Mechanical problems I encountered and solved
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This post was last edited by Wu Wuyinhuer on 2010-4-20 10:50 It has been almost 20 years since I started working. I have been engaged in the installation, debugging and maintenance of mechanical equipment. Now I am older and engaged in quality management. I've been bored lately, so I've sorted out the problems and solutions I encountered at work for reference by those who are interested. 1. The problem of vibration during test runs of imported steam turbines happened in 1999, and it is considered my most famous work. At that time, a pneumatic unit imported from the United States, driven by a steam turbine, vibrated during a single test of the steam turbine, automatically tripped and shut down, and failed to operate normally for thirteen consecutive trials. The fundamental reason is that the design parameters are wrong, the minimum operating temperature is designed to be the maximum operating temperature, and the spring force of the outlet and inlet spring brackets is too large. When the unit reaches the operating temperature, the pipeline stress causes the turbine casing to deform, resulting in a smaller internal gap, and friction between dynamic and static parts causing vibration. At that time, the entire device had been put into production. It was impossible to recheck the stress and replace the spring bracket just after the air compressor was running. We could only use the simplest means to get the steam turbine to start up and operate normally. Based on the structure of the steam turbine, I proposed adding a gasket behind the thrust bearing of the steam turbine to change the relative position of the rotor and stator and increase the inlet side clearance. The data provided was 0.25 mm. At that time, the American manufacturer was dubious and decided to try adding half of the gasket. As a result, the no-load test was successful, but the compressor still vibrated. Finally, the other half was added and the load test was successful. A year later, the machine was shut down for maintenance, the stress was recalculated, and the spring brackets of the inlet and outlet pipelines were replaced, completely solving the problem.
I really admire it! ! Please explain how to determine the following 0.25mm gasket.
I hope the poster can share your experience so that those of us who come after you can also learn from it.* Got a chance!
Regarding adding 0.25 mm of spacer, my* As a rule, when starting up the engine, especially the thermal engine, the meter will be read at each sliding expansion position to observe the expansion amount. When the expansion data of each sliding end is almost compared, it will start normally. This time, the bearing support of the steam turbine is a flexible support. I put a dial indicator on the support plate. It expanded normally during preheating. When it was shut down and tripped, the data of about 0.3 mm suddenly disappeared. According to the equipment structure diagram, the maximum clearance on the inlet side is only 0.5 mm, and the actual measurement is about 0.3 mm. I judge that the 0.3mm that suddenly disappears when the machine is stopped should be caused by the deformation of the casing. Therefore, I think that a gasket should be added after the thrust bearing to increase the clearance on the inlet side. After the casing is deformed, there will still be a clearance on the inlet side, and the rotor and stator will not scratch, and the machine can be started normally. As for why it is 0.25 mm, it is because the manufacturer's gasket thickness is 0.125 mm, haha. In fact, this may seem mysterious, but to put it bluntly, it’s nothing.
Although I am not a mechanical major, this type of post is the type I personally prefer. Most of the experience of the predecessors comes from practice and thinking, and the ability to weigh a thousand pounds with four measures is the realm that every technician pursues. Looking forward to more content. (My personal suggestion is to post this kind of posts, including the thought process and experience, to the workplace so that more young people can learn from it. * one time)
study* Now, looking forward to more content!
2. Some minor problems in practice. In 1995, in Jiujiang, a crane in a coal handling plant was out of sync, commonly known as rail climbing. I observed below that the left one moves first and the right one moves later. This is relatively simple. The holding brake on the right side is a bit tight, causing the startup to be out of sync. Just adjust the holding brake. In addition, there is a small crane that cannot be started. It trips when the start button is pressed. Look at the current and switch load on the nameplate. It is no problem. The maintenance staff at that time suspected that there was something wrong with the motor and prepared a reverse chain to remove the motor for maintenance and inspection. I happened to pass by and asked about the phenomenon. I determined that the brake on the motor was not disengaged. I opened the motor guard and adjusted the brake, which solved the problem. In Xianyang in 1997, when debugging the cranking device of a centrifugal compressor unit, it was found that everything was normal, but the cranking device did not move. The electrical inspection showed that everything was normal, and there was a current display on the power supply. There was no problem with manual cranking. I asked the power to be re-energized and listened carefully to the motor with a listening pin. There was a slight sound inside, so I judged that the motor rotor and shaft were separated, and opened the inspection. Sure enough, it was so.
In fact, empirical knowledge is also very important.
Thank you, sir. I will have more experience in the future.
Thank you Master, please post more similar ones so that we can make progress together.
So sweet! Everything at the bottom of the box has been taken out, looking forward to more@!