Relationship Between Main Steam Pressure Fluctuation vs Axial Float


Thread Starter


Dear Sir/Madam

currently I am working as a Instrumentation engineer in the field of Power plant. now i need your help for to solve the issues of Axial float of Steam turbine, i.e, once our turbine synchronised with grid it run with load mode. In that condition if there is any fluctuations in steam header pressure (Not much fluctuations only 2 to 3kg/cm2), it ultimately reduce the load and governor will try to match the load at desired set point level by open the hydraulic valve so Steam flow increased. Now i come to point as follows.

1. Main steam pressure varies from 1 to 2kg/cm2. will it affect the Turbine Axial float? Now our Axial value is 0.78mm so we reduce operating header steam pressure from 86.5 kg/cm2 to 76.5 kg/cm2. but axial still raising, and corresponding Thrust pad temperature also Raised, and Steam flow Rate is 80.5TPH and MW is 19.5MW.

2.Instead of Load mode, we put our Governor to Pressure control Mode. will it control Axial float?

Boiler Details Before Revamping

Operating Pressure: 96.5 kg/cm2
Temperature: 540 deg centigrade
Flow: 120 TPH

After Revamping
Operating Pressure: 86.5 kg/cm2
Temperature: 540 deg centigrade
Flow: 100 TPH

Turbine Details
Make: Siemens
Rpm: 3000 RPM
Capacity: 27.3MW
uncontrolled Extractions: 2
controlled Extractions: 1
Type: condensing.