How many PSI do I need to get 2CFM?

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In summary: The pump will just deliver the set flow rate. In summary, the project that the author is working on requires 2 cfm of air flow to work optimally. The fish experts say that the author needs 2 cfm of air flow to push through the stone diffuser. The author is trying to figure out if there is a formula that could tell him how much air pressure he needs to set his regulator to in order to achieve this flow. The author is considering a fixed displacement air pump that will deliver the set flow rate.
  • #1
texamwalker
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The project that I am working on.
I am aerating a pond with an air stone diffuser. The diffuser requires 2 CFM of air flow to work optimally.
Im feeding this diffuser with 1/2" pvc line at a distance from compressor to stone is approx. 200 feet.

The stone is placed 10 feet deep under the water.
At what psi would in need to set my regulator to maintain an even volume of 2 CFM to my diffuser.
This will help me size my compressor which is what I am trying to do. If the answer is X psi then when I hook it up I need to keep sizing my compressor up until it can generate enough air to over overcome X psi and overcome the amount of air being released into the line through my regulator. Hope this question makes sense.
 
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  • #2
Welcome to PF.
There will be a small pressure loss in the pipeline and some in the stone but the most significant pressure requirement is the hydrostatic pressure at 10 feet, which will be about 5 psi.
 
  • #3
Thanks. That answers part of my question. I'm pretty sure that whatever air compressor/pump I use, will be able to produce pressures well over that to overcome the weight of the water. I'm more concerned with being able to push enough volume(cfm) of compressed air to my stone diffuser.
The fish experts say that I need 2 cfm of air being pushed through the stone.
So, without using some sort of fancy meter that I would have to install inline that could read air flow in cfm, I'd like to know if there is some formula that could give me my answer.
Something that would say, you need to set your regulator @ ?psi to achieve a flow of 2cfm at the end of your 200' long 1/2" PVC line that is 10 foot under water.
 
  • #4
I think you need to regulate flow rather than pressure.
Maybe you should consider a fixed displacement air pump running at a fixed speed.
There are many choices, consider a vane, gear or piston pump. If possible, lubricated with water.
That will be most energy efficient since there is no regulator.
 
  • #5


To determine the necessary PSI for 2 CFM of airflow to your diffuser, we first need to understand the relationship between pressure and flow rate. In this case, the ideal gas law can be used to calculate the pressure needed to achieve 2 CFM of airflow.

First, we need to convert 2 CFM to a standard unit of measurement, such as cubic meters per minute (m3/min). This can be done by multiplying 2 CFM by 0.00047 (1 CFM = 0.00047 m3/min), resulting in 0.00094 m3/min.

Next, we need to calculate the volume of air that can be delivered by your 1/2" PVC line at a distance of 200 feet. Assuming the line has a diameter of 1/2 inch (0.0127 meters), the cross-sectional area would be 0.000126 m2 (πr2, where r is the radius of the pipe). Multiplying this by the length of the line (200 feet = 60.96 meters) gives us a volume of 0.0077 m3.

Now, we can use the ideal gas law (P = (mRT)/V) to calculate the pressure needed to achieve 0.00094 m3/min of airflow through a volume of 0.0077 m3. Assuming the temperature is constant at 25°C (298.15 K) and the mass of air is 1 kg, we can rearrange the equation to solve for pressure (P = (mRT)/V).

P = (1 kg * 8.314 J/mol*K * 298.15 K) / 0.0077 m3

P = 3325.59 J/m3

P = 3325.59 Pa or 0.48 PSI

Therefore, to achieve 2 CFM of airflow to your diffuser, you would need to set your regulator to 0.48 PSI. However, it is important to note that this calculation assumes ideal conditions and does not account for any loss of pressure due to friction or other factors. It may be necessary to slightly increase the pressure to compensate for these losses.

Additionally, as you mentioned, the compressor must be able to generate enough air to overcome this pressure and continuously supply 2 CFM of airflow. It may be necessary to size up the compressor to ensure it can meet these requirements.
 

1. What is PSI and CFM?

PSI stands for pounds per square inch and is a unit of measurement for air pressure. CFM stands for cubic feet per minute and is a unit of measurement for air flow rate.

2. Why do I need to know how many PSI I need to get 2CFM?

Knowing the required PSI and CFM is important for selecting the right air compressor for a specific task. Different tools and equipment require different levels of pressure and flow, so it's important to match the PSI and CFM to the tool's requirements.

3. How do I calculate the required PSI for 2CFM?

The formula for calculating PSI is: PSI = (CFM x 14.7) / (RPM x 2), where RPM is the pump's revolutions per minute. For 2CFM, the required PSI would be: (2 x 14.7) / (RPM x 2). Keep in mind that this is a general formula and may vary depending on the specific tool or equipment being used.

4. Is 2CFM enough for my project?

It depends on the specific project and the tools or equipment being used. Some tools and equipment may require more than 2CFM, while others may require less. It's best to consult the tool's manual or manufacturer for the recommended CFM for optimal performance.

5. What happens if I use the wrong PSI for 2CFM?

Using the wrong PSI for 2CFM can result in inefficient or inadequate performance of the tools or equipment. It can also potentially damage the tools or equipment and lead to safety hazards. It's important to always use the recommended PSI for the specific tool or equipment being used.

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