Air Receiver Vessel & Tank Installation, Repair & Maintenance
What Is a Compressed Air Receiver Tank?
An air receiver tank (sometimes called an air compressor tank or compressed air storage tank) is what it sounds like: a tank that receives and stores compressed air after it exits the air compressor. This gives you a reserve of compressed air that you can draw on without running your air compressor.
An air receiver is a type of pressure vessel; it holds compressed air under pressure for future use. The tanks come in a range of sizes and in both vertical and horizontal configurations.
The Purpose of an Air Receiver Tank
An air receiver tank provides temporary storage for compressed air. It also helps your air compression system run more efficiently. The air receiver tank has three main functions in your compressed air system:
- It stores compressed air that can be used for short, high-demand events.
- It provides a steady air signal to compressor controls.
- When used as a “wet tank”, it acts as a secondary heat exchanger, increasing the efficiency of your air dryer.
Compressed Air Storage
The primary role of an air receiver tank is to provide temporary storage for compressed air. Storing compressed air allows the system to average the peaks in compressed air demand over the course of a shift. You can think of your air receiver tank as a battery for your compressed air system, except it stores air instead of chemical energy. This air can be used to power short, high-demand events (up to 30 seconds) such as a quick burst of a sandblaster, dust collector pulse, or someone using a blowgun to dust themselves off. The air in the tank is available even when the compressor is not running. Storing compressed air reduces sudden demands on your air compressor, prolonging the life of your system. Using an air receiver tank may also allow you to use a smaller horsepower compressor for larger jobs.
The air receiver tank provides a steady stream of air to compressor controls, eliminating short-cycling and over-pressurization. Uneven compressed air utilization causes uneven demand on the air compressor, resulting in rapid cycling of the compressor controls as the compressor turns on and off to meet moment-by-moment demand. Each time the system turns on and off (or loads/unloads) is called a “cycle”; it is better for the compressor motor to keep these cycles as long as possible. Over time, frequent short cycling will lead to premature failure of switches and other compressor components. Rapid cycling can result in excessive wear of the motor contactor or even a direct motor short because of winding insulation. The air receiver tank eliminates short cycling and provides more consistent system pressure to controls.
As air is compressed under pressure, its temperature increases; this is a simple law of physics known as the Pressure-Temperature Law. Depending on the type of air compressor you are using, the air discharged from the compressor may be as hot as 250 – 350°F. This is too hot for most air-operated equipment to use directly. Hotter air also contains more moisture, which will result in excess water vapor that will condense in control lines and tools if it is not removed. The condensed air must be cooled and dried before it is utilized. A heat exchanger is used to remove excess heat caused by compression. The air receiver tank acts as a secondary heat exchanger; as air sits in the tank or slowly flows through it, it naturally cools over time. The air receiver tank supports the work of a primary heat exchanger; lowering the temperature of the air an additional 5 – 10°F is not uncommon.
Efficiency Benefits of Air Receiver Tanks
Adding an air receiver tank significantly improves the efficiency of your compressed air system. They do this by:
- Reducing waste of compressed air from excessive sump blowdowns
- Lowing the pressure requirements for the air compressor and air network
- Increasing the efficiency of the air dryer by reducing moisture
Reduce Waste of Compressed Air
As the air compressor cycles on and off, compressed air can be wasted. Every time a rotary screw air compressor unloads, the sump tank (oil tank) is vented. Compressed air is released during the venting. Over time, this adds up to the loss of thousands of cubic feet of compressed air that could otherwise have been used to power processes in your facility. A properly sized air storage tank reduces frequent cycling and venting.
Reduce Operating Pressure for the Air Compressor
Compressed air storage also allows you to reduce the pressure at which your air compressor operates. Without a store of compressed air to draw on, the system will have to operate at higher pressures, so it is always ready to meet peak demands. In essence, you are asking your system to operate as if your facility is always running at maximum demand. This leads to increased energy use and wear and tear on the system. On average, for every 2 PSI that you increase the pressure of your system increases the energy demand by 1%. This can lead to hundreds or thousands of dollars added to your energy bills annually. As explained above, adding an air receiver tank to your compressed air system will even out these peaks in demand, allowing you to meet intermittent periods of high demand without increasing the overall pressure of your system.
Increase the Efficiency of the Dryer
The heat exchanger function of the air receiver tank helps to improve the efficiency of your air dryer. As air passes slowly through the receiver tank, it cools. Cooler air can’t hold as much moisture as warm air, so excess moisture condenses and falls out of the air as a liquid. The water drains out of a valve at the bottom of the tank. By removing some moisture in advance, the air receiver tank reduces the amount of work the air dryer needs to do. This improved efficiency translates to additional energy savings for your system.