What causes the turbine speed not to increase?
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The cycle hydrogen compressor in our company’s diesel and gasoline hydrotreating unit is driven by a turbine; it is a back-pressure type turbine with a power output of 931 KW, a rated speed of 10,966 r/min, a rated steam flow rate of 16 tons per hour. The steam temperature ranges from 380–420°C, while the steam pressure is between 3.3–3.7 MPa. At present, the steam control valves are fully open; the actual steam temperature is 400°C, the pressure is 3.3–3.5 MPa, and the flow rate is 14–15 tons per hour. The set speed is 10,500 r/min, but in reality the speed only reaches around 9,600 r/min. The anti-surge valve of the centrifuge is open to a certain extent, and the vibration and displacement of both the compressor and the turbine are within normal limits. I don’t know what the reason is – is it scaling on the leaves or something else?
Is the control steam valve fully open on site?
Confirmed fully open, secondary oil pressure 0.46 MPa.
Has there been any change in the pressure in the turbine housing, and what is it now?
What is the backpressure? It’s also necessary to check the quality of the steam to see if it meets the requirements. It’s very likely that there is fouling on the impeller, which results in low efficiency of the turbine; even with the steam valves fully open, it’s difficult to reach the turbine’s rated speed. If the input speed is sufficient and there isn’t much change in the backpressure despite using medium-pressure steam, it means the turbine has reached its maximum power output. You can also call the manufacturer to ask what’s going on
How do the steam pressure and temperature under backpressure compare to the normal values?
The backpressure steam is around 0.93 MPa, and the temperature is around 180°C, remaining basically constant.
If the pressure in the cylinder chamber is high, it indicates that the quality of the steam is poor and scaling has led to a decrease in efficiency. Additionally, wear on the mating surface between the valve stem and the valve beam can cause the valve disc beneath the valve beam not to open fully, even when the valve is fully opened, resulting in the failure to reach the rated speed.
There are various reasons why the rotation speed cannot be increased; I know of three such reasons, which I can share for your reference. 1. Turbine rotor scaling ； 2. Wear of the valve disc in the control valve, along with the detachment of the valve core, has caused one of the air inlets to become blocked ； 3. The purity of the circulating hydrogen is insufficient, and its molecular weight is much higher than the designed value; as a result, the output power of the turbine has reached its limit. Based on your current operation, the steam consumption does not reach the designed value, and the other parameters are also basically normal; the second possibility is more likely. You need to check how long your turbine has been in operation. I’m currently facing an issue where, after one year of operation, the valve core of the control valve falls off and blocks the air inlet.
The static commissioning of the turbine was not done properly; the opening degree of the control valves and the stroke of the hydraulic actuators were not adjusted accordingly, so it had to be stopped for readjustment