This standard specifies measurement and evaluation of mechanical vibration of displacement compressors (hereafter referred to as simply "compressors").
This standard is applicable to compressors with rated speed from 120r/min to 12000r/min.
2 Terms and Definitions
For the purpose of this standard, the following terms and definitions apply.
2.1
Vibration displacement
The vector of position variation of one object relative to a certain reference coordinate, in mm.
2.2
Vibration velocity
The vector related to time rate of change of vibration displacement, in mm/s.
2.3
Virtual value of vibration velocity
2.3.1 During simple harmonic vibration, the virtual value of vibration velocity is times of the peak value of vibration velocity, see Formulas (1) to (3):
vrms= (1)
vrms= (2)
vrms= (3)
Where,
vrms - the virtual value of vibration velocity, mm;
- the amplitude value of vibration displacement, s(t)= cos(ωt+s), mm;
- the amplitude value of vibration velocity, v(t)= cos(ωt+s), mm/s;
- the amplitude value of vibration acceleration, a(t)= cos(ωt+s), mm/s2;
ω - the angular frequency, (ω=2πf), rad/s;
s(t), v(t) and a(t) are respectively instantaneous vibration displacement, instantaneous vibration velocity and instantaneous vibration acceleration.
2.3.2 During nonsimple harmonic oscillation, the effective value of vibration velocity shall be determined in accordance with Formula (4).
vrms= (4)
Mechanical vibration of the surface of compressors is complicated vibration composed with limited simple harmonic vibration at different frequencies; as a result, the following formulas may be obtained by Fourier transform or frequency spectrum analysis to the measurement:
vrms= (5)
vrms= (6)
vrms= (7)
2.4
Vibration severity
Vibration severity is a commonly used word representing the intense degree of the vibration. This standard specifies that the virtual value of vibration velocity is used to represent the vibration severity of compressors with unit in mm/s.
3 Measuring Instrument
Measuring instrument for vibration shall be able to directly display the virtual value of vibration velocity of compound vibration with frequency response being selected from the scope from 2Hz~3 000Hz and the instrument precision shall not be lower than 5%.
