Steam turbine extraction control issue
Thread Content
In exhaust steam condensing turbines, during startup, the travel of the exhaust steam control valve (as indicated by the on-site valve position scale), the secondary oil pressure, and the control valve opening are all consistent. After one year of operation, however, the travel of the intermediate exhaust steam control valve has become smaller – while before startup 100% corresponded to a travel of 51.1 mm, it now corresponds to 43 mm. The secondary oil pressure has increased from 0.45 MPa to 0.47 MPa. Under the current operating conditions, with the exhaust steam valve fully open, the flow rate of intermediate exhaust steam is high; an increase in load leads to an increase in both the inlet steam volume and the intermediate exhaust steam volume, exceeding the specified limits. It is currently assumed that the on-site opening degree of the intermediate exhaust steam valve is too small, which results in an excessive flow rate of intermediate exhaust steam. May I ask the experts what could cause the travel of the intermediate exhaust steam control valve to differ from the secondary oil pressure and the control valve opening? How can this situation be processed online?
This should be related to the instrument; I think the instrument isn’t properly calibrated. It is caused by a discrepancy between the commanded valve opening and the actual valve opening. This may require stopping the machine to recalibrate the valve; it’s generally quite difficult to handle it without stopping the machine. Mainly, the instruments require significant adjustments to the valve opening, which in turn affects the operation of the turbine.
Doubt? Just compare it on-site with the control room and you’ll know. In addition to instrument failures, it is also necessary to check whether issues such as aged valve packing are causing problems with the opening and closing of the valves~
It wasn’t checked properly during the maintenance process.
Before starting up, the valve position travel, secondary oil pressure, and control valve opening were adjusted to the correct values. After operation, when intermediate extraction steam is introduced (with the intermediate control valve reduced by 55%) and then the opening is increased to 100%, the flow rate of intermediate extraction becomes too high, resulting in a significant discrepancy between the actual valve position travel and the control valve opening values
It’s still likely a problem with the locator; it needs to be recalibrated.
By ‘positioner’, do you mean a wrong throttle or a fuel actuator?
Even with the same valve opening, the pumping volume is not necessarily the same; it depends on changes in the unit’s load, changes in S1 pressure, and changes in the pressure in the S2 pipeline network...
Other parameters should not change much~~