JPS58200905A - Measuring device for water level of drain in heat exchanger - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a drain water level measuring device for a heat exchanger using a diaphragm seal mechanism.

[Technical background of the invention]

Feedwater heaters are used in power plants to improve the overall thermal efficiency of the power plant.

This feed water heater has the function of exchanging heat between the water that has been cooled once in the condenser and the extracted steam drawn from the middle stage of the turbine, and the extracted steam that has been cooled by heat exchange becomes drain water. After being stored in the water heater, it is configured to be sent to other feed water heaters as a heating source.

In such a heat exchanger, if the water level of the drain water stored in the vessel is not well controlled, the heat exchange efficiency may deteriorate.
There is an inconvenience in that the drain water rises abnormally and flows back into the turbine, causing the so-called "temporal cooling" phenomenon of the turbine.

For this reason, conventionally, a liquid level gauge 2 is connected to the feed water heater 1 as shown in FIG. Drain water generated by heat exchange with water reaching the water outlet 6 is constantly detected.

In addition, a second
As shown in the figure, a buoyancy transmitter 8 is connected between balance tubes 7m and 7b provided above and below the feed water heater 1.

As shown in FIG. 3, this buoyancy transmitter has a flow 8b placed in a container 8a connected to a water level converter 8d via a torque tube 8c, and the output of the water level converter 8d is used to adjust the water level (not shown). The meter is manually operated to compare the preset standard water level setting value and the actual water level, and when a deviation occurs, the drain water discharge value is adjusted using a water level control valve (not shown).

In addition, between the balance pipes 7m and 7b in FIG. A second level switch 5F-10 is connected, which operates in the event of a so-called extremely high water level phenomenon in which drain water rises extremely abnormally due to damage. It is configured to emit steam.

According to the water level detection device described above, since the drain water level can be automatically detected and controlled, compared to the case using only the liquid level needle 2,
Reliability can be improved, and accuracy can be further improved by approximating the actual temperature inside the feed water heater and the actual temperature at the detection end.

[Problems with background technology]

By the way, the temperatures of the drain water of the feed water heater and the detection end drain water are close to the saturation temperature of the extracted steam pressure.

When the turbine load decreases, the extracted steam pressure also decreases in proportion to the decrease, but the drain water cannot follow this rapidly, so a so-called drain water flash phenomenon may occur.

When a flash line of sight occurs, a nozzle is generated within the buoyancy transmitter 8.
) 8b moves up and down violently, and the water level conversion unit 8d interprets this as a sudden up and down movement of the water level and transmits it as a water level of No. 4.4.

As a result, although the actual water level does not change, the opening degree of the water level control valve changes due to hunting, causing the problem that the water level is traversed to the actual water level.

In addition, in Fig. 2, from the actual standard water level, the balance pipe 7b
If the height H is 800 u, even if the heat retention effect is perfect, the actual standard water level will be about 100 u due to the difference in extraction pressure between 20% and 100% turbine load, that is, the difference in specific gravity with respect to the saturation temperature. This is extremely inconvenient in a control system that normally aims at stable control within ±150 U of the standard water level. .

[Purpose of the invention]

The present invention was made in response to the above-mentioned circumstances, and does not cause any change in water level measurement even if the internal pressure of the heat exchanger changes, and moreover automatically calculates changes in the specific gravity of the drain water level. ,
The object of the present invention is to provide a heat exchanger water level measuring device that enables highly accurate water level detection by extracting pressure.

[Summary of the invention]

The drain water level measuring device for a heat exchanger of the present invention includes a pair of diaphragm seal mechanisms connected at one end near the top and bottom of the heat exchanger, and a differential pressure transmission system connected between the other end sides of these diaphragm seal mechanisms. and a computing unit that corrects the output signal from the differential pressure transmitter according to the specific gravity cap C2 of the drain inside the heat exchanger and outputs an actual drain water level signal.

[Embodiments of the invention]

Hereinafter, an embodiment of the drain water level measuring device for a heat exchanger according to the present invention will be described with reference to FIGS. 4 and 5.

In these figures, the same parts as in FIGS. 1 and 2 are given the same reference numerals.

In FIG. 4, a diaphragm seal mechanism 12 is mounted on a water level detection seat 11 provided near the bottom of the feed water heater 1, and the pressure (Lm + Lb) guided by this diaphragm seal mechanism is transmitted to a differential pressure transmitter. It is applied to the HP side pressure opening of No. 16.

The other end of the diaphragm seal mechanism 14 branched from the upper balance pipe 7a of the feed water heater 1 is connected to a differential pressure transmitter 13, and the internal pressure guided by this diaphragm seal mechanism is transmitted by differential pressure. is applied to LPIjA of the device 16.

Therefore, the differential pressure transmitter 13 offsets the internal pressure of the feed water heater 1 and then outputs the actual static water head Lb.

15 indicates a temperature detector for calculating specific gravity.

FIG. 5 shows an example of the signal circuit in the drain water level measuring device of the heat exchanger shown in FIG. The output signal is input to the calculator 16 as a water level signal.

On the other hand, the signal from the temperature detector 15 for drain temperature measurement passes through the arithmetic unit 17, is converted into a unified signal, and is then input to the arithmetic unit 16.

The computing unit 16 corrects the actual still water QLb using the specific weight, performs proportional, integral, differential calculations, etc. 1, and outputs it to the water level adjustment needle 18 to open and close the water level adjustment valve 19.

20 indicates a water level indicator needle.

The diaphragm seal mechanism 12.14 has silicone oil etc. sealed in the capillaries f and -b, and the wetted side is insulated from the steam side and drain side via a diaphragm. The head La of silicone oil etc. on the LP side of 16 has been corrected in advance, and the actual static head Lb (fight)
is simply converted and output as (La + Lb) - (La).

Here, even if the water level detection seat 11 branches from the lower part of the balance tube 7b, the error is slight, so the branching position may be anywhere below the minus side of the needle side range.

Also, the water level indicator 2 uses the output signal of the calculator 16 as the actual water level.
If the output is set to 0, the on-site liquid level gauge 2
It is also possible to omit.

In the above explanation, the method of determining the specific weight based on the drain temperature of the heat exchanger was described, but the present invention is not limited to this. The water level signal may be corrected by converting the specific weight.

〔Effect of the invention〕

As explained above, according to the present invention, a differential pressure transmitter equipped with a diaphragm seal mechanism is used instead of using a buoyancy transmitter as in the conventional water level transmitter, so there is no drain water level flash phenomenon. Moreover, by providing a specific gravity calculation and correction device, the difference between the true water level and the measured water level becomes extremely small, allowing highly accurate water level detection, which greatly contributes to control and operation monitoring.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing a conventional drain water level measuring device for a heat exchanger, Fig. 2 is a system diagram of Fig. 1, Fig. 6 is a longitudinal cross-sectional view illustrating a buoyancy transmitter, and Fig. FIG. 5 is a circuit diagram showing an example of the electrical system of the water level transmitter shown in FIG. 4. 1 ・・・・・・・・・・・・ Feed water heater 2 ・・・・・・・・・ Liquid level needle 6 ・・・・・・・・・ Steam inlet 4 ・・・・・・・・・ Drain outlet 5 ...... Water inlet 6-... Water outlet am, 7b... Balance tube 8 ...... Buoyancy transmitter 8a... ... Container 8k... Float 8c... Torque tube 8d...
... Water level converter 9 ...... First level switch 10
...... Second level switch 11 ・
...... Water level detection seat 12.14... Earphragm seat mechanism 13 ...... Differential pressure transmitter 15 ...... Temperature detector 16. 1
7... Arithmetic unit 18... Water level adjustment needle 19...
・・・・・・ Water level control valve 20 ・・・・・・・・・
Water Level Indicator Needle Representative Patent Attorney Satoshi Suyama - Figure 1 Figure 2 Figure 3 Figure 3 Tou Figure

Claims (1)

[Scope of Claims] 1. A pair of diaphragm seal mechanisms connected at one end near the top and bottom of a heat exchanger, a differential pressure transmitter connected between the other ends of these diaphragm seal mechanisms, and 1. A drain water level measuring device for a heat exchanger, comprising a calculation unit that corrects an output signal from a differential pressure transmitter according to the specific weight of the drain in the heat exchanger and outputs an actual drain water level signal. 2. Claim 71, characterized in that a signal from a temperature detector for measuring the temperature of condensate in a heat exchanger is guided to an arithmetic unit to perform correction according to the specific weight of the condensate. A drain water level measuring device for a heat exchanger according to item 1. 6. The drain water level measuring device for a heat exchanger according to claim 1 or 2, wherein the heat exchanger is a feed water heater of a power generation plant.