Hydraulic turning gear system of the steam turbine
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I have a question recently: The turbine is operating normally. In the turbine’s hydraulic turning system, the pressure in the upper chamber of the turning piston is 0.85 MPa, the pressure at the outlet of the gear pump is 0, while the pressure in the lower chamber of the turning piston is 2.5 MPa. Why is this? It’s the pressure gauge that’s problematic; also, how do I drain the oil from the turning piston? Waiting online, dear
The pressure in the upper chamber of the turntable piston is equal to the pressure of the control oil entering the system; it is the drive oil that causes the hydraulic turntable rod to move downward and engage with the turntable gears. The pressure in the lower chamber of the cranking piston is supplied by a gear pump, which drives the entire rotor of the unit to carry out cranking. When it reaches its maximum level, the cranking hook can disengage from the cranking gear of the unit’s rotor, thereby preventing damage to the gears that could lead to accidents during startup. As for the methods of draining oil from the crankshaft piston, there’s no need to explore them while the unit is in operation; after it stops running, one can find out that it can be done via DCS settings, manually, or through even simpler methods that require no technical expertise
After the steam turbine unit needs to have its turning gear stopped, the power supply to the motor is turned off and the solenoid valve is de-energized in the DCS. As a result of the oil pump ceasing to operate and the solenoid valve being de-energized, the pressure in the lower chamber of the cylinder becomes zero; meanwhile, the upper chamber of the cylinder remains connected to the control oil via a check valve. Due to the oil pressure, the valve stem of the cylinder moves downward, remaining in this lowered position at all times when the turning gear is not in use, thereby preventing contact with the ratchet on the turbine rotor and avoiding accidents. There must be something wrong with the pressure in the chamber when your unit is running – either the pressure gauge is faulty, or the gasket at the connection is blocked during installation. The oil drainage for the cranking piston is controlled by the solenoid valve, which is that red device. The answer given yesterday was incorrect; I’m sorry about that. I checked the relevant information today, and the pressure at the outlet of the oil pump is generally 7 MPa, while the pressure in the lower chamber is 6 MPa
There must be a problem with the lower chamber pressure gauge; otherwise the piston would move upward and cause an accident. The oil pressure for the cranking piston is established and released through solenoid valve switches in the oil circuit.