Just a small confusion related to Dynamic analysis !!

In order to avoid resonance, our system to be designed within range of W/Wn <<1 (i.e. Ratio of forced frequency to Natural frequency should be in range of << 1).

Could any one suggest till what limit...

Suppose in the case of compressor piping....

We know natural frequency of connecting pipe system above 9 HZ is safe but what if compressor run 540 rpm during warm up then is it resonance work ??

If it's offset by 30 percent it's ok