Next, let me talk about... Condensing steam turbine What’s going on with the闷缸?

A condensing steam turbine is one in which the steam expands and does work within the turbine, and except for a small amount of leakage from the shaft seals, all the steam is directed into the condenser, where it condenses into water. So, what exactly is "cylinder trapping" during the operation of a condensing steam turbine?

I. Definition of a Stagnant Tank

Refers to the steam turbine cylinder of a condensing type with isolation. After shutdown, close all valves connected to the cylinder to maintain the temperature difference between the upper and lower cylinders. Every 30 minutes, manually rotate the rotor by 180 degrees to align it properly and prevent rotor bending.

II. The Origin of “Stewing the Jar”

Condensing steam turbine After the unit is shut down, for certain reasons, the turning gear cannot be put into operation (including manual turning). When plant power supply frequently shuts down completely, the lubricating oil pump and the jacking oil pump cannot be started either. Since the cylinder temperature remains high immediately after shutdown, the turning gear is not activated in a timely manner. Under the influence of the temperature difference between the upper and lower cylinders, the shaft may bend—a phenomenon explicitly described in the operating procedures to prevent excessive bending of the main shaft.

III. Proposed Measures

1. Lock all steam sources entering the condensing turbine.

2. The water gate after the cylinder drain is locked.

3. Seal the shaft seals of each cylinder with thermal insulation cotton to prevent air intake.

4. When Condensing steam turbine When the high- and medium-pressure cylinder temperatures reach the rotor’s ductile-to-brittle transition temperature, manually rotate the rotor by 180 degrees.

IV. Operational Measures for Handling Stagnant Tanks

1. Vacuum to 0 kPa.

2. Close all water traps connected to the cylinder block.

3. Stop supplying steam to the shaft seal.

4. Unless the plant’s auxiliary power is lost or the oil system catches fire, the top-lift oil pump and the lubricating oil pump should be kept running as much as possible.

5. If the shaft of a condensing steam turbine fails to rotate, pay close attention to the temperature difference between the upper and lower cylinders (typically less than 20°C for 600 MW units). Generally, no immediate action is required. However, if the temperature difference becomes excessively large or increases too rapidly, suspect the possible presence of water or cold air. Promptly inspect the system and eliminate any abnormalities.

The exhaust pressure of a condensing steam turbine significantly affects operational economy. The primary factors influencing the vacuum level in the condenser are the inlet temperature of the cooling water and the cooling rate. The former is related to the region where the power plant is located, the season, and the method of water supply; the latter represents the ratio between the designed flow rate of cooling water and the exhaust steam from the turbine. The higher the cooling rate, the higher the vacuum level. However, as the cooling rate increases, so do the electricity consumption of the circulating water pumps and the capital investment required for equipment. Typically, the cooling rate for surface-type condensers is designed to be between 60 and 120. Given the large volume of circulating water required by steam turbines, water source conditions have become one of the key factors in selecting a site for a power plant.

That’s all for today’s explanation on “What causes the condensing steam turbine to ‘choke’?” Does everyone understand now? We hope the information provided above has been helpful to you.