Method and apparatus for operating a steam turbine plant having feed water heaters

Claim 2

Rapid load limiting apparatus for a steam turbine plant having a turbine driven by steam from a boiler and feed water heaters in which feed water supplied to the boiler is preheated by steam extracted from the turbine, said apparatus comprising: means for detecting drain water level in the feed water heater, control means for automatically reducing the amount of steam supplied to the turbine when the drain level in the feed water heater reaches an abnormal level and stopping the extraction of steam from the turbine to the feed water heater.

Claim 3

The rapid load limiting apparatus of claim 1, further including means for bypassing the supplied feed water past the feed water heater, when the drain level in the feed water heater reaches the abnormal level.

Claim 4

The rapid load limiting apparatus of claim 1, wherein said control means comprises first means for detecting a first abnormal level and second means for detecting a second abnormal level which is higher than the first abnormal level in the feed water heater, means for automatically reducing the amount of steam supplied to the turbine to a predetermined amount of steam supplied to the turbine when the drain level in the feed water heater reaches the first abnormal level, first means for stopping the extraction of steam from the turbine to the feed water heater when the reduction of steam supplied to the turbine is completed, and second means for stopping the extraction of steam from the turbine to the feed water heater when the drain level in the feed water heater reaches the second abnormal level.

Claim 5

The rapid load limiting apparatus of claim 3 further including means for bypassing the supplied feed water past the feed water heater, when the drain level in the feed water heater reaches both the first and second abnormal levels.

Claim 6

The rapid load limiting apparatus of claim 4, wherein said control means further includes third means for detecting a third abnormal level which is lower than the first abnormal level, and said control means further including means for providing an alarm when the drain level in the feed water heater reaches the third abnormal level.

Claim 7

In a steam turbine plant having a steam turbine driven by steam obtained by a boiler through a control valve, a feed water heater wherein feed water for the boiler is preheated by steam extracted from the turbine through an extraction stop valve, the improvement comprising in combination rapid load limiting apparatus to insure the safety in an abnormal operating condition of the feed water heater, comprising: a level gauge for detecting the drain water level of extraction steam condensed in the feed water heater, means for closing the control valve to a predetermined degree of opening in accordance with a signal from said level gauge when the drain level in the feed water heater reaches a first abnormal level, means for detecting the degree of opening of the control valve to produce a signal when the control valve is closed to the predetermined degree of opening, means for fully closing the extraction stop valve in accordance with the signal produced in said means for detecting the degree of opening of the control valve, and separately in accordance with a signal produced in said level gauge when the drain level reaches a second abnormal level that is higher than the first abnormal level.

Claim 8

In a steam turbine plant having a steam turbine driven by steam obtained by a boiler through a control valve, a feed water heater wherein feed water for the boiler is preheated by steam extracted from the turbine through an extraction stop valve, the improvement comprising in combination rapid load limiting apparatus to insure the safety in an abnormal operating condition of the feed water heater, comprising: a level gauge for detecting the drain water level of extraction steam condensed in the feed water heater, means for closing the control valve to a predetermined degree of opening in accordance with a signal from said level gauge when the drain level in the feed water heater reaches a first abnormal level, means for detecting the degree of opening of the control valve to produce a signal when the control valve is closed to the predetermined degree of opening, means for fully closing the extraction stop valve in accordance with the signal produced in said means for detecting the degree of opening of the control valve, and separately in accordance with a signal produced in said level gauge when the drain level reaches a second abnormal level that is higher than the first abnormal level.

Claim 9

The steam turbine plant according to claim 6, further including a plurality of feed water heaters, each having a level gauge for detecting the drain water level of extraction steam condensed in the feed water heater, and said means for closing the control valve determining the number of such feed water heaters having an abnormal drain water level as determined by the signals from said level gauges and correspondingly closing the control valve an amount correlated to such number of abnormally operating feed water heaters.

Claim 10

The steam turbine plant of claim 7, further including means for automatically bypassing the feed water around any feed water heater having an abnormal drain water level as determined by said level gauges.

Claim 11

The steam turbine plant of claim 6, including means for bypassing the feed water around said feed water heater automatically and simultaneously with the closing of the extraction stop valve.

Claim 14

A method for operating a steam turbine of claim 10, further including the step of automatically bypassing the feed water past the abnormally operating feed water heater.

Claim 15

A method for operating a steam turbine of claim 10, in which said step of detecting the abnormal operating condition includes a step of monitoring the drain level in the feed water heater, and said step of runbacking the load on the turbine comprising a step of reducing the amount of steam supplied to the turbine connected to the feed water heater.

Claim 16

A method for operating a steam turbine of claim 12, wherein said step of detecting the drain level in the feed water heater includes a first step of detecting a first abnormal drain level and a second step of detecting a second abnormal drain level that is higher than the first abnormal drain level, said step of running back occurring when the drain level reaches the first abnormal drain level and reducing the amount of steam supplied to the turbine to a predetermined amount thereof, and said step of stopping occurs when the drain level reaches the second abnormal drain level.

Claim 17

A method for operating a steam turbine of claim 13, wherein said step of detecting is automatic and said step of running back automatically occurs in response to said step of detecting when there is an abnormally operating feed water heater, and said step of stopping occurring automatically in response to the detecting of the abnormally operating feed water heater.

Claim 18

A method for operating a steam turbine of claim 10, wherein said step of detecting is automatic and said step of running back automatically occurs in response to said step of detecting when there is an abnormally operating feed water heater, and said step of stopping occurring automatically in response to the detecting of the abnormally operating feed water heater.