JPS62209291A - Baking-resistant high airtight oil well pipe joint - 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 (Field of Industrial Application) The present invention particularly relates to a threaded joint for oil country tubular goods having excellent seizure resistance.

(Prior Art) Oil country tubular joints are required to have seizure resistance so that the male and female threads of the joint will not seize even after repeated screwing. Many special oil well pipe joints maintain airtightness through metal-to-metal contact, but in such joints, the seizure resistance of this metal-to-metal contact area is poor against repeated screwing. becomes a problem.

In recent years, there has been a particularly high demand for anti-seizure properties for oil country tubular joints, which have become increasingly demanding. Furthermore, in terms of design, the larger the diameter and thicker the pipe, the more the overlapping margin of the metal-to-metal contact portion should be selected in consideration of seizure resistance.

The larger the overlap, the higher the surface pressure will be generated in the metal-to-metal contact area, which is suitable for airtightness, but this high surface pressure and the longer sliding between the metals during the threading process Therefore, the joint has the contradictory phenomenon that the metal-to-metal contact part easily seizes.

Seizure resistance is affected by metal-to-metal contact pressure, sliding length, sliding speed 1 surface properties, temperature resistance, lubricant, etc., and consideration must be given to contact pressure and sliding length when designing joints. It won't happen.

Seizing is more likely to occur when the contact surface pressure or surface length increases.Reducing either or both of these is effective for anti-seizure sail surfaces, but the contact surface The pressure is determined from the viewpoint of joint airtightness, and there is a limit to the reduction of the final contact surface pressure.

FIG. 2 shows the tightening length t, which is proportional to the slip length, and the contact surface pressure of the maximum surface pressure generating portion (A or B) for each type of joint.

Tie 7'l (Figure 2 (a) # (b)), Tie 7'
In the joint shown in Figures 2(e) and 2(d), the contact surface pressure increases approximately in proportion to the increase in the length of the joint.

Therefore, the seizure resistance of such a joint is determined by minimizing the area of the shaded area and obtaining a brown final contact surface pressure.

In addition, joints such as type III joints (Fig. 2 (e) # (f)), which rapidly increase the contact surface pressure due to the effect of the box shoulder at the final stage of tightening, are common in oil wells. Under a certain tensile load, an increased surface pressure (S
) is eliminated, so in terms of airtightness, it is necessary to ensure some contact surface pressure before reaching the T point. therefore,
In the type ■ joint shown in Figure 3 (e) Cf), T
Minimize the area of the shaded area at the point arrival (7, and high T
It is necessary to obtain the contact surface pressure at A. This is because a threaded joint with a positioned airtight surface and a non-threaded surface following the threaded part is known from Japanese Patent Publication No. 59-44552 (same applicant). However, when the airtight surfaces come into contact at the initial stage of tightening, no measures have been taken to reduce at least the contact surface pressure during this period, and this is fundamentally different from the present invention.

(Problems to be Solved by the Invention) The present invention obtains the necessary surface pressure for airtightness at the airtight metal-to-metal contact portion of an oil country pipe joint when the joint is tightened, but during the tightening process, the contact surface It relates to oil country tubular joints whose purpose is to reduce pressure and slip length and improve seizure resistance.

(Means for Solving the Problems) The present invention will be specifically described below based on embodiments shown in the drawings.

FIG. 1(a) shows the fitted state of the present invention,
FIG. 1(b) is an enlarged view of its main parts. Pipe body 1
is machined with a male thread 2, the tip of the male thread 2 has shoulders 3 and 4, and a tapered airtight surface (
A conical surface 6 (hereinafter simply referred to as an airtight surface) 5 is machined, and a conical surface 6 is located between the shoulder portion 4 and the male screw 2, and the pin consisting of this portion and the acid screw r are followed by the shoulder portions 3' and 4'. are machined to correspond to the pin shoulders 3, 4, and the shoulders 3', 4'
Due to the metal-to-metal contact between the tapered airtight surface (hereinafter simply referred to as airtight surface) 5' and the pin airtight surface 5, virtual airtightness is ensured. In such a configuration, the present invention particularly provides a DexF having one conical surface 6' between the shoulder part A and the male thread 2', and the interference between the conical surfaces 6 and 6' occurs during screwing, that is, during the process of tightening or loosening the joint. The radial contraction M of the pin 10 or the radial expansion of the box 7 (
By reducing the contact surface pressure or sliding length between the airtight surfaces 5 and 5', seizure occurring on the airtight surfaces is prevented. Moreover, at the end of tightening, 5.5'
To prevent interference between the two, the space between 6 and 6' is kept in a non-contact state, and a high surface pressure necessary for airtightness is applied to the airtight surfaces 5 and 5'.

Therefore, the relative contact relationship between the airtight surface and the non-threaded surface in order to obtain such a contact state will be explained generally using FIG. T, Unthreaded surface chi/4: To1 airtight airtight surface metal allowance: 13, Unthreaded surface fitting allowance: M.

and the distance from the airtight surface to the non-threaded surface: L. By combining and changing these factors, the optimum shape can be obtained.

Figure 4 shows an example of such a reed, and Figure 4 (,) shows that the unthreaded interface TD1 does not have a taper and has a radius at the tip, so that the surface pressure on the unthreaded surface suddenly increases at the beginning of tightening. Then, as the screws are tightened, the airtight surfaces interfere with each other, and eventually the non-threaded surfaces are separated from each other (that is, the surface pressure is zero).

Figure 4(b) shows the unthreaded surface TD2 having a taper that is opposite to the taper of the airtight surface, and Figure 4(c) shows the unthreaded surface TD2 having a taper that is the opposite of the taper of the airtight surface. The non-threaded surface on the side of the bottle and box has a convex contact portion H of a constant length formed at the tip.

FIG. 5 shows the surface pressure behavior of the joint when using the example of the joint shown in FIG. 4(a). At the initial stage of tightening, due to the interference of part B, there is no surface pressure on the airtight surface A, or there is very low pressure, and at the opening of the middle part of tightening, both parts A and B are flat. However, when tightening is complete, part B is in a non-contact state.

Sufficient contact pressure for airtightness is applied to the airtight surface A section, and the contact pressure here does not decrease even under axial force.

FIG. 6 shows a comparison between the airtight surface surface pressure behavior 2 of the conventional joint and the surface pressure behavior 5 according to the present invention. The contact pressure at the end of tightening is the same, but during the tightening process, both the contact pressure and the length of the joint of the present invention are in the low range, and it is clear that the seizure resistance is improved. Even in the joint loosening process,
A similar phenomenon can be obtained, and the anti-seizure effect can be further improved.

In addition, in conventional joints, the surface with seizure resistance and the surface with airtightness were the same, so surface treatment and surface finishing that had excellent characteristics of both seizure resistance and airtightness were required. In the present invention, since the airtight surface 5.5' surface and the surfaces 6 and 6' where only seizure resistance is an issue are independent, 6
, 6' surface has the advantage that surface treatment and surface finishing such as original plating, sandblasting with extremely rough surface roughness, etc. can be applied without considering airtightness. Therefore, it becomes possible to design the optimal surface pressure behavior of the section A or section B in FIG. 5 over a wider range.

In FIG. 1, shoulders 4 and 4' are shown in a non-contact state or
Even if the 4' portion does not have a shoulder, the effects of the present invention remain the same, but the airtight surfaces 5, 5' are not affected by the increase in contact pressure due to excessive tightening. It is desirable that the shoulders 4, 4' contact each other.

For the same reason, it is desirable that the shoulders 3, 3' be in a non-contact state or in slight contact. Also, 6.6'
The shape of is not limited to a conical surface, but it is important that it be in contact during the tightening and loosening process and non-contact when tightening is complete.

(Effects of the Invention) As explained above, according to the present invention, the problem of seizure on airtight surfaces is separated to the non-threaded surface, so high airtightness is ensured for airtight surfaces, and it does not contribute to airtightness. Seizure resistance can be improved with a non-threaded surface.

When galvanizing is applied to a 103/1 inch joint.

Seizing occurred on the airtight surface after tightening and loosening 6 times, but the joint according to the present invention did not cause seizure even after tightening and loosening 10 times, and was also able to withstand gas internal pressure equivalent to the yield of the tube. ,
The same high airtightness as before with no leakage was achieved.

[Brief explanation of drawings]

Figures 1 (a) and (b) are explanatory diagrams showing the surface pressure behavior of each joint, and Figure 2 (a) # (b) ? (e) I
(d), (e) t (f) is an explanatory diagram showing the point in time when tightening of the main parts of the present invention is completed, Figure 3 is a diagram showing the concept of the joint shape according to the present invention, Figure 4 (L) P (
b) # (e) is a diagram showing a specific shape example, Figure 5 (a)
) v (b) is a diagram showing the contact pressure behavior of the joint according to the present invention, and FIG. 6 is a diagram showing a comparison between the contact pressure behavior of the joint according to the present invention and the contact pressure behavior of a conventional joint. 1: Pipe body 2: Male thread 3: Shoulder 4: Shoulder 5: Airtight surface 6: Conical surface agent Teruo Taniyama: , -2-concave main small Masayuki Hiragishida Shinbe Koji Figure 1 Ca> B : Yen fl @ Figure 3 Figure 4 <a> To+

Claims (1)

[Claims] A pin consists of an unthreaded surface following a male screw carved on the outer surface, two stepped shoulders at the tip, and a tapered airtight surface located in between, and a pin carved on the inner surface. In a pin joint consisting of a threadless surface following a female screw provided therein, two shoulder portions located in a step-like manner deep within the box, and a box consisting of a tapered airtight surface located in the middle, the pin and The relative contact relationship between the tapered airtight surface and the non-threaded surface of the box is such that at the initial stage of screw engagement, the contact surface pressure of the tapered airtight surface is lower or zero than that of the non-threaded surface. , on the other hand, when the shoulder parts collide and the threaded connection is completed, the contact surface pressure of the non-threaded surface is low or zero compared to the required contact surface pressure of the tapered airtight surface. Comes with a highly airtight oil well pipe fitting.