The pressure aluminum pipe used is affected by itself and the external environment, and is in industrial production. It will cause the pipeline to vibrate. If the pipeline is affected by vibration for a long time, it will produce a sense of fatigue in the stress-concentrated part, which will cause the pipeline to break, which will cause a more serious safety accident, which will cause the leakage of the medium, so in the production It is necessary to minimize the vibration of aluminum pipes to avoid unnecessary safety accidents. 1 Pressure aluminum pipe vibration source analysis The aluminum pipe, bracket and connected equipment of the pressure aluminum pipe constitute a structural system. When there is an exciting force, the system will vibrate. Vibration sources of pressure aluminum pipes can be roughly divided into two categories: from the system itself and from outside the system. ①From the system itself, there are mainly vibrations of the machine connected to the aluminum pipe and vibration caused by the unstable flow of the fluid in the pipe; ②From the outside of the system, there are earthquakes and wind, etc.
Vibration is a kind of alternating load to the pressure aluminum pipe, and its degree of damage depends on the size of the excitation force and the vibration resistance of the aluminum pipe itself. The main influencing factors are as follows:
① The natural frequency of the air column. The fluid filled in the aluminum pipe is an elastic air column. Whenever the compressor or the cylinder of the pump sucks or exhausts air from the aluminum pipe, the air column in the aluminum pipe is disturbed and vibrates.
② Mechanical natural frequency. The piping system is a continuous elastic body, and there is a natural frequency of the structure. If the machine excitation frequency is equal to the natural frequency of the piping structure, resonance will also increase the vibration of the piping system. Vibration caused by pipe flow pulsation. The aluminum pipe fluid is in a pulsating state under the action of a compressor or a pump. When flowing through aluminum pipe components such as elbows, reducers, tees, valves, etc., the force on the aluminum pipe is also constantly changing. A certain exciting force that changes with time is produced, and vibration is generated.
④Vibration caused by two-phase flow. The aluminum tube pipeline system is mostly dominated by the two-phase flow of gas and liquid. It should be that the compressibility of the gas is greater than that of the liquid. When the two-phase flow in the aluminum tube pipeline forms a flow pattern with larger bubbles, different areas The air bubbles are compressed differently, causing the aluminum pipe to vibrate.
⑤ Liquid shock vibration. The valve in the aluminum pipe is suddenly closed or opened, and the fluid velocity changes suddenly, which has a great impact on the piping system and generates vibration. Liquid shock is a very important source of vibration in the aluminum pipe piping system. Sometimes it can cause great changes in the pressure in the aluminum pipe, and in severe cases, the pipe may burst.
⑥The fluid velocity in the aluminum pipe is too fast, and the turbulence is formed due to the separation of the fluid boundary layer, which causes the aluminum pipe to vibrate.
⑦Earthquakes and wind from outside the system threaten aluminum pipes. Once a strong earthquake occurs, buried aluminum pipes may be damaged.
Although overhead pipelines are not directly affected by earthquakes, most of the aluminum pipe supports are based on the ground. , When an earthquake occurs, the support frame is damaged, and the aluminium coil collapses accordingly, causing damage to the ring. The influence of wind is irregular. As long as the aluminum pipe is fixed firmly, although the aluminum pipe will vibrate due to interference, the effect is not very large. 2 Measurement of vibration of aluminum pipes For a pipe system with vibration, to reduce or eliminate vibration, it is necessary to fully grasp the relevant parameters and take appropriate vibration damping measures.
① Vibration measurement of aluminum pipe structure: Vibration measurement is to measure the displacement of vibration. The measuring device is composed of three parts: sensor, amplifier and recorder. The sensor is a speed sensor, and the output voltage is proportional to the measured vibration speed. The signal obtained is converted into a displacement signal after one integration, which is amplified by the amplifier and sent to the recorder. As shown in Figure 1)
②Aluminum pipe pressure pulsation measurement: The most basic part of the airflow pressure pulsation measurement device in the aluminum pipe is the sensor, amplifier and recorder. The function of the sensor is to convert the signal of pressure change into a signal of power change, and the amplifier accurately linearly amplifies the electrical signal obtained from the sensor, and pushes the recorder to record the pressure pulsation curve. As shown in Figure 2)
③The natural frequency measurement of the aluminum pipe system: generally use the tapping method to excite the pipe system, tap one or several points of the aluminum pipe to record the attenuated vibration signal, and quickly analyze the signal. The natural frequency of each order, this method is very simple and commonly used. 3 Measures to reduce and eliminate the vibration of the pressure aluminum pipe 3.1 Change the natural frequency of the aluminum pipe According to the vibration theory: the multi-degree-of-freedom vibration equation of a mechanical system can be expressed by the matrix differential equation: MX+CX+KX=F where: M Is the mass matrix, X is the node displacement vector, C is the damping matrix, K is the stiffness matrix, and F is the interference force and the excitation force vector. It can be seen from the above formula that to change the vibration characteristics of the pipeline system, the following considerations can be considered: ① Install a balance weight on the aluminum pipe system and change the mass matrix to change the natural frequency of the system to avoid resonance of the aluminum pipe.