Receivers or storage tanks are typically installed on compressed air systems to serve several purposes. Their main function is to provide a buffer for the system demand to draw from while the compressor catches up. It is quite common to see a total installed receiver capacity of around 15-20% of the compressor capacity in a compressed air system. However, we recommend your receiver capacity should be between 50-65% of the trimming compressors capacity for the reasons listed below.
By adding more receiver capacity, you can slow down the change in pressure caused by sudden demands because there is more compressed air stored in the system to draw from. This can have a number of benefits in the efficiency of the system.
- It gives the compressors time to react – compressors take a short time to start and often this delay can lead to multiple compressors reacting simultaneously rather than just one. In the case of VSDs they can steadily increase or decrease their speed inline with the changes in demand rather than over and under shooting constantly.
- The compressors spend more time loaded and unloaded – A compressor that rapidly cycles between load and unload will have a higher average power consumption than one that cycles more slowly. For example, a compressor loaded at 50% but cycling between load and unload every 5 seconds will use around 20% more energy than the same compressor cycling every 20 seconds. The difference is additional receiver capacity.
- You can lower your minimum system pressure – Most systems are setup to compensate for a lack of receiver capacity by having a higher set pressure. This means that more air is stored from the higher pressure giving the system something to draw from. However, this also increases the energy consumption of the compressor by between 3-5% per bar of pressure increase.
As a rule of thumb your receiver capacity should be between 50-65% of the trimming compressors capacity. It can be split between the wet and dry side but have no less than 1/3rd of it on the wet side. That means if your trimming compressor is for example a 10 m³/min machine have between 5-6.5 m³ of storage. Your compressors and your energy bills will thank you for it!
Receiver Location
Receivers can be installed in several locations, typically these are:
- The wet side of the system before the dryer
- The dry side of the system after the dryer
- At point of use or high demand locations
They can also be connected to the system as a flow through receiver where compressed air enters one port and exits another or as a buffer tank where only one port is open to the system. Either way can be effective depending on the location.
Receivers with flow through connections are typically in the compressor room and can serve a secondary purpose of helping to remove condensate. It is important to ensure that flow through style receivers is not the cause of some pressure loss, this typically occurs when the port sizes of the receiver are smaller than the pipe size of the main supply. The change in size will cause some level of pressure loss dependent on the flow rate. It’s best to ensure the port size is at least equal to or bigger than the pipe supplying it.
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