Causes and elimination measures of valve pipeline vibration

March 12, 2019
Industry News

The fundamental causes of the pipeline vibration of the unit system are the design, installation, operation and running of the unit. The pipeline vibration of the 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 set out the feasible and effective treatment measures to eliminate the vibration hazard to a minimum.

Causes and elimination measures of valve pipeline vibration

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. Pipeline vibration caused by motor vibration

No.	Causes of valve pipeline vibration	Elimination measures	Remarks
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

2. Pipeline vibration caused by pump vibration

No.	Causes of valve pipeline vibration	Elimination measures	Remarks
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

3. Pipeline vibration caused by other reasons of the water supply system

No.	Causes of valve pipeline vibration	Elimination measures	Remarks
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

4. Pipeline vibration caused by other reasons of compressed air system

No.	Causes of valve pipeline vibration	Elimination measures	Remarks
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.

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Causes and elimination measures of valve pipeline vibration

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