Short list in-plant compressed air application. Make a list of equipment in the plant Consuming compressed air and expected air flow requirement in CFM and the required pressure in PSIConsider the duty cycle of your compressors as most compressors are not meant to run all the time.Decide on the sizecapacity of the tank. The more use of equipments means the need for larger tank. Choosing a larger tank than the need will ensure optimum use of the Compressor.Consider 10% more capacity compressor to compensate the air misuse or leaks and pressure drop in the system.