JPH0618003A - Water supplying and replacing device - Google Patents

Abstract

PURPOSE:To prevent occurrance of flushing within a suction pipe and to realize operation of water supply pumps which has been out of operation, by providing a replacing passage which runs from a minimum flow valve outlet pipe of one of the water supply pumps up to an outlet pipe of the other water supply pump, and also providing a valve within the replacing passage. CONSTITUTION:A discharge valve 8B and a check valve 13B of a water supply pump 6B are closed. A valve 10A is wholly closed or half opened. In the case that turbine load is decreased suddenly, causing a decrease in an amount of water supplied to a steam generator 1, discharged water from a water supply pump 6A in operation is partly supplied to an outlet pipe of another water supply pump 6B through a minimum flow pipe 14A, a minimum flow valve 9A, a replacing pipe 11A, a check valve 13A and a stop valve 12A. The water, thus supplied, flows farther through the water supply pump 6B which is a provisional pump and also a passage 7 up to a deaerator 5. By this effect, high temperature water which has been filled and retained in the passage 7B is pushed to flow by low temperature water coming from the water supply pump 6A, so that the former is replaced by the latter, whereby flushing can be prevented within the passage 7B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a feedwater replacement device for a steam plant for nuclear power generation or thermal power generation.

[0002]

2. Description of the Related Art FIG. 2 is a system diagram showing an example of a conventional steam plant. The steam generated by the steam generator (1) becomes water in the condenser (3) after working in the turbine (2), and is sent to the deaerator (5) by the condensate pump (4),
Further, water supply pumps (6A), (6
Water is supplied to the steam generator (1) by B). Minimum water flow pipes (14A), (14B), minimum flow valve (9A),
(9B), valves (10A), (10B) are provided. The water discharged from the deaerator (5) is supplied to the water supply pumps (6A) and (6B) through the pipelines (7A) and (7B). (8
A) and (8B) are discharge valves of the water supply pumps (6A) and (6B).

[0003]

SUMMARY OF THE INVENTION Now, the water supply pump (6
It is assumed that A) is a regular machine and the water supply pump (6B) is stopped as a standby machine. During normal operation, the deaerator (5) is heated by bleed air (not shown) from the turbine (2), and the pressure inside the deaerator (5) is constant (for example, 10
kg / cm ² G). Then, high temperature water having a saturation temperature corresponding to the pressure fills the pipes (7A) and (7B). However, when the load on the turbine (2) is suddenly reduced, the heating bleeding of the deaerator (5) is stopped, so that the pressure inside the deaerator (5) is drastically decreased and the water supply pump (6) that is stopped is stopped.
The high temperature water filled in the pipe line (7B) which is the suction pipe of B) is flushed into a state containing bubbles.

The water supply pump (6B) is a water supply pump (6
As a standby machine of A), it is necessary to keep the machine ready for operation at any time. However, when the above flush phenomenon occurs in the pipeline (7B), the water supply pump (6
Since the NPSH (pushing pressure necessary for operation) of B) is not secured, the water supply pump (6B) may not be able to operate.

[0005]

In order to solve the conventional problems, the present invention condenses a steam generator, a turbine driven by steam generated by the steam generator, and exhaust gas of the turbine. Condenser, a deaerator equipped with a water storage tank, a condensate pump for supplying the condensate to the deaerator, and the deaerator in parallel with each other to supply water to the steam generator. In a steam plant having a plurality of water supply pumps provided and a minimum flow valve of those water supply pumps, a replacement pipe line from the minimum flow valve outlet pipe of one water supply pump to the outlet pipe of the other water supply pump is provided, The present invention proposes a water supply replacement device characterized in that a valve is provided in this conduit.

[0006]

In the present invention, the following actions occur. When the load on the turbine suddenly decreases, the amount of feed water supplied to the steam generator decreases, so part of the discharge water of the feed pump during operation passes through the minimum flow valve and the replacement pipe, and the other It is supplied to the outlet pipe of the water supply pump, and further flows to the deaerator through the inside of the water supply pump which is stopped and its suction pipe.
By this action, the high-temperature water filled in the suction pipe and stagnant is washed away by the low-temperature water coming from the water feed pump in operation and is replaced with the low-temperature water, so that the flash generation in the suction pipe occurs. It is possible to operate the water supply pump while it is stopped.

[0007]

FIG. 1 is a system diagram showing an embodiment of the present invention. In this figure, the same parts as those of the conventional one described with reference to FIG. 2 are designated by the same reference numerals to avoid redundancy, and detailed description thereof is omitted.

In this embodiment, the water supply pump (6A)
The replacement pipe line (11A) from the outlet pipe of the minimum flow valve (9A) to the outlet pipe of the water supply pump (6B) is provided, and the stop valve (12A) and the check valve (13) are provided in the substitution pipe line (11A).
A) is provided. The arrangement of the stop valve (12A) and the check valve (13A) may be reversed. Regarding the water supply pump (6B),
As in the case of the water supply pump (6A), the replacement pipe (11
B), stop valve (12B) and check valve (13B) are provided.

In the following description, the water supply pump (6A) is a regular machine and the water supply pump (6B) is a standby machine. The discharge valve (8B) and the check valve (13B) of the water supply pump (6B) are closed. The valve (10A) is fully closed or has an intermediate opening. When the load on the turbine (2) is suddenly reduced, the amount of water supplied to the steam generator (1) is decreased. Therefore, a part of the discharge water of the water supply pump (6A) during operation is partially discharged from the minimum flow pipe (14).
A), minimum flow valve (9A), replacement line (11)
A), the check valve (13A) and the stop valve (12A), and is supplied to the outlet pipe of the water supply pump (6B).
It flows into the deaerator (5) through the pipe (7B) inside the B). By this action, the high temperature water filled in the pipe line (7B) and staying therein is washed away by the low temperature water coming from the water supply pump (6A) and is replaced with the low temperature water.
B) The occurrence of flash in the inside is prevented, and the water supply pump (6
The operation of B) becomes possible.

[0010]

As is apparent from the above description, according to the present invention, it is possible to prevent a flush from occurring in the inlet pipe line of the water supply pump on the standby machine side when the load on the turbine is suddenly reduced. The standby water pump can be started and operated smoothly, which greatly contributes to the improvement of plant reliability.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing an example of a conventional steam plant.

[Explanation of symbols] (1) Steam generator (2) Turbine (3) Condenser (4) Condensate pump (5) Deaerator (6A), (6B) Water supply pump (7A), (7B) Pipe Line (8A), (8B) Water supply pump discharge valve (9A), (9B) Minimum flow valve (10A), (10B) Valve (11A), (11B) Replacement pipe line (12A), (12B) Stop valve ( 13A), (13B) Check valve (14A), (14B) Minimum flow pipe

Claims (1)

[Claims] 1. A steam generator, a turbine driven by steam generated by the steam generator, a condenser for returning exhaust gas of the turbine to condensate, a deaerator having a water storage tank, and A condensate pump for supplying condensed water to the deaerator, a plurality of water supply pumps provided in parallel with each other for supplying water from the deaerator to the steam generator, and a minimum flow valve of the water supply pumps. In a steam plant equipped with
A feed water replacement device characterized in that a replacement pipe line is provided from the minimum flow valve outlet pipe of one water feed pump to the outlet pipe of the other water feed pump, and a valve is provided in this pipe line.