Upper Ball Joint Force Variations due to Riser Tensioner and Vessel Motions—Part I: Derivation of General Equations

1990 ◽  
Vol 112 (3) ◽  
pp. 188-199 ◽  
Author(s):  
T. J. Kozik ◽  
J. E. Lowell ◽  
A. Ertas
Keyword(s):  
General Equation ◽  
Ship Motion ◽  
Joint Motion ◽  
Ball Joint ◽  
Joint Force ◽  
Breakaway Torque ◽  
Cable Forces

General equation for the tensioner cable forces and for the forces exerted on the riser upper ball joint by the ship joint-tensioner system are derived. An analysis of the variation of forces acting on the upper ball joint of a riser string due to drill ship motion and riser tensioner dynamic has been conducted. The analysis includes the effect of breakaway torque on the tensioner sheaves while assuming vessel and upper ball joint motion to be independent.

Upper Ball Joint Force Variations due to Riser Tensioner and Vessel Motions—Part II: Analysis and Computer Simulation

1990 ◽  
Vol 112 (3) ◽  
pp. 200-207 ◽  
Author(s):  
T. J. Kozik ◽  
J. E. Lowell ◽  
A. Ertas
Keyword(s):  
Computer Simulation ◽  
General Equation ◽  
Ship Motion ◽  
Joint Motion ◽  
Ball Joint ◽  
Joint Force ◽  
Field Operation ◽  
Breakaway Torque ◽  
Cable Forces

An analysis of the variation of forces acting on the upper ball joint of a riser string due to the drill ship motion and riser tensioner dynamic has been conducted. The analysis includes the effect of breakaway torque on the tensioner sheaves while assuming vessel and upper ball joint motion to be independent. General equation for the tensioner cable forces and for the forces exerted on the riser upper ball joint by the ship joint-tensioner system derived in Part I are solved. The variation in the tensioner cable forces is compared to data generated in field operation.

Riser Tensioner Force Variations

1978 ◽  
Vol 18 (06) ◽  
pp. 399-408
Author(s):  
T.J. Kozik ◽  
J. Noerager
Keyword(s):  
Support System ◽  
Strong Dependence ◽  
Technical Conference ◽  
Ball Joint ◽  
Joint Force ◽  
Support Mechanism ◽  
Original Manuscript ◽  
Drilling Operations ◽  
Force Variation ◽  
Tank Pressure

Original manuscript received in Society of Petroleum Engineers office Feb. 24, 1976. Paper accepted for publication June 14, 1977. Revised manuscript received Aug. 21, 1978. Paper (SPE 6309, OTC 2648) first presented at the Eighth Annual Offshore Technical Conference, held in presented at the Eighth Annual Offshore Technical Conference, held in Houston, May 3-6, 1976. Abstract Excessive riser-force variation on the upper joint in a riser string can lead to buckling and excessive fatigue. This variation is caused by two components of the riser support system - the riser tensioning system and the telescopic, or slip, joint. Using specific examples, two conclusions are reached. First, the force variation at the top of the riser string may be much greater than that indicated by monitoring the tensioner system's air-tank pressure. Second, a major contribution to this pressure. Second, a major contribution to this variation can be pressure drop in the air valves. Introduction The riser tensioners and slip joint (Fig. 1) form the support system for the riser string used in floating drilling operations. Although tensioners are the primary support mechanism, their forces are transmitted through the slip joint to the upper joint in the riser string. In many deep-water drilling operations, the riser string is isolated in bending by an upper ball joint from the more massive telescopic joint. This upper ball joint interacts directly with the riser string; therefore, the forces seen at that joint become riser-string forces because of the tensioner support system. Ideally, the tensioner support-system forces at the upper ball joint should provide a net axial load on the riser string and should be constant in magnitude as well as direction. However, the nonideal behavior of the riser tensioners - as well as the inertia and geometrical effects associated with vessel, slip joint, and riser-string motions - result in load variations. Generally, the upper ball-joint force vector depends on time. No limits as yet have been determined for allowable variations of the riser-string forces resulting from the riser support mechanism. Nevertheless, measuring these variations analytically and qualitatively is important when assessing the effectiveness of the support mechanism or when providing important information about the boundary providing important information about the boundary conditions necessary to analyze the riser string. Our paper has two purposes. First, to emphasize by numerical examples the strong dependence of riser-tensioner force variations on the character of the assumed losses (pressure chop) in the tensioner-system air valves. Second, to present an analytical expression and numerical results for the tensioner-system force variations at the upper ball joint, thereby emphasizing the strong effects of vessel motion on riser-string force. TENSIONER ANALYSIS The typical drilling riser tensioner is a hydropneumatic mechanical system (Fig. 2) that provides tension in the cable attached to and supporting the outer barrel of the slip joint. Kozik studied the cable tensioner variation (r) resulting from cable motion. A convenient form for his equation is .....................(1) SPEJ P. 399

Experimental and Numerical of Sloshing Effect on Heave and Pitch Motions of FLNG Vessel

2014 ◽  
Vol 664 ◽  
pp. 153-157 ◽  
Author(s):  
Luhut Tumpal Parulian Sinaga ◽  
I.K.A.P Utama ◽  
A. Sulisetyono
Keyword(s):  
Natural Gas ◽  
General Equation ◽  
Wave Amplitude ◽  
Numerical Models ◽  
Critical Role ◽  
Liquefied Natural Gas ◽  
Ship Motion ◽  
Fluid Level ◽  
Strongly Nonlinear ◽  
Impulsive Response

Recently the demand of sloshing analysis is rising for building FLNG (Floating Liquefied Natural Gas) vessel. This study considers the experimental and numerical observations on strongly nonlinear sloshing flows in ship motion. The FLNG (Floating Liquefied Natural Gas) vessel was considered to be rigid body supported by non-permanent pole with distributed spring damper. Based on the general equation of the ship motion in waves, and various wave amplitude, various heading, wave period and critical fluid level on the cargo tank period governing equation induced by sloshing were derived. Several physical issues are introduced in the analysis of sloshing flows, and the corresponding numerical models are described. To study the sloshing effects on ship motion, a ship motion program based on impulsive response function (IRF) is coupled with the developed numerical models for sloshing analysis. The results show that the nonlinearity of sloshing-induced forces and moments plays a critical role in the coupling effects.

Clinical Update: Measuring Shoulder Joint Motion

1998 ◽  
Vol 3 (5) ◽  
pp. 4-5
Author(s):  
Christopher R. Brigham
Keyword(s):  
External Rotation ◽  
Joint Motion ◽  
Fourth Edition ◽  
Single Plane ◽  
Reconstructive Procedures ◽  
Results Of Treatment ◽  
Shoulder Disorders ◽  
Shoulder Motion ◽  
Motion Measurements ◽  
Upper Extremity Impairment

Abstract Accurate measurement of shoulder motion is critical in assessing impairment following shoulder disorders. To this end, measuring and recording joint motion are important steps in diagnosing, determining the severity and progression of a disorder, assessing the results of treatment, and evaluating impairment. Shoulder movement usually is composite rather than in a single plane, so isolating single movements is challenging. Universal goniometers with long arms are used to measure shoulder motion, and testing must be performed and recorded consistently. Passive motion may be carried out cautiously by the examiner; two measurements of the same patient by the same examiner should lie within 10° of each other. Shoulder extension and flexion are illustrated. Maximal flexion of the shoulder also includes slight external rotation and abduction, and controlling or eliminating these components during evaluation is challenging. Abduction and adduction are illustrated. Deficits in external rotation may occur in patients who have undergone reconstructive procedures with an anterior approach; deficits in internal rotation may result from issues with shoulder instability. The authors recommend recording the shoulder's range of motion measurements according to the Upper Extremity Impairment Evaluation Record in the AMA Guides to the Evaluation of Permanent Impairment, Fourth Edition.

NATO adaptation to current challenges and mechanisms of Ukraine’s cooperation with the North Atlantic Treaty Organization

2019 ◽  
pp. 73-81
Author(s):  
Oleh Poshedin
Keyword(s):  
North Atlantic ◽  
Task Force ◽  
Response Force ◽  
Cyber Attack ◽  
Adaptation Measures ◽  
Joint Force ◽  
Security Environment ◽  
The North ◽  
The North Atlantic ◽  
Area Of Influence

The purpose of the article is to describe the changes NATO undergoing in response to the challenges of our time. Today NATO, as a key element of European and Euro-Atlantic security, is adapting to changes in the modern security environment by increasing its readiness and ability to respond to any threat. Adaptation measures include the components required to ensure that the Alliance can fully address the security challenges it might face. Responsiveness NATO Response Force enhanced by developing force packages that are able to move rapidly and respond to potential challenges and threats. As part of it, was established a Very High Readiness Joint Task Force, a new Allied joint force that deploy within a few days to respond to challenges that arise, particularly at the periphery of NATO’s territory. NATO emphasizes, that cyber defence is part of NATO’s core task of collective defence. A decision as to when a cyber attack would lead to the invocation of Article 5 would be taken by the North Atlantic Council on a case-by-case basis. Cooperation with NATO already contributes to the implementation of national security and defense in state policy. At the same time, taking into account that all decision-making in NATO based on consensus, Ukraine’s membership in the Alliance quite vague perspective. In such circumstances, in Ukraine you often can hear the idea of announcement of a neutral status. It is worth reminding that non-aligned status did not save Ukraine from Russian aggression. Neutral status will not accomplish it either. All talks about neutrality and the impossibility of Ukraine joining NATO are nothing but manipulations, as well as recognition of the Ukrainian territory as Russian Federation area of influence (this country seeks to sabotage the Euro-Atlantic movement of Ukraine). Think about it, Moldova’s Neutrality is enshrined in the country’s Constitution since 1994. However, this did not help Moldova to restore its territorial integrity and to force Russia to withdraw its troops and armaments from Transnistria.

Controllable Compliance Joint For Human Oriented Robots

2013 ◽  
Vol 43 (1) ◽  
pp. 47-60
Author(s):  
Mihail Tsveov ◽  
Dimitar Chakarov
Keyword(s):  
Numerical Experiments ◽  
Position Control ◽  
Joint Stiffness ◽  
Joint Motion ◽  
Compliance Control ◽  
Leaf Springs ◽  
Antagonistic Actuation

Abstract In the paper, different approaches for compliance control for human oriented robots are revealed. The approaches based on the non- antagonistic and antagonistic actuation are compared. In addition, an approach is investigated in this work for the compliance and the position control in the joint by means of antagonistic actuation. It is based on the capability of the joint with torsion leaf springs to adjust its stiffness. Models of joint stiffness are presented in this paper with antagonistic and non-antagonistic influence of the spring forces on the joint motion. The stiffness and the position control possibilities are investigated and the opportunity for their decoupling as well. Some results of numerical experiments are presented in the paper too.

Shoulder Joint Motion Analysis of Daily Living Activities Using a Global Coordinate System

2013 ◽  
Vol 50 (10) ◽  
pp. 840-844
Author(s):  
Yukiya INOUE ◽  
Mayumi KIHARA ◽  
Junko YOSHIMURA ◽  
Naoki YOSHIDA ◽  
Kenji MATSUMOTO ◽  
...  
Keyword(s):  
Coordinate System ◽  
Motion Analysis ◽  
Shoulder Joint ◽  
Daily Living ◽  
Global Coordinate System ◽  
Joint Motion ◽  
Daily Living Activities

Advances in implementing ship motion predictors

1980 ◽  
Author(s):  
W. LIVINGSTON ◽  
D. NEWMAN
Keyword(s):  
Ship Motion
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