What would happen if the compressor driven by the turbine started without pressure during startup?
Thread Content
What would happen if the compressor driven by the turbine started without pressure during startup? What happens if there is no gas flow at the compressor inlet at startup?
Idle operation damages the blades and bearings; once the speed reaches a certain level, a motor without any load operates at its lowest efficiency. An increase in speed can easily create negative pressure inside the air chamber, and under the influence of external forces, balance is lost. What is meant by a rigid body being damaged is not necessarily under compressive stress (within the design limits), but rather in a state of imbalance. The reason for this is that a person can walk on an egg, but not when that egg is struck against a hard object – this is a principle of mechanics
If the seal oil for the compressor has been supplied, it may cause oil leakage. Without seal oil, friction between the rotor and the seal will occur, damaging the bearings. If there is insufficient airflow, the anti-surge valve will be fully open at this time, and surge generally does not occur.
What does starting without pressure mean? When the compressor starts, the outlet vent valve and the anti-surge valve are open. It should be without pressure right after startup. There should be inlet flow when the vent valve is opened.
If the vent is not activated when anti-surge should be engaged, it is normal for there to be no flow at the inlet.
In the case of a floating ring seal, the absence of pressure at startup prevents the floating ring from rising, and no effective gap is formed between the floating ring and the rotor for the sealing oil to pass through; this results in dry friction between the rotor and the floating ring, and the consequences are obvious!
There is no flow control at the inlet; care should be taken to prevent overspeeding during startup, as the speed can increase rapidly when there is no load. Therefore, the control valve should be opened gradually during startup.
As long as it doesn’t exceed the minimum control speed of the DCS, there’s no problem. The issue mentioned by the original poster is similar to that of a centrifugal pump where the inlet valve isn’t opened, yet the pump still has to run – are they trying to cause damage?