Charlesworth, Chris, Eng.D. (2011) Ultrasonic phased array testing in the power generation industry : novel wedge development for the inspection of steam turbine blades roots. EngD thesis, University of Warwick.

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Abstract

The thesis presented herein comprises of the work undertaken to research novel methods
of Phased array ultrasonic inspection of complex steam turbine blade roots as found in the
power generation industry. The research was conducted as part of the Engineering Doctorate
scheme, administered by the Research Centre for Non-Destructive Evaluation (RCNDE), in
conjunction with RWE npower and the University of Warwick.
Steam turbine blades, and in particularly last stage blades of low pressure steam turbines,
are amongst the most highly stressed components on a power generating plant. Two of the
most common blade root fixing types include ‘curved axial entry fir tree roots’ (CAEFTR),
and axial pinned roots, both of which are prone to cracking due to the high stresses to which
they are subjected under operating conditions. Failure of the blade root fixings of such
components, leading to the release of the blades, has historically led to the catastrophic
failure and destruction of the whole turbine; the cost of collateral damage to plant
components and the loss in generating income are seconded only by the risk these failures
pose to life. Due to the high price of failure, NDT plays a critical part in the support and
management of engineering maintenance, offering insight into the condition and integrity of
turbine components through regular planned inspection regimes.
It will be shown in this thesis how the invention of a novel continuous wedge, used to
refract ultrasound into the critical regions of the blade roots, has significantly improved the
ability to detect defects. Combined with the development of bespoke scanning frames these
wedges facilitate the efficient and accurate acquisition of scanned data to assess the integrity
of the component. By combining the latest reverse engineering, modelling and simulation
tools with novel application of rapid prototyping, the author has been able to demonstrate
significant reduction in design cycles whilst improving accuracy, sensitivity and
repeatability of the applied inspections. Furthermore, application of this design philosophy
has led to the development of inspection techniques which have facilitated the inspection of
remote regions of the blade roots where manual access is limited or impossible.
The developments and techniques invented during this research have been successfully
deployed across numerous RWE npower and customer projects, leading to estimated savings
in excess of £1m.

Item Type:	Thesis or Dissertation (EngD)
Subjects:	T Technology > TJ Mechanical engineering and machinery
Library of Congress Subject Headings (LCSH):	Steam-turbines -- Blades -- Inspection, Steam-turbines -- Blades -- Defects
Official Date:	November 2011
Dates:	Date Event November 2011 Submitted
Institution:	University of Warwick
Theses Department:	School of Engineering
Thesis Type:	EngD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Bilson, Duncan ; Hutchins, David C.
Sponsors:	RWE npower (Firm)
Extent:	xx, 293 leaves : ill.
Language:	eng
URI:	http://wrap.warwick.ac.uk/id/eprint/49401

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