You may already read my blog about how to size air compressor and instrument air capacity. Please check this link if you have not read the article. I hope you find it useful.

As a continuation of the post, I want to share you how to size capacity of compressed air receiver.

Compressed air receiver is used as buffer and storage medium between the compressor and air consumers.

A common formula used to size compressed air receiver is as followed:

**V = (t/60) x C x p _{a}/(p_{1}-p_{2})**

Where:

V = volume of receiver tank (m^{3})

t = time for the receiver to go from upper to lower pressure limit (minute)

C = air consumption (m^{3}/h)

p_{a} = atmospheric pressure (1.01 bara)

p_{1} = maximum tank pressure (bara)

p_{2} = minimum tank pressure (bara)

**Example Sizing of Compressed Air Receiver**

For an air compressor system with air consumption 100 Nm^{3}/h, with actual supply pressure 8 barg (8.84 atma) and actual supply temperature 30^{o}C (303.15 K), maximum tank pressure 9 barg (10.01 bara), minimum tank pressure 7 barg (8.01 bara) and 15 minutes time for the receiver to go from upper to lower pressure – the volume of the receiver tank can be calculated by following step.

**Step 1: Calculate air consumption (C) at actual condition**

Air consumption at actual condition can be simply calculated by using the following formula:

P_{1} x V_{1}/ T_{1} = P_{2} x V_{2}/T_{2}

Where:

P_{1} = Pressure at standard condition (1 atma)

T_{1 }= Temperature at standard condition (273 K)

V_{1} = Air consumption at standard condition (Nm^{3}/h)

P_{2} = Pressure at actual condition (atma)

T_{2} = Temperature at actual condition (K)

V_{2} = Air consumption at actual condition (m^{3}/h)

Equation above is modified into:

V_{2} = P_{1} x (V_{1}/ T_{1}) x (T_{2}/P_{2})

V_{2} = 1 x (100/273) x (303.15/8.84)

V_{2} = __12.56 m ^{3}/h__

So, air consumption at actual condition is 12.56 m^{3}/h.

**Step 2: Calculate air receiver capacity**

Use this formula to estimate air receiver capacity:

**V = (t/60) x C x p _{a}/(p_{1}-p_{2})**

V = (15/60) x 12.56 x 1.01/(10.01-8.01)

V = 1.58 m^{3}

So, estimated air receiver capacity is 1.58 m^{3}.

I hope you find this post useful.

Tired of calculationg by yourself? Click this link to download spreadsheet of preliminary sizing of air receiver capacity.

In Step 2 of your calculation, you have used the flow rate at actual conditions for C instead of standard conditions as shown in most other references. Is this correct?

Hello,

I rechecked the references. My mistake, the correct one is using flow at standard condition.

Thank you for correcting me.

We are sizing of a receiver, but what if initially we don’t have an air receiver, so how to find time for this formula?? Please clear my doubt..

And there is also a thumb rule of sizing air receiver by multiplying compressor cfm by 1.5 and receiver size get in gpm

In Design Basis, we usually define how long the buffer time of air receiver. Most company use 15-30 minutes buffer time. You can use 15 minutes for initial sizing.

I am not sure about rule of thumb that you mentioned. I usually using buffer time, initial pressure, and final pressure, to get size of receiver.

We are sizing of an air receiver, so what if initially, we don’t have an air receiver then how to measure time?

Please clear my doubt.

Also, there is a thumb rule of multiplying compressor cfm by 1.5 and receiver capacity get in gallons.

Hi Rifka,

Thanks for sharing you calculation but I’ve confusion on Step 2. The flowrate, C to be used is either at Standard (Nm3/h) or Operating (m3/h)? Most of other example show that Standard (Nm3/h) to be used but your example is using the Operating flowrate @ 8bar. Appreciate your feedback. TQ

Hi Chen. There is a mistake in the calculation. You are correct. It should be multiply by flowrate in standard condition, not operating condition. I will update the blog in near future.

Hi. I think for sizing air receiver tank, need to use actual volume @ 8 bar. Since, depending on storage pressure, the actual volume would change even if normal volume is same.