High Modulus Polyethylene Ropes Research Articles

Experimental measurement for dynamic tension fatigue characteristics of HMPE fibre ropes

This paper presents a full-scale experimental investigation for the fatigue properties of HMPE (high-modulus polyethylene) fibre ropes under dynamic loads. Three ropes with different constructions have been tested under various loading averages, amplitudes and periods. The results indicate that the stability of the inner structure plays an important role in fatigue resistance. Therefore, the 2 × 12 braided HMPE rope with more strands of a smaller diameter generally showed a longer fatigue life. An existing empirical equation is validated against the available data and the present experimental results, while a poor agreement is found in the cases of long loading periods. On this account, an equation is further proposed by taking into account the influences of loading period and rope configuration. After setting a proper base for the logarithm of failure time, a good convergence for the iterative fitting in the regression calculation and reasonable agreement against the experimental results have been found.

Experimental investigation of spooling test on the multilayer oceanographic winch with high-performance synthetic fibre rope

Compared with steel wire ropes, synthetic fibre ropes have a better performance in deep sea and gradually replaced the former in subsea launch and recovery systems. However, serious damage will be introduced to the winch structure when synthetic fibre ropes wound in multiple layers on the winch drum. In order to comprehensively explore the relationship between the mechanical properties of the winch drum barrel and the synthetic fibre rope, biaxial strain gauges and laser profile scanners have been used to monitor the oceanographic winch using a high-modulus polyethylene (HMPE) rope with the length of 13000 m. The full-size test rig was first introduced as an attempt to quantify the effect of winding fibre rope and evaluate the stresses on the winch with multilayer winding fibre rope. The results reveal that a loss elimination effect on rope windings may occur during the spooling experiment of fibre rope owing to the hysteresis property of the fibre, which differs significantly from the results published previously. Moreover, a more concise winding model is developed to estimate the spoolingand deformation states of the synthetic fibre rope, which can well simulate the cross-section deformation of the wound HMPE rope.

Dynamic stiffness of braided HMPE ropes under long-term cyclic loads: A full-scale experimental investigation

This paper presents a full-scale experimental investigation to study the nonlinear dynamic stiffness of high-modulus polyethylene (HMPE) fibre rope under long-term cyclic loading. Three kinds of ropes with different constructions and diameters were selected as test samples. The influences of mean load and load amplitude on axial stiffness and the corresponding evolution process were respectively studied. The experimental results showed that various braided ropes' dynamic stiffness was slightly different, which was mainly caused by the different twist angles. Furthermore, the non-dimensional stiffness of small-scale rope was lower than the large samples to some extent. This should be related to the small-scale ropes without an outer jacket were much softer and thus had more distinct deformation. The validations against two existing empirical expressions have also been performed. The results pointed out that these equations had some errors predicting the evolution procedure of the dynamic stiffness and the magnitude of small-scale sample's stiffness. On these accounts, a set of empirical expressions, taking into account braid constructions, diameter and input load conditions, has been newly derived. The comparison against the present experimental results proved its good reliability.

Computer vision and thermal monitoring of HMPE fibre rope condition during CBOS testing

Fibre rope usage in deep sea lifting operations is gaining more prominence in recent times. With rope minimum break loads (MBL) comparable to that of their steel wire counterparts, the use of high modulus polyethylene (HMPE) ropes is seen as a viable option for use in subsea construction cranes. The ropes are worn out during use and visual inspection remains one of the main methods of determining whether a fibre rope is to be retired from use, therefore a natural extension is condition monitoring through computer vision. Creep and temperature are constraining with HMPE ropes and should be monitored continuously, particularly when the rope is cyclically bent over sheaves. Additionally, interpreting the thermal history of the rope during use could give insight into deterioration. In this paper, a condition monitoring system based on combined computer vision and thermal monitoring is used during cyclic bend over sheave tests performed on 560 kN break load of 12 strand braided HMPE ropes. New monitoring features such as local length and width through computer vision algorithms combined with surface thermal monitoring and global elongation are presented and their effectiveness as condition monitoring features is assessed.

Virtual prototyping: a case study of positioning systems for drilling operations in the Barents Sea

ABSTRACTThis study proposes a framework for comparative study on three different positioning solutions for mobile offshore drilling units (MODUs) using high modulus polyethylene (HMPE) ropes, including active mooring with an HMPE rope, conventional dynamic positioning (DP) and active hybrid position-keeping (AHP-K). The goal of the positioning systems is to keep the MODU above the wellhead with acceptable riser-angle loading, minimal energy consumption, reduced underwater noise generation, and harmful emissions. This is the first time a holistic study has been performed on positioning that factors in the financial and environmental costs. The time domain simulation, which includes sea-state, wind, and current profiles, is performed with a well-developed software architecture and control algorithms for MODU position-keeping. The case study addresses a MODU drilling in the Barents Sea. Simulation results show that AHP-K is more efficient compared to the other two positioning solutions for drilling operations in the studied environment.

An Investigation on Creep and Creep-Rupture Behaviors of HMPE Ropes

Creep tests of high modulus polyethylene (HMPE) samples are performed to obtain the corresponding creep and creep-rupture curves. The results show that the secondary creep stage is especially pronounced, and its creep rate is nearly constant. Based on this fact, the creep rate at the secondary stage has been utilized as the representative value of each case. Therefore, the similarity criterion of creep rate at secondary stage is proposed to analyze the corresponding relationship between engineering creep rate and that in laboratory tests. Besides, an empirical expression of HMPE yarns is proposed to account for the effects of both loading level and test temperature on the creep rate at the secondary stage. Moreover, an equation for calculating the creep lifetime of HMPE samples is derived and verified by test data. This study will help to improve the understanding of creep behaviors of HMPE ropes and provide a significant reference for the application of HMPE ropes in mooring engineering.

An experimental investigation on fatigue behaviors of HMPE ropes

With offshore oil and gas exploration moving into deeper waters, HMPE (high modulus polyethylene) ropes have been widely investigated. However, the tension-tension fatigue behavior of HMPE ropes, especially the effect of mean load on the fatigue life of HMPE ropes, is still lack of sufficient and quantitative understanding. Therefore, to capture the fatigue behavior of HMPE ropes, fatigue tests of HMPE ropes are systematically performed in the present work utilizing a specially designed experimental system. An experimental procedure is proposed and test results show the whole fatigue process of HMPE ropes including tension-time, strain-time and tension-strain curves. The dynamic stiffness of HMPE ropes is also investigated, which shows that it increases with increasing mean load, while decreases with increasing loading amplitude. An empirical expression that accounts for the relationship of the mean load, loading amplitude and fatigue life is proposed to describe the damage evolution of HMPE ropes under long-term cyclic loading. The present work is beneficial to understanding the fatigue resistance ability of HMPE ropes and to application of HMPE ropes in deepwater moorings.

섬유로프 계류시스템의 크리프 효과가 부유체의 운동응답 및 계류선의 장력 변화에 미치는 영향에 관한 연구

Growing demand and rapid development of the synthetic fiber rope in mooring system have taken place since it has been used in deep water platform lately. Unlike a chain mooring, synthetic fiber rope composed of lightweight materials such as Polyester(polyethylene terephthalate), HMPE(high modulus polyethylene) and Aramid(aromatic polyamide). Non-linear stiffness and another failure mode are distinct characteristics of synthetic fiber rope when compared to mooring chain. When these ropes are exposed to environmental load for a long time, the length of rope will be increased permanently. This is called 'the creep phenomenon'. Due to the phenomenon, The initial characteristics of mooring systems would be changed because the length and stiffness of the rope have been changed as time goes on. The changed characteristics of fiber rope cause different mooring tension and vessel offset compared to the initial design condition. Commercial mooring analysis software that widely used in industries is unable to take into account this phenomenon automatically. Even though the American Petroleum Institute (API) or other classification rules present some standard or criteria with respect to length and stiffness of a mooring line, simulation guide considers the mechanical properties that is not mentioned in such rules. In this paper, the effect of creep phenomenon in the fiber rope mooring system under specific environment condition is investigated. Desiged mooring system for a Mobile Offshore Drilling Unit(MODU) with HMPE rope which has the highest creep is analyzed in a time domain in order to investigate the effects creep phenomenon to vessel offset and mooring tension. We have developed a new procedure to an analysis of mooring system reflecting the creep phenomenon and it is validated through a time domain simulation using non-linear mooring analysis software, OrcaFlex. The result shows that the creep phenomenon should be considered in analysis procedure because it affects the length and stiffness of synthetic fiber rope in case of high water temperature and permanent mooring system.

A creep–rupture model of synthetic fiber ropes for deepwater moorings based on thermodynamics

The synthetic fiber ropes such as polyester, aramid and high modulus polyethylene (HMPE) are increasing applied to deepwater mooring systems for oil and gas exploitation. Due to that mooring ropes generally bear tensions for a long period, synthetic fiber ropes that are composed of the viscoelastic material would present creep behaviors and even the creep rupture, which is the failure mode of greatest concern especially for HMPE ropes and on which still less study can be found. A creep damage analysis of synthetic fiber ropes is of necessity to ensure the safe and economic operation of mooring systems. Therefore further investigation on the creep–rupture behavior is beneficial to fully establishing confidence in the viability of synthetic fiber ropes for deepwater moorings. In the present study, a creep–rupture model is proposed within the framework of thermodynamics to investigate the creep and damage behaviors of synthetic fiber ropes. Methods for identifying the model parameters are also proposed in detail, which apply to any component of fiber ropes such as the fiber, yarn, strand and rope. Experimental data of aramid yarns available from the literature are utilized to validate the constitutive model. Creep and creep–rupture tests of HMPE strands at different loading levels are specially performed to further examine the present model. The present work demonstrates that the proposed model can effectively describe the viscoelastic property and damage evolution of synthetic fiber ropes at different loading levels.

Mechanical behaviour of HMPE and aramid fibre ropes for deep sea handling operations

This paper describes the mechanical behaviour of ropes used for deep sea oceanographic operations. First the requirements of deep sea handling ropes are presented. Two high performance fibres are commonly used, aramid co-polymer and high modulus polyethylene (HMPE), and these are then compared. Results from tests on single fibres and 50 ton break load braided ropes are presented, which show that the initial stiffness of a new HMPE rope increases with load level in a bedding-in process resulting from both molecular alignment and construction reorientation. The aramid rope is less sensitive to this effect and shows a high stiffness from first loading. Measurements made at sea on oceanographic ropes of both materials using an elastic recoil method are presented, and apparent modulus values are consistent with laboratory measurements. Once both ropes have been fully bedded-in the HMPE is significantly stiffer, particularly under dynamic loads. Creep tests indicate that aramids creep less quickly than HMPE under constant loads over a 6 h period at 20 °C. Bending over sheave tests indicate longer lifetimes for the aramid but further tests on wet aramid are required to complete this conclusion.

Modelling creep tests in HMPE fibres used in ultra-deep-sea mooring ropes

Due to its low density and high strength, HMPE (high modulus polyethylene) fibres are being increasingly used in synthetic ropes for offshore mooring. Nevertheless, the occurrence of creep at sea temperature can be a shortcoming for its practical use. Creep tests performed at different load levels in a sub-system of the HMPE rope (yarn) are frequently used as a first step to obtain some information about the susceptibility to creep deformation at a given temperature. The present paper is concerned with the phenomenological modelling of creep tests in HMPE yarns. In this macroscopic approach, besides the classical variables (stress, total strain), an additional scalar variable related with the damage induced by creep process is introduced. An evolution law is proposed for this damage variable. The predicted lifetimes and elongations of HMPE specimens in creep tests at different load levels and room temperature are compared with experimental results showing a good agreement.

Bending fatigue in high-strength fibre ropes

Bending fatigue tests on parallel lay (Parafil) ropes of the aramid fibre Kevlar 49, and helically laid ropes of Kevlar 29 and high-modulus polyethylene (HMPE) are reported. The Parafil ropes were subjected to three different regimes: free bending-tension tests intended to produce failures at the mouth of a termination, sheave bending through 45° under varying axial load, and sheave bending through 180° at constant axial load. The Kevlar 29 and HMPE ropes were tested over a 180° sheave. Full descriptions of the various procedures are given, and more than 20 separate results presented. Although the free bending-tension tests were intended to produce failures at the mouth of the termination, most failures occured elsewhere: one test was stopped after one million cycles. The 45° sheave bending tests produced lifetimes of about 4000 cycles when tested at up to 50% of the static breaking strengh. The 180° sheave bending test gave lives of 157 cycles at 25% of the static breaking load (SBL) for the Parafil ropes, and 100 to 400 cycles at about 40% SBL for the helically laid Kevlar 29 ropes. The HMPE rope gave nearly 6000 cycles at a load of 40% SBL.