JPS5938600A - Fatigue inhibitor for heat transmitting tube - Google Patents

Abstract

PURPOSE:To prevent heat transmitting tubes from being damaged, by flame- spraying metallic powder to the surfaces of heat transmitting tubes which are supported by baffle plates. CONSTITUTION:A heat transmitting tube 10 is preliminarily treated so as to be ready to be flame-sprayed, by hardening the surface of the tube 10 by means of shot blasting or sandblasting, and by defatting using trichlene. Then, the mixed powder, consisting of less than 94wt% of titanium dioxide, oxide powder of 4- 8wt% of aluminum, and 2-6wt% of vanadium, and nickel and chrome alloy powder consisting of 12-18wt% of chrome, 5-9wt% of iron, and nickel for the remainder wt%, is flame-sprayed to the surface of a heat transmitting tube. In this case, less than 1mm. is enough for the thickness of a layer to be flame- sprayed, but for fear that a little number of pin holes will be formed in the flame-sprayed layer, it is necessary to fuse the part by heating it with flames immediately after flame-spraying.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a fatigue suppressant for heat exchanger tubes used, for example, in heat exchangers.

[Technical background of the invention]

Conventionally, turbine plants have used heat exchangers, such as condensers, to improve thermal efficiency, but because the amount of steam discharged from the turbine every minute is large, about 2 More than one heat transfer tube is required. Also, heat transfer′d
Seawater is often used as the coolant that passes through the tubes, and for this reason, titanium heat transfer tubes have recently become preferred and increasingly used in order to prevent corrosion.

However, since condensers require a large amount of heat exchange, problems arise due to vibration due to the steam flow sent from the turbine, and material fatigue problems due to repeated loads due to vibrations.

By the way, Figure 1 shows the system of a typical turbine plant. Steam generated in the boiler (7) is sent to the high-pressure turbine (1), and the steam that has finished its work here is sent to the reheater ( 8) where it is heated again, and the reheated steam is introduced into a low-pressure turbine (3) via an intermediate-pressure turbine (2), which rotates a heat generator (4) to produce electrical output.

The steam that has undergone expansion work in the low-pressure turbine (3) is condensed in a condenser (5) to recover its heat, and is returned to the boiler (7) via a pump (6) as pumped water.

In this way, the water pumped from the turbine exhaust (21-ru condenser) is
Generally, a structure as shown in FIG. 2 is adopted.

That is, code (9) indicates a condenser, and this condenser (9)
) on both sides (second is the ice chamber a4.α rays are connected through the tube plate 0 stage and α mountain, and the heat transfer tube uO is connected between the tube plate (rb, +, (l[)).
) are disposed across the length of the condenser (9). In addition, the condenser (9) (second is the turbine exhaust E (
In order to prevent vibration of the heat transfer tube (10), baffles 0υ are installed at strategic points, and baffles (II) 1″-
As shown in FIG. 3, the heat exchanger tube section is mounted through the hole (7) which has a relatively large margin.

Furthermore, as shown in FIG. Passages (5a) and (5b) are provided to collect the generated gas.

Therefore, the turbine exhaust E sent to the condenser t9+ is
As shown in the second figure, the seawater sent through the ice chamber A4 and a certain prince are exchanged with each other, and after receiving and receiving heat, the seawater passes through the water tank and goes outside, and the turbine exhaust E is condensed and collected in the hot well ([4J]. The water is fed from here to the boiler (2).

[Problems with background technology]

By the way, the baffle I, which supports many heat exchanger tubes, is drilled with a margin in its hole diameter, so that the heat exchanger tubes are subjected to repeated concentrated loads at the edge of the hole. , and the gap between the holes Uη and the turbine exhaust E
is constantly passing through. For this reason, in combination with the intense vibration acting on the heat exchanger tube +IG, electrochemical corrosion such as stress corrosion cracking may occur, which may induce further destruction of the material itself.

(Object of the Invention) In view of these circumstances, the present invention provides a fatigue suppressant for heat exchanger tubes that prevents damage by thermally spraying metal powder onto the surface of heat exchanger tubes supported by baffles. The purpose is to

[Summary of the invention]

The above purpose is to prepare the surface of the heat exchanger tube (-5 titanium dioxide 94% by weight or less, aluminum 4-8tLi%, vanadium 2-6% by weight).
oxidized powder, chromium 12-18 ml 1 t, iron 5-9 M 1
This is accomplished by thermal spraying a mixed powder of nickel-chromium alloy powder consisting of nickel and nickel.

[Embodiments of the invention]

Table 1fi of the heat exchanger tube (2) The following measures are taken beforehand: First, the heat exchanger tube is subjected to shot blast surface hardening, which is removed with trichloride to make the sprayed area easier (
Two pre-treatments are performed so that two treatments can be performed.

However, oxidized powder with titanium dioxide of 94 gm or less, aluminum of 4 to 8 gm, vanadium of 2 to 6 m, and nickel consisting of a large amount of chromium 12 to 18, iron 5 to 9 g, and the balance nickel. The mixed powder with chromium alloy powder is thermally sprayed on the surface of the heat transfer tube (-). In this case, the thermal spray no.
The following is sufficient, but since some pinholes may be generated, immediately after thermal spraying, heat with flame and perform bath melting.

Although the present invention has been described with respect to a titanium heat exchanger tube, this J
The following methods are recommended for thermal spraying not only 1, but also other lysate materials.

In other words, when using cupronickel tubes or monel tubes as heat transfer tubes, copper coating ~ 30j [lid, nickel 70
When using a powder alloy consisting of ~80 heavy jt [aluminium 8-11 heavy electric tube,
If using a stainless steel heat exchanger tube, use a powder consisting of 1% to 2% iron and 0.03% to 0.1% carbon.
Heavy violet, nickel 8-10 heavy jt, chromium 18-20
It is sufficient to thermally spray an alloy powder consisting of iron in the balance by weight%. In addition, although the present invention is described as using thermal spraying of the above-mentioned gold powder on the surface of the heat exchanger tube (2), this invention is not limited to the surface of the heat exchanger tube (2), and the hole of the baffle supporting the heat exchanger tube (2) Good too.

[Effects of the Invention] As explained above, the present invention provides thermal spraying of the above-mentioned metal-containing mixed powder on heat transfer tubes or on turbine exhaust pipes.
Fatigue of the heat exchanger tubes due to this is suppressed. Therefore, even if excessive stress is applied to the heat exchanger tube (such as #J), damage is suppressed, and there are advantages such as being able to withstand the opening of the tube in the open position.

[Brief explanation of the drawing]

Figure 1 is a system diagram of a conventional general turbine plant;
The figure is a schematic diagram showing an example of a condenser, and Figure 3 is A in Figure 2.
FIG. 4 is a schematic cross-sectional view taken from the direction of the IV-IV arrow in FIG. 2; l...High pressure turbine 2...Intermediate pressure turbine 3...Low pressure turbine 5...Condenser 7...Boiler 9...Condenser 10...Heat transfer also 11...Baffle (7317) Agent -) FM officer Nori Chika Ken (and 1 other person) Figure 1

Claims (1)

[Claims] The surface before heat transfer (oxidized powder of titanium dioxide 7θ4% or less, aluminum 4-8N value, vanadium 2-6% by weight,
A fatigue suppressant for heat transfer tubes which is sprayed with a mixed powder of a nickel-chromium alloy powder consisting of 12 to 18 chromium, 5 to 9 iron, and nickel.