JPH0518208A - Rotational speed rise prevention device of condensing turbine - Google Patents

Abstract

PURPOSE:To rotate a turbine rotor at a prescribed rotational speed which is an allowable rotational speed or less by steam leaking from a steam regulating valve in fully closed condition when a main steam stop valve is opened, at the time of starting a condensing turbine. CONSTITUTION:A control means is provided in order to control a vacuum breaking valve 6 for breaking vacuum of a condenser 5 by the deviation between a rotational speed detected from a rotor 2 and the target value of a prescribed rotational speed so that the vacuum degree of the condenser 5 may be reduced so as to control the rotational speed of the rotor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents the rotation speed of a rotor from rising above an allowable value due to leaked steam from a steam control valve that is in a fully closed state when the main steam stop valve is opened when the condensing turbine is started. The present invention relates to a device for preventing a rotation speed increase of a condensate turbine.

[0002]

2. Description of the Related Art In a condensing turbine equipped with a condenser for condensing exhaust steam from a steam turbine to maintain a predetermined degree of vacuum, air in the condenser is extracted by an ejector or the like when the turbine is started. To maintain a predetermined vacuum level, open the main steam stop valve, and then open the steam control valve to allow steam to flow into the turbine and rotate the rotor.The steam control valve controls the amount of inflow steam and the rotor To the rated speed.

By the way, in the steam control valve, in order to reduce the force for opening the valve from the fully closed state, a balance hole is provided in the valve body, and the valve body and the valve seat are connected so that the valve body and the valve seat do not stick to each other. There is a gap between them.

Therefore, even when the steam control valve is fully closed and the main steam stop valve is opened at the time of starting the turbine, leakage steam flows from the steam control valve into the turbine through the balance holes and gaps before the steam control valve is opened. In general, the rotor rotates at a low speed, and the steam control valve is opened from this speed to increase the rotor rotation speed to the rated rotation speed.

[0005]

When the main steam stop valve is opened to rotate the rotor at the time of starting the condensing turbine, even if the steam control valve is fully closed, the steam control valve is operated as described above. Leaked steam flows into the turbine, but if there is a lot of this leaked steam and the condenser vacuum is high, the rotation speed of the rotor will be higher than the permissible value. There is a problem of approaching the frequency.

An object of the present invention is to prevent the rotational speed of the rotor from exceeding an allowable value even when leaking steam from the steam control valve in the fully closed state when the main steam stop valve is opened at the time of starting the turbine. The present invention is to provide a condensate turbine rotation speed increase prevention device.

[0007]

In order to solve the above problems, according to the present invention, there is provided a steam turbine, and a condenser for condensing exhaust steam from this turbine to a predetermined degree of vacuum. When the condensing turbine starts up, when the turbine rotor is rotated by the steam passing from the main steam stop valve to the steam control valve, leakage of steam from the fully closed steam control valve may cause the rotor to rise above the allowable rotation speed. In the condensing turbine rotation speed increase prevention device for preventing the rotation speed, a rotation speed increase prevention means for reducing the vacuum degree of the condenser to keep the rotation speed of the rotor at a predetermined value is provided.

The above-mentioned rotation speed increase preventing means includes a vacuum breaking valve for breaking the vacuum of the condenser, a rotation speed detector for detecting the rotation speed of the rotor, and a rotation speed detected by this detector and a predetermined rotation speed. The control means controls the vacuum breaking valve based on the deviation from the target value.

[0009]

When the main steam stop valve is opened during startup of the condensate turbine, and when the turbine rotor rises above the allowable rotation speed due to leaked steam from the steam control valve in the fully closed state,
A rotation speed increase prevention means, which controls the opening of the vacuum break valve from the deviation between the detected rotation speed of the rotor detected by the rotation speed detector and the target value of a predetermined rotation speed not more than the allowable rotation speed, The degree of vacuum of the water container is reduced and the fluid resistance when the rotor is rotated is increased so that the rotation speed of the rotor maintains a predetermined rotation speed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a system diagram of a condensate turbine equipped with a rotation speed increase prevention device according to an embodiment of the present invention. In FIG. 1, a steam turbine 1 is provided with a rotor 2, and a main steam stop valve 3 and a steam control valve 4 are provided at a steam inlet thereof. Condenser 5
Is connected to the steam outlet of the steam turbine 1, and the exhaust steam from the steam turbine 1 is condensed to a non-condensable gas in the condenser by an unillustrated ejector to maintain a predetermined vacuum degree. A vacuum breaking system 7 having a vacuum breaking valve 6 is connected to the condenser 5.

The rotation speed detector 8 detects the rotation speed of the rotor 2. Further, the rotation speed adjuster 9 is the rotation speed detector 8
The signal of the detected rotation speed is input, and the vacuum breaking valve 6 is controlled based on the deviation between the detected rotation speed and the target value of the predetermined rotation speed which is equal to or lower than the allowable rotation speed.

With this configuration, when the condenser turbine is started, the air in the condenser 5 is extracted by an ejector (not shown) or the like to keep the condenser 5 at a predetermined vacuum level. Then, in this state, the main steam stop valve 3 is opened to rotate the rotor 2. At this time, even if the steam control valve 4 is fully closed, when the rotor 2 is rotated by the leaked steam from the steam control valve 4 as described above and the rotor 2 is rotated at a speed equal to or higher than the allowable rotation speed,
The rotation speed detector 8 detects the rotation speed of the rotor 2, and a signal of the detected rotation speed is input to the rotation speed adjuster 9, which adjusts the detected rotation speed and a predetermined rotation speed equal to or lower than the allowable rotation speed, for example, 500 rpm. The vacuum breaking valve 6 is controlled on-off based on the deviation from the target value to reduce the degree of vacuum in the condenser 5, and the rotation speed of the rotor 2 is controlled to the predetermined rotation speed.

FIG. 2 is an operation block diagram of the vacuum breaking valve 6 described above. In FIG. 2, the steam stop valve indicated by 11 is opened,
The vacuum break valve 6 is turned on-o under the condition that the steam control valve shown by 12 is closed and the rotation speed of the rotor shown by 13 exceeds the allowable value.
The ff control is performed, and the rotor is maintained at a predetermined rotation speed equal to or lower than the allowable rotation speed.

[0014]

As is apparent from the above description, according to the present invention, when the condensing turbine is started, the rotation speed of the rotor is detected so that the rotation speed of the rotor becomes equal to or lower than the allowable rotation speed. Since the rotation speed rise prevention means for controlling the vacuum break valve is installed in the rotor, the rotor rotates at a rotation speed higher than the allowable rotation speed due to leakage steam from the steam control valve in the fully closed state when the main steam stop valve is opened. In such a case, the vacuum level in the condenser is reduced by controlling the vacuum break valve to control the rotor rotation speed to a predetermined rotation speed that is less than or equal to the allowable rotation speed. There is an effect that there is no need to change the above, and there is no need to replace the steam control valve with one that leaks less steam.

[Brief description of drawings]

FIG. 1 is a system diagram of a condensate turbine equipped with a rotation speed increase prevention device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing the operation of the vacuum break valve.

[Explanation of symbols]

1 steam turbine 2 rotor 3 Main steam stop valve 4 Steam control valve 5 condenser 6 Vacuum break valve 8 Rotation speed detector 9 Rotation speed controller

Claims (2)

[Claims] 1. When a condensing turbine equipped with a steam turbine and a condenser for condensing exhaust steam from the turbine to maintain a predetermined degree of vacuum, the main steam stop valve goes through a steam control valve at the time of startup. When rotating the turbine rotor with steam, prevent the rotor from rising above the permissible rotation speed due to leakage steam from the steam control valve in the fully closed state. A rotation speed increase prevention device for a condensate turbine, characterized in that rotation speed increase prevention means for reducing the degree of vacuum to maintain the rotation speed of the rotor at a predetermined value is provided. 2. The condensing turbine rotation speed increase prevention device according to claim 1, wherein the rotation speed increase prevention means includes a vacuum break valve for breaking the vacuum of the condenser and a rotation speed for detecting the rotation speed of the rotor. An apparatus for preventing an increase in the number of revolutions of a condensate turbine, comprising: a detector; and control means for controlling a vacuum break valve based on a deviation between a detected rotation speed of the detector and a target value of a predetermined rotation speed.