JPS6016811Y2 - feed water heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a feed water heater, and more particularly to an improvement in a feed water heater equipped with a probe for detecting the degree of damage to the inner wall of the main body at or near the steam inlet.

Generally, a steam turbine power generation plant has a feedwater heater, which uses turbine bleed steam to heat the boiler or reactor feedwater to a predetermined temperature in order to improve the thermal efficiency of the entire plant. It is set up for.

Conventionally, this type of feed water heater has a steam inlet port 3 on one side of the main body shell 6 and a drain outlet port 9 on the other side, as shown in FIG. The turbine bleed steam collides with the impingement plate 4 directly below the impingement plate 4, and the turbine bleed steam after the collision flows into a tube bundle 8 made up of a large number of densely packed heating tubes 1.

The impingement plate 4 is for mitigating as much as possible the impact of steam entering from the steam inlet port 3, thereby preventing damage to the tube bundle 8.

The turbine extracted steam passing through the impingement plate 4 flows from the gap 7 to the tube bundle 8, where it exchanges heat with the supply water passing through the heating tube 1. After heat exchange, it is generated as drain, and from the drain outlet 9 to the vessel. It is being discharged outside.

The tube bundle 8 is held by a support plate 5, and this support plate 5
is fixed by the stay pipe 2 to prevent vibrations occurring during heat exchange and drift of turbine bleed steam as much as possible.

Further, the outer surface of the main body shell 6 is covered with a heat insulator 12 to suppress heat release.

By the way, if moisture is contained in the turbine oil vapor supplied to the main body shell 6, when the moisture collides with the impingement plate 4, the reaction force causes the moisture to violently collide with the inner wall of the main body shell 6. .

For this reason, the inner wall of the main body shell 6 is gradually eroded, and if left untreated, there is a risk that a hole will be formed in the main body shell of the feed water heater, leading to a serious accident.

In particular, the turbine bleed steam of a light water reactor nuclear coupler is
Since the pressure is low and the humidity is high, the above-mentioned phenomenon is extremely likely to occur.

To explain the above-mentioned phenomenon a little further with reference to FIG. 2, the humid turbine bleed steam flowing in from the steam inlet port 3 collides with the impingement plate 4, and then due to its reaction, it hits the inner wall 10 of the main body shell 6. The bounced bleed steam is returned to the impingement plate 4 again, and the returned bleed steam further bounces against the inner wall 11. During this time,
The retained heat of the extracted steam is lost and the moisture content increases.

For this reason, the inner wall 11 parallel to or after the impingement plate 4 supported by the stay pipe 2 is eroded relatively frequently.

Thus, when the bleed steam exhibiting the above-mentioned phenomenon passes through the gap 7, it becomes a high-speed flow and flows into the tube bundle B formed by the closely packed heating tubes 1, while incorporating a plow of the bouncing bleed steam.

By the way, if the above-mentioned phenomenon is left unaddressed, the function of the feedwater heater will no longer be fulfilled, and the steam turbine plant will have to be shut down.In addition, if high-temperature, high-pressure bleed steam is injected outside the plant, it will cause damage to the surrounding area. This will have a major impact on equipment and workers, creating an extremely dangerous situation.

This is especially true when the plant is exposed to radioactivity, such as in a nuclear power plant.

In order to prevent such accidents, it is necessary to consider changing the structure of the feed water heater itself, but no fundamental solution has been found for many minutes. The insulation was removed and an ultrasonic thickness gauge was attached to the outer wall of the main body, which detected the wall thickness of the main body, and a decision was made as to whether or not to replace it with a new product based on the detected amount.

However, in nuclear power plants, when inspecting the body wall thickness of the feed water heater, even if it is during a regular inspection, staying there for a long time poses the risk of radiation exposure, and it is necessary to keep it warm before each inspection. Removing it poses the problem of exposing peripheral equipment to radioactive contamination unless subsequent treatment is appropriate.

Therefore, in light of the above circumstances, in this research, an ultrasonic thickness gauge that can detect the thickness of the body body is installed in advance, and this allows the thickness of the body body to be continuously and accurately monitored. The purpose of the present invention is to provide a feed water heater that makes it possible to

In order to achieve the above object, the present invention is characterized in that a cooling chamber is enclosed in the outer surface wall of the main body body, and a probe is attached to this cooling chamber, so that the probe is kept cool at all times. This aims to continuously and accurately monitor the thickness of the main body.

A practical example of the present invention will be explained below with reference to the attached drawings.
Components that are the same as those in FIGS. 1 and 2 are given the same reference numerals.

In FIG. 3, a probe 13 of an ultrasonic thickness gauge is installed as a permanent installation near the steam entry port 3 and the main body shell 6.

The thickness indicator connected to the probe 13 can be installed in a location (not shown) where there is no risk of radiation exposure, such as a central control room, so that it can be monitored continuously or at any time during operation or periodic inspections. can do.

The probes 13 can be attached to any position assuming the area where erosion occurs, and by attaching a plurality of probes, it is possible to accurately grasp the state of thinning over time at a fixed position.

In other words, compared to conventional measurement methods, the method of the present invention eliminates errors caused by minute deviations of wall thickness measurement points, errors caused by roughness of the measurement surface and thermal effects of contact areas, and errors caused by individual measurement skills. .

In addition, since there is no need to remove the heat insulator 12 every time a measurement is made, it leads to a reduction in work in the radiation controlled area, and it also prevents the diffusion of radioactive substances that inevitably occur when the heat insulator is removed, so the atomic couplant can be removed. This is also a big advantage in terms of maintenance.

For the above-mentioned probe 13, it is normal to measure with one pair of thickness indicators, but when multiple probes are installed, one thickness indicator is installed and one pair of thickness indicators is used to measure the number of probes. It is also possible to measure the total number using a switching device.

FIG. 4 shows a specific example of means for attaching the probe to the main body.

The outer surface wall of the main body shell 6 has a cooling medium inlet 17 on one side.
A cooling chamber 14 having a cooling medium outlet 18 is welded to the other end, and the probe 13 is housed in the cooling chamber 14 via a seal ring 15.

The reason for providing the cooling chamber 14 in this way is that the probe 13 has a usage limit of about 70°C due to the fact that its characteristics generally change in high-temperature regions. This is because the outer surface temperature of the probe 6 is about 70'C to 250C, so the probe 13 needs to be cooled.

Oil or water is generally used as a cooling medium, but in power plants, condensate (condensed from turbine exhaust steam in a condenser) is close to pure water and has a temperature of 30°C to 40°C.
, or because make-up water is plentiful, use these as cooling media.

The cooling water 16 selected as the cooling medium has a cooling medium population of 1.
7 toward its outlet 18, so even if the heat dissipation from the main body body 6 is high, there is no stagnation of the cooling water, and as a result, the probe 13 is cooled well, and the detection accuracy is also improved. You can expect it.

As explained above, in order to continuously detect the wall thickness of the main body of the feed water heater, the present invention provides a cooling chamber for housing the probe on the outer surface wall of the main body, so the probe is fixed. Moreover, as a result of being constantly cooled, it is possible to perform detection with good accuracy, and has the advantage that there is no need to remove the heat insulation or perform maintenance each time, unlike in the past.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 are diagrams showing a schematic embodiment of a conventional feed water heater, Fig. 3 is a partial view of a feed water heater showing an embodiment of the present invention, and Fig. 4 is an example of mounting a probe. FIG. 1... Heater, 2... Stay pipe,
3... Steam entry account, 4... Impingement plate, 5... Support plate, 6...
・・Main body, 7・・Gap, 8・・Pipe bundle, 9・・Drain outlet, 10.11・Curved・Inner wall, 12・・・・Heat retention, 13...Probe, 14...Cooling chamber, 15...Tool ring, 17...Cooling medium inlet, 18...Curved cooling medium outlet .

Claims (1)

[Scope of utility model registration request] In order to reduce damage to the tube bundle from impact caused by steam sent into the main body shell from the steam input port, the outer surface of the main body shell is A feed water heater characterized in that a cooling chamber is fixedly installed on a face wall, and a probe for measuring damage to the inner wall of the body body is attached to the cooling chamber.