Tham khảo tài liệu 'intro predictive maintenance 2e episode 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 132 An Introduction to Predictive Maintenance Figure 7-11 Relationship of vibration amplitude. broadband narrowband or component. The unit of measurement is useful when the analyst needs to know the total displacement or maximum energy produced by the machine s vibration profile. Technically peak-to-peak values should be used in conjunction with actual shaftdisplacement data which are measured with a proximity or displacement transducer. Peak-to-peak terms should not be used for vibration data acquired using either relative vibration data from bearing caps or when using a velocity or acceleration transducer. The only exception is when vibration levels must be compared to vibration-severity charts based on peak-to-peak values. Zero-to-peak. Zero-to-peak A or simply peak values are equal to one half of the peak-to-peak value. In general relative vibration data acquired using a velocity transducer are expressed in terms of peak. Root-mean-square. Root-mean-square RMS is the statistical average value of the amplitude generated by a machine one of its components or a group of components. Referring to Figure 7-11 RMS is equal to of the zero-to-peak value A. Normally RMS data are used in conjunction with relative vibration data acquired using an accelerometer or expressed in terms of acceleration. Machine Dynamics The primary reasons for vibration-profile variations are the dynamics of the machine which are affected by mass stiffness damping and degrees of freedom however care Vibration Monitoring and Analysis 133 must be taken because the vibration profile and energy levels generated by a machine may vary depending on the location and orientation of the measurement. Mass Stiffness and Damping The three primary factors that determine the normal vibration energy levels and the resulting vibration profiles are mass stiffness and damping. Every machine-train is designed with a dynamic support system that is based on the following the mass of the dynamic .
