JPS5842815A - Stud bolt - 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 The present invention relates to a stud bolt, and more particularly to a stud bolt that has a short bolt top to prevent rust from forming and improve workability.

The upper cover mirror (hereinafter referred to as the "upper mirror") of the reactor pressure vessel is attached to the pressure vessel body using as few as a dozen stud bolts, and as many as 100 or more stud bolts. Due to the nature of nuclear reactors, leakage of the internal fluid of the pressure vessel must be avoided at all costs, and for this reason the upper mirror must be installed extremely carefully. On the other hand, as it is necessary to confirm the safety of nuclear reactors, pressure vessels are inspected periodically, for example, once a year.
Every time a periodic inspection is carried out, all the nuts screwed into the stud bolts are removed, the upper mirror is removed, and the interior is inspected. Since pressure vessels are inspected in environments where there is a risk of exposure to radiation, it is necessary to quickly attach and detach nuts.
On the other hand, installation of the upper mirror in particular requires careful work, so as long as the current shape of stud bolts is used, there is a limit to how quickly the work can be done. Particularly when installing the upper mirror, it is sometimes necessary to use a tensioner to apply hydraulic tension to each stud bolt in order to equalize the tightening force of each stud bolt, but in the past, this work took a lot of time. However, the workability was poor. FIG. 1 shows a state in which a tensioner is attached to a conventional stud bolt.

In the figure, the stud bolt 3' is threaded at its base with the seventh flange 2a of the pressure vessel body, and is inserted through the seventh flange la of the upper mirror L and screwed with the nut 4, thereby attaching the upper mirror L to the pressure vessel body. stick.

On the other hand, the upper part of the stud bolt 3' is threadedly engaged with a connecting ring 7 within the tensioner 6, and is connected via this connecting ring 7 to a shaft 8' that is similarly threadedly engaged with the connecting ring 7. In the above state, the shaft 8' is pulled upward with a constant force by a hydraulic system (not shown), and the nut 4 is tightened by the amount that the bolt 3 is extended. In this way, by pulling each bolt with a uniform force using the tensioner and tightening the nut, the upper mirror l is attached to the main body with a uniform force.

However, in the above method, since it is necessary to screw the upper part of the bolt 3' into the connecting ring 7, it is necessary to make the extra length part 3a' long so that it projects high above the nut 4. For this reason, rust forms on the protruding extra length of the bolt 3a' during operation of the reactor, but this rust must be removed when removing the nut 4, which requires a long time to clean the bolt. .

Working in a contaminated environment is extremely difficult, and there is a risk of internal radiation exposure if workers inhale floating dust, rust, etc. Moreover, as a result of the extra length 3a' being long, it takes a long time to remove the nut 4.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and to provide a stud bolt that can be easily attached to and detached from the stud bolt without reducing workability when tightening with a tensioner.

In short, the present invention is configured such that the upper part of the stud bolt is shortened so that there is almost no extra length, and a deep hole is formed in the upper part of the stud bolt to connect it to the tension nanoshaft.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 2, the upper part 3a of the stud bolt 3 has a height that is almost the same as the height H of the nut 4 and the washer 5, with almost no extra length protruding from the upper part of the nut 4 when the nut 4 is screwed. shorten.

A screw hole 3b is formed in the upper part 3a, and the tensioner 6
A shaft 8 is threadedly connected to this screw hole 3b.

When tightening the stud bolt 3, the tensioner body 6 is placed on top of the stud bolt 3, and the tip of the shaft 8 is screwed into the screw hole 3b. When the connection is completed, the shaft 8 is pulled upward while pressing the tensioner main body 6 against the flange 1a of the upper mirror 1 using a hydraulic device (not shown). As a result, tension is applied to the stud bolt 3, the amount of elongation thereof is measured, and the screwed nut 4 is tightened. 5 is a washer interposed between the nut 4 and the 7 flange 1&.

Tighten all the stud bolts using the above method until the amount of elongation is uniform, and attach the upper mirror to the pressure vessel body with equal force.

On the other hand, when removing nut 4, there is almost no extra length of the stud bolt, so there is almost no need to clean the bolt.
Moreover, the nut can be removed in a short time.

FIG. 3(B) shows the installation state of the stud bolt according to the present invention, and once the tightening work with the tensioner is completed, the screw hole 3b is sealed by screwing the closing bolt 9 into the screw hole 3b. , to prevent the screw hole 3b from rusting and to prevent foreign matter from entering.

Note that in the figure (N indicates a conventional stud bolt 3, the stud bolt 3 according to the present invention has almost no extra length, so it can be formed to be shorter by length L than the conventional stud bolt 3. Note that the diameter is usually about 25 cm.

By carrying out the present invention, the cleaning work of the stud bolt can be significantly reduced when removing the readout, and the nut can be easily removed.

Furthermore, since the overall length of the stud bolt can be formed short, the manufacturing cost of the bolt can be kept low.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing a conventional stud bolt and a tensioner, Fig. 2 is a cross-sectional view showing a tensioner attached to a stud bolt according to the present invention, and Fig. 3 (A) is a side view of a conventional stud bolt. , (B) are side views of the stud bolt according to the present invention. 1... Upper mirror 1a... Upper mirror flange 3... Stud bolt 4... Nut 5... Washer 6...・Tensioner 8...Shaft 9...Blocking bolt drawing number 1

Claims (1)

[Scope of Claims] 1. In the case where the mirror is attached to the pressure vessel body by screwing a nut onto a part of the bolt 1 which is screwed into the pressure vessel body and passed through the upper mirror flange, the length of the upper part of the bolt is A stud having a height approximately equal to the total height of a nut to be screwed into the bolt and a washer placed between the nut and the upper mirror, and having a threaded hole in the upper part of the bolt to be screwed into the shaft of a tensioner. bolt. 2. The stud bolt according to claim 1, wherein a closing bolt is screwed into the screw hole, and the screw hole is sealed after the upper mirror is attached.