Problems with Mitsubishi centrifugal units
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The original imported Mitsubishi compressor units we have experienced a problem with the speed control valves becoming malfunctioning after one year of operation. I will now briefly explain the symptoms of this fault as well as our configuration. Our speed control system uses a Woodward control system; the control room outputs a current of 4-20mA, which is then amplified to 20-160mA by two TM25 signal amplifiers. The on-site EG3P electro-hydraulic actuator is connected to the oil motor via a throttle valve. Our engine speed when we jumped out of the car was 12,600 revolutions per minute. The problem at present is that the control room sets a target rotation speed of, for example, 10700, but the actual rotation speed is 10550. As a result, the speed control valve operates and its opening degree increases. However, even though the valve opens, the rotation speed does not increase accordingly. This leads to the valve continuing to open further; when the control valve’s opening degree reaches 100, the gauge on the hydraulic actuator on site should indicate 220 mm. However, our value does not match around 190, and it continues to decrease over time – by about 7 mm per day. At present, the gauge for the hydraulic actuator reads 130, while the position of the main control valve remains at 100%, and it can no longer operate at full capacity. We are still unable to analyze the reason; please help solve it, fellow Hydro users. . . . . .
Before turning it on, run a static test first. It is about adjusting the relationship between electrical signals, oil pressure, and valve positions.
I know; this is a problem that has arisen after 130 days of continuous operation
It might be a problem with the hydraulic actuator; we’ve had issues with similar hydraulic actuators before, but the situation was different from yours. It was sent to Shanghai for repair
Could you tell me more in detail about your situation?
I think the throttle slide valve is stuck due to wrong oil. This causes oil to flow back slowly on the side of the hydraulic actuator.
In your case, the steam inlet valve of the turbine is fully open. This situation usually results from a decrease in steam pressure; at the same time, there is an increase in steam flow and a decrease in steam temperature. This is because steam tends to change from high-pressure superheated steam to saturated steam. Under such conditions, it becomes impossible to increase the speed of the compressor; on the contrary, reducing the speed leads to a slight decrease in the opening degree of the valve. Another possible cause is that the design of the steam inlet pipeline is too narrow, resulting in insufficient steam flow. As the speed increases, the steam consumption rises, until the valve is fully open and the steam volume reaches the maximum level permitted by the pipeline design – this can also lead to the situation you described!
My thought is: since the rotation speed decreases on its own, according to the principles of regulation, it should remain at the maximum opening position of the air valve. But in the case described by the original poster, the valve gradually closes, which seems quite strange to me.
Our steam pressure and temperature parameters are within the acceptable range, and there are no issues with the pipeline design. This problem occurred after 112 days of operation; everything was normal before that