Compressor vibration issues
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Our factory has two M180/54 type compressors used for compressing synthetic methanol. Since these machines were put into operation, they have experienced severe vibration, and it was not possible to increase the pressure at one of the inlets. Later, the pipes and foundations were reinforced, and the machines were brought back online for use. They have been in operation for 3 years now, but the vibration levels of the equipment itself and the pipes connected to it still remain well above acceptable levels. If this continues, it could pose a risk to safe production. The equipment manufacturer claims that there are too many pipe bends in the design, while the design team blames the equipment manufacturer; both sides are shifting responsibility. Is there any way to address this issue?
For reciprocating compressors, eliminating vibration is a critical issue that must be taken seriously based on their working principle. As long as the compressor is a mature product manufactured by major domestic companies such as Shangya and Shenqi, there are generally no problems; moreover, having been in operation for 3 years, any issues would have shown up already. So, in my opinion, the main issue lies in the design of the process pipelines; the natural frequency of these pipelines happens to be the same as the pulsation frequency of the compressed gas, resulting in resonance. No matter how much reinforcement is applied, it won’t have much effect in such a situation. It is recommended to find another qualified, larger design firm to carry out new design calculations for the pipelines, and to replace them during a major system overhaul. If the designers continue to shirk responsibility, it is recommended that they be taken to the site where the same model is manufactured by the same factory for an on-site inspection. :lol
Things in the world really do happen by chance! Our factory encountered a similar problem as well. The methanol production unit at our plant was put into operation 10 years ago, and its syngas compressors were imported; they worked normally. Last year, the unit was upgraded to increase its production capacity by half, which required the addition of another syngas compressor to be used in parallel with the original imported compressors. As a result, vibrations occurred in the cylinders of the imported compressors as well as in their outlet pipes. This forced operators to measure the vibration levels of those cylinders every two hours. The problem has not yet been resolved, and the cause of the vibrations remains unknown. However, just last month, we found strong evidence to help identify the issue. Our plant also has several 75-ton circulating fluidized bed boilers. A similar phenomenon was observed during one of the startups last month. The situation was as follows: after starting one of the fans, natural gas was used to ignite and heat the boiler (the ignition air came from the outlet duct of the fan, so the ignition air duct operated in parallel with the normal primary air duct). After ignition, the ignition air merged with the primary air inside the ignition burner, before entering the distribution chamber to heat the bed material. Once ignition was successful, due to the high volume of ignition air (which wasn’t noticed at the time), significant vibrations occurred in the ignition burner, the air ducts, the primary fan, and even the entire boiler body. The operators assumed that water hammer was occurring inside the fan, so they stopped the fan for inspection; however, no water was found inside the fan. The boiler was restarted, and vibrations persisted after ignition. Eventually, by adjusting the flow rate of the ignition air and redistributing the amounts of primary air and ignition air, the vibrations gradually decreased until they disappeared altogether. Analysis of the cause of vibration: The design of the primary air duct and the ignition air duct is unreasonable; during operation, this can lead to poor distribution of air flow, resulting in intense turbulence that causes vibration. The frequency of this vibration matches the natural frequency of the fan, leading to resonance and thereby intensifying the vibration. Insight: Two syngas compressors are used in parallel, and vibration occurs at the point where they meet; the frequency of this vibration is identical to the natural frequency of the older compressor, which makes resonance likely. As a result, the existing syngas pipelines can no longer meet the new operating conditions, and they need to be redesigned in order to eliminate vibration: handshake
The two guys on the 2nd and 3rd floors said it very well. Haha Gasification also has two units of the same model as ours, and they experience vibration as well, but it’s not as severe as in our units. The compressors are newly manufactured, but their machines work very well in other factories. I really would like to find a experienced design firm to make some changes. Do any of you have any recommendations?
We have this situation here as well; we would like to hear the teachers' opinions
May I ask, what definition is used to state that \"the pipeline vibration level is still well above the acceptable range\"? Are there any standards to define it?
To eliminate vibration in compressors, actions are generally taken from the following aspects: 1. The moving parts must be statically and dynamically balanced; otherwise, inherent vibration factors will arise. 2. The concentricity of the compressor and the motor must be adjusted correctly. 3. The foundation of the compressor must be constructed in strict accordance with the design drawings. There shall be no rigid connection between the foundation and any structure of the building. 4. Vibrations caused by airflow fluctuations require that auxiliary equipment and pipes be equipped with secure supports and clamps; for cantilevered structures, reinforced brackets should be used, and shims should be used to secure them in place. 5. The tightening torque of the machine’s foot screws must be consistent ； 6. The frame (base) must have sufficient stiffness.
Check to see if there is water present; even slight liquid impact can result in high vibration levels
It seems that vibration problems at the compressor outlet are still common, especially in modified systems. Initially, two compressors were in operation with one as a backup, and everything was fine; but after adding another compressor, issues arose with the configuration of two in operation and one as backup. While the capacity increased, the vibration also increased. This is likely due to problems with the system’s piping. Therefore, when expanding such systems in the future, I suggest that both compressors be upgraded in terms of capacity
Is it the case that the natural frequency of the pipeline is close to the operating frequency of the machine or the pulsation frequency of the airflow, resulting in vibration? The solution should involve first having some organizations conduct analyses, modifying the pipelines, or addressing the issue of an improperly designed airflow pulsation suppressor
It seems that the phenomenon mentioned by the original poster is related to the piping system – either the pipe diameter is too small or the piping layout is not proper. Additionally, as mentioned on floor 3, running two machines in parallel can also increase vibration levels. Vibration of the equipment itself is different from vibration in the pipelines; the fact that the equipment can operate for 3 years after the pipelines are reinforced proves that there are no issues. Additionally, by reducing the load or operating the equipment without any load, the equipment itself should not vibrate.
Install buffer devices at home, reinforce pipes, or reroute them
Built raw? Then consider it after-sales service. For several compressors operating in parallel, care should be taken to increase the size of the collector. The principle is: the flow area of the collector should be more than 3 times the total flow area of the inlet pipes.
If it is resonance, reinforcing the pipe should be effective, as reinforcement can change its natural frequency and avoid the resonance point. However, pipe vibration is often not resonance; as mentioned earlier, it may be due to factors related to pipe design, such as too many bends.