Equipment Vibration Standards
Selection and marking of equipment vibration measurement points
1. Selection of monitoring points
The measurement points should preferably be selected where the vibration energy is transferred to the elastic foundation or other parts of the system. For equipment including rotating mass, it is recommended to select the measurement points at the bearing or the housing installation of the machine. Other measurement points can also be selected, but they must be able to reflect the operating status of the equipment. When measuring at the bearing, it is generally recommended to measure vibration in three directions. The vertical direction is marked as V, the horizontal direction is marked as H, and the axial direction is marked as A, see Figure 1.
Figure 1 Monitoring point selection
FIG. 2 is a schematic diagram of the positioning of a vibration sensor when measuring vibration on a machine housing.
2. Marking of vibration monitoring points
Horizontal machines: This numerical sequence starts with the bearing seat on the non-driven side of the driver, which is assigned the number 001, and continues in numerical order toward the driven equipment until the last bearing on the first axis. On multi-axis (gear-driven) machines, the order of the bearing seats starts from the driver and continues in numerical order down the second axis to the driven, and then down the third axis to the end of the unit. Several common marking methods are shown in Figure 3.
Figure 3 Marking of vibration monitoring points
Vertical machine: Follow the same method as horizontal machine.
3. On-site machine measurement point marking method
The vibration measurement points of the casing can be marked with paint or by sticking a steel plate on the casing. The latter method is preferred. When using a steel plate, the casing should be well treated. The steel plate is 5mm thick and 30mm in diameter. It is bonded with a strong adhesive to ensure good vibration transmission characteristics.
Determination of equipment vibration monitoring cycle If the vibration monitoring cycle is set too long, it is easy to miss the information about the equipment starting to deteriorate. If the cycle is set too short, the workload and cost of monitoring will be increased. Therefore, the vibration monitoring cycle should be reasonably selected according to the structural characteristics, transmission mode, speed, power and failure mode of the equipment. When the equipment is in a stable operation period, the monitoring cycle can be longer; when the equipment has defects and failures, the monitoring cycle should be shortened. When determining the equipment monitoring cycle, the following principles should be followed:
In the initial stage of equipment operation after installation or large-scale maintenance, the cycle should be short (such as monitoring once per hour). After the equipment enters a stable operation period, the monitoring cycle can be appropriately extended.
The inspection cycle should be as fixed as possible.
For full-time equipment monitoring at inspection stations, the monitoring cycle of most equipment can generally be set at 7 to 14 days; for high-speed rotating equipment close to or above 3000 rpm, it should be monitored at least once a week.
For workshop-level equipment monitoring, the monitoring cycle can generally be set once a day or once per shift.
When the measured vibration value is close to or exceeds the alarm standard value of the equipment, the monitoring cycle should be shortened. If the measured vibration value is close to or exceeds the shutdown value of the equipment, the equipment should be shut down in time for maintenance. If the equipment cannot be shut down due to production reasons, monitoring should be strengthened and the monitoring cycle can be shortened to 1 day or less.
Equipment vibration monitoring information collection
1. Selection of vibration monitoring parameters
For ultra-low frequency vibration, it is recommended to measure vibration displacement and velocity; for low frequency vibration, it is recommended to measure vibration velocity and acceleration; for medium-high frequency vibration and high frequency vibration, it is recommended to measure vibration acceleration. Explanation as follows:
Equipment vibration is classified by frequency. According to the frequency of vibration, equipment vibration can be divided into the following types:
Ultra-low frequency vibration, vibration frequency below 10Hz;
Low frequency vibration, vibration frequency between 10Hz and 1000Hz;
Medium-high frequency vibration, vibration frequency between 1000Hz and 10000Hz;
High frequency vibration, vibration frequency above 10000Hz.
Displacement is peak-to-peak value; velocity is effective value; acceleration is effective value; sometimes, velocity and acceleration are measured at peak value as needed.
2. Several "sames" in vibration monitoring
To ensure the comparability of measurement results, the following "sames" should be noted in vibration monitoring:
Same measuring instrument;
Same measuring instrument settings;
Same measuring point location and direction;
Same equipment working conditions;
Same background vibration.
Measurement work should be completed by the same person as much as possible.
3. Vibration data collection
The equipment should be regularly monitored strictly according to the monitoring path and monitoring cycle. When collecting equipment vibration data, it is usually necessary to record other process parameters of the equipment, such as temperature, pressure and flow, for comparison and trend management. Equipment monitoring personnel should organize and back up test records in a timely manner, verify data records with doubts in a timely manner, analyze and process measurement data in a timely manner, and make trend predictions and simple diagnoses.
