Tag: reservoir

Wet Receiver Tanks: Why Use Them, and How to Size Them

Published on by John BallLeave a comment
9500-60 Receiver Tank

Compressed air is used to operate pneumatic systems within a facility, and it can be separated into three categories; the supply side, the demand side, and the distribution system.  The supply side will include the air compressor, after-cooler, dryer, and receiver tank.  It produces and treats the compressed air before it travels into the distribution system.  They are generally located in a compressor room somewhere in the corner of the plant.  In this blog, I would like to cover the wet receiver tank that is used as part of the supply side.

What is a receiver tank?  I like to compare pneumatic systems to electrical systems.  The receiver tanks store the pneumatic energy produced by an air compressor like a capacitor stores electrical energy.  The reason for this is to have a ready source of energy to increase efficiency and speed through the ebbs and flows of demand. 

A wet receiver, like the name imparts, is positioned downstream of the air compressor but before the air dryer.  A dry receiver would be located after the air dryer.  Some systems will utilize both types.  With the wet receiver, you remove some of the load of water that reaches the air dryer, which helps to make the air dryers more efficient and extends the life cycle.  When ambient air is compressed, the humidity will condense, making water.  Also, as air cools in the wet receiver, water vapor turns into liquid condensate—often mixed with traces of oil and dirt from the air compressor. To get rid of the contaminants, a condensate drain will be required to get rid of this unwanted liquid.

For sizing the wet receiver, it is roughly 1 to 3 gallons per cfm for a compressor.  So, for a 100 SCFM air compressor, you should have a tank that is roughly 100 to 300 gallons.  If you have large fluctuations on the demand side, you can also use Equation 1 below to calculate the minimum tank volume.  If you are using wet and dry receiver tanks in your system, you can divide the total volume.  The wet receiver tank should be one-third of the volume, and the dry receiver tank should be two-thirds of the volume. 

Equation 1:

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

Where:

V – Volume of receiver tank (cubic feet)

T – Time interval between pressure limits (minutes)

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

Pa – Absolute atmospheric pressure (PSIA)

P1 – Upper Pressure limit (PSIG)

P2 – Lower Pressure limit (PSIG)

Compressed air systems are the backbone of countless industries and operations.  But behind the scenes, components like the wet receiver and condensate drain play pivotal roles in ensuring these systems deliver clean, reliable air.  If you wish to discuss more ways to optimize your compressed air system, EXAIR has Application Engineers that would like to help you. 

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Six Steps To Optimizing Your Compressed Air System — Step 5: Intermediate Storage

Published on by Russ BowmanLeave a comment

If you use compressed air for ANYTHING, odds are EVERYTHING you use it for has a minimum supply pressure for proper operation. And if the supply pressure drops below that:

  • Blowoff devices won’t develop enough flow & force to effectively clean or dry the object(s) you use them for.
  • Air-operated chucks on CNC machines won’t hold the piece steady enough for proper cutting, and tool changers will operate slowly/sluggishly. This is a bad combination…increasing the time it takes to make something, AND making it poorly.
  • Pneumatic cylinders will actuate slowly…if at all. This can cause a big problem if, for instance, they’re used to lift a lid on a mixing tank for an automated chemical add, which ends up pouring all over the partially closed lid of the tank instead of going inside it.

These are just a few of the problems that inadequate supply pressure can lead to, and I list them specifically because I experienced them all during my storied (and strange) career path before EXAIR made me the compressed air know-it-all expert I am today. It wasn’t my job to fix those problems (I was on site doing field service on a scale, a hydraulic motor, and a chemical pump, respectively), so I had no idea HOW to fix the compressed air-related problems…but I do now.

One quick & easy fix would have been to increase the compressor discharge pressure. That’d work just fine, but it comes with a cost. Every 2psi increase in discharge pressure increases the power consumption of the compressor’s motor by 1%. Let’s say you increased the discharge pressure from 100psig to 120psig – that’s a 10% increase in power consumption…and operating cost. To add insult to injury, that also increases the magnitude of any leaks in your system, making them more costly as well.

EXAIR Model 9500-60 60 Gallon Receiver Tank.

Actually, that probably IS what I’d have done as a scale, hydraulics, or industrial pump technician. The RIGHT answer, though, is intermediate storage. A properly sized Receiver Tank, located close enough to those operations, would have prevented those problems without increasing operating costs. In fact, it could have even brought them down, if the compressed air header pressure was already set to overcome any pressure drops on the way to those air guns, CNC machine, or mixing tank lid cylinders. Every 2% DECREASE in discharge pressure will also decrease the compressor motor’s power consumption by 1%. Which is actually Step 6 in our Six Steps To Optimizing Your Compressed Air System.

You electrical-types out there could also think of it as a capacitor – absorbing demand spikes & helping the circuit run more evenly.

Sizing a Receiver Tank is fairly straightforward, and we’ve written about it here, here, and here. You can, of course, always contact an Application Engineer to do (or check) the math…give me a call.

Russ Bowman, CCASS

Application Engineer
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