How should fluctuations in the steam inlet pressure of a turbine be handled?
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1. When the steam inlet pressure of the turbine fluctuates, what aspects should be taken into consideration during the operation of the turbine and the compressor it drives? (The inlet pressure of the turbine in our plant is 4.9 MPa.) What effects does the level of steam inlet pressure have on the turbine and its auxiliary equipment? And what impact does the inlet temperature have on the turbine and its auxiliary equipment? ? (The inlet temperature of the turbine in our factory is 470 degrees.) 2. What should be done when the steam parameters change?
For turbines, shaft displacement and vibration levels have some impact, but the fluctuations are not significant. The most important thing is to pay attention to fluctuations in rotational speed; on-site, check the secondary oil pressure as well as the pressure in the wheel housing, the pressure behind the extraction valve (in the case of a condensing turbine), the pressure fluctuations in the extraction line, and the negative pressure in the surface cooler. First, it is necessary to stabilize the steam inlet pressure at the turbine as soon as possible, and to adjust the pressure in the steam extraction network promptly. In terms of process control, it is necessary to pay attention to the impact of turbine speed fluctuations on the compressor, focusing mainly on factors such as inlet pressure and the anti-surge line. Fluctuations in the compressor speed will inevitably cause fluctuations in the load at the front end; attention should be paid to making adjustments in such cases.
1; If the inlet pressure is lower than the designed value, it reduces the efficiency of the turbine. The amount of steam required at the same load increases, which leads to an increase in axial thrust. As a result, the stress on the blades in the later stages rises, and in severe cases, this can cause the blades to deform. Additionally, if the steam pressure is too low and the nozzle cross-section does not allow an increase in steam flow, the turbine’s load will decrease, affecting its economic efficiency. An inlet pressure higher than the designed value is advantageous from an economic perspective, but it is not acceptable from a safety standpoint. This is because metal mechanical properties deteriorate rapidly at high temperatures, which shortens the service life of various turbine components and may also cause the blades in the earlier stages to become loose. The inlet temperature should be maintained at above the saturated temperature corresponding to that pressure plus 50 degrees, as steam requires a certain degree of superheat. If the saturated temperature at that pressure is used, it could lead to water hammer and corrosion. 2: Reduce the load promptly and take appropriate action.
Blade shroud? That’s my guess. Let’s continue the discussion
If the pressure fluctuates too much, the steam temperature will also fluctuate, resulting in changes in thermal expansion of the moving and stationary parts inside the turbine, which is very dangerous.
When there are fluctuations in steam pressure, it is generally necessary to first check the changes in steam temperature before contacting the boiler operators to increase the steam pressure. If the steam pressure continues to drop slowly and cannot be brought under control, then it is necessary to reduce the load or the speed of operation. If the steam pressure reaches the limit that the unit can tolerate, an emergency shutdown must be carried out.
Fluctuations in steam pressure can be dangerous even when there is no liquid present; too low a pressure may cause the compressor to lose its load and shut down, while too high a pressure can lead to the compressor running out of control. It is best to install a steam pressure interlock.