JPH081352Y2 - Steel pipe fittings - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a joint for connecting steel pipes that transport corrosive fluids with each other by a mechanical structure such as a screw.

(Prior Art) Conventionally, when connecting a steel pipe for recovering and transporting a corrosive liquid or gas, a metal-metal sealed part is used as shown in FIG. 6 especially in order to prevent the outflow of fluid from the connected part. The joint in which the resin ring 4 such as Teflon is attached to the tip of the steel pipe is often used as shown in FIG.

In the figure, 1: coupling, 2,2 ': steel pipe (pin), 3,3': pin shoulder (stopper) and seal part, 4: resin ring (plastic ring), 5: corrosion-resistant ceramic coating (example), 6: coupling shoulder, 7: groove is shown.

However, in the joint shown in FIG. 6, the corrosive liquid often enters the pin shoulder (seal portion) 3 or corrosion progresses due to an electrochemical reaction. In addition, in the joint shown in FIG. 7 (a), the seal portion can be prevented from corrosion, but as shown in FIG. 7 (b), the corrosion resistant coating 5 such as ceramic is applied to the inner surface and the tip of the steel pipe. When applied, the corrosion resistance coating 5 in the portion sandwiched between the steel pipe 2 and the resin ring 4 is often damaged by the tightening force at the time of connecting the steel pipe, and deterioration of the corrosion resistance often occurs. Also, the sixth
Both the joints shown in FIGS. 7 and 7 have a drawback that the shoulder 6 of the coupling 1 is directly exposed to the fluid.

Further, the joint of the embodiment shown in FIG. 7 has difficulty in control of fastening when the joint is fastened, has poor workability, and is rarely used in general.

(Problems to be solved by the invention) The present invention is a steel pipe joint whose first purpose is to easily control the fastening, to prevent the brittle coating film of ceramic or the like from being damaged, and to isolate the coupling shoulder from the fluid. Is proposed.

(Means for Solving the Problem) The present invention relates to a threaded joint for joining steel pipes, in which the diameter of the taper screw becomes smaller toward the tip of the pipe.
Step shoulders are provided, metal shoulders are formed between these shoulders, a coating layer of corrosion-resistant ceramic or the like is arranged at least at the joint tip portion, between the steel pipe tips or between the steel pipe tip and the coupling shoulder, A groove in which a plastic resin ring of Teflon or the like is interposed and in which this resin ring is mounted is a steel pipe joint characterized in that its width is wider than the ring width and the position of the groove bottom is deeper than the tip shoulder.

That is, the first feature of the present invention is that the above-mentioned object is completely solved by taking advantage of the characteristics of the conventional steel pipe joint having two shoulders and devising the resin ring attachment.

Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 1 shows the structure of the joint of the present invention. That is, this joint is constituted by screwing the coupling 1 and the steel pipes 2, 2'as shown in the figure, and has a taper-shaped screw B having a diameter decreasing toward the pipe end, and a tip from the screwing surface. 2 shoulders 3,
3'is formed, and between the shoulders 3 and 3'is a screw-free metal sealing surface. This structure itself is known from Japanese Patent No. 1268969 (Japanese Patent Publication No. 59-44552) of the same applicant.

A resin ring 4 is inserted into the tip of the steel pipe 2, and the torque and tightening amount at the time of fastening the joint are controlled by the shoulder 3 ', and the deformation of the ring is kept within the optimum range. On the other hand, since the coupling 1 is completely shielded from the corrosive liquid existing inside the pipe, it is not necessary to use a corrosion resistant material.

Further, as shown in FIG. 3 (a), in the case of a joint provided with a corrosion resistant coating 5 such as ceramics, the shoulder 3'acts as a stopper at the time of fastening, and at the same time the resin deformation is optimized, the steel pipe is It is possible to prevent the portion of the ceramic 5 sandwiched between the tip and the resin from undergoing excessive compressive deformation, and it is possible to minimize damage and peeling of the ceramic.

In the case of a joint that requires a certain thickness in the center of the coupling, it is possible to provide a coupling shoulder 6 as shown in FIG. in this case,
The coupling part will also be exposed to the corrosive fluid,
As shown in FIG. 3 (b), the joint can be protected by applying a corrosion resistant coating film 5 of ceramic or the like on the inner surfaces of the steel pipe and the coupling portion.

In this case, as in the case of FIG. 3 (a), the shoulder portion 3 'serves as a stopper to prevent damage and peeling of the coating film.

By the way, in the joint shown in FIGS. 1 and 3,
When mounting the ring properly, the resin ring 4 should be appropriately filled between the ends of the steel pipes or between the ends of the steel pipes and the coupling shoulder at the time of fastening the joint, and also be prevented from protruding from the groove of the resin ring. Must be (purpose of Figure 2).

Therefore, the present invention further provides, as shown in FIG.
Groove 7 slightly wider than the ring width in the center of the coupling
And, as shown in FIG. 4 (b), the groove 7
The groove bottom 7-1 is deeper than the tip shoulder so that a stepped groove 7-2 is formed outside the tip shoulder when the joint is tightened.

When the steel pipe 2 is fastened, the resin ring 4 moves in the groove 7 as shown in FIG. 4 (b), and the resin ring 4 is prevented from jumping out of the groove 7 by an asymmetric force.

On the other hand, by fastening the opposing steel pipes 2 ', the resin ring 4 is deformed as shown in FIG.
It can be filled within moderately.

Note that FIG. 5 is an application example in the embodiment of FIG. 1 that does not use a coupling.

(Effect of the Invention) Since the present invention has the two-stage shoulder structure, it is easy to control the fastening of the oil well pipe and the transportation line pipe for recovering corrosive liquid or gas.

[Brief description of drawings]

FIG. 1 is an explanatory view of the present invention, FIGS. 2 to 5 are explanatory views of another example of the present invention, and FIGS. 6 and 7 are explanatory views of a conventional steel pipe joint. 1: Coupling 2,2 ': Steel pipe (pin) 3,3': Pin shoulder (stopper) and seal part 4: Resin ring (plastic ring) 5: Corrosion resistant ceramic coating (example) 6: Coupling shoulder 7: Groove

Continuation of the front page (56) References JP-A-59-126191 (JP, A) JP-A-62-98088 (JP, A) Actually-opened Sho-58-142475 (JP, U) JP-B-59-44552 (JP) , B2) Jikkouhei 1-12051 (JP, Y2)

Claims (1)

[Scope of utility model registration request] 1. A threaded joint for joining steel pipes, in which 2 is provided from the end of a taper screw whose diameter decreases toward the pipe tip.
Step shoulders are provided, metal shoulders are formed between these shoulders, a coating layer of corrosion-resistant ceramic or the like is arranged at least at the joint tip portion, between the steel pipe tips or between the steel pipe tip and the coupling shoulder, A steel pipe joint characterized in that a groove in which a plastic resin ring such as Teflon is interposed and in which this resin ring is mounted is wider than the ring width and the groove bottom position is deeper than the tip shoulder.