JPH06257962A - Heater drain discharge device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to prevent a water hammer caused by a flash of a drain that occurs when a turbine is started or stopped. [Constitution] The heater drain discharge device of the present invention comprises a service line for accepting drain as a heat source medium from a drain tank for storing drain to a feed water heater, an emergency line for discharging drain to a condenser, and an emergency line for these lines. The route bypasses the control valve that controls the flow rate of the drain that flows out from the drain tank, the check valve that shuts off the drain that flows back from the feed water heater and the condenser to the drain tank, and the control valve that is installed in the service line. With a remote operated bypass valve,
The bypass valve is installed at a position higher than the control valve installed on the service line and is opened by the signal under generator load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drain system in a feed water heater, a deaerator, a moisture separator or a moisture separator heater of a power plant, and particularly occurs when a load is changed and when starting and stopping. The present invention relates to a drain discharge device for preventing a water hammer generated due to a steam portion in a drain pipe generated by flashing a drain.

[0002]

2. Description of the Related Art As a typical example, a system around a moisture separator will be described.

In FIG. 2, reference numeral 10 is a moisture separator, reference numeral 1
Is a moisture separator drain tank, reference numeral 2 is a low-pressure side feed water heater that receives the drain generated in the moisture separator as a heat source medium, and reference numeral 3 is a condenser. The drain line 4 connecting the moisture separator drain tank 1 and the feed water heater 2 and the drain line 5 connecting the moisture separator drain tank 1 and the condenser 3 are provided with control valves 6a and 6b and check valves 7a and 7b. ,is set up. Standard water level detector 11 in the moisture separator drain tank 1
And a high water level detector 12 are provided, and the detection signal from the standard water level detector 11 is added to the control valve 6a via the controller 13 in the steady operation state, and the water level in the drain tank 1 is controlled while controlling the water level. The drain is supplied to the feed water heater 2 on the low pressure side. On the other hand, when the turbine load changes suddenly and the load decreases, it becomes difficult to discharge the drain as described above, and the drain water level rises, so the high water level detector 12 operates and the detection signal is the controller. It is added to the control valve 6b via 14 and the drain is directly discharged to the condenser. The check valves 7a and 7b installed on the drain lines 4 and 5 prevent the drain from flushing and flowing backward.

[0004]

By the way, at the time of fluctuations in turbine load and start / stop described above, the amount of turbine bleed air decreases and the pressures in the feed water heater 2 and the drain tank 1 decrease, so that they stay inside. The drain that is present and the drain in the drain tubes 4 and 5 become supersaturated and start flushing. In addition, there is usually no pressure difference between the moisture separator drain tank 1 and the feed water heater 2, and the flow is achieved by the difference in the head of the water. The speed of the pressure drop of the drain tank 1 is faster than the speed of the water heater 2.
The pressure of the feed water heater 2 becomes higher than the pressure of the moisture separator drain tank 1, and the phenomenon that the drain cannot be discharged due to this gravity occurs. In this case, the check valve 7a
Is closed, and the drain to the feed water heater 2 side cannot be performed. Therefore, the drain in the drain pipe 4 loses its escape area and stays in the pipe between the control valve 6a and the check valve 7a, and the feed water heater 2 A vapor layer is formed due to the flash due to the pressure drop of.

Since the drain cannot be discharged through this line, the water level in the drain tank 1 rises,
The high water level detector 12 operates and the drain in the drain tank 1 is discharged to the condenser 3 through the drain pipe 5.
Therefore, the drain in the drain tank 1 is sequentially replaced with a low temperature (low energy) drain under a lighter load.

When the load continues to rise after passing through such a state, the pressure in the drain tank 1 is restored to the original state due to the increase in the turbine extraction amount, so that the drain in the drain tank 1 again moves toward the feed water heater 2. Although the flow starts, the drain in the drain tank 1 that is flowing in is in a subcooled state with respect to the drain and the vapor layer trapped in the drain pipe 4, so the vapor layer in the pipe is rapidly condensed by the inflow drain. , Due to water collision at the moment of disappearance of the vapor layer,
So-called water hammer occurs. This water hammer often causes damage to the support member that supports the piping and causes the control valve 6a to malfunction.

In view of the above points, the present invention is intended to prevent a water hammer which is generated when a drain is flushed at the time of starting and stopping a turbine and a steam portion is generated and disappears in a drain pipe, thereby discharging a heater drain. The purpose is to provide a device.

[0008]

A heater drain discharge device of the present invention comprises a service line for receiving drain as a heat source medium from a drain tank for storing drain in a feed water heater,
An emergency line for discharging the drain to the condenser, and a control valve for adjusting the flow rate of the drain flowing out of the drain tank and a drain for backflowing from the feed water heater and the condenser to the drain tank are provided in the paths of these lines. A heater drain discharge device provided with a check valve for shutting off, which is characterized in that a remotely operated bypass valve for bypassing a control valve installed in a service line is provided. Further, it is characterized in that the remotely operated bypass valve is arranged at a position higher than the control valve installed in the service line. On the other hand, the remote control bypass valve is opened by the generator load drop signal.

[0009]

In the turbine bypass test and the like, when the turbine load changes, the turbine extraction amount decreases, and the equipment for storing the drain, for example, the moisture separator drain tank, and the equipment for receiving the drain, for example, the feed water heater, etc. The internal pressure of, decreases. Therefore, the drain of these devices and the drain accumulated in the drain pipe become supersaturated,
Part of the drain flashes and steam is generated. At this time, when the internal pressures of these two devices reverse, a reverse flow of the drain pipe occurs, the check valve is closed, and the flash vapor becomes a vapor layer and stays in the drain pipe between the control valve and the check valve. To do. At this time, the drain between the check valve and the control valve can be forcibly discharged to the feed water heater by opening the bypass valve of the control valve installed in the service line. Therefore, high-energy fluid is not trapped between the check valve and the control valve, and a hammer is prevented.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of the present invention. The same parts as those of the conventional heater drain discharge device shown in FIG.

In FIG. 1, the control valve 6a installed in the regular drain pipe 4 is located lower than the feed water heater 2, and the drain pipe is raised from the control valve 6a and connected to the feed water heater 2. On the other hand, the bypass valve 8 of the control valve 6a is located higher than the control valve 6a. Here, the bypass valve is a pneumatically-operated valve having a small resistance.

When the turbine load fluctuates in a turbine bypass valve test or the like at a low load, the pressure in the drain pipes 4 and 5 drops, and some of the drain flashes to generate steam. In this case, according to the conventional technique, the volume increases due to the flash vapor, and the apparent flow rate increases due to the flow rate passing through the control valve 6a becoming a gas-liquid two-layer flow. The gas-liquid two-layer flow in the drain pipe 4 flows backward to the device 1 and vice versa because the internal pressures of the drain tank 1 that stores the drain and the feed water heater 2 that receives the drain reverse. The stop valve 7a is closed, and the generated steam gradually becomes a large mass to form the control valve 6a and the check valve 7a.
However, in the embodiment of the present invention, by forcibly opening the bypass valve 8 when the load drops, the high-energy fluid that stays between the check valve 7a and the control valve 6a is Since the water escapes to the water heater 2 due to the difference in level, the drain is not trapped and the water hammer can be prevented.

[0013]

As described above, according to the present invention, the bypass valve of the control valve installed in the service line is forcibly opened when the load drops, and the turbine load fluctuation due to the turbine bypass valve test or the like causes Since it is possible to eliminate the retention of the high-energy drain in the service line that is generated, it is possible to reliably prevent the water hammer that is caused by the rapid flow of the drain due to the rapid condensation of the vapor layer in the drain pipe. Therefore, according to the present invention, there is an excellent effect that damage to the components of the power plant is prevented.

[Brief description of drawings]

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

FIG. 2 is a system diagram showing a conventional example.

[Explanation of symbols]

1 ... Equipment that stores drain, (moisture separator drain tank, etc.) 2 ... Equipment that receives drain, (feed water heater, etc.) 3 ... Equipment that drains drain, (condenser, etc.) 4 … Regular drain pipe 5… Emergency drain pipe 6a, 6b… Control valve 7a, 7b… Check valve 8… Bypass valve 10… Moisture separator 11… Standard water level detector 12… High water level detector 13,14… Regulation Total

Claims (3)

[Claims] 1. A normal line for receiving the drain as a heat source medium from a drain tank for storing the drain into a feed water heater, an emergency line for discharging the drain to a condenser, and a path for these lines, In the heater drain discharge device provided with a control valve for adjusting the flow rate of drain flowing out from the drain tank and a check valve for shutting off drain flowing back to the drain tank from the feed water heater and the condenser, in the regular line, A heater drain discharge device comprising a remote control bypass valve that bypasses an installed control valve. 2. The heater drain discharge device according to claim 1, wherein the remote operated bypass valve is arranged at a position higher than a control valve installed in the service line. 3. The heater drain discharge device according to claim 1, wherein the remotely operated bypass valve is opened by a generator load drop signal.