Lifetime Calculation of Irregularly Oscillating Bearings in Offshore Winches

Abstract

The fatigue lifetime calculation of rolling bearings has been intensively researched in the past and has been well documented in standards. The majority of the conducted research in the field of bearing life expectancy only applies to bearings under continuously rotating conditions as can be found in many technical systems, such as vehicle transmissions. However, there are many other technical applications in which bearings perform oscillating motions, for which the fatigue life calculation is currently not standardized. For such oscillatory behaviour, there exist several modifications for the standardized lifetime calculation. The available modification approaches, however, assume purely sinusoidal oscillations. Thus, irregular non-sinusoidal oscillations require approximation with a simple sinusoidal oscillation to comply with the available approaches, which can lead to a loss of information. In this paper, a numerical calculation approach to modify the lifetime calculation for oscillating bearings underlying irregularly reversing speeds and varying loads is presented. The lifetime calculation results of this approach are compared to results of existing calculation approaches for fatigue life calculation of oscillating bearings. For this, the approaches are applied on simple sinusoidal speeds and loads. Subsequently, results of all calculation approaches are shown for irregularly varying speeds and loads, using the example of the drivetrain of an offshore crane winch with Active Heave Compensation (AHC). The calculation results indicate, that available lifetime modification approaches for oscillating bearings seem to overestimate the lifetime for irregularly oscillating conditions.

Wind Turbine Drivetrain Reliability and Wind Plant Operations and Maintenance Research and Development Opportunities

“…Because pitch bearings are not under constant rotation, ISO/TS 16281 is used as a design specification and requires detailed simulations of the bearing to be sufficiently precise. Other life calculation methods have been proposed for oscillatory applications (Houpert 1999;Wöll, Jacobs, and Kramer 2018), including guidance to prevent fretting corrosion and false brinelling.…”

Impact of fiber versus steel ropes on the lifetime of crane winches

“…Drivetrain Winch Figure 4: Simplified schematic of winch drum and drivetrain analysed (Wll et al, 2017b) 3) The component stresses of each component in the winch gearbox are classified using a counting method suited for oscillating bearings, developed by Wll et al (2018). The load spectra produced by these counting methods are then compared to the bearable loads of the bearings in the gearbox calculated using (DIN ISO 281) for bearing fatigue, and the bearable loads of the gears in the gearbox calculated using (DIN 3390) for tooth strength and pitting resistance.…”

“…In recent times, attempts have been made to replace (Wll et al, 2018) conventional heavy steel ropes in crane winches with high-strength fibre ropes made of high-strength synthetic fibres such as aramid fibres (HMPA), aramid/carbon fibre mixtures or high-modulus polyethylene fibres (HMPE) (Baldinger et al, 2018). Fibre ropes are believed to be able to unlock the full lifting potential of a crane winch, because they are virtually weightless when submerged in water and therefore no matter how much rope is paid out, this does not add any significant extra load to the crane winch and so larger payloads can be lifted at large depths than what was possible with steel ropes.…”

“…The lifetime calculation is based on the methodology outlined in (Neumann et al, 2016) and utilises a code suited specifically to calculate the lifetime of components in a gearbox typically used in crane winches with a 150 tons lifting capacity, being able to calculate the lifetime of oscillating bearings in the gearbox, as described in (Wll et al, 2018). Since taking the effect of rope dynamics and different rope materials into account in the lifetime calculation of a crane winch is something that has not been done yet, this paper addresses this area in order to provide more clarity about the effects of replacing steel ropes with fibre ropes.…”

Effect of wind speed distribution and site assessment on pitch bearing loads and life

“…The bearing fatigue life calculation is documented in the National Renewable Energy Laboratory design guideline (DG03) [12]. Despite the existence of other work done by Woll et al [13] or Breslau et al [14] to calculate the slewing bearing fatigue life, the DG03 calculation process is referred in standards [15]. A wind turbine and its components are designed based on standards, such as IEC 61400 [7].…”