is small compared to fluid exiting the pipeline) and we would get the velocity of the fluid through the pipeline as:

v2 = sqrt(2[P1-P2]/rho)    rho=fluid density

This is the Bernoulli Equation under all the stated assumptions, thus giving us stream velocity.  Since the area of the pipeline bore is A=1/4(ID^2) then the volumetric flow of your stream is:

V' = v2 X A    Volumetric Flow Rate

You have enough information to get stream velocity, but failed to state pipeline size and schedule. I cannot compute a final, approximate answer.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

RE: Can anyone help me on determining the flow rate of argon?

The area of the pipeline bore is "1/4 pi (ID^2)", I forgot the coefficient of pi=3.14156 in the original post.  Sorry.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

RE: Can anyone help me on determining the flow rate of argon?

Hi WayneLee.  As StoneCold mentions, the 480,000 SCFH is rather high.  That's the equivalent of roughly 4200 gallons of liquid argon per hour.  You'd need a decent sized ASU on site to furnish that, not a tank.  

I'd agree with the folks saying you should check your delivary records, but there's an even better way to get more accurate and time dependant data.  You could chart the tank liquid level directly.  Most, if not all of your industrial gas companies use something called "telemetry".  What happens is there's an electronic box attached to the dP guage that's used to determine tank quantity.  That box takes readings every 15 minuts or every few hours, depending on how it's hooked up.  It then stores a large number of data points, on the order of thousands, and then when it is programmed to, it phone calls the industrial gas supplier and downloads that information to a database.  

I'd suggest you ask your industrial gas provider for that information in EXCEL format and then you can plot the data over any period of time.  It should be as easy as them pulling it down from their database and emailing it to you.  They should also be able to correlate for you the liquid contents versus dP if they don't already have that in the database.  Also, if the data they have is not taken in small enough time increments for what you need, you could ask them to set the telemetry to almost any time period you want and have them send you that data over any time interval.  You could for example, ask them to have the telemetry record a data point as little as every 15 seconds.  Just tell them what you want and they should be able to pull it down from a database or create a special one for you.

Anyway, talk to your industrial gas salesman for this type of information.  He should be glad to send it to you, and if he doesn't, tell us what company it is you get the Argon from and I suspect someone here could "help you out" so to speak.

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Im sorry, I meant to put 48,000 scfh. There is a meter on the tank outside of what level of liquid argon is left in the tank. Maybe I could see if there is some type of delivery record. The pipe size is 1 inch and schedule is 40. Also, could I just put a anemometer at the end of the hose that connects to the vessel. This would give me a velocity, which I can then use bernoulli's  equation to get flow rate in the pipe.

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Is it safe to use bernoulli's equation and neglect any any elevation change.

p1+rho*v1^2/2=p2+rho*v2^2/2

let v2 be negligible
p1=80psi
p2=0

Solving for v1 gives me p2-p1=-80psi
Can I just take the absolute value? To solve for v1 I would need a positive number under the square root. However, I end up with a negative number under the square. Please can anyone tell this is feasible?

RE: Can anyone help me on determining the flow rate of argon?

Yes you can neglect elevations,because gas density doesn't change much with small elevation changes, but you must adjust rho at different pressures.  P2 does not equal 0.  You must use absolute pressures (add 14.696 psi to each gauge pressure) and absolute temperatures must also be used if temperatures are to be considered. You are also assuming that it is an ideal gas, which probably doesn't matter too much, but you might want to check the compressibility factor for argon to be sure.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Well, the only way know how to solve the problem is: assume ideal gas and use equation of state.

P1*V1/T1=P2*V2/T2

(180+14.7)psia*24000scfh=(80+14.7)psia*V2 (neglect temperature change)

I end up with 900 scfm

Tell me, is this is a sufficient enough answer to size my flow meter?

Also, I am using scfm, do I need to convert to acfm to size my flow meter?

When converting to acfm, do you have to take into account that the fluid is argon?


Please any help will be greatly appreciated.

RE: Can anyone help me on determining the flow rate of argon?

1. How can you assume ideal gas with a liquid supply?

2. The temperature change is 90 degrees, I wouldn't neglect that, not to mention phase change at some point.

3. Assuming the 24000 scfh is only accurate if both circuits after the "T" have equivalent losses.

4. With your bournoulli equation above, you need to solve for v2, v1 is the tank velocity which is assumed 0.  That equation only applies if the mass flow rate at both points 1 and 2 are equal which, if I understand correctly, is not the case.

RE: Can anyone help me on determining the flow rate of argon?

Insult,


Bernoulli across the orifice,
(note i left out the density variable on purpose)

1.  If its gas before the meter and gas after the meter and the meter only loses 10-20 psi with no temperature change across the meter, yes I would assume an ideal gas to size the meter.

2.  The temperature changed is 90 degrees from where?  If it doesn't change 90 degrees across the meter its not relavent.

3.  Why not assume flow can be controlled to be equal?

4.  V1 is the flow upstream, V2 and downstream of the meter, V1 = V2 (assuming upstream and downstream piping is the same diameter).  What is missing is the head loss of the flow across the orifice.

H1 + V1^2 + P1- Hlo = H2 + V2^2 + P2

assume pressure loss is 10-20 psi, T1 = T2, ideal gas
Same pipe diameter upstream and downstream, V1 = V2
Estimate orifice diameter first using ideal gas
for small pressure drop rho1 = rho2
Assume elevation upstream = elevation downstream
H1 = H2

V1^2 + P1- Hlo= V2^2 + P2

V1 = V2
P1 - Hlo = P2
=====================================================
Lee,
To estimate size the meter (an orifice plate with dP)
Use Bernoulli upstream of orifice and through (inside) the orifice

V1 = velocity upstream
V2 = velocity through orifice
H1 = H2
rho1 = rho2, small pressure drop
T1 = T2

H1+V1^2 + P1= H2 + V2^2 + P2
V1^2 + P1= V2^2 + P2
P1-P2 = V2^2-V1^2

then downstream
P2 - P3 = V3^2 - V2 + orifice flow recovery factor * (P2-P3)

iterate until you only have a small pressure drop

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

BigInch, I understood what you were saying, but he wasn't applying it correctly.  I think he was trying to follow cockroach's instructions.

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Insult

I believe it is a gas supply. It is supplied from a 6050 gallon vessel, which then flow through a vaporizer.   

Big Inch

I dont believe I have access to an oriface plate. Unless I am not understanding something, are you referring to bernoulli's equation or is that the actual equation?

RE: Can anyone help me on determining the flow rate of argon?

If you can measure the pressure and temperature at two locations along that 80 psig line (preferably straight in between), you can then use Bernoulli's equation to back into the velocity because you know that the mass flow at each point must be equal.  Furthermore, if the pipe is uniform and the temperature and pressure changes are small, then the stream velocity at each point must be equal as well so you could simply the equation.

RE: Can anyone help me on determining the flow rate of argon?

oh, forgot to mention...

"I believe it is a gas supply. It is supplied from a 6050 gallon vessel, which then flow through a vaporizer."

If is flows through a vaporizor, then the tank must contain a liquid.

RE: Can anyone help me on determining the flow rate of argon?

(OP)
insult

Yes it does contain liquid in the vessel. Are you saying that I could have a two phase mixture on my hands. If pressure and temperature are small and the height doesn't change then, along a stream line it is constant. I still dont know what the velocity upstream or downstream. All I have is:

Outside (at the vessel)
Pressure after the vaporizer: 180 psig
Flow rate at the regulator: 24000 scfm(assumed from 48000/2)
Temp leaving vaporizer: -20 degrees below ambient


Inside (near the purging system)
Pressure regulated down to: 80 psig
Temp( Assuming Ambient): 70 F

Vessel    Vaporizer              Inside
_____      _  _  _
[     ]    || || ||        (+100ft of piping)
[     ]    || || ||        (elevation change of 15ft)     
[     ]    ||_||_||        (numerous elbows)
[___  ]---|      |---0-----/     /-------0------= exit

              P=180psig                   P=80psig
              T=70F                       T=70F   
              Q=24000scfh                 Q=?
               




            


RE: Can anyone help me on determining the flow rate of argon?

After the vaporizer it should be all vapor.  I was addressing your application of bournoulli's equation which you were applying from the tank and setting one of the velocities to 0.

Try this:

Point 1:
P_1 = 180 psig    T_1 = 70 F     z_1 = 15 ft

Point 2:
P_2 = 80 psig    T_2 = -20 F     z_2 = 0 ft

For conservation of mass, m_dot_1 = m_dot_2; therefore, rho_1*A_1*v_1 = rho_2*A_2*v_2

Assuming A_1 = A_2, then v_1 = v_2*(rho_2/rho_1)

Plug everything into bournoulli:

P_1 + rho_1*{[v_2*(rho_2/rho_1)]^2}/2 + rho_1*g*z_1 = P_2 + rho_2*(v_2^2}/2

Look up or calculate the values for the densities and solve for v_2.  Just be careful with units.

RE: Can anyone help me on determining the flow rate of argon?

wink

RE: Can anyone help me on determining the flow rate of argon?

(OP)
insult

Thank you very much. Please excuse my ignorance and lack of experience.


RE: Can anyone help me on determining the flow rate of argon?

Cheers.  We like this.  Better than working a real job. cheers  

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

(OP)
One last question, the velocity to calculate the flowrate, does this mean its acfm or scfm? I am assuming acfm.

RE: Can anyone help me on determining the flow rate of argon?

OK last answer.  

Everything is always acfm, acfm acfm, unless you're writing up a report or selling the stuff.  Then its acfm converted to scfm at the sales contract custody transfer conditions.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

(OP)
thanks

never assume anything?

RE: Can anyone help me on determining the flow rate of argon?

your bill is in the mail!  tongue

RE: Can anyone help me on determining the flow rate of argon?

(OP)
insult

you are an insult to injury

RE: Can anyone help me on determining the flow rate of argon?

(OP)


correction :you add insult to injury

RE: Can anyone help me on determining the flow rate of argon?

(OP)
I am getting 1646 ft/s. Is this number to high?

RE: Can anyone help me on determining the flow rate of argon?

That number seems a bit larger than expected.  I would have expected something much less.  Double check your math and units.

RE: Can anyone help me on determining the flow rate of argon?

Too high. 1646 ft/sec = 1122 miles/hr (Mach 2). Hard to believe 80 psig producing that flow through any significant length piping.  The problem isn't entirely defined, but easy to solve if 24000 scf/hr is correct.  Simplified calculation  using ideal gas law in form V' = (T'/T) x (P/P') x V:

Convert 24000 scf/hr (scf @ 60oF (288.7 K, 14.73 psia) to cf/hr  at at 70oF (294.3 K) and 80 psig (94.7 psia):

= (294.3/288.7) x (14.73/94.73) x 24000
= 3804 cf/hr at 70oF (294.3 K) and 80 psig (94.7 psia).
= 1.0567 cf/sec.

A 1" Sch 40 pipe has inside cross-section π(1.049)2/4 = 0.864 sq. inches = 0.006002 sq. ft.
Hence, linear flow rate
= 1.0567(cf/sec)/0.006002 sq. ft
= 176 ft/sec

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Here is how I set up the problem:

P1=(180+14.7)psia
T1=(70+460)R
Z=0

P2=(80+14.7)
T2=(70+460)R
Z2=15 ft


I got the density for the different pressures. Then, like insult said, used convervation of mass to be able to solve for V2.

P1+rho1*(rho2/rho1*V2)^2/2=P2+rho2*V2^2/2+rho2*g*Z2

I also used mathcad to check my calculations. I went through the calcualation several times. I dont see anything wrong, but I could be wrong.

RE: Can anyone help me on determining the flow rate of argon?

Excuse me, but it seems you are treating the 80 psig regulator as a pressure measured on a piping system.*  Unless the upstream portion isn't adequately supplying the regulator to maintain the 80 psig output, it doesn't matter.  Could be a 12" diameter pipe at 2000 psi upstream -- doesn't matter.
What is downstream of the 80 psig regulator??

*OK if 80 psig was measured with the regulator valve fully open, with max usage downstream.

RE: Can anyone help me on determining the flow rate of argon?

WayneLee,

Is the pipe the same dimension at the 180 and 80 psi?  If not, the bournoulli simplification won't be right.  Also, I just realized that I omitted the head loss term in that equation so don't forget about that.  Even without that term though, I don't think it should produce such a high velocity.

RE: Can anyone help me on determining the flow rate of argon?

(OP)
Well, I tried a different approach. Tell me if I'm doing this right. Same approach, just solving for v1. This is at the exit point.

P1=(80+14.7)psia
T1=(70+460)R

P2=14.7psia
T2=(70+460)R

Here, I just assumed A1=A2. Then let V2=(rho1/rho2*V1). I end up with 452 ft/s for V1.

RE: Can anyone help me on determining the flow rate of argon?

Hi WayneLee.  If you're trying to determine the velocity of flow through a pipeline due to pressure drop, Bernoulli's isn't needed and won't work.  Only the continuity equation is needed (ie: mass flow per unit time = velocity x area x density).  Of course, this means you have to accurately know all but one of the variables which from reading your thread seems like you don't.

If you're trying to determine mass flow from the available information, you're not going to get there.  You don't have enough info.  Pressure drop and frictional flow calculations are nicely summarized in the Crane Paper #410 and many other references, but Bernoulli's doesn't work for frictional flow, it is only a conservation of energy equation.

RE: Can anyone help me on determining the flow rate of argon?

Bernoulli's works for frictional flow when you include the head lost due to flow friction.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

WayneLee,

This thread is getting too long and you still don't have the answer you need.  

If you want to try to contact me directly, go to my webspace page, profiles tab and get my e-mail address.  Send me a e-mail and I'll help you finish with this thing.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

"Bernoulli's works for frictional flow when you include the head lost due to flow friction. "

That's the point, the calculations above don't include head loss due to flow.  The point is that you can't determine flow or pressure drop without considering frictional flow.  Besides which, trying to determine flow rate from pressure drop in a pipeline is fraught with inaccuracies.

PS: How long does a thread need to be before it is "too long"?  

RE: Can anyone help me on determining the flow rate of argon?

I'd say after 4 or 5 stitches, it should be finishing up, or somebody needs to get on either MSMessenger or the telephone.

   Going the Big Inch! worm
http://virtualpipeline.spaces.msn.com

RE: Can anyone help me on determining the flow rate of argon?

(OP)
A thread is never too long.

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