Dangers of pipeline vibration
In the rotating equipment and flowing media of the unit, low-intensity mechanical vibration is inevitable. The mechanical vibration of the rotating equipment is transmitted to the system pipeline through the system connecting parts and media, thus posing a great threat to the safe operation of the unit. The hazards of pipeline vibration mainly include the following points:
1. Hazards to staff:
It interferes with the vision of workers and reduces construction efficiency; workers feel tired; it leads to quality accidents and even safety accidents; long-term work in a vibration environment of considerable intensity may cause greater harm or impact to the health of construction workers.
2. Hazards to buildings:
Due to the different intensity and frequency of pipeline vibration, the building structure of some buildings will be damaged (common damage phenomena include cracks in the foundation and walls, peeling off of walls, and sliding of stones. In severe cases, the foundation of the building may be damaged. deformation, etc.).
3. Harm to precision instruments:
Pipeline vibration will affect the normal operation of the system’s precision instruments and meters, affect the accuracy and reading speed of the instrument’s scale reading, and even make it impossible to read. If the vibration is too large, it will directly affect the service life of the instrument and even be damaged; For some sensitive electrical appliances, such as sensitive relays, vibration may even cause them to malfunction, which may cause some major accidents.
4. Harm to the main equipment of the system:
Long-term pipeline vibration will cause uneven output of the main equipment of the system, affecting the mechanical performance and normal operation of the main equipment.
Causes of pipeline vibration and measures to eliminate it
The fundamental cause of unit system pipeline vibration lies in the design, installation, operation and operation of the unit. System pipeline vibration directly reflects the mechanical performance and operating conditions of the rotating equipment. When system equipment and pipelines vibrate, the possible causes of vibration should be analyzed one by one according to the specific situation. After identifying the crux of the problem, feasible and effective treatment measures can be formulated through careful discussion and analysis to eliminate them and reduce the vibration hazard. to the bare minimum.
The following is an analysis based on the causes and elimination measures of vibrations in rotating equipment and pipelines, as a reference for preventing and eliminating pipeline vibrations during on-site construction.
1. Motor vibration causes pipeline vibration
| Number | Vibration Causes | Elimination Measures |
| 1 | Bearing eccentric wear: the unit is not concentric or the bearings are worn | Recalibrate the concentricity of the unit, adjust or replace the bearings |
| 2 | Stator and rotor friction: uneven air gap or bearing wear | Readjust the air gap, adjust or replace the bearings |
| 3 | The rotor cannot stop at any position or the power is unbalanced | Recalibrate the static and dynamic balance of the rotor |
| 4 | Axial looseness: loose screws or poor installation; | Tighten the screws and check the installation quality |
| 5 | Foundation vibration: poor foundation stiffness or loose anchor bolts | Reinforce the foundation or tighten the bottom corner screws |
| 6 | Three-phase current instability: torque reduction, rotor cage bar or end ring failure | Inspect and repair rotor cage bars or end rings |
2.Pump body vibration causes pipeline vibration
| Number | Vibration Causes | Elimination Measures |
| 1 | Difficulties in manual turning: the pump shaft is bent, the bearings are worn, the unit is not concentric, and the impeller hits the pump casing. | Straighten the pump shaft, adjust or replace the bearings, recalibrate the concentricity of the unit, and readjust the clearance. |
| 2 | The pump shaft swings too large: the bearings and journals are worn or the clearance is too large | Repair journal, adjust or replace bearings |
| 3 | Hydraulic imbalance: the impeller is unbalanced, and individual blade grooves of the centrifugal pump are clogged or damaged. | Recalibrate the static and dynamic balance of the impeller, eliminate blockage, repair or replace the impeller |
| 4 | Foundation vibration: poor foundation stiffness or loose anchor bolts or resonance | Reinforce the foundation and tighten the anchor screws |
| 5 | Axial flow pump shaft power is too high: the water level in the inlet pool is too low, the impeller is not submerged deep enough, debris wraps around the impeller, pump cavitation damage varies, and the impeller is defective | Raise the water level of the inlet pool, lower the installation height of the water pump to remove debris, and set up a sewage barrier to repair or replace the impeller. |
| 6 | The efficiency of the centrifugal pump unit drops sharply or the efficiency of the axial flow pump unit drops slightly, accompanied by cavitation noise | Change the speed of the water pump, avoid the resonance area, find out the cause of cavitation, and take measures to eliminate cavitation. |
3. Pipeline vibration caused by other reasons in the water supply system
| Number | Vibration Causes | Elimination Measures |
| 1 | The sewage rack is clogged and the water level in the inlet pool is reduced. | Cleaning the sewage fence and adding a sewage fence cleaning device |
| 2 | The design of the front pool and the inlet pool is unreasonable, and the inlet channel and pump are not matched, which worsens the water inlet conditions. | To clean the sewage boom, add a sewage boom cleaning device and rationally design the front pool, the inlet pool and the water inlet channel. |
| 3 | Rapid changes in pressure and water hammer in the outlet pipe | Other anti-hammer measures such as slow-closing valves and pressure regulating wells |
| 4 | The siphon formation takes too long, causing the unit to operate under non-design conditions for a long time. | Add a vacuum device and rationally design and improve the siphon outlet channel |
| 5 | The door hits the door seat repeatedly or the impact force is too high when it is closed. | An exhaust hole is provided in front of the outlet of the flow channel (or pipe), and the flap door is reasonably designed and control measures are taken to reduce the impact force when the flap door is closed. |
| 6 | The water inlet pipe is not firmly fixed or causes resonance | Add and strengthen pipeline supports (supports should be installed at the maximum amplitude and vibration source as much as possible); change operating parameters to avoid resonance areas |
| 7 | The sequence of starting and stopping the unit is unreasonable, causing the water inlet condition of the water pump to deteriorate. | Optimize startup and shutdown sequence |
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