JP2006078327A - Method for inspecting screw part of special screw joint for oil well pipe - Google Patents

Method for inspecting screw part of special screw joint for oil well pipe Download PDF

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JP2006078327A
JP2006078327A JP2004262383A JP2004262383A JP2006078327A JP 2006078327 A JP2006078327 A JP 2006078327A JP 2004262383 A JP2004262383 A JP 2004262383A JP 2004262383 A JP2004262383 A JP 2004262383A JP 2006078327 A JP2006078327 A JP 2006078327A
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screw
taper
pin
diameter
box
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JP4604616B2 (en
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Shigeo Nagasaku
重夫 永作
Masahiko Iwamoto
理彦 岩本
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To develop a means for directly controlling the amount of screw interference to realize seizure prevention by directly measuring the diameter of a screw part by means of an NGS (numerical gauging system). <P>SOLUTION: Screw outer diameters are measured on at least three positions, comprising a complete thread part, an incomplete thread part close to an end of a pin, and an incomplete thread part of a raise part of the pin. Also as to a box, screw inner diameters are measured at places standing opposite to the measurement positions on the pin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、油井管用特殊ねじ継手のピン用の雄ねじおよび/またはボックス用の雌ねじのねじ部の検査方法に関する。   The present invention relates to a method for inspecting a thread portion of a male screw for a pin and / or a female screw for a box of a special threaded joint for oil well pipes.

油井管用特殊ねじ継手の製造にあたり、ピンまたはボックスのねじのテーパは所定の公差内の基準テーパになるように製造されている。
そのようにして製造されたねじ継手の検査に際しては、ねじの形状そのものをゲージとして使用する従来のハードゲージシステムにおいては、ねじのテーパの変動はねじの先端からのゲージの位置(スタンドオフ)の変動の一要素となる。この場合、スタンドオフを管理することにより、ねじ全体の干渉が管理されるので、そのような検査を行う限り、テーパの変動による焼付き等が問題となることは少なかった。
In the production of a special threaded joint for oil country tubular goods, the taper of the pin or box screw is manufactured to be a reference taper within a predetermined tolerance.
When inspecting a threaded joint manufactured in this way, in a conventional hard gauge system that uses the shape of the screw itself as a gauge, fluctuations in the taper of the screw are caused by the position of the gauge (standoff) from the tip of the screw. It becomes a factor of fluctuation. In this case, since the interference of the entire screw is managed by managing the standoff, as long as such an inspection is performed, seizure or the like due to taper variation is rarely a problem.

しかし、ねじのある1点における径をマイクロメータのような手段で測定する直接径測定法[NGS(Numerical Gauging System)] の採用により、ねじのテーパの変動、特にピンの不完全ねじ部のテーパの変動がねじの干渉へ影響を与え、継手における焼付きが起こり易くなってきている。特に、これはメタルシール部を有する特殊ねじ継手や、表面に潤滑層を有するねじ継手において顕著となる。API のBTC 、RTC 等のネジのみの継手においても、NGS を使用する場合は同様の傾向となる。   However, by adopting the direct diameter measurement method [NGS (Numerical Gauging System)] that measures the diameter at one point of the screw by means such as a micrometer, the fluctuation of the taper of the screw, especially the taper of the incomplete screw part of the pin The influence of the fluctuation affects the interference of the screw, and seizure of the joint is likely to occur. This is particularly noticeable in special threaded joints having a metal seal part and threaded joints having a lubricating layer on the surface. The same tendency is observed when NGS is used for joints with only screws such as API BTC and RTC.

このような状況に鑑み、今後はNGS での検査が主体となる特殊ねじ継手の製造に際して、ねじのテーパの変動の影響を軽減化するために、より正確にねじ部の測定を行なう検査方法が求められてきている。   In view of this situation, in the future, when manufacturing special threaded joints that will mainly be inspected by NGS, in order to reduce the effects of fluctuations in the taper of the screw, there is an inspection method for measuring the thread part more accurately. It has been demanded.

特許文献1には、管用テーパねじのカップリング構造の技術が開示されている。この技術は、カップリングのみに限定しており、API 規格のねじをベースとして、これを多段ねじテーパとしている。   Patent Document 1 discloses a technique of a coupling structure of a pipe taper screw. This technology is limited to coupling only, and is based on an API standard screw, which is a multi-stage screw taper.

特許文献2には、耐焼き付き性の優れたねじ継手の技術が開示されており、それによれば、ピンの不完全ねじ部にのみねじテーパの限定を与えて、それに数値限定をすることで、焼き付き性能の改善を提唱している。   Patent Document 2 discloses a technique of a threaded joint with excellent seizure resistance, and according to it, by limiting the thread taper only to the incomplete thread portion of the pin and limiting the numerical value to it, Advocates improvement of seizure performance.

これら2つの特許文献が開示するのは、ハードゲージシステム(HGS)による径測定を前提としたねじ継手の製造方法であり、これは、NGS を前提にした特殊ねじ継手の製造方法については何1つ規定するものはない。
特開昭60−116994号公報 特開平4−157282号公報
These two patent documents disclose a method of manufacturing a threaded joint on the premise of diameter measurement by a hard gauge system (HGS), and what is the method of manufacturing a special threaded joint based on NGS? There are no provisions.
JP-A-60-116994 JP-A-4-157282

本発明の目的は、NGS を前提とした特殊ねじ継手のねじ部の検査方法であり、ねじ干渉量を正確に管理できる新しい測定方法にもとづく特殊ねじ継手の検査方法を提供することである。   An object of the present invention is to provide a method for inspecting a thread portion of a special threaded joint on the premise of NGS, and to provide a method for inspecting a special threaded joint based on a new measuring method capable of accurately managing the amount of screw interference.

ハードゲージシステムにおいては、ねじのテーパの変動はスタンドオフの変動の要因となる。つまり、ねじテーパが基準よりきついピンは、スタンドオフが規定されているため、ねじ径が小さくなる。逆に、ねじテーパがゆるいピンはねじ径が大きくなる。これはボックスにおけるねじ径の測定においても同様である。   In a hard gauge system, fluctuations in the taper of the screw cause standoff fluctuations. That is, since the standoff is defined for the pin whose screw taper is tighter than the reference, the screw diameter becomes small. Conversely, a pin with a loose screw taper has a large screw diameter. The same applies to the measurement of the screw diameter in the box.

ここに、ピンの雄ねじおよびボックスの雌ねじを総称して単にねじあるいはねじ部といい、それらの外径、内径を総称して単に径という。
従来は、ねじの干渉により発生するトルクは、基本的には、ねじ全長に対する平均的なねじ干渉により規定されていたから、上述のようなスタンドオフによる管理はこれに適合するものである。
Here, the male screw of the pin and the female screw of the box are collectively referred to as a screw or a threaded portion, and the outer diameter and the inner diameter thereof are collectively referred to as a diameter.
Conventionally, the torque generated by the screw interference is basically defined by the average screw interference with respect to the entire length of the screw. Therefore, the management by the standoff as described above is suitable for this.

しかしながら、NGS の採用により、ねじの干渉は、一断面の径管理により規定され、その結果ねじテーパの変動は、この方法では管理できない要因となった。
NGS で管理されるねじ継手は、ねじテーパの変動によるピンおよびボックスのねじの径の変化がそのままねじの干渉量に反映する。よって、NGS で管理されていてもテーパの変動による締付けトルクは大きく変動することとなる。
However, with the adoption of NGS, screw interference is defined by the diameter management of one section, and as a result, fluctuations in screw taper become a factor that cannot be managed by this method.
For threaded joints managed by NGS, changes in pin and box thread diameters due to variations in thread taper are reflected directly in the amount of thread interference. Therefore, even if it is managed by NGS, the tightening torque due to taper variation will vary greatly.

以上より、NGS による検査を伴うねじ継手の製造方法においては、ピン、ボックスのねじのテーパをどのように管理するかが課題となる。
当然、ねじのテーパの影響を少なくするため、公差を極めて狭くすることも可能であるが、製造が極めて困難となる。
From the above, in the manufacturing method of the threaded joint accompanied by the inspection by NGS, the problem is how to manage the taper of the screw of the pin and the box.
Naturally, in order to reduce the influence of the taper of the screw, it is possible to make the tolerance extremely narrow, but the manufacturing becomes extremely difficult.

そこで、発明者は種々検討を重ねた結果、NGS によるねじ部の径の測定方法を規定することでねじの干渉量を適切に制御し、ねじ継手の焼き付きを防止することができることを知り、本発明を完成した。   Therefore, as a result of various studies, the inventor has learned that by controlling the thread diameter measurement method using NGS, the amount of thread interference can be controlled appropriately and seizure of the threaded joint can be prevented. Completed the invention.

これらの多段ねじ径測定を実現する手段として、油井管用特殊ねじ継手のねじ部の測定に際して、完全ねじ部において2箇所、不完全ねじ部において1箇所、少なくとも3箇所測定して、その数値を管理することが効果的であることを見出した。このときの利点は、後述するように、従来は1箇所であった測定点が3箇所に増え、作業の手間が増加するという不利益を相殺して余りある。   As a means to realize these multistage screw diameter measurements, when measuring the threaded part of special threaded joints for oil well pipes, measure the numerical value by measuring at two places in the complete threaded part, one place in the incompletely threaded part, and at least three places. I found that it was effective. As will be described later, the advantage at this time more than offsets the disadvantage that the number of measurement points, which used to be one in the past, is increased to three and the work is increased.

本発明によれば、NGS でのねじテーパの変動による締付けトルクへの影響を低減することが可能である。
また、ねじ同士の干渉量が部分的に高くなるために起こるねじの焼き付きも、同時に減少させることができる。
According to the present invention, it is possible to reduce the influence on the tightening torque due to the variation of the screw taper in the NGS.
Further, the seizure of the screw, which occurs because the amount of interference between the screws partially increases, can be reduced at the same time.

そして、ピン、ボックスのねじの径を個別に管理することにより、ねじテーパが公差内で変化させられた場合でも各々のねじの干渉量を管理することができ、締付トルクのバラツキを低減することができる。   And by managing the screw diameter of the pin and the box individually, even when the screw taper is changed within the tolerance, the interference amount of each screw can be managed, and the variation of the tightening torque is reduced. be able to.

したがって、本発明によれば、NGS にて製造する特殊ねじにおいて、特にピンの不完全ねじ部で発生する焼き付きを防止すると共にショルダリングトルクをハードゲージシステムで検査しているものと同等のレベルに管理できるものであって、その実用上の価値は高い。しかも、3箇所という少ない測定点でもって、焼付きの原因となるテーパの変動を管理することができ、その実際上の利益は大きい。   Therefore, according to the present invention, in the special screw manufactured by NGS, the seizure generated particularly in the incomplete thread portion of the pin is prevented, and the shouldering torque is at the same level as that inspected by the hard gauge system. It can be managed and its practical value is high. In addition, the taper variation that causes seizure can be managed with as few as three measurement points, and the actual profit is great.

ねじのかみ合いによるトルクは、一山毎に干渉量を規定して計算することができる。
NGS により求めた径の基準値に対して、ピンのねじのテーパの変動により、各ポイントでのねじの相互の干渉量が規定される。その一山毎のねじの干渉から発生するトルクを積算することにより、ねじ全体でのトルクが規定される。これは主として、FEM による計算にて求めることができる。
The torque due to screw engagement can be calculated by defining the amount of interference for each mountain.
The amount of interference between the screws at each point is defined by the variation in the taper of the pin screw with respect to the diameter reference value obtained by NGS. By integrating the torque generated from the interference of the screws for each mountain, the torque for the entire screw is defined. This can be determined mainly by FEM calculations.

次に、添付図面を参照して、具体的に多段ねじにおけるねじ部の径の測定方法について説明する。
図1は、ボックスの場合の多段ねじのねじ部の径の測定方法の測定点の説明図であり、図中、各記号は次の通りである。
Next, with reference to the attached drawings, a method for measuring the diameter of the threaded portion of the multistage screw will be specifically described.
FIG. 1 is an explanatory diagram of measurement points of a method for measuring the diameter of a threaded portion of a multi-stage screw in the case of a box. In the figure, each symbol is as follows.

A: (ボックスシール先端部から距離aにある) 内径測定での完全ねじ部内における第一測定部
B: (ボックスシール先端部から距離bにある) 設計図面のピッチ径の径指定部におけるねじ部第二測定部
C: (ボックスシール先端部から距離cにある) ボックス端面から2山目の距離に対応する完全ねじ部内における第三測定部
図2は、ピンの場合の多段ねじ径の測定方法の測定点の説明図であり、図中、各記号は次の通りである。
A: First measurement part in the complete screw part in the inner diameter measurement (at a distance a from the box seal tip) B: Thread part in the pitch designation diameter designation part of the design drawing (at a distance b from the box seal tip) Second measuring part C: (a distance c from the tip of the box seal) Third measuring part in the complete thread part corresponding to the distance of the second crest from the box end face FIG. 2 shows a method for measuring the multistage screw diameter in the case of a pin Is an explanatory diagram of the measurement points, in which the symbols are as follows.

A: (ピンシール先端部から距離aにあるねじ径測定) での完全ねじ部内における第一測定部
B: (ピンシール先端部から距離bにある) 設計図面のピッチ径の径指定部ねじ部における第二測定部
C: (ピンシール先端部から距離cにある) ボックス端面から2山目の距離に対応するピンの位置での不完全ねじ部内における第三測定部
本発明におけるねじ部の径の測定手段は特定のものに制限されないが、一般的にはねじ径測定機器(MRP) を用いて容易に測定可能である。
A: First measurement part in the complete threaded part (measured by a screw diameter at a distance a from the pin seal tip) B: (located at a distance b from the pin seal tip) Second measuring part C: (the distance c from the tip of the pin seal) The third measuring part in the incomplete thread part at the position of the pin corresponding to the distance of the second crest from the box end surface The means for measuring the diameter of the thread part in the present invention Is not limited to a specific one, but can generally be easily measured using a screw diameter measuring instrument (MRP).

図3は、ボックスおよびピンにおける各3点でねじ干渉量を計算する場合の実際の計算方法の要領の説明図である。
(1) ねじ干渉量の規定からApおよびAbに対しては径測定公差が規定される。
FIG. 3 is an explanatory view of the point of the actual calculation method when calculating the screw interference amount at each of the three points in the box and the pin.
(1) The diameter measurement tolerance is specified for Ap and Ab from the specification of the amount of screw interference.

→Ap十α/-β、Ab+γ/-δ
ねじ干渉量は(Ap+α/-β)−(Ab+γ/-δ)
=(Ap−Ab)+(α+δ)−(β+γ)
(2) ピッチ径の規定部における測定部位Bp 、BB は、ねじテーパの公差分での外径変動の影響を配慮するので、以下となる。
→ Ap + α / -β, Ab + γ / -δ
Screw interference amount is (Ap + α / -β)-(Ab + γ / -δ)
= (Ap−Ab) + (α + δ) − (β + γ)
(2) measurement site at a defined portion of the pitch diameter Bp, B B, so that consideration of the influence of the outside diameter variations in tolerances portion of the screw taper becomes less.

例えば、ねじテーパが1/16の場合(6.25%)で公差が+0.3 %/-0.1 %であれば、
外径への変動として+X1P、−Y1Pとして
+X1P=+ (LB −LA ) ×(0.0625 +0.003)、
−Y1P=− (LB −LA ) ×(0.0625 −0.001)
となる。
For example, if the thread taper is 1/16 (6.25%) and the tolerance is +0.3% /-0.1%,
+ X 1P as variation to the outer diameter, + X 1P = − (L B −L A ) × (0.0625 +0.003) as −Y 1P ,
-Y 1P = - (L B -L A) × (0.0625 -0.001)
It becomes.

(3) ピンの不完全ねじ部での測定部位Cp は、ねじ干渉量の低減をはかるためCp の径による基準より、小さくする対応が必要である。
例えば、ねじテーパが1/16 の場合(6.25%)で公差が−0.3 %/−0.7 %であれば、外径への変動を+X2P、−Y2pとすると
+X2P=+(LB -LA ) ×(0.0625+0.003)+(LC −LB ) ×(0.0625-0.003)
−Y2P=−(LB -LA ) ×(0.0625−0.001)−(LC −LB ) ×(0.0625-0.007)
となる。
(3) The measurement site Cp at the incomplete thread portion of the pin needs to be made smaller than the standard based on the diameter of Cp in order to reduce the amount of screw interference.
For example, if the screw taper of 1/16 (6.25%) tolerances -0.3% / - if 0.7%, the variation in the outer diameter + X 2P, when the -Y 2p + X 2P = + ( L B - L A ) × (0.0625 + 0.003) + (L C −L B ) × (0.0625-0.003)
−Y 2P = − (L B −L A ) × (0.0625−0.001) − (L C −L B ) × (0.0625−0.007)
It becomes.

ここに、ボックスのねじに関してはBb の部位とCb の部位は同じ完全ねじ部でBb での外形変動はテーパの変動を加味すれば、ねじテーパが1/16の場合(6.25%)で、公差が±0.2 %であれば、
+X1B=+(LB -LA )×(0.0625+0.002)
−Y1B=−(LB -LA )×(0.0625-0.002)
となる。
Here, regarding the box screw, the Bb part and Cb part are the same completely threaded part, and the outer shape fluctuation at Bb is 1/16 (6.25%), if the taper fluctuation is taken into account. Is ± 0.2%,
+ X 1B = + (L B -L A ) × (0.0625 + 0.002)
−Y 1B = − (L B −L A ) × (0.0625−0.002)
It becomes.

Cb での外形変動は、テーパの変動を加味すれば、ねじテーパが1/16の場合(6.25%)で公差が+0.20%/−0.20%であれば、
+X2B=+(LB -LA )×(0.0625+0.0002) +(Lc -LB )×(0.0625+0.0020)
−Y2B=−(LB -LA )×(0.0625-0.002)+(Lc -LB )×(0.0625-0.002)
となる。
If the taper is 1/16 (6.25%) and the tolerance is +0.20% /-0.20%, considering the taper variation,
+ X 2B = + (L B -L A ) × (0.0625 + 0.0002) + (L c -L B ) × (0.0625 + 0.0020)
−Y 2B = − (L B −L A ) × (0.0625−0.002) + (L c −L B ) × (0.0625−0.002)
It becomes.

以上より、各部位でのねじ干渉量は次のようになる。
A部位: (AP −Ab ) 、+(α+δ)/-(β+γ)
B部位: (AP −Ab ) 、+(α+δ)+ (X1P+Y1b)/-(β+γ)-(X1b+Y1P )
C部位: (AP −Ab ) 、+(α+δ)+ (X1P+Y1b) + (X2P+Y2b)
/-(β十γ)−(X1b+Y1P) −(X2b+Y2P)
A部、B部でのねじの干渉量にて、焼き付きは、発生していないので、C部をB部と同じねじ干渉量にすることが、焼き付きを発生させないポイントである。
From the above, the screw interference amount at each part is as follows.
A site: (A P -A b), + (α + δ) / - (β + γ)
B site: (A P −A b ), + (α + δ) + (X 1P + Y 1b ) / − (β + γ) − (X 1b + Y 1P )
C site: (A P −A b ), + (α + δ) + (X 1P + Y 1b ) + (X 2P + Y 2b )
/-([Beta] + [gamma])-( X1b + Y1P )-( X2b + Y2P )
Since the seizure does not occur in the interference amount of the screw in the A part and the B part, the point that the C part is set to the same screw interference amount as that in the B part is a point where the seizure does not occur.

ねじテーパの管理でなく、各製品のC部位で実際のねじ部の径を計ることにより、実際の製品のねじ干渉量を規定値に確実に管理できる。
B部位とC部位のねじ干渉量を同等以下とするためには、上記の式から、下記が得られる。
By measuring the actual thread diameter at the C part of each product instead of managing the screw taper, the screw interference amount of the actual product can be reliably managed to the specified value.
In order to make the screw interference amount of the B part and the C part equal or less, the following is obtained from the above formula.

(X1P+Y1b)+(X2P+Y2b)≦(X1P+Y1b
つまり
2P+Y2b≦ 0
図3の場合を例とすれば、次の通りである。
(LC−LB) *(0.0625−TPP)+(LC−LB)*(0.0625−TPB)≦ 0
(TPP :ピンの不完全ねじ部のテーパ公差上限補正値)
(TPB :BOX の管端2山部でのテーパ公差下限補正値)
これを整理すれば、
(LC−LB)*(TPP +TPB)≦ 0
ここで、一例として、LA=17mm、LB=32.78mm 、LC=58.905mmの場合を考えると次のようになる。
(X 1P + Y 1b ) + (X 2P + Y 2b ) ≦ (X 1P + Y 1b )
That is
X 2P + Y 2b ≦ 0
Taking the case of FIG. 3 as an example, it is as follows.
(LC−LB) * (0.0625−TPP) + (LC−LB) * (0.0625−TPB) ≦ 0
(TPP: Taper tolerance upper limit correction value for incomplete thread of pin)
(TPB: Taper tolerance lower limit correction value at 2 ridges on the pipe end of the BOX)
If you organize this,
(LC−LB) * (TPP + TPB) ≦ 0
Here, as an example, the case of LA = 17 mm, LB = 32.78 mm, and LC = 58.905 mm is considered as follows.

(58.905−32.78) *(TPP +TPB)≦ 0
これを整理すれば
TPP ≦−TPB
ケース l:TPB :0.002 であれば、TPP ≦−0.002
ケース 2:TPB :0.001 であれば、TPP ≦−0.001
ケース 3:TPB :0 なら TPP ≦ 0
ここに、ケース1であれば、ピンのC部位での外径測定レンジは、次のように規定できる。
(LB−LA)*(0.0655)+(LC−LB)*(0.0625+0)+Ap+α
(LB−LA)*(0.0615)+(LC−LB)*(0.0625−0.004)+Ap−β
さらにボックスのC部位での外径測定レンジは、次のように規定できる。
(LB−LA)*(0.0645)+(LC−LB)*(0.0625+0.002)+Ab+γ
(LB−LA)*(0.0605)+(LC−LB)*(0.0625−0.002)+Ab−δ
ケース 2であればピンのC部位での外径測定レンジは、次のように規定できる。
(LB−LA) *(0.0655)+(LC−LB)*(0.0625+0.001)+Ap+α
(LB−LA)*(0.0615)+(LC−LB)*(0.0625−0.003)+Ap−β
さらにボックスのC部位での外径測定レンジは、次のように規定できる。
(LB−LA) *(0.0645)+(LC−LB)*(0.0625+0.003)+Ab+γ
(LB−LA)*(0.0605)+(LC−LB)*(0.0625−0.001)+Ab−δ
ケース 3であれば、ピンのC部位での外径測定レンジは、次のように規定できる。
(LB−LA) *(0.0655)+(LC−LB)*(0.0625+0.002)+Ap+α
(LB−LA)*(0.0615)+(LC−LB)*(0.0625−0.002)+Ap−β
さらにボックスのC部位での外径測定レンジは、次のように規定できる。
(LB−LA) *(0.0645)+(LC−LB)*(0.0625+0.004)+Ab+γ
(LB−LA)*(0.0605)+(LC−LB)*(0.0625−0.00 )+Ab−δ
同様の作業を、各サイズの継手に適用して、A、B、Cの各部位での測定に対して、設定値を規定することができる。
(58.905−32.78) * (TPP + TPB) ≦ 0
If you organize this
TPP ≤ -TPB
Case l: If TPB is 0.002, TPP ≤ -0.002
Case 2: If TPB is 0.001, TPP ≤ -0.001
Case 3: TPB: 0, TPP ≤ 0
If it is case 1, here, the outer diameter measurement range in the C site | part of a pin can be prescribed | regulated as follows.
(LB−LA) * (0.0655) + (LC−LB) * (0.0625 + 0) + Ap + α
(LB−LA) * (0.0615) + (LC−LB) * (0.0625−0.004) + Ap−β
Furthermore, the outer diameter measurement range at the C part of the box can be defined as follows.
(LB−LA) * (0.0645) + (LC−LB) * (0.0625 + 0.002) + Ab + γ
(LB−LA) * (0.0605) + (LC−LB) * (0.0625−0.002) + Ab−δ
In case 2, the outer diameter measurement range at the C part of the pin can be defined as follows.
(LB−LA) * (0.0655) + (LC−LB) * (0.0625 + 0.001) + Ap + α
(LB−LA) * (0.0615) + (LC−LB) * (0.0625−0.003) + Ap−β
Furthermore, the outer diameter measurement range at the C part of the box can be defined as follows.
(LB−LA) * (0.0645) + (LC−LB) * (0.0625 + 0.003) + Ab + γ
(LB−LA) * (0.0605) + (LC−LB) * (0.0625−0.001) + Ab−δ
In case 3, the outer diameter measurement range at the C part of the pin can be defined as follows.
(LB−LA) * (0.0655) + (LC−LB) * (0.0625 + 0.002) + Ap + α
(LB−LA) * (0.0615) + (LC−LB) * (0.0625−0.002) + Ap−β
Furthermore, the outer diameter measurement range at the C part of the box can be defined as follows.
(LB−LA) * (0.0645) + (LC−LB) * (0.0625 + 0.004) + Ab + γ
(LB−LA) * (0.0605) + (LC−LB) * (0.0625−0.00) + Ab−δ
The same operation can be applied to the joints of each size, and the set value can be defined for the measurement at each part of A, B, and C.

このような計算式を踏まえてそれぞれ3箇所での測定をすることで、ねじ干渉量を確実に規制する測定法を実施でき、その結果として、焼付きが発生せず、またショルダリングトルクのレベルを管理するねじが製造できる。   By measuring at three locations based on these formulas, it is possible to implement a measurement method that reliably regulates the amount of screw interference. As a result, seizure does not occur and the level of shouldering torque Can be manufactured.

このように、本発明によれば、3点という少ない測定点でもって焼付きの原因となるテーパの変動を管理することができる。
さらに、この方法で管理した場合、ピンの不完全ねじ部のテーパは完全ねじ部のテーパとは全体的にずれた範囲で管理される。すなわち、ピンであれば、先端の不完全ねじ部のテーパは完全ねじ部のテーパよりも大きい、つまり傾斜が大きく、ボックスとの干渉量は少ない範囲で管理され、根元の不完全ねじ部のテーパは完全ねじ部のテーパより小さい、つまり傾斜が小さく、ボックスとの干渉量が少ない範囲となる。これはボックスにおいても同様である。このテーパの変動の範囲はねじ継手の設計の範囲内で管理されることになるが、それぞれ独立して管理する場合、ハードゲージシステムで全体を管理する場合に比べて、焼付きに影響のない範囲で緩い管理をすることになり、ねじの製造能率が向上し、コストの低減に寄与する。
As described above, according to the present invention, it is possible to manage the taper variation that causes seizure at a few measurement points.
Further, when managed by this method, the taper of the incomplete thread portion of the pin is managed within a range that is entirely deviated from the taper of the complete thread portion. In other words, in the case of a pin, the taper of the incomplete threaded portion at the tip is larger than the taper of the completely threaded portion, that is, the inclination is large and the amount of interference with the box is controlled within a small range. Is smaller than the taper of the complete threaded portion, that is, the inclination is small and the amount of interference with the box is small. The same applies to the box. The range of this taper variation will be managed within the design range of the threaded joint, but when managing each independently, there will be no effect on seizure compared to managing the whole with a hard gauge system. The loose management will be performed within the range, which improves the screw manufacturing efficiency and contributes to cost reduction.

比較例として1箇所測定したもので合格したものについて、締め付けテストを行いトルクの変化および焼付きを調べた。   As a comparative example, what was measured at one place and passed was subjected to a tightening test to examine changes in torque and seizure.

種々の外径・肉厚(単位長さ当りの質量)・鋼種でメタルシールを有する特殊ねじ継手を有する油井管およびカップリングを作製した。その際、ねじのテーパを規格内で変化させた。その油井管をNGS にて検査した。そして本発明例 (3箇所測定) および比較例として1箇所測定したもので合格したものについて、締め付けテストを行い、トルクの変化および焼付きを調べた。   Oil well pipes and couplings having special threaded joints with various outer diameters, wall thicknesses (mass per unit length), and steel types and metal seals were prepared. At that time, the taper of the screw was changed within the standard. The oil well pipe was inspected by NGS. The invention example (measured at three points) and the one measured as one comparative example were passed, and a tightening test was performed to examine torque change and seizure.

測定地点は図3における通りであり、それぞれの場合の測定点の距離は表1にまとめて示す。   The measurement points are as shown in FIG. 3, and the distances of the measurement points in each case are shown in Table 1.

Figure 2006078327
Figure 2006078327

表中のPNBNは、ピン(P) がノミナル(N) でボックス(B) もノミナル(N) の場合であり、PFBSはピンがファースト(F) 、ボックスがスロー(S) の場合であり、PSBFの場合はピンがスロー、ボックスがファーストの場合である。ここで、ノミナル(N) とはテーパが基準値通りのもの、ファースト(F) とは、テーパが基準値よりきついもの、スロー(S) とはテーパが基準値よりゆるいものである。   The PNBN in the table is when the pin (P) is nominal (N) and the box (B) is also nominal (N), and PFBS is when the pin is fast (F) and the box is slow (S). For PSBF, the pin is slow and the box is fast. Here, the nominal (N) means that the taper is as the reference value, the first (F) means that the taper is tighter than the reference value, and the slow (S) means that the taper is looser than the reference value.

また、ショルダリングトルク比率は、締め付け時のショルダリングトルク/締付点 推奨トルクであり、これが多すぎると締付不良となる。
ピンに本発明の径測定を実施することにより、ショルダリングトルク比率の低減と、ねじの焼き付きを防止することが可能となった。
The shouldering torque ratio is the shouldering torque / tightening point during tightening. Recommended torque. If this is too much, tightening will be poor.
By carrying out the diameter measurement of the present invention on the pin, it became possible to reduce the shouldering torque ratio and prevent the seizure of the screw.

Figure 2006078327
Figure 2006078327

ピンに本発明の径測定を行うことにより、ショルダリングトルク比率が、従来の検査方法に較べ、確実に低下することが確認できた。   By performing the diameter measurement of the present invention on the pin, it was confirmed that the shouldering torque ratio was reliably reduced as compared with the conventional inspection method.

但し、本発明のねじ径測定の採用により、PSBFの場合、ショルダリングトルク比率が、一段テーパのPSBFの場合よりさらに低くなる。ショルダリングトルクが低すぎても締付け不良となるので、これを従来のショルダリングトルク比率の範囲へ入れるためには、ピンのねじテーパの目標値を変更する必要がある。   However, by adopting the screw diameter measurement of the present invention, in the case of PSBF, the shouldering torque ratio becomes even lower than in the case of PSBF with a single-step taper. Even if the shouldering torque is too low, a tightening failure is caused. Therefore, in order to bring this into the range of the conventional shouldering torque ratio, it is necessary to change the target value of the thread taper of the pin.

つまり、PSBFの場合、ピンは6.05%がテーパ目標値で、ボックスは6.45%がテーパ目標値である。全体のショルダリングトルクをあげるために、ピンは6.15%をテーパ目標値とする。よって、NOMINAL 値は6.35%となり、MAX テーパは6.55%となる。製造を考慮してレンジとして0.4 %とした。この方法で再度油井管を作製し、テストを実施した結果を、以下の表3に記載する。   That is, in the case of PSBF, the pin has a taper target value of 6.05% and the box has a taper target value of 6.45%. In order to increase the overall shouldering torque, the taper target value is 6.15%. Therefore, the NOMINAL value is 6.35% and the MAX taper is 6.55%. In consideration of manufacturing, the range is set to 0.4%. Table 3 below shows the results of producing an oil well pipe again by this method and carrying out the test.

Figure 2006078327
Figure 2006078327

また、ピン不完全ねじ部のねじ底での焼き付き発生レベルを検証した。その結果を以下の表4に記す。   In addition, the level of occurrence of seizure at the bottom of the pin incomplete thread portion was verified. The results are shown in Table 4 below.

Figure 2006078327
Figure 2006078327

表4で示された通りピンの3箇所でねじ径測定を行い、PSBFのピンのねじテーパを従来の一段ねじテーパより、きつくすること[PS(6.05%)→(6.15%)]により、PFBSでのショルダリングトルクを、従来の一段ねじテーパでのショルダリングトルクより低くしつつ、PSBFでのショルダリングトルクを、従来の一段ねじテーパでのショルダリングトルクと同等にすることが可能になる。   As shown in Table 4, measure the screw diameter at three locations of the pin, and tighten the PSBF pin taper taper from the conventional one-step screw taper [PS (6.05%) → (6.15%)] It is possible to make the shouldering torque at PSBF equal to the shouldering torque at the conventional one-stage screw taper while lowering the shouldering torque at the conventional one-stage thread taper.

Figure 2006078327
Figure 2006078327

Figure 2006078327
Figure 2006078327

表5、6で示された通り本発明の多段ねじ径測定品にすることにより、ねじ底で発生する焼き付きが大幅に低減したことが、分かる。   As shown in Tables 5 and 6, it was found that by using the multistage screw diameter measurement product of the present invention, the seizure generated at the screw bottom was greatly reduced.

ボックスの場合の本発明にかかる多段ねじ径の測定方法の測定点の説明図である。It is explanatory drawing of the measurement point of the measuring method of the multistage screw diameter concerning this invention in the case of a box. ピンの場合の本発明にかかる多段ねじ径の測定方法の測定点の説明図である。It is explanatory drawing of the measuring point of the measuring method of the multistage screw diameter concerning this invention in the case of a pin. ボックスおよびピンにおける各3点でのねじ径を測定する場合の実際の計算方法の要領の説明図である。It is explanatory drawing of the point of the actual calculation method in the case of measuring the screw diameter in each 3 points | pieces in a box and a pin.

Claims (2)

油井管用特殊ねじ継手のねじ部の検査方法であって、完全ねじ部において2箇所、不完全ねじ部において1箇所の少なくとも3箇所のねじ径を測定し、得られた測定値と管理範囲とを比較することを特徴とする油井管用特殊ねじ継手のねじ部の検査方法。   A method for inspecting a threaded portion of a special threaded joint for oil well pipes, measuring at least three screw diameters, two at a complete threaded portion and one at an incompletely threaded portion. A method for inspecting a threaded portion of a special threaded joint for oil well pipes, characterized by comparison. 請求項1においてピンのねじ部の3箇所のねじ径を測定することを特徴とする油井管用特殊ねじ継手のねじ部の検査方法。   3. The method for inspecting a threaded portion of a special threaded joint for oil well pipes according to claim 1, wherein the thread diameters of the threaded portion of the pin are measured at three locations.
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WO2009119713A1 (en) * 2008-03-27 2009-10-01 住友金属工業株式会社 Device for measuring screw element at pipe end, system for measuring screw element and method for measuring screw element
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