scholarly journals Improving the fatigue life of the tool-joint of drill pipes by optimizing the variable pitch of the box thread

2021 ◽  
Vol 1166 (1) ◽  
pp. 012017
Author(s):  
V B Kopei ◽  
O R Onysko ◽  
A G Panchuk ◽  
A P Dzhus ◽  
V R Protsiuk
Keyword(s):  
Fatigue Life ◽  
Variable Pitch ◽  
Drill Pipes ◽  
Tool Joint

A comparison of the turbine tower damping effects of a series of back twisted active pitch-to-stall blades for a spar and a semi-submersible FOWT

2021 ◽  
pp. 1-21
Author(s):  
Dawn Ward ◽  
Maurizio Collu ◽  
Joy Sumner
Keyword(s):  
Fatigue Life ◽  
Twist Angle ◽  
Offshore Wind ◽  
Life Extension ◽  
Variable Speed ◽  
Initiation Point ◽  
Variable Pitch ◽  
Floating Offshore Wind Turbines ◽  
The Impact ◽  
Axial Fatigue

Abstract Floating offshore wind turbines are subjected to higher tower fatigue loads than their fixed-to-seabed counterparts, which could lead to reductions in turbine life. The worst increases are generally seen in the tower axial fatigue, associated with the tower fore-aft bending moment. For a spar type platform this has been shown to increase by up to x2.5 and, for a semi-submersible platform, by up to x1.8. Reducing these loads would be beneficial, as the alternative of strengthening the towers leads to increases in cost. Here, two offshore floating wind turbine systems, of the spar type, are analysed and selected responses and tower fatigue compared: one incorporates a variable speed, variable pitch-to-stall blade control system and a back twisted blade, and the other a conventional pitch-to-feather control. The results are then compared to those obtained in an earlier study, where the same turbine configurations were coupled to a semi-submersible platform. A weighted wind frequency analysis at three mean turbulent wind speeds highlights that the impact of the back twist angle magnitude and initiation point on tower axial fatigue life extension was the same for both platform types. Compared to their respective feather base models, an increase in the tower axial fatigue life of 18.8% was seen with a spar platform and 10.2% with a semi-submersible platform, when a back twist angle to the tip of −6° was imposed along with the variable speed, variable pitch-to-stall control.

scholarly journals THREAD RESTORATION TECHNOLOGY OF TOOL-JOINT IN DRILL PIPES BY METHOD OF ELECTRIC CONTACT WELD DEPOSITION INTO UPSET GROOVE

2018 ◽  
Vol 2018 (7) ◽  
pp. 19-25
Author(s):  
Андрей Паренко ◽  
Andrey Parenko ◽  
Константин Макаренко ◽  
Konstantin Makarenko
Keyword(s):  
Drill Pipe ◽  
Thermal Impact ◽  
Electric Contact ◽  
Major Repair ◽  
Impact Area ◽  
Drill Pipes ◽  
Tool Joint

In connection with a relatively high cost of drill pipes large companies loss caused by rejection achieves tens millions of rubles. And at the same time it is necessary to take into account that the tool-joint thread rejection does not mean at all unworthiness to operation a drill pipe itself as having restored an inter-lock it is possible to continue the operation of a res-tored product. In such a way, one of the priority direc-tions at major repair of drill pipes is a restoration of interlock geometrical joints. In this paper there is considered a technology for repair of a worn thread in an interlock of drill pipes and its updating at the expense of electric contact weld deposition used into an upset groove. The method of-fered allows keeping a pipe without its shortening at repair at the expense of additional metal application directly upon a thread area and decreasing a thermal impact area and also increasing operation properties of a restored pipe.

Effects of Standoff Tolerances on the Fatigue Life of a Tool-Joint Pin

1966 ◽  
Vol 88 (2) ◽  
pp. 211-215 ◽  
Author(s):  
John Finke
Keyword(s):  
Fatigue Life ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Negligible Effect ◽  
Plastic Model ◽  
Cyclic Bending ◽  
Bending Loads ◽  
Tool Joint

A 4 1/2-in. API full-hole, tool-joint pin is stress-analyzed photoelastically over a range of standoffs. A three-dimensional plastic model is loaded to different values of makeup torque. At each torque a range of cyclic bending loads and a range of cyclic tensile loads are simulated. The results show that makeup torques must be raised for extreme hand-tight, shoulder-gap standoffs if a given pin tension is to be maintained. Maximum static root stresses are shown to be nearly independent of standoff if a constant pin tension is maintained. Further analysis indicates that the fluctuating pin-root stresses are also nearly independent of standoff if complete relieving of the shoulder compression loads is prevented. These considerations indicate that standoff has a negligible effect on the fatigue life of a tool-joint pin if relieving of the joint shoulders under operating conditions is prevented.

scholarly journals Analytical investigations of the accuracy of the small diameter tool-joint tapered thread made by a lathe machining

2019 ◽  
Vol 2 (1) ◽  
pp. 268-276
Author(s):  
Oleh Onysko ◽  
Volodymyr Kopei ◽  
Iulia Medvid ◽  
Vitalii Panchuk ◽  
Lolita Pituley ◽  
...  
Keyword(s):  
Small Diameter ◽  
Rake Angle ◽  
Drill String ◽  
Influential Factor ◽  
Tangential Displacement ◽  
Profile Angle ◽  
Operational Characteristics ◽  
Thread Profile ◽  
Drill Pipes ◽  
Tool Joint

Abstract The drill string consists of connected drill pipes and other elements. The connection is carried out by screwing of the drill string elements with the help of tool-joint tapered thread. The operational characteristics of the drill pipes depend of the manufacture precision of these tool-joints mostly. The accuracy of the thread is regulated by the accuracy of its profile and the accuracy of its pitch diameter value. The accuracy of the tapered thread manufacturing on the lathe in its depending on the values of the geometric parameters of the lathe tool and the values of deviations of its installation relatively to the workpiece axis is investigated. It is proved that for the tapered thread of form VI profile used for connection of drill pipes with the diameter from 30 mm to 44 mm the most influential factor, in relation to the accuracy of the thread profile is the value of the rake angle. Application of the rake angle value up to −5° according to the research data leads to a deviation from the specified profile of 0.3°, which is more than 35% of the declared standard tolerance on deviations from the profile. Also, the influence of the back rake angle value on the value of the deviation from the standard pitch diameter of the thread is proved. It is proved that the magnitude of the tangential displacement of the nose of the cutter relatively to the axis of the thread up to −0.2 mm can cause a deviation of the profile angle of 0.18°, which is 27% of the standard tolerance.

The Differential Geometry of the General Helix as Applied to Mechanical Springs

1988 ◽  
Vol 55 (4) ◽  
pp. 831-836 ◽  
Author(s):  
Yuyi Lin ◽  
Albert P. Pisano
Keyword(s):  
Experimental Data ◽  
Differential Geometry ◽  
Fatigue Life ◽  
Pitch Angle ◽  
Helical Spring ◽  
Variable Pitch ◽  
Helical Springs ◽  
Spring Force ◽  
Variable Helix ◽  
Curvature And Torsion

In order to improve the performance of helical springs, such as increasing the fatigue life and suppressing resonance, variable pitch angle and variable helix radius may be incorporated into the helical spring geometry. Employing the tool of differential geometry, new and complete formulae of curvature, torsion, and spring force are derived. It is shown that these formulae are more general and accurate than Kelvin’s curvature and torsion formulae, than commonly used force formulae (Wahl, 1963). Possible simplifications to the complete formulae and the corresponding errors introduced are both discussed and compared with experimental data.

Aluminum Drill Pipe Fatigue Analysis

2004 ◽  
Author(s):  
Guilherme Farias Miscow ◽  
Joa˜o Carlos Ribeiro Pla´cido ◽  
Paulo Emi´lio Valada˜o de Miranda ◽  
Theodoro Antoun Netto
Keyword(s):  
Fatigue Life ◽  
Structural Integrity ◽  
Crack Nucleation ◽  
Drill Pipe ◽  
Drill String ◽  
Small Scale ◽  
Second Phase ◽  
Horizontal Section ◽  
Steel Drill ◽  
Drill Pipes

While drilling extended reach wells, the weight per foot of the drill string is a critical design parameter that can limit the depth to be reached. One practical solution is the use of drill pipes made of alternative materials to the conventional steel drill pipes. The most direct options are titanium and aluminum. Titanium is in general impaired due to its high cost, although the titanium alloy Ti-6Al4V has already been used in the airplane industry. More recently, Russia has been manufacturing drill pipes using aluminum alloys of the system Al-Cu-Mg, similar to alloys 2024, also used in airplanes. These pipes present a reasonable commercial cost. Drill pipe fatigue damage occurs under cyclic loading conditions due to, for instance, rotation in curved sections of the well. Failures caused by crack nucleation and propagation are one of the highest risks to the structural integrity of these pipes. Usually, failure mechanisms develop in the transition region of the tool joint. Several mechanical and metallurgical factors affect the fatigue life of drill pipes. The former are mainly geometric discontinuities such as transition zones, pits and slip marks. The latter are related to the size and distribution of crystalline grains, phases and second phase particles (inclusions). In this study, the roles played by both factors in the fatigue life of drill pipes are studied through an experimental test program. The fundamental fatigue mechanisms are investigated via laboratory tests in small-scale coupons performed in an opto-mechanical fatigue apparatus. Additionally, full-scale fatigue testes on three aluminum drill pipes were performed. The pipes tested are being used in the horizontal section of some extended reach wells in the Northeast of Brazil.

Research on Drill Pipe’s Fatigue Life Prediction Based on Reliability

2019 ◽  
Vol 944 ◽  
pp. 975-980
Author(s):  
Fang Po Li
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Tensile Stress ◽  
Life Prediction ◽  
Stress Amplitude ◽  
Fatigue Cracks ◽  
Drill Pipe ◽  
Fatigue Life Prediction ◽  
Probability Density Distribution ◽  
Tool Joint

Fatigue life of drill pipe is studied systematically based on reliability analysis. Calculation results show that bending and tensile stress in drill pipe body is significantly greater than that in the tool joint during drilling process. Drill pipe body’s fatigue strength is about 500MPa under the condition that the stress ratio is -1. The fatigue strength of tool joint is about 360MPa under the condition that the average tensile stress is 496MPa. The fatigue fracture position of drill pipe is concentrated on pipe body, and most fatigue cracks originate from pipe’s outer surface. Compared with material fatigue life, the fatigue life of whole drill pipe is significantly lower. Under the condition that the confidence level is 95% and deviation is 5%, drill pipe’s fatigue life distribution is normal distribution while the stress amplitude is 660MPa, 620MPa, 580MPa and 540MPa respectively. With the decreasing of stress amplitude, the peak of logarithmic fatigue life’ probability density distribution curve decreases gradually, and its dispersion increases gradually. Drill pipe’s fatigue life prediction equations whose reliability are 50%, 90%, 99% and 99.9% are calculated separately.

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