Most information required to undertake an investigation or design evaluation is maintained in-house (such as material fatigue properties), or readily available from the operating records (history of hours and starts, flow conditions, load ramp rates).
Basic information needed to start:
Additional information :
TTI has routinely relied on drawings, component samples or electronic scans to start an investigative or design evaluation. Para-solid files (.et) are preferred. In cooperative situations, confidentiality agreements with the manufacturers can be arranged to gain access to a description of the necessary geometry.
Inlet/Outlet Flow Parameters
A heat balance diagram is normally sufficient to identify the overall inlet and exit flow rates, pressures and temperatures, which are used to calculate the stage-to-stage flows and bending forces around the blades of interest. Diagrams for partial load conditions are sought if the unit follows load frequently.
Depending on the objective of the project, the following additional information can be used to strengthen and check the validity of the analysis.
In cases where cracking or failure has occurred the results of a metallurgical analysis are sought which established the type of material, whether it met code and features of fatigue, corrosion etc. found on the fracture surface.
Rotor and/or Flow Path Geometry
An electronic file (CAD or scanned) of a blade geometry is preferred along with a blade count of the row and reasonably detailed cross section of the rotor/disc. The outer tip diameter of the assembled wheel is used as a check of the FE model. For any CFD analysis, a longitudinal diagram and count of the upstream guides are requested.
To independently process BVM data, measurements of tip displacements are sought, with particular attention to peak responses obtained during start-up or during load changes.
TTI is used to working with operators who may have limited information at their disposal.
A summary of starts and operating hours is sought from when the component went into service to when damage was discovered. These records are used to correlate against the stress-based predictions of crack initiation and propagation. For load following units, examples of the daily load swings and their frequency are requested.