Centralized Compressed Air System – Three Compressor System
Example – total demand is 300CFM, total actual is 250CFM and max pressure 6 bar (msot of manufacturing plats are not running under max demand, so total actual should be calculated base of requrement to privent from selection of oversize compressors)
Three screw compressors can be selected as follows:-
1.30KW VSD rotary screw (175 CFM at 8bar) When this compressor is running, pressure for the production is set to 6.5bar. Because it is variable speed, it automatically ramps up air production to meet demand up to its maximum capacity of 175 CFM.
2.30KW VSD rotary screw (175 CFM at 8bar) If demand exceeds this point, pressure in the system will start to fall; when pressure drops to 6.2bar, this compressor kicks in automatically to provide an additional 175 CFM (for a maximum of 350 CFM for both compressors together).
3.22KW fixed-speed rotary screw (125 CFM at 8bar) only activating when needed or during maintenance
Large fixed speed is not suitable to couple with a small VSD Thumb rule is VSD should be equal or more than the 1.5 x fixed speed to privent from control gaps.
Benefits:-
Having two compressors in parallel with a standby unit can provide complete redundancy and ensure continuous operation (In situations where downtime is unacceptable).
Energy efficiency and cost savings