Receiver Tank Calculations

Receiver Tank

My colleague, Lee Evans, wrote a blog about calculating the size of receiver tanks within a compressor air system.  (You can read it here: Receiver Tank Principle and Calculations).  But, what if you want to use them in remote areas or in emergency cases?  During these situations, the air compressor is not putting any additional compressed air into the tank.  But, we still have potential energy stored inside the tanks similar to a capacitor that has stored voltage in an electrical system.  In this blog, I will show how you can calculate the size of receiver tanks for applications that are remote or for emergency systems.

From Lee Evans’ blog, Equation 1 can be adjusted to remove the input capacity from an air compressor.  This value is Cap below.  During air compressor shutdowns or after being filled and removed, this value becomes zero.

Receiver tank capacity formula (Equation 1)

V = T * (C – Cap) * (Pa) / (P1-P2)

V – Volume of receiver tank (cubic feet)

T – Time interval (minutes)

C – Air requirement of demand (cubic feet per minute)

Cap – Compressor capacity (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P1 – Tank pressure (PSIG)

P2 = minimum tank pressure (PSIG)


Making Cap = 0, the new equation for this type of receiver tank now becomes Equation 2.

Receiver tank capacity formula (Equation 2)

V = T * C * (Pa) / (P1-P2)

With Equation 2, we can calculate the required volume of a receiver tank after it has been pre-charged.  For example, EXAIR created a special Air Amplifier to remove toxic fumes from an oven.  The Air Amplifier was positioned in the exhaust stack and would only operate during power failures.  In this situation, product was being baked in an oven.  The material had toxic chemicals that had to cross-link to harden.  If the power would go out, then the product in the oven would be discarded, but the toxic fumes had to be removed.  What also doesn’t work during power outages is the air compressor.  So, they needed to have a receiver tank with enough volume to store compressed air.  From the volume of the oven, we calculated that they need the special Air Amplifier to operate for 6 minutes.  The compressed air system was operating at 110 PSIG, and the Air Amplifier required an average air flow of 10 cubic feet per minute from the range of 110 PSIG to 0 PSIG.  We are able to calculate the required receiver volume to ensure that the toxic fumes are evacuated from the oven in Equation 2.

Receiver tank capacity formula (Equation 2)

V = T * C * Pa / (P1 – P2)

V = 6 minutes * 10 cubic feet per minute * 14.7 PSIA / (110 PSIG – 0 PSIG)

V = 8 cubic feet.

Receiver tanks are more commonly sized in gallons.  In converting 8 cubic feet to gallons, we get a 60-Gallon Receiver Tank.  EXAIR recommended the model 9500-60 to be used near the oven to operate the special Air Amplifier during power outage.

Another way to look at Equation 2 is to create a timing equation.  If the volume of the tank is known, we can calculate how long a system will last.  In this example for scuba diving, we can use this information to configure the amount of time that a tank will last.  The diver has a 0.39 cubic feet tank at a pressure of 3,000 PSIG.  I will use a standard Surface Consumption Rate, SCR, at 0.8 cubic feet per minute.  If we stop the test when the tank reaches a pressure of 1,000 PSIG, we can calculate the time by using Equation 3.

Receiver tank timing formula (Equation 3):

T = V * (P1 – P2) / (C * Pa)

T – Time interval (minutes)

V – Volume of receiver tank (cubic feet)

C – Air demand (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P1 – Initial tank pressure (PSIG)

P2 – Ending tank pressure (PSIG)

By placing the values in the Equation 3, we can calculate the time to go from 3,000 PSIG to 1,000 PSIG by breathing normal at the surface.

T = 0.39 cubic feet * (3,000 PSIG – 1,000 PSIG) / (0.8 cubic feet per minute * 14.7 PSIA)

T = 66 minutes.

What happens if the diver goes into deeper water?  The atmospheric pressure, Pa, changes.  If the diver goes to 100 feet below the surface, this is roughly 3 atmospheres or (3 * 14.7) = 44.1 PSIA.  If we use the same conditions above except at 100 feet below, the time will change by a third, or in looking at Equation 3:

T = 0.39 cubic feet * (3,000 PSIG – 1,000 PSIG) / (0.8 cubic feet per minute * 44.1 PSIA)

T = 22 minutes. 

If you have any questions about using a receiver tank in your application, you can contact an EXAIR Application Engineer.  We will be happy to solve for the proper volume or time needed for your application.


John Ball
Application Engineer
Twitter: @EXAIR_jb

When to Use a Receiver Tank for a Compressed Air Application

Recently, I worked with a production engineer at a Tier 1 supplier for the auto industry.  An upcoming project was in the works to install a new line to produce headlight lenses.  As a part of the process, there was to be a “De-static / Blow-off” station, where a shuttle system would bring a pair of the parts to a station where they would be blown off and any static removed prior to being transferred to a painting fixture and sent off for painting.  For best results, the lenses were to be dust and lint free and have no static charge, ensuring a perfect paint result.

The customer installed a pair of 18″ Gen4 Super Ion Air Knives, to provide coverage of the widest 16″ lens assembly, that were staged in pairs.

The Super Ion Air Knife Kit, and Everything that is Included.

The customer was limited in compressed air supply volume in the area of the plant where this process was to occur. 50 SCFM of 80 PSIG was the expected air availability at peak use times, which posed a problem –  the Super Ion Air Knives would need up to 105 SCFM if operated at 80 PSIG.  A further review of the design parameters for the process revealed that the system needed to blow air for only 4 seconds and would be off for 25 seconds to meet the target throughput.

This scenario lends itself perfectly to the use of a Receiver Tank.  Running all of the design numbers into the calculations, showed that the 60 Gallon Receiver Tank we offer, would allow for a 20 second run-time, and require 13.1 seconds to refill.  These figures were well within the requires times, and would allow for the system to work as needed, without having to do anything to the compressed air supply system.

60 Gallon Receiver Tank

The moral of the story is – if you have a process that is intermittent, and the times for and between blow-off, drying, or cooling allows, a Receiver Tank can be used to allow you to get the most of your available compressed air system.

Note – Lee Evans wrote an easy to follow blog that details the principle and calculations of Receiver Tanks, and it is worth your time to read here.

If you would like to talk about any of the EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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Removing Condensation Is Key To Maintaining Performance

When air is compressed, it is heated to a point that causes the water or moisture  to turn to vapor. As the air begins to cool, the vapors turn to condensation, which can cause performance issues in a compressed air system. Many times this condensation forms in the basic components in the system like a receiver tank, dryer or filter.

Condensation is formed from water vapor in the air

It’s important to remove this condensation from the system before it causes any issues. There are four basic types of condensate drains that can be used to limit or prevent loss of air in the system.

The first method would be to have an operator manually drain the condensation through a drain port or valve. This is the least reliable method though as now it’s the operator’s responsibility to make sure they close the valve so the system doesn’t allow any air to escape which can lead to pressure drops and poor end-use device performance.

Example of a float drain

Secondly, a float or inverted bucket trap system can be used in plants with regular monitoring and maintenance programs in place to ensure proper performance.. These types of drain traps typically require a higher level of maintenance and have the potential to lose air if not operating properly.

An electrically actuated drain valve can be used to automatically drain the condensate at a preset time or interval. Typically these incorporate a solenoid valve  or motorized ball valve with some type of timing control.  These types of systems can be unreliable though as the valve may open without any moisture being present in the line, which can result in air loss or it may not be actuated open long enough for acceptable drain off. With these types of drains, it’s best to use some type of strainer to remove any particulate that could cause adverse performance.

Lastly,  zero air-loss traps utilize a reservoir and a float or level sensor to drain the condensate and maintain a satisfactory level. This type of setup is very reliable but does require the reservoir be drained frequently to keep the system clean and free of debris or contaminants.

If you have any questions or would like to discuss a particular process, contact an application engineer for assistance.

Justin Nicholl
Application Engineer


Condensation image courtesy of Anders Sandberg via creative commons license

Float drain image courtesy of the Compressed Air Challenge

Receiver Tank Principle and Calculations


Visualization of the receiver tank concept

A receiver tank is a form of dry compressed air storage in a compressed air system.  Normally installed after drying and filtration, and before end use devices, receiver tanks help to store compressed air.  The compressed air is created by the supply side, stored by the receiver tank, and released as needed to the demand side of the system.

But how does this work?

The principle behind this concept is rooted in pressure differentials.  Just as we increase pressure when reducing volume of a gas, we can increase volume when reducing pressure.  So, if we have a given volume of compressed air at a certain pressure (P1), we will have a different volume of compressed air when converting this same air to a different pressure (P2).

This is the idea behind a receiver tank.  We store the compressed air at a higher pressure than what is needed by the system, creating a favorable pressure differential to release compressed air when it is needed.  And, in order to properly use a receiver tank, we must be able to properly calculate the required size/volume of the tank.  To do so, we must familiarize ourselves with the receiver tank capacity formula.

An EXAIR 60 gallon receiver tank

Receiver tank capacity formula

V = ( T(C-Cap)(Pa)/(P1-P2) )



V = Volume of receiver tank in cubic feet

T = Time interval in minutes during which compressed air demand will occur

C = Air requirement of demand in cubic feet per minute

Cap = Compressor capacity in cubic feet per minute

Pa = Absolute atmospheric pressure, given in PSIA

P1 = Initial tank pressure (Compressor discharge pressure)

P2 = minimum tank pressure (Pressure required at output of tank to operate compressed air devices)

An example:

Let’s consider an application with an intermittent demand spike of 50 SCFM of compressed air at 80 PSIG.  The system is operating from a 10HP compressor which produces 40 SCFM at 110 PSIG, and the compressed air devices need to operate for (5) minutes at this volume.

We can use a receiver tank and the pressure differential between the output of the compressor and the demand of the system to create a reservoir of compressed air.  This stored air will release into the system to maintain pressure while demand is high and rebuild when the excess demand is gone.

In this application, the values are as follows:

V = ?

T = 5 minutes

C = 50 CFM

Cap = 40 SCFM

Pa = 14.5 PSI

P1 = 110 PSIG

P2 = 80 PSIG

Running these numbers out we end up with:

This means we will need a receiver tank with a volume of 24.2 ft.³ (24.2 cubic feet equates to approximately 180 gallons – most receiver tanks have capacities rated in gallons) to store the required volume of compressed air needed in this system.  Doing so will result in a constant supply of 80 PSIG, even at a demand volume which exceeds the ability of the compressor.  By installing a properly sized receiver tank with proper pressure differential, the reliability of the system can be improved.

This improvement in system reliability translates to a more repeatable result from the compressed air driven devices connected to the system.  If you have questions about improving the reliability of your compressed air system, exactly how it can be improved, or what an engineered solution could provide, contact an EXAIR Application Engineer.  We’re here to help.

Lee Evans
Application Engineer

How Much Compressed Air Can YOU Save?

I had the pleasure of speaking with a service technician with a pneumatics company recently…he was finishing up a large project for a customer that involved modifying some machinery to reduce compressed air consumption. After the performance of the newly modified machinery was verified, the customer wanted to know how they could be sure they were indeed saving the amount of air that the project engineer estimated that they would save. That’s when he called to ask about EXAIR Digital Flowmeters.

EXAIR Digital Flowmeters are available for iron pipe up to 6", and copper pipe up to 4".
EXAIR Digital Flowmeters are available for iron pipe up to 6″, and copper pipe up to 4″.

If you follow the famous (to EXAIR blog readers, anyway) Six Steps To Optimizing Your Compressed Air System, you know that this is Step #1. So, was it too late to apply a measurement device? Of course not…in this case, the machinery’s original published compressed air consumption rates were used to compare the new actual usage according to the Digital Flowmeter, and it was simple arithmetic from there.  They installed a Model 9095 Digital Flowmeter for 2″ Iron Pipe on the header supplying the machinery, and were not only impressed with the results of the upgrade, but also enjoy the at-a-glance verification of air flow.

Naturally, if you ask for our assistance in the planning stages of a compressed air optimization project, we’ll encourage you to follow the Six Steps in order. Depending on the nature of the problem(s) and the size & complexity of your system, there may be more or less attention paid to certain steps than others.

For instance, a system that was originally equipped with Receiver Tanks at predetermined locations might allow us to skip right over Step #5. If engineered or automated controls, like our EFC Electronic Flow Control & Pressure Regulators are already incorporated, we can check off Steps #4 and #6.

Receiver Tanks are an ideal solution for intermittent demands for high volumes of compressed air.
Receiver Tanks are an ideal solution for intermittent demands for high volumes of compressed air.
The EFC Electronic Flow Control uses a photoelectric sensor to turn air flow on & off, as needed.
The EFC Electronic Flow Control uses a photoelectric sensor to turn air flow on & off, as needed.
Use an EXAIR Pressure Regulator to limit your air supply pressure to the value necessary to accomplish the task.
Use an EXAIR Pressure Regulator to limit your air supply pressure to the value necessary to accomplish the task.

Regardless of “where” you start with your optimization project, “when” you start should be right now. Leaks and inefficiencies won’t fix themselves. Give us a call, and let’s get started.

Russ Bowman
Application Engineer
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The Solution To Intermittent Compressed Air System Loads

I recently had the pleasure of assisting an EXAIR Cold Gun user with an application: the parts that the Cold Guns were supposed to be cooling weren’t always getting as cool as they wanted…they’re thermistors being assembled onto a component, and they need to be below a certain temperature when they test them, so they can make sure they’re set properly. Some were getting to the test station while they were at a temperature above their setpoint, which resulted in a rejection of that part. The user wanted to know what could make the Cold Gun work better at times, and worse at other times.

The Cold Gun Aircoolant System has a Vortex Tube with a preset Cold Fraction (that’s the percentage of air supply that is directed to the cold end), so, assuming a constant compressed air supply pressure and temperature, it’ll produce the same amount of cold air flow, at the same low temperature, continuously. The user told me that they used some pneumatic tools in the area, and that these were supplied off the same header as the Cold Guns. We supposed that, during the tools’ operation (which is largely intermittent, as are the Cold Guns’), that portion of the compressed air system may be experiencing a pressure drop, possibly large enough to affect the Cold Guns’ temperature drop.

This could have resulted in a complicated re-plumbing of the compressed air supply in this area, but they were in luck…they had an unused receiver tank, and were able to install it upstream of the feed to the Cold Guns. This resulted in an undisturbed supply of air at a constant 100psig, regardless of whether, or how many, pneumatic tools were being operated at the same time in this area.

This kind of intermittent pressure drop could just as easily affect an Air Knife used for blow off (causing it to not be able to remove moisture/debris in some spots but not others), a Line Vac’s conveyance rate, an E-Vac’s suction power…and the list goes on…not to mention the reduced performance of the pneumatic tools.

If this situation sounds familiar, give us a call. We can look at your supply and demand conditions, and see if a receiver tank might be the solution. Oh, and if you don’t have one, we do: our Model 9500-60 60 Gallon Receiver Tank is ASME rated, and is ideally sized for a wide range of intermittent demands. Let us know if we can help determine if this is a viable solution for your needs.

Russ Bowman
Application Engineer
EXAIR Corporation
(513)671-3322 local
(800)923-9247 toll free
(513)671-3363 fax

Video Blog: Receiver Tanks, When to Use One and How to Set One Up


In the grand scheme of compressed air systems, Receiver Tanks are an oft overlooked component to a well designed system. The following video discusses when to use a secondary receiver tank and how to set one up. Enjoy!

Neal Raker
Application Engineer