Having a large air receiver in your compressed air system is always a good thing — in fact, if the tank does not surprise visitors to your compressor room with its size, it is probably not big enough.
Storage receivers slow down pressure fluctuations and allow your compressors to better control the system pressure while maintaining optimal compressor efficiency. The typical requirement for lubricated screw compressors running in load/unload mode is between 5 and 10 gallons per cfm output of your trim compressor. For a 10-hp compressor, this would be between 200 and 400 U.S. gallons in size.
When adding storage, there are a few choices to consider when you are locating it and making piping connections.
- Does it get installed before or after the dryer as “wet” or “dry” storage?
- Do you T-tap the piping or should the air flow thorough the tank?
In most cases, it is desirable to install both wet and dry storage with about two-thirds of the volume as dry storage. The wet storage is of benefit because it provides a location with the compressed air output of the compressor can cool and drop some of its moisture. This reduces the load on the air dryer, likely saving you some troubles down the road. The dry storage is good because there is an already dried volume of clean compressed air immediately available for any transient flows. This saves the air dryer from peak flows that might exceed its capacity.
When piping the connections to the tank, it is recommended to allow the air to flow through the storage receiver — place the inlet at the bottom connection to the tank and the outlet at the top rather than T-tapping This allows gravity to help in separating the water droplets that form when the saturated compressed air cools. By piping it this way, you also provide a smoother flow of air. Air has weight; if it must quickly change the direction of flow it will take a bit of time … better protection against transient flows is provided if the air is always flowing in one direction.
And if you are changing out an old reciprocating compressor with a newer one, and the storage receiver it was sitting on is still in good condition, leave it in the system. The larger the storage in any system, the better!