JP2012102867A - Pipe joint with torque control function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pipe joint with a torque control function which is screwed with small torque in the initial screwing operation when executing the screwing connection of a piping member, and capable of sensing the approach to the adequate screwing amount by the abrupt increase of the fastening torque when the screwing amount approaches an adequate value, and completing the screwing; and to provide a pipe connecting method capable of obtaining the consistent fastening torque irrespective of presence/absence of cutting oil at a fore end screw part of a pipe to be screwed with the pipe joint.SOLUTION: In a pipe joint to be screw-connected, the coating range of a lubricating sealant which is coated in advance on a female screw section or a male screw section is set to be 0.1n to 0.9n from the screwing fore end side with respect to the standard screw threads n. The fastening torque is abruptly increased during the screwing operation, and any excessive fastening is prevented thereby.

Description

  The present invention relates to a pipe joint that is effective for optimizing the screwing amount in a screw-type piping member, and more particularly, to a pipe joint in which a lubricating sealant is previously applied to a threaded portion.

“Ministry of Land, Infrastructure, Transport and Tourism:“ Ministry of Land, Infrastructure, Transport and Tourism ” “Supervision Department of Government Office” has been issued.
FIG. 4 shows a guide for the number of screw threads and the standard tightening torque with respect to the nominal thread diameter described in the 2007 edition.
In addition, the numerical value shown in Table [] shows the screwing amount.
Depending on the site of the piping work, it may not be possible to perform the screwing work according to the standard tightening torque. In this case, the actual situation is that the screwing work is performed based on the guideline of the number of screw threads.

As a manufacturing method of metal pipe joints, cutting screws that form threads by cutting have been the mainstream so far, but in recent years, rolling is performed by plastic working of threads using a rolling roller (rolling die). An increasing number of screws are formed.
A rolled screw retains a fiber flow generated during plastic deformation in a metal structure, is accompanied by work hardening, and is excellent in mechanical properties such as strength.
As described above, there are mainly two types of threading and rolling screws for threading. However, since the forming method of the screw part is different, there is a difference in the tightening torque at the time of screwing.
On the other hand, for the purpose of ensuring the sealability of the screw joint, a tape-like sealing material used for wrapping or a liquid sealing agent used by applying has been mainly used so far, but these sealing materials (agents) have been used. Is poor in workability because it is necessary to be applied immediately before screw connection, and in recent years, the use of a precoat type sealant in which a sealant is applied and dried in advance on the threaded portion of a joint is increasing.
Therefore, the present inventor has investigated in detail the relationship between the number of screw threads and the tightening torque with a combination of (cutting screw, rolled screw) × (seal tape, liquid sealant, precoat sealant).
As a result, when a precoat sealant with lubricity is used, even if it is screwed up to the standard number of screw threads described in the “Guideline for Management of Construction of Mechanical Equipment”, it will be reduced to about 1/2 or less of the standard tightening torque. The degree of rolling screws was greater than that of cutting screws, and it was found that when tightened to the standard tightening torque, it was overtightened.
For example, in a pipe end anti-corrosion joint 12 or the like having a substantially cylindrical resin core 13 attached to the inner side as shown in FIG. When the coating is applied, the tightening torque decreases, and when tightening to the standard torque, the core 13 may drop or break at the tip of the steel pipe 11.

Further, in threaded piping, a threaded portion is cut or rolled at a tip portion of a pipe that is screwed into a joint, and at that time, cutting oil or the like is used.
The cutting oil adhering to the threaded portion of the pipe is either simply wiped off with a waste cloth or the like and completely removed using a degreasing agent.
According to the investigation by the present inventor, it has been clarified that there is a large difference in tightening torque depending on whether or not the cutting oil adheres to the thread portion on the pipe side.

As a result of conducting a prior search by the present applicant, nothing similar to the present invention was found.
Patent Document 1 discloses a technology that prevents excessive sealant from protruding by forming a parallel threaded part on the back side of the taper threaded part. However, the screwing amount and tightening torque are optimized with the sealant. Not a thing.

JP 2007-51690 A

In the present invention, when a pipe member is screwed and connected, it can be screwed with a small torque at the beginning of screwing, and the tightening torque suddenly increases as the screwing amount approaches, so that it can be detected that the screwing has approached the screwing amount. The purpose is to provide a pipe joint with a torque control function that completes screwing.
It is another object of the present invention to provide a pipe connection method capable of obtaining a stable tightening torque regardless of the presence or absence of cutting oil at the tip thread portion of a pipe screwed into a pipe joint.

  The pipe joint with a torque control function according to the present invention is a pipe joint that is screwed and connected, and the application range of the lubricant sealant previously applied to the female thread part or the male thread part is determined from the screwing tip side by the standard screw thread number n. On the other hand, it is characterized in that over-tightening is prevented by setting the torque from 0.1n to 0.9n so that the tightening torque increases rapidly from the middle of screwing.

Here, the standard screw thread number n is a guideline set in accordance with the diameter designation shown in FIG. 4 specifically described in the “Machine Equipment Construction Management Guidelines” issued by the Ministry of Land, Infrastructure, Transport and Tourism. The value of the number of screw threads.
Therefore, the application range of the lubricant sealant is set from 0.1 n to 0.9 n with respect to the standard screw thread number n from the screw tip side. For example, when the standard screw thread number is six threads, FIG. to illustrate, the female screw portion standard screw-threads per about 6 mountains of relative standard screwing amount L _0, the application range of lubricating sealant coated from screwing the distal end side to 0.6 mountains at minimum, screwing tip up It means that 5.4 peaks are applied from the side.
Therefore, L is a value of (0.1 to 0.9) × L _{0 in} the application dimension.

The torque control function according to the present invention will be described with reference to FIG. 2. First, tightening by hand (hand tightening position), and then when tightening with a tool, it can be screwed with a small torque f at first. When the coating range is exceeded, the tightening torque f suddenly increases, and the brake is applied to the screwing.
In the graph of FIG. 2, f ₀ is a standard tightening torque, n ₀ is a standard screw thread number, f (n) is a screw thread number at which a brake starts to be applied, and is controlled by a sealant application range (this Graph showing invention pipe joint).
In contrast, when the pipe thread is wrapped with a sealing tape or a liquid sealing material is applied and joined to a conventional pipe joint, the tightening torque gradually increases as shown in the curve graph.
Therefore, it is difficult to manage the optimum screwing amount with the conventional joining method.

This is because if the application range of the sealant is less than 0.1n, there is a problem in the sealing performance, and if it exceeds 0.9n, the timing at which torque control is applied may be delayed, resulting in an overtightened state.
Stable torque control is obtained, and the coating range is preferably 0.2n to 0.6n in order to control the coating amount to be small by keeping the coating range small.
The lubricating sealant is preferably a fluorine sealant that can be uniformly applied.

Cutting oil adhering to the male thread on the tip of the pipe material joined to a pipe joint pre-coated with a fluorine-based sealant is wiped with a waste cloth (with cutting oil attached) and a degreasing agent. A comparison of screwing with a screw with a screwing torque of 100 [N · m] was made after completely removing the cutting oil (no cutting oil adhered).
As a result, the pipe with the cutting oil adhesion material was screwed up to about 8.5 threads, but the pipe without cutting oil adhesion was only screwed up to about 6.5 threads, and there was a difference in the number of threads. .
As a result of studying countermeasures by the present inventor, it has been clarified that the precoat film on which the fluorine-based sealant is applied and dried has a rubbery property, so that friction resistance exists more than the conventional liquid sealant. .
Therefore, as a result of applying a small amount of oil such as rust preventive oil to the pre-coated surface of the pipe joint, it became clear that the tightening torque was stable regardless of whether the cutting oil was attached to the thread on the pipe material side. .

  That is, in the pipe connection method according to the present invention, oil such as rust preventive oil is applied in advance to the threaded portion of the pipe joint according to claim 1 or 2, and threadedly connected to the threaded portion processed at the tip of the pipe material. It is characterized by that.

In the pipe joint according to the present invention, by using a precoat type sealant in which a lubricant sealant is applied in advance to a predetermined range of the threaded portion and dried, a conventional seal tape or the like is used for rolling and cutting. While there was a large torque difference with the screw (rolled screw was about 1.5 to 2.0 times higher), the difference in tightening torque was smaller and the application range was further controlled. Regardless of the threading method, the torque control function appears, and the standard number of screw threads and the standard tightening torque can be matched.
This facilitates on-site screw connection work.
In addition, in the pipe end prevention joint, the core can be prevented from being damaged or dropped due to overtightening.
Further, when oil is applied to the precoat surface of the pipe joint and the pipe material is connected by piping, tightening is stabilized regardless of whether the cutting oil is attached to the thread portion on the pipe material side.

The standard screw thread number of the threaded portion and the application range of the sealant are schematically shown. An explanatory view of a torque control function is shown. The measurement results of the application range and tightening torque are shown. The table described in the 2007 “Guidelines for Management of Mechanical Equipment Construction” is shown. The results of comparing tightening torques with and without oil (rust preventive oil) applied to the surface of the sealant precoat and with or without cutting oil on the pipe side are shown. The example of a cross section of a pipe end anti-corrosion joint is shown.

First, as a preliminary evaluation, a female threaded pipe joint having a nominal diameter of 25A was manufactured with both a rolled screw and a cutting screw, and a threaded joint evaluation was performed on the male thread of the steel pipe.
Tightening torque was evaluated by screwing a seal tape so that thread n = 6 threads were joined, and applying a fluorine-based lubricant sealant to the female thread side and drying the n = 6 thread. .
As a result, the one using the seal tape had a value of 73 N · m for the rolling screw and 40 N · m for the cutting screw, and the torque of the rolling screw was higher.
On the other hand, in the case of using the lubricant sealant, the tightening torque was reduced to 30 N · m for the rolling screw and 26 N · m for the cutting screw, and the difference between the rolling screw and the cutting screw was reduced.
Moreover, since tightening is performed with a torque of 1/3 or less with respect to the standard tightening torque of 100 N · m, there is a risk of overtightening.

Next, as shown in FIG. 3, the tightening torque was evaluated at the number of screw threads n = 6 when the application range of the fluorine-based sealant from the tip of the female thread portion was changed (average torque of five measurements). Value).
As a result, as shown in Comparative Example 12, it is difficult to tighten those that are not applied at all, and the torque control function acts when the application range is from 0.1 n to 0.9 n from the screwed tip side, as in Comparative Examples 11 and 13. The tightening torque is higher than that of the whole application.
In particular, when the application range is from 0.2n to 0.6n with respect to the standard number of threads from the screwing tip side to the back, the first half of screwing has a small hand tightening torque and is easy to tighten. It became clear that the torque increased and over-tightening was effectively prevented.
As shown in the table of FIG. 3, the range of Examples 2 to 6 is in the range of about ± 20% of the standard torque 100 N · m, and a tightening torque that is more stable than that of Examples 7 to 9 is obtained.
In addition, in pipe joints with large diameters such as 50A and 150A, galling occurs when screwed without a sealant, and a coating range of 0.2n or more is preferable, but if the coating range exceeds 0.8n, the tightening torque is increased. It suddenly decreased.
FIG. 6 shows a cross-sectional view of an elbow type pipe end anticorrosion joint 12 as an example.
A resin core 13 is provided inside the opening of the pipe end anticorrosion joint 12, and a resin coating 14 is formed between the cores on both sides of the opening.
The tube 11 is screwed and joined between the core 13 and the female screw portion 12a.
The pipe 11 is rustproofed with an outer peripheral covering portion 11b such as resin on the outer side of the steel material and an inner peripheral covering portion 11a such as resin on the inner side, and the sealant 3 is precoated between the male screw portion 11c and the female screw portion 12a.
In this case, as shown in FIG. 6, the lower opening is hatched, and the sealant 3 is partially precoated so that the tube 11 is screwed as shown in the upper opening in FIG. Then, the portion of the sealing agent indicated by the thick solid line disappears in the middle, and the tightening torque increases rapidly, so that the core 13 can be prevented from being damaged by over-tightening.

In the table shown in FIG. 5, the oil coated on the pre-coated surface of the pipe joint pre-coated with a sealant having a nominal diameter of 32A was prepared as an oil with or without applying anti-rust oil in this experiment, and the pipe material was cut at the tip. Prepare the one with the cutting oil that has been threaded with oil and wiped the cutting oil lightly with the waste, and the one without the cutting oil that has completely removed the cutting oil with the degreasing agent. The result of measuring the torque is shown.
The tightening torque indicates the torque value when the number of screw threads n = 7, and the values shown in the table are the ranges of the torque measured for each two.
From the results shown in the table, when the rust preventive oil is not applied to the sealant precoat surface of the pipe joint, the tightening torque is 45 to 70 [N・ M], but without the cutting oil with the cutting oil removed, it was very large at 165 to 170 [N · m], and there was a difference of about 100 [N · m] in the tightening torque. It was.
In this case, if the screwing amount is managed by the tightening torque, the screwing amount may be insufficient without cutting oil, and liquid or air leakage may occur. Conversely, if the screwing amount is managed by the number of tightening threads, the tightening torque increases and workability decreases. To do.
On the other hand, with a small amount of oil applied to the surface of the precoat, there is little difference in the tightening torque at the standard screw thread number n = 7 regardless of whether or not the cutting oil is attached to the pipe thread. It was.
Thereby, if the pipe material is screwed and connected after applying oil to the precoat surface of the pipe joint, the tightening amount is stabilized.

DESCRIPTION OF SYMBOLS 1 Female thread part 2 Male thread part 3 Sealing agent 11 Pipe | tube 11a Inner periphery coating | coated part 11b Outer periphery coating | coated part 11c Male thread part

Claims (3)

A pipe joint for screw connection,
The application range of the lubricant sealant previously applied to the female thread or male thread
With a torque control function characterized by the fact that the tightening torque suddenly rises from the middle of screwing to prevent over-tightening by setting it from 0.1n to 0.9n with respect to the standard screw thread number n from the screw tip side. Pipe fittings.   The pipe joint with a torque control function according to claim 1, wherein the application range of the lubricating sealant is set to 0.2n to 0.6n with respect to the standard screw thread number n.   A pipe connection method, wherein an oil such as a rust preventive oil is applied in advance to the threaded portion of the pipe joint according to claim 1 or 2, and the threaded portion processed into a tip portion of the pipe material is screwed and connected.

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