Causes and elimination methods of pipeline vibration
Common pipeline vibration
- Extraction pipeline vibration
- Live steam pipeline vibration
- The heating pipeline is vibrating
Harm of pipeline vibration
In the rotating equipment and flowing medium of the unit, low-intensity mechanical vibration is unavoidable. The mechanical vibration of the rotating equipment is transmitted to the system piping through the system connecting parts and medium, which poses a great threat to the safe operation of the unit. The hazards of pipeline vibration mainly include the following:
- Hazard to the staff: Interfere with the vision of the staff, reduce the construction efficiency; the staff feels tired; cause quality accidents or even safety accidents; working in a vibrating environment with considerable strength for a long time may cause great harm to the construction workers Or influence.
- Hazard to buildings: Due to the different vibration strength and frequency of the pipeline, the building structure of some buildings will be damaged (common damage phenomena are based on cracks in the foundation and walls, spalling of the wall, sliding of the stones, The heavy one can deform the foundation of the building, etc.).
- Hazards to precision instruments: Pipe vibration will affect the normal operation of the system’s precision instruments and instruments, affecting the accuracy and reading speed of the scale reading of the instrument, and even the reading cannot be read. If the vibration is too large, it will directly affect the instrument. The service life of the instrument is even damaged. For some sensitive electrical appliances, such as sensitive relays, the vibration may even cause its malfunction, which may cause some major accidents.
- Hazard to the main equipment of the system: Long-term pipeline vibration causes uneven output of the main equipment of the system, affecting the mechanical performance and normal operation of the main equipment.
Causes and elimination measures of pipeline vibration
- The pipe support is loose and broken, and it can not be fixed and suspended. It should be re-sturdy and replaced.
- The pipeline is too long, the number of supports is insufficient or the arrangement position is unreasonable. The number of slings should be increased and the position repositioned.
- Gas is accumulated inside the oil pipeline and the water pipeline. The air door on the pipe should be opened to drain the air.
- The equipment or pump connected to the pipeline is not working properly, and the pump outlet pressure fluctuates too much. The equipment and pump should be stopped, or the spare equipment and pump should be switched and the cause checked for elimination.
- The valve operation speed on the pipeline is too fast, causing a sharp change in the flow velocity of the medium inside the pipeline, forming a water hammer and causing the pipeline to vibrate. The operation should be resumed immediately or the small valve should be closed to extend its operating time.
- The drain pipe of each heater appears to flow in the hatch, causing the pipe to vibrate. The heater water level and pressure should be controlled to avoid the operation of the water level.
- Water is accumulated inside the steam pipe. The drain door on the corresponding pipe should be opened to drain the water.
- The position of the hydrophobic point at the natural compensation bend of each pipeline is improperly arranged or insufficient. The hydrophobic pathway should be improved or the hydrophobic point should be increased.
- The operation mode of the unit is unreasonable, so that the main steam main pipe has dead steam that does not flow. The unit operating mode should be readjusted or the micro-opening trap should be kept hydrophobic.
- When the various extraction pipes are put into operation, the warm pipes are not enough to make the internal temperature difference of the pipes large, causing excessive thermal stress and causing the pipe vibration. The valve opening should be controlled during the heating pipe, and the warming time should be extended to control the temperature rise rate.
In short, pipeline vibrations occur frequently. Strengthen the inspection of equipment and report abnormal conditions in time. At the same time, when performing various types of system operations, it should be operated strictly in accordance with the regulations to avoid the occurrence of various accidents caused by pipeline vibration.
The fundamental reason for the vibration of the unit system pipeline is the design, installation, operation and operation of the unit. The vibration of the pipeline system directly reflects the mechanical performance and operation of the rotating equipment. When the system equipment and pipelines vibrate, the causes of vibration may be analyzed one by one according to the specific conditions. After identifying the crux of the problem, carefully analyze and analyze the feasible and effective treatment measures to eliminate the vibration hazard. To a minimum.
The following analysis is based on the causes and elimination measures of rotating equipment and pipeline vibration, as a reference for preventing and eliminating pipeline vibration during on-site construction.
|1||Eccentric wear of bearing: the eccentric unit or bearing wear||Recalibrate the unit concentricity, adjust or replace the bearing|
|2||Fixed rotor friction: uneven air gap or bearing wear||Re-adjust the air gap, adjust or replace the bearing|
|3||The rotor cannot be stopped at any position or the power is unbalanced||Recalibrate rotor static balance and dynamic balance|
|4||Axial looseness: loose screws or poor installation;||Tighten the screws to 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 is unstable: torque is reduced, rotor cage or end ring is out of order||Check and repair the rotor cage or end ring|
|1||Difficulty in hand turning: pump shaft bending, bearing wear, unit decentration, impeller and pump case bumping||Straighten the pump shaft, adjust or replace the bearing, recalibrate the unit concentricity, and reset the gap|
|2||Pump shaft swing is too large: bearing and journal wear or excessive clearance||Repair the journal, adjust or replace the bearing|
|3||Hydraulic imbalance: impeller imbalance, individual groove of centrifugal pump blocked or damaged||Recalibrate the impeller static balance and dynamic balance, eliminate blockages, repair or replace the impeller|
|4||Foundation vibration: poor foundation stiffness or loose anchor bolts or resonance||Reinforce the foundation and tighten the anchor screw|
|5||The shaft power of axial flow pump is too large: the water level in the inlet pool is too low, the submerged depth of the impeller is not enough, the debris twines around the impeller, the degree of cavitation damage of the pump is different, and the impeller is damaged.||Raise the water level of the inlet tank, reduce the installation height of the pump, remove the debris, install a screen trash, and repair or replace the impeller|
|6||The efficiency of the centrifugal pump unit drops sharply or the efficiency of the axial flow pump unit decreases slightly, accompanied with cavitation noise||Change the pump speed, avoid the resonance area, find out the cause of cavitation, and take measures to eliminate cavitation|
|1||The trash rack is blocked and the water level in the inlet pool is lowered.||Clean the screen trash and install the sewage disposal unit.|
|2||The design of the front pool and the inlet pool is unreasonable, and the inlet flow passage and the pump are not matched, which makes the water inlet conditions worse.||Clean the screen trash and install the sewage disposal unit. Reasonably design the front pool, the inlet pool and the inlet passage.|
|3||Rapid pressure change and water hammer action in the outlet pipe||Slow closing valves and surge tanks and other measures such as waterproof hammer.|
|4||The formation time of siphoning is too long, so that the unit runs in non-design conditions for a long time.||Add vacuuming device, reasonably design and improve the siphonic outlet channel|
|5||flap valve repeatedly hits the door seat or the impact force of closing is too large||Provide ventilation holes in front of the outlet of the flow channel (or pipe), reasonably design the flap valve to take control measures, and reduce the impact force when the flap valve is closed|
|6||Inlet pipe is not fixed firmly or causes resonance||Add and reinforce the pipe support (set the support where the amplitude is maximum or at the vibration source as much as possible); change the operating parameters and avoid the resonance zone|
|7||The order of starting and stopping the unit is unreasonable, resulting in deterioration of the water inlet conditions of the pump.||Optimize boot and shutdown sequence|
|1||System excitation force is too large and mechanical resonance||
a. Add a pipe frame and a pipe clamp at the vibration source and the maximum amplitude;
b. The pipe clamps at the elbows and tees should be dispersed and fixed at multiple points to reduce the additional stress on the pipes
c. Design the strength and rigidity of the pipe frame according to the direction of excitation force generation;
d. The fixed position of the pipe is in a free state. Do not add friction to the pipe and increase the additional load.
|2||The airflow pulsation is strong and causes vibration||
a. Add a hole plate (the pipe at the container vibrates; the hole plate is added at the flange near the front of the container or at the rear of the container);
b. Add a buffer
c. Add an acoustic filter;
|3||Improper design leads to excessive excitation force or gas column resonance||
a. Change the design, shorten the length of the pipe, reduce the number of elbows and reducers, reduce the excitation force, and avoid the length of the resonance pipe;
b. Increase the stiffness and quality of the piping to change the mechanical vibration frequency.
Source: China Steel Pipeline Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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