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EP-4739910-A1 - INSPECTION OF BOLTED CONNECTIONS IN A WIND TURBINE

EP4739910A1EP 4739910 A1EP4739910 A1EP 4739910A1EP-4739910-A1

Abstract

A method and system for scheduling inspection of a bolted connection on a wind turbine, the bolted connection comprising a bolt under tension. At a first sample time, a first tension parameter of the bolt is determined, having an associated upper uncertainty bound, and, at a second sample time, a second tension parameter of the bolt is determined, having an associated lower uncertainty bound. Thereafter, a linear relationship is determined based on the upper uncertainty bound of the first tension parameter and the lower uncertainty bound of the second tension parameter. Based on that linear relationship, a third sample time is determined in the future, at which a further tension parameter is determined. Based on the third sample time, an inspection event is scheduled. A benefit of the invention is that inspection events are scheduled in an adaptive manner in a way that is responsive to the difference in values of those measurements, but which takes account of the inherent uncertainty in such measurements without compromising safety. In this way, inspection events can be scheduled less frequently that is currently the case which presents a much- reduced maintenance cost which still ensuring the integrity of the bolted connection.

Inventors

  • ÖSTERBERG, David
  • LIMA CARNEIRO CAVALEIRO, Pedro Manuel

Assignees

  • VESTAS WIND SYSTEMS A/S

Dates

Publication Date
20260513
Application Date
20240702

Claims (18)

  1. 1. A method for scheduling inspection of a bolted connection (32) on a wind turbine, the bolted connection comprising a bolt under tension, the method comprising: at a first sample time (T1), determining (104) a first tension parameter (P1) of the bolt, having an associated upper uncertainty bound (P1 U), at a second sample time (T2), determining (106) a second tension parameter (P2) of the bolt, having an associated lower uncertainty bound (P2L), determining (110) a linear relationship (R1) based on the upper uncertainty bound (P1 U) of the first tension parameter (P1) and the lower uncertainty bound (P2L) of the second tension parameter (P2), and, based on the linear relationship (R1), determining (112) a third sample time (T3) in the future for determining a further tension parameter (P3); and scheduling (112) an inspection event based on the determined third sample time.
  2. 2. The method of Claim 1 , wherein: if the time interval between the first sample time (T1) and the second sample time (T2) is less than a predetermined minimum time interval, adjusting (109) the second sample time (T2) to match or exceed the minimum sample interval.
  3. 3. The method of Claim 1 , wherein: if the time interval between the first sample time (T1) and the second sample time (T2) is less than a predetermined minimum time interval, identifying one or more previously measured tension parameters to take into account in the determination of the linear relationship (R1).
  4. 4. The method of any one of Claims 1 to 3 wherein: determining (112) the third sample time (T3) includes identifying the time point at which the extrapolation falls below a minimum bolt tension threshold (MAP).
  5. 5. The method of any one of the preceding claims, wherein: the step of determining (104) the first tension parameter (P1) of the bolt and/or the step of determining (106) the second tension parameter (P2) are conducted using an ultrasonic measurement system (42).
  6. 6. The method of any one of the preceding claims, wherein: if the second tension parameter (P2), and optionally the lower uncertainty bound (P2L) thereof, is greater than the first tension parameter (P1) and, optionally, the upper uncertainty bound (P1 U) thereof, then it is identified that the second tension parameter (P2) is an invalid value.
  7. 7. The method of Claim 6, wherein in the event that the second tension parameter is identified as an invalid value, the method further comprises re-determining the second tension parameter at a later date.
  8. 8. The method of any one of the preceding claims, wherein step of determining (110) the linear relationship determining (R1) based on the upper uncertainty bound (P1 U) of the first tension parameter (P1) and the lower uncertainty bound (P2L) of the second tension parameter (P2) includes applying a linear regression technique.
  9. 9. The method of any one of the preceding claims, wherein the linear relationship is based on the first tension parameter (P1), the second tension parameter (P2) and one or more further tension parameters.
  10. 10. The method of any one of the preceding claims, wherein the determined first tension parameter (P1) and the determined second tension parameter (P2) are recorded in a computerised data store (44).
  11. 11. The method of Claim 10, wherein in recording the first and second tension parameters (P1 ,P2) said parameters are communicated to the data store (44) over a telecommunications network (52).
  12. 12. The method of Claim 10 or Claim 11 , wherein the steps of: determining a linear relationship (R1) based on the upper uncertainty bound (P1 U) of the first tension parameter (P1) and the lower uncertainty bound (P2L) of the second tension parameter (P2), based on the linear relationship (R1), determining (112) a third sample time (T3) for determining a further tension parameter (P3); and scheduling (112) an inspection event based on the determined third sample time (T3), are performed by a computerised planning system (46) that retrieves the determined first tension parameter (P1) and the determined second tension parameter (P2) from the data store (44) over a telecommunications network (52).
  13. 13. The method of any one of the preceding claims, wherein the step of scheduling (112) an inspection event includes recording the inspection event in a computerised planning system (46).
  14. 14. The method of any one of the preceding claims, further comprising outputting the scheduled inspection event to a computerised user-device (62).
  15. 15. A system for scheduling inspection of a bolted connection (32) on a wind turbine, the bolted connection comprising a bolt under tension; the system comprising a measurement system (42) configured to: to determine (104), at a first sample time (T1), a first tension parameter (P1) of the bolt, having an associated upper uncertainty bound (P1 U), and to determine (106), at a second sample time (T2), a second tension parameter (P2) of the bolt, having an associated lower uncertainty bound (P2L), the system further comprising a computerised planning system (46) configured to: determine (110) a linear relationship (R1) based on the upper uncertainty bound (P1 U) of the first tension parameter (P1) and the lower uncertainty bound (P2L) of the second tension parameter (P2), based on the linear relationship (R1), determine (112) a third sample time (T3) in the future for determining a further tension parameter; and schedule (112) an inspection event based on the determined third sample time (T3).
  16. 16. The system of Claim 15, wherein the measurement system (42) comprises an ultrasonic probe (60) adapted to measure the tension in the bolted connection (32).
  17. 17. The system of Claims 15 or 16, wherein the computerised planning system (46) is adapted to communicate with the measurement system (42) over a telecommunications network (52).
  18. 18. The system of Claim 17, wherein the measurement system (42) and the computerised planning system (46) are adapted to communicate with a data store (44) over the telecommunications network.

Description

INSPECTION OF BOLTED CONNECTIONS IN A WIND TURBINE Technical Field This disclosure relates to systems, apparatus and methods adapted to schedule inspections of bolted connections in wind turbines. Background Wind turbines are complex structures that require regular maintenance and inspection to ensure their safe and efficient operation. One critical aspect of wind turbine maintenance is the inspection and maintenance of bolted connections which are used to join various components of the wind turbine together. For example, typically bolted connections are used at the flanged interface between a foundation of a wind turbine and the lowermost tower section in order to provide a secure connection of the wind turbine to the foundation. Bolted connections also feature in the connection between a hub and the blades of a wind turbine, and also at the interface between tubular tower sections of the wind turbine. Such connection arrangements are known to the skilled person. To achieve a high-strength connection, it is known to pre-stress each bolt in the bolted connection. This may be achieved by using a machine to elongate the bolt. This technique achieves a particularly strong bolted connection which may be suitable in bolted connections between the foundation and the wind turbine tower, for example, n It is also known that bolted connections can ‘relax’ over time due to settling in mating surfaces, material creep, and turning back of nuts, in the event nuts are used, which reduces the tension in the bolted connection. For this reason, organizations responsible for maintaining wind turbine installations implement set schedules for checking the tension of bolted connections to ensure that the connection is sound. If one of more bolts in the bolted connection is found to be out of tension tolerance, action can be taken to retension that bolt to ensure the performance of the bolted connection. This is typically done by re-applying the tension using the same type of tools as used in installation. Tension checking of bolted connections is a time consuming and physically demanding maintenance task, particularly when considering the number of bolted connections in a single wind turbine and factoring in the number of wind turbines in a typical wind farm, which may number in the tens to the hundreds. One known approach is to provide indicia or markings on bolted connections so that visual inspection can reveal whether nuts have moved relative to the bolt which will reduce tension in the bolt. A wrench can be used to re-torque the bolt. However, the rotational position of the nut does not accurately reflect the tension within the bolt. An approach proposed by EP3040701 is to use an ultrasonic system to test tension in bolted connections, whereby the system is a permanent installation for ongoing monitoring. However, such a system could be very costly, and may be prone to failures, thereby requiring further diagnostic action. Furthermore, ultrasonic measurement systems are subject to uncertainty in their measurements. A solution to reduce the maintenance burden of bolted connections in wind turbine installation is therefore desirable. It is against this background that the invention has been devised. Summary of the Invention According to a first aspect of the invention, there is provided a method for scheduling inspection of a bolted connection on a wind turbine, the bolted connection comprising a bolt under tension. The method comprises at a first sample time, determining a first tension parameter of the bolt, having an associated upper uncertainty bound, and, at a second sample time, determining a second tension parameter of the bolt, having an associated lower uncertainty bound. Thereafter, a linear relationship is determined based on the upper uncertainty bound of the first tension parameter and the lower uncertainty bound of the second tension parameter. Based on that linear relationship, a third sample time in the future is determined, at which a further tension parameter is determined. Based on the third sample time, an inspection event is scheduled. A benefit of the invention is that inspection events are scheduled in an adaptive manner in a way that is responsive to the difference in values of those tension measurements but which takes account of the inherent uncertainty in such measurements without compromising safety. In this way, inspection events can be scheduled less frequently than is currently the case which presents a much-reduced maintenance cost while still ensuring the performance of the bolted connection. The tension parameters in the above context may be a direct measurement or may be a statistical quantity calculated from a plurality of measurements. The sample times as referred to above may also be expressed as calendar dates at which the tension parameters are determined/measured. The invention extends to and therefore also embraces a system for scheduling inspection of a bolted connection on a wi