JPH01167403A - Closed plate installation part structure for high pressure casing pipe board - Google Patents

Abstract

PURPOSE:To improve the welding performance and workability by installing a cross-around pipe onto a high pressure turbine casing pipe base, after installing a short pipe which is made of soft steel and onto which a closed plate is welded previously is installed. CONSTITUTION:A ring 2 is welded onto a short pipe 1 made of soft steel, and a closed plate 3 is welded onto the ring 2. The short pipe 1 is welded onto a high pressure turbine casing 4. In this state, the pressureproof test is carried out, and the turbine casing 4 is transported at the site, and a cross-around pipe 5 is welded onto the short pipe 1. Therefore, the need of the opened top adjustment of the short pipe at the site can be obviated, and welding performance and workability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-factory pressure-resistant casing of a high-pressure casing for a steam turbine of a nuclear power plant, and a mounting structure for a closing plate for on-site pressure-resistant of a cross-around pipe connected thereto.

[Conventional technology]

As described in Japanese Unexamined Patent Publication No. 123331/1982, the conventional technology is to conduct a pressure resistance test of the cross-around pipe after connecting the high-pressure casing and the cross-around pipe when setting up a steam turbine for a nuclear power plant. Therefore, the high-pressure casing had a structure with a pressure-resistant closing plate inside the nozzle. This closing plate is attached to the cast steel casing nozzle by welding via a ring.
It will be removed after completing the in-factory casing pressure test and the on-site cross-around pipe pressure test. According to this method,
After setting the high-pressure casing, that is, after connecting the cross-around pipe to the casing, the cross-around pipe can be subjected to a pressure test, which can greatly reduce the construction period of a nuclear power plant.

[Problem that the invention attempts to solve]

As mentioned above, the above conventional technology can be expected to shorten the construction period, but there is a difficult problem in the method of attaching the closing plate. That is, the steam turbine high-pressure casing is made of cast steel, and has poor weldability with the attached mild steel closing plate and mild steel ring.

The problems of the prior art will be explained in detail below.

Figures 2, 3, and 4 describe the conventional technology.
A system diagram of each steam turbine.

Piping diagram and closure plate mounting structure. The steam that has done work in the high-pressure steam turbine 6 is led to the low-pressure turbine 7 through the cross-around pipe 5, but on the way it passes through a moisture separator 8 for reducing the humidity of the steam. Regarding these installation methods, the optimum procedure has been established by providing the closing plate 3 in the nozzle stub of the high pressure casing 4 according to the above-mentioned known example.

However, the high-pressure casing 4 and the cross-around pipe 5 are welded using cast steel and mild steel, and in the environment of on-site installation, heat management such as preheating, heat input, and afterheating, and management of welding rods and welding machines, etc. It was a very difficult situation. Further, in the factory work, there is a technical problem in welding the mild steel glue jig 2 and the cast steel layer nozzle stub 4.

That is, the procedure for installing the closing plate 3 is to first weld the ring 2 to the nozzle 4, and then weld the closing plate 3 to the ring 2J, but when welding the ring 2 to the nozzle 4, the two All of the weld lines are joints of dissimilar materials, which is difficult to manage as mentioned above.Furthermore, among these weld lines, the ones close to the inside of the casing require the operator to go inside the nozzle stub 4, making it difficult to manage them.
The welding line in the book is also welded in an upward position, which is poor workability. The same goes for the welding work of the ring 2 and the closing plate 3, where welding must be performed in an upward position and there are problems such as the occurrence of cracks. In addition, deformation occurred due to the influence of heat, and it was necessary to adjust the grooves of the nozzle stub 4 and cross-around pipe 5 on site. In response to these conditions, the scope of technical solutions in known examples include complete implementation of heat management during welding, improvement of workability by devising scaffolding, and training for workers, which are also financially problematic. there were.

The present invention improves welding conditions while conducting pressure resistance tests on high-pressure casings and cross-around pipes in the same manner as in the past, thereby simplifying management and improving quality.

[Means for solving problems]

The above purpose was to manufacture a short pipe made of mild steel with a closing plate attached in advance, conduct a pressure resistance test on the casing with this pipe welded to a high-pressure casing nozzle stub at the factory, and then weld and connect it to a cross-around pipe on site. This is achieved by conducting a pressure test of the cross-around tube.

[Effect]

The short tube with closing plate, the mounting ring, and the closing plate are all made of mild steel. Since these are manufactured individually, it is possible to roll them up and down during manufacture, and it is possible to improve the welding posture. This, along with the good weldability between mild steels, is a major advantage in terms of quality control. In addition, the on-site welds are made of mild steel, making management easier. In addition, the short tube is
By machining both ends after welding the closing plate, there is no need for on-site bevel adjustment. These effects have improved weldability and workability, which were problems of the conventional technology, and made it possible to improve quality including prevention of deformation.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows a short tube and high pressure turbine casing nozzle, cross-around tube according to the invention.

First, the ring 2 is welded to the short tube 1 made of mild steel. At this time, the welding part 9 was constructed from the top of the short pipe, and then.

The short pipe 1 is turned up and down, and the welded portion 10 is then constructed. Next, after temporarily attaching the closing plate 3, welding portions 11 are constructed. Welding parts 9, 10.11 are both welded in a downward position and made of the same material. The short tube with a closing plate completed in this way is machined at both ends, a bevel is removed,
After correcting the distortion caused by welding, it is attached to the separately manufactured steam turbine high-pressure casing 4, and the welded portion 12 is constructed. The welded part 12 is a dissimilar material joint between the cast steel high-pressure casing 4 and the mild steel short pipe 1, and is subjected to a predetermined heat treatment.

In this state, a pressure test is performed by applying a predetermined pressure inside the high-pressure casing 4. The high-pressure casing 4 that has passed the pressure test is transported to the site with the closing plate 3 still attached. At the site, after the high-pressure casing 4 is temporarily set, the cross-around pipe 5 is installed and the welded portion 13 is constructed. After connecting the cross-around pipe 5, the high-pressure casing 4 enters the main setting, and in parallel with this, a pressure test of the cross-around pipe 5 and the welded portion 13 is carried out. If the test is passed, the closing plate 3 and ring 2 are removed to complete the installation. The removal is carried out by a person entering the high-pressure casing 4 from the outside.

〔Effect of the invention〕

According to the present invention, it is possible to improve the quality of the welded part, and to achieve an ideal bevel by performing one machining process after manufacturing a short pipe.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a short pipe according to an embodiment of the present invention, Fig. 2, Fig. 3
The figure is a system diagram around a conventional steam turbine, and FIG. 4 is a sectional view of a conventional closing plate. DESCRIPTION OF SYMBOLS 1... Short pipe, 2... Mounting ring, 3... Closing plate, 4... High pressure turbine casing, 5... Cross-around pipe. Figure 1 Figure 2

Claims (1)

[Claims] 1. When installing a cross-around pipe and a closing plate for high-pressure casing pressure resistance on a high-pressure turbine casing nozzle for nuclear power generation, attaching a short mild steel pipe with the closing plate welded in advance to the high-pressure turbine casing nozzle. High-pressure casing nozzle closing plate mounting structure.