JPS6232319A - Detector for liquid level - Google Patents

Abstract

PURPOSE:To detect a liquid level in a water tank with high accuracy by a difference between the lower end pressure of the reference pressure detecting pipe and the bottom pressure of the water tank by providing a reference pressure detecting pipe in the water tank. CONSTITUTION:Condensation from a condensate pump is supplied to a deaerating chamber 2 through a condensate pipe 1 and atomized by a spray valve 5, and mixed and heated and temperature-raised by steam from a heating steam pipe 3 and is once stored in the water tank 4 through a connecting pipe 6. The stored water is supplied to a boiler through a downcast pipe 8. The reference pressure detecting pipe 12 is provided in the tank 4 and the lower end of the detecting pipe 12 pierces through the lower part of the tank 4 and is connected with the high pressure side of a differential pressure type liquid-level detector 16 and a connecting pipe 15 connected with the lower part of the tank 4 is connected with the low pressure side of the detector 16. Further, the water filling piping 11 pours a small quantity of condensation which is overflowed from an opening part of the upper end of the detecting pipe 12 in the tank 4. Then, since the different pressures are applied to the high pressure side and the low pressure side of the detector 16 respectively, the detector 16 detects these differential pressures which are transmitted to a level gage 18 to measure a water level of the tank 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to liquid level detection in a turbine plant, and more particularly to liquid level detection in a heat exchanger using saturated water.

[Background of the invention]

As described in Japanese Unexamined Patent Publication No. 48-58201, the conventional device uses a differential pressure type water level detector to measure the water level of a water storage tank. A make-up water supply port is installed at the top of this reservoir, and water is extracted from the condensate pipe at the deaerator inlet, injected into this supply port, and then communicated with the bottom of this reservoir. One end of the pipe was connected, and this communication pipe was passed through the outer wall of the water storage tank and connected to the high pressure side of a differential pressure type liquid level detector, and the low pressure side of this differential pressure type liquid level detector was connected to the bottom of the water storage tank. Please be sure to measure the water level in the water tank by connecting to the impulse pipe.

Since the reservoir and the connecting pipe are arranged in a water storage tank, and water is injected into the reservoir provided at the upper end of the connecting pipe, the water in the connecting pipe does not flow except through natural convection, and therefore, the water temperature inside the connecting pipe and the stored water When the tank water temperatures match and the pressure inside the water storage tank is stable, the specific gravity of the water in the connecting pipe and the specific gravity inside the water storage tank are the same, and the liquid level in the water storage tank can be detected with high accuracy. However, if the pressure inside the water storage tank suddenly drops, the stored water will flush, and in severe cases, the flushed water surface can rise by more than 500 cubic meters. At this time, the water temperature in the connecting pipe is the same as the water temperature in the water storage tank, so it flushes in the same way and raises the water surface in the reservoir, but it does not flow out into the water storage tank from the overflow hole in the reservoir. There was a problem in that the hydrostatic head in the connecting pipe became small, causing an error in the water level in the water storage tank.

On the other hand, as described in Japanese Patent Application Laid-Open No. 59-197828, in a method in which the reservoir is installed outside the water storage tank and the cooling water is injected from the lower side of the pressure impulse, etc., since the impulse pipe is outside the tank, the water storage Even when the tank internal pressure suddenly drops, the water in the reservoir hardly flushes, but the water temperature in the impulse pipe below the reservoir is usually about 10% lower than the water temperature in the storage tank.
The temperature difference between the water temperature in the water storage tank and the water temperature in the impulse pipe at the bottom of the reservoir changes depending on the operating conditions, such as a temperature difference of 100C or more, especially at startup when heating steam is supplied to the VC. There was a problem that the error in liquid level measurement became large.

[Purpose of the invention]

An object of the present invention is to provide a liquid level detection device that can accurately detect the liquid level in a water storage tank even when the pressure and temperature of the water storage tank change.

[Summary of the invention]

In order to eliminate measurement errors with differential pressure type liquid level detectors, it is necessary to make the water storage tank temperature and the water temperature inside the reference pressure detection pipe the same.For this reason, the reference pressure detection pipe is installed inside the water storage tank, but the To prevent the water in the reference pressure detection pipe from flushing even when the tank pressure suddenly drops, the water temperature in the water storage tank should be
A small amount of condensate at the deaerator inlet is injected from the lower end of the reference pressure detection tube to keep it at a slightly lower temperature, and overflow is allowed to occur in the water storage tank through the opening at the upper end. The injected condensate moves upward while being gradually heated and heated by the storage tank water in the reference pressure detection tube, and eventually overflows from the opening at the upper end of the reference pressure detection tube, so the water temperature in the reference pressure detection tube decreases. The temperature in the upper part becomes high, and the middle and lower part of the reference pressure detection tube cannot be flanched. Therefore, there will be no overflow of more than make-up water. A very small flash occurs at the top end of the reference pressure detection tube, but the flash scatters and injects more water than the running water, making it possible to maintain a constant water level in the reference pressure detection tube. The liquid level in the water storage tank is accurately measured from the pressure difference between the lower end pressure of the tank and the lower pressure of the water storage tank.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained with reference to the 1X1 diagram.

The condensate supplied from the condensate pump is supplied to the degassing chamber 2 through the condensate pipe 1, where it is atomized by the spray valve 5, mixed and heated by steam supplied from the heating steam pipe 3, and dissolved. The water from which oxygen has been removed passes through the connecting pipe 6 to the water storage tank I.
C The water is temporarily stored.

Water stored in the water storage tank 4 is supplied to the boiler via a downcomer pipe 8 by a water supply pump. The water storage tank 4vc is provided with a reference pressure detection pipe 12. The upper end of this reference pressure detection pipe 12 opens at the upper part of the water storage tank 4, and the lower end passes through the lower part of the water storage tank 4 to transmit a guiding pressure 'W14. A pressure guiding pipe 15 connected to the high pressure side of the differential pressure type liquid level detector 16 through the water storage tank and connected to the lower part of the water storage tank is connected to the low pressure side of the differential pressure type liquid level detector 16. The water injection pipe g11 is connected to the lower end of the condensate pipe 1 and the reference pressure detection pipe 12, and injects a small amount of condensate so that it overflows into the water storage tank 4 through the upper end opening of the reference pressure detection pipe 12. There is.

The pressure Pa shown in equation (1) is applied to the high pressure side VC of the differential pressure type liquid level detector 16, and the pressure Pt shown in equation (2) is applied to the low pressure side. Differential pressure D shown in the formula
P is detected and transmitted to the liquid level gauge 18 to measure the water level in the water storage tank 4.

PFI ”Po + r+ ・HI+ r2 ・H2・
”(1) PL = pa + ro −Ho + rfi
T Hx −(2) DP=Pr Pt=r
l・Hl−r, −1(, −・(3) PR: High pressure side pressure of the differential pressure type liquid level detector PL: Low pressure side pressure of the differential pressure type liquid level detector Po = Water storage tank internal pressure ro: Water in the water storage tank The average specific gravity r of the water in the pressure sensing tube 14, the average specific gravity r of the water in the pressure sensing tube 14, the average specific gravity of the water in the impulse tube 15, Ho: the water storage tank H0, the two reference pressure sensing tube water level, as shown in equation (3). Furthermore, if the average specific gravity r1 of the water in the reference pressure detection pipe and the average specific gravity r0 of the water in the water storage tank are approximately the same value, the error in liquid level measurement will also be approximately zero.

The diameter of the reference pressure detection tube 12 is approximately 50+m and the height is approximately 400m.
However, if the water injection flow rate is approximately 1.6 kg/min, the standard pressure detection pipe flow velocity is 80 crIt/min, which is extremely low.
The speed becomes very slow, and the pressure loss within the reference pressure detection tube becomes almost zero. If the pressure in the water storage tank 4 suddenly decreases, it generally takes about ten minutes at the shortest, but the water in the standard pressure detection tube is completely replaced in about 5 minutes. , it can be kept at a very low temperature, and there is no chance that the water in the reference pressure detection-#12 will cause a flash. 71- is a pressure equalizer.

FIG. 2 is a piping system diagram showing another embodiment of the present invention, in which a heating tube 13 is provided in the middle of the water injection pipe 11, and the water injected into the reference pressure detection pipe is heated and heated by water stored in the water storage tank 4.
Increase the water injection temperature. Reference pressure detection tube 1 compared to Fig. 1
Since the water temperature No. 2 and the specific gravity of the water stored in the water storage tank 4 become closer to the set values, the accuracy of liquid level measurement is improved.

〔Effect of the invention〕

According to the present invention, the temperature of the water stored in the water storage tank and the specific gravity of the water in the reference pressure detection pipe can be kept almost the same at all times, so that the specific gravity is automatically corrected in accordance with changes in the pressure and temperature of the water storage tank, and deaeration is performed. This has the effect of accurately measuring the liquid level in the water storage tank no matter how the chamber and water storage tank are operated.

[Brief explanation of drawings]

1 and 2 are piping system diagrams of an embodiment of the present invention. 1... Condensate pipe, 2... Deaeration chamber, 3... Heating steam pipe, 4... Water storage tank, 5... Spray valve, 6...
Communication pipe, 7... pressure equalization pipe, 8... downcomer pipe, 11...
Water injection pipe, 12... Reference pressure detection tube, 13... Heating tube, 14... Impulse tube, 15... Impulse tube, 16
...Differential pressure type liquid level detector.

Claims (1)

[Claims] 1. A reference pressure detection pipe disposed in a container containing saturated water stored in a heat exchanger, and having a pressure detection pipe in the lower part of the container, an opening for maintaining a reference liquid level, and the heat exchanger. A liquid level detecting device characterized in that a pipe branching from a condensate pipe that supplies condensate to a lower end of the reference pressure detecting pipe is arranged to guide the condensate as cooling water.