Sealing tile

The generator sealing washers (sealing rings) are critical spare parts at both ends of a hydrogen-cooled steam turbine generator. They are installed between the rotor journal and the end cover at the steam end and the excitation end of the generator, serving to seal the high-pressure hydrogen within the machine.

I. Primary Functions

1. Hydrogen sealing: Prevents high-pressure hydrogen, which is flammable and explosive, from leaking outward through the shaft clearance within the generator, thereby mitigating the risk of explosion.

2. Air isolation: Prevent external air and moisture from entering the machine to avoid degradation of hydrogen purity, formation of condensation within the machine, and ensure optimal insulation performance.

3. Lubrication and cooling: The sealing oil forms an oil film in the minute clearance between the journal and the bearing (approximately 0.2 mm), thereby lubricating the friction pairs and carrying away the frictional heat.

II. Common Types

Shuangliu circumferential sealing ring (a mainstream choice for large-capacity units, widely adopted in Shanghai Electric, Dongfang Electric, and Harbin Electric Groups 300 MW, 600 MW, and 1000 MW units)

The vessel contains two independent oil tanks: one for the gas side and one for the hydrogen side.

Hydrogen-side oil line: located near the generator, with the oil flowing toward the interior of the generator;

Air-side oil circuit: located near the atmosphere, with oil flowing toward the bearing side.

The two oil pressure lines should be kept as balanced as possible to minimize oil cross-contamination, making it easier to maintain hydrogen purity; however, this approach involves a more complex structure and imposes higher precision requirements.

The sealing ring body is predominantly constructed from a copper alloy substrate, with a inner circular cavity cast from a bearing alloy (tungsten alloy); this design offers high wear resistance and facilitates the formation of an oil film. Some designs feature a two-half assembly, while others employ a four-lobed assembly; these components must be resistant to impact and deformation, and must meet extremely stringent requirements regarding circularity and inner diameter tolerances.

III. Common Faults and Causes of Replacement

Wear, scratches, and galling on the tungsten gold surface;

Body deformation, ovalization, excessive clearance, and high hydrogen leakage rate;

Local delamination and electrochemical corrosion of the tungsten alloy;

The card locking mechanism has failed, and the sealing pad cannot self-center.