A compressed air receiver tank (sometimes called an air compressor tank or compressed air storage tank) is a type of pressure vessel that holds compressed air under high pressure. Air enters the air receiver tank after it exits the air compressor and is held there for future use. It provides a reserve of compressed air that you can draw on without running your air compressor.
What is the Purpose of an Air Receiver Tank?
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
Storing compressed air allows the system to even out the peaks in compressed air demand and provide extra energy for short, high-demand events (up to 30 seconds). The air receiver tank is like a battery for your compressed air system. The air in the tank is available even when the compressor is not running. Using an air receiver tank minimizes stress on your air compressor and may allow you to use a smaller horsepower compressor.
Compressed air from the air receiver tank provides more consistent system pressure to compressor controls. This eliminates “short cycling,” or rapid on/off cycles in the compressor motor. Short cycling results in excessive wear on switches and other compressor components that can lead to premature failure or even a direct motor short. The even stream of air provided by the air receiver tank minimizes stress on the air compressor.
Air exiting the air compressor is too hot for most air-operated equipment to use directly. It also contains excess moisture that must be removed before it is utilized. Most compressed air systems use a heat exchanger to remove excess heat caused by compression. The air receiver tank acts as a secondary heat exchanger, lowering the temperature an additional 5 – 10°F as air sits in or flows through the tank.
The Benefits of an Air Receiver Tank
Adding an air receiver tank significantly improves the efficiency of your compressed air system—and can even save you money. Your air receiver tank reduces energy consumption and saves wear and tear on your system
Compressed Air Savings
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.
Compressed air storage allows you to reduce the pressure at which your air compressor operates by evening out peaks in demand. 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 maximum demand. This leads to increased energy use, which can add hundreds or thousands of dollars to your energy bills annually.
Moisture and Dirt Removal
As air cools in the air receiver tank, excess liquid condenses and falls out of the air. This results in less work for the air dryer and less energy consumption. As the liquids condense, they will also capture particulates in the air from compressor motor exhaust, corrosion within the system, or dirty facility air. The excess dirt is then simply drained away with the liquids. As a result, the air entering the air dryer is both cleaner and drier than air directly from the air compressor.
The air receiver tank functions as a pulsation dampening device, absorbing vibrations from the air compressor motor and pulsations in the air stream. This reduces fatigue on piping and other system components.
Do You Need Wet or Dry Compressed Air Storage?
There are two types of compressed air storage: wet or dry. The difference is in the location of the air storage tank in your compressed air system; there is no difference in tank construction or design.
Wet Compressed Air Storage
“Wet” storage tanks are located before the air drying system. Air flows through the tank in this configuration, entering through the bottom port from the compressor and exiting out the top to the dryer. A wet air receiver tank has several benefits.
- Wet storage increases the efficiency of your air dryer by allowing excess water and lubricant to condense out of the air before it hits the dryer.
- A wet air storage tank prolongs the life of the pre-filter element (located in between the wet storage tank and the dryer) by removing excess liquid and dirt from the air.
- Wet air storage provides a steadier pressure signal to the compressor controller because the air does not go through filtration before entering the tank, eliminating back pressure.
Dry Compressed Air Storage
“Dry” storage tanks are located after the air dryers to store compressed air that has already been dried and filtered. Dry compressed air is ready to use right out of the tank. It is not necessary to flow the compressed air through the tank for dry storage.
Without a dry air tank, air from the wet tank will have to go through the air dryer before it is used. During periods of high demand, the dryer is at risk of becoming over-capacitated as the system tries to pull air through at higher volumes than the dryer is rated for. If the dryer cannot keep up with the demand, drying efficiency is reduced, potentially leading to unwanted water in the air lines.
Finding the Right Ratio of Wet to Dry Air Storage
For most applications, it makes sense to have a combination of wet and dry storage. The recommended ratio of compressed air storage is 1/3 wet to 2/3 dry capacity. Dry air storage needs to be greater than wet storage to minimize the risk of over-capacitating the air dryer during periods of high demand.
An exception to this rule is for applications that have steady airflow without sharp peaks in demand. In this case, there is no need for a dry storage tank because air will simply flow through it without being stored up. This is often the case in robotic manufacturing facilities where airflow is consistent and predictable.
Let us help you find the right compressed air storage strategy for your facility. Call us today and ask for pricing.