Intermediate Storage Tanks & How To Size Them

When evaluating processes that utilize compressed air and adhering to the Six Steps to Compressed Air Optimization, intermediate storage proves to be a critical role coming in at step number five. Intermediate storage tanks may already be in place within your facility and often times can be implemented as modifications to aid existing lines that are struggling to maintain proper availability of compressed air to keep the line at peak performance.

EXAIR Receiver Tank in 60 Gallon Capacity

When determining whether or not a production line or point of use compressed air operation would benefit from a receiver tank/intermediate storage we would want to evaluate whether the demand for compressed air is intermittent.  Think of a receiver tank as a capacitor in an electrical circuit or a surge tank in a water piping system.  These both store up energy or water respectively to deliver to during a short high demand period then slowly charge back up from the main system and prepare for the next high demand.   If you look from the supply point it will see a very flattened demand curve, if you look from the application side it still shows a wave of peak use to no use.

Intermittent Applications are prime for rapid on/off of compressed air.

One of the key factors in intermediate storage of compressed air is to appropriately size the tank for the supply side of the system as well as the demand of the application.  The good news is there are equations for this.  To determine the capacity, use the equation shown below which is slightly different from sizing your main compressed air storage tank.  The formulate shown below is an example.

Where:

V – Volume of receiver tank (ft3 / cubic feet)

T – Time interval (minutes)

C – Air demand for system (cubic feet per minute)

Cap – Supply value of inlet pipe (cubic feet per minute)

Pa – Absolute atmospheric pressure (PSIA)

P1 – Header Pressure (PSIG)

P2 – Regulated Pressure (PSIG)

One of the main factors when sizing point of use intermediate storage is, they are being supplied air by smaller branch lines which cannot carry large capacities of air.  That limits your Cap value. The only way to decrease the V solution is to increase your Cap. The other key point is to ensure that all restrictions feeding into the tank and from the tank to your point of use are minimized in order to maintain peak performance.

If there are intermittent applications that are struggling to keep up with the production demands within your system, please reach out and speak with an Application Engineer.  We are always here to help and we may even be able to help you lower the demand needed by utilizing an engineered point of use compressed air solution.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

Candy Producer Saves $4600 in Compressed Air with EXAIR’s EFC

A few months ago, I took a phone call from a manufacturing engineer who worked at a large candy production facility here in the United States. Extra chocolate was dripping out of the candy molds onto the conveyor belt below.  Within a few hours the belt was dirty enough they would have to stop the line and clean the residual chocolate off the belt. 

The best solution I found was a 72” 316 Stainless Steel Super Air Knife. It worked great when powered at 60 psig inlet pressure. The laminar flow of the Super Air Knife was perfectly suited for this application.  The knife was mounted between the mold and the belt to help solidify and blowoff the excess drips of chocolate. There was one drawback, the Super Air Knife was not needed to blow the belt continuously and the continuous demand was not desirable during peak production.

The simple solution for this was the EXAIR Electronic Flow Control, the EFC minimizes compressed air use by turning off the air when a sensor is triggered. Since there was a 4.5-minute time gap between each mold set this was a great solution. When the photoelectric eye saw a mold, it then told the solenoid valve to open and supply the knife with compressed air for 30 seconds while the mold was open and the excess chocolate would be dripping. See the Savings calculations below;

efcapp

Without using the EFC

(* Using $ 0.25 per 1000 SCFM used)

  • 72” Super Ion Air Knife = 165.6 SCFM @ 60 PSIG
  • 165.6 SCFM x 60 minutes x $ 0.25 / 1000 SCFM = $ 2.48 per hour
  • $ 2.48 per hour x 8 hours = $ 19.84 per 8-hour day
  • $ 19.84 x 5 days = $ 99.20 per work week
  • $ 99.20 per week x 52 weeks =$5,158.40 per work year without the EFC control

 

With the EFC installed (turning the compressed air off for 4 minutes 30 seconds with a 30 second on time = 6 minutes/hour compressed air usage)

  • 165.6 SCFM x 6 minute x $ 0.25 / 1000 SCFM = $ 0.25 per hour
  • $ 0.25 per hour x 8 hours = $ 2.00 per 8-hour day
  • $ 2.00 x 5 days = $ 10.00 per work week
  • $ 10.00 per week x 52 weeks = $520.00 per work year with the EFC control 

$ 5,158.40 per year (w/o EFC) – $ 520.00 per year (w/ EFC) = $4,638.40 projected savings per year by incorporating the EFC.

EFC287x250

This example illustrates, clearly, why choosing the EFC is a good idea. It has the ability to keep compressed air costs to a minimum and saves compressed air for use within other processes around the plant. With this type of compressed air savings, the unit would pay for itself in less than 3 months.

If you would like to see how we might be able to improve your process or provide a solution for valuable savings, please contact one of our Application Engineers.

Jordan Shouse
Application Engineer
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When to use Compressed Air Receiver Tanks (and More)

I was recently working with a process Engineer at a food packaging plant on installing a Super Air Knife to blow excess water off a food product. This product was moving single file on a conveyor belt with about 6 feet between each product. The belt was moving pretty slow so we wanted to turn the air knife on only when the product was in front of the knife, which saves compressed air and energy. To do this we used the ELECTRONIC FLOW CONTROL (EFC). If the knife ran the entire time it would be wasting any air blowing during one of the 6′ long gaps. This would also put an unnecessary strain on their already taxed compressed air system. The EFC let him only supply air to the Knife when it saw a product on the belt. To read more about the EFC click here!

efcapp
EXAIR Electronic Flow Control

This application worked perfectly, but they had one other issue. Throughout the day it seemed as if they were losing compressed air pressure at the knife. What they found was during peak compressed air usage in the plant the compressor couldn’t keep up with the demand. Fear not, the Super Air Knife was only running for 7 seconds and was off for 20 seconds. This was a perfect application for EXAIR’s Receiver Tank.

Receiver Tanks are great for applications that require an intermittent demand for a volume of compressed air. This can cause fluctuations in pressure and volume throughout the compressed air system with some points being “starved” for compressed air. EXAIR’s Model 9500-60 60 Gallon Receiver Tank can be installed near the point of high demand so there is an additional supply of compressed air available for a short duration. The time between the high volume demand occurrences should be long enough so the compressor has enough time to replenish the receiver tank.

Receiver Tank
Receiver Tank

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. If you need any assistance calculating the need for a receiver, please let us help.

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.

Jordan Shouse
Application Engineer
Send me an email
Find us on the Web 
Like us on Facebook
Twitter: @EXAIR_JS