Bidaut, Yves

Muller, Ch.

Texas A&amp;M Repository

Blade Failure on an Axial Compressor Caused by Unexpected Operating at Choke Y. Bidaut & Ch. Müller - MAN Diesel & Turbo Schweiz AG Contents 1 Background 2 Description of the machine 3 Findings 4 Root Cause Failure Analysis (RCFA) 5 Actions 6 Conclusion 2 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 Background 3 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  Two parallel trains consisting of axial air compressors driven by steam turbines  Application: blast furnace  In operation since more than forty years (trouble free)  Recently : shutdown (planed) of one train with inspection of the compressor.  After three months of operation break-down of this compressor.  Blades damaged  RCFA performed:  Reasons of the damage  Countermeasures  Description of the machine 4 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  Axial compressor, 19 stages  gas handled : wet air  ps= 1.0 bara  pd= 5.5 bara  V = 450,000 Nm3/h  P = 40.7 MW  noperation = 3,200 rpm   nmin        = 2,856 rpm (89%)   nmax       = 3,360 rpm (105%) 1 Background 2 Description of the machine 3 Findings 4 Root Cause Failure Analysis (RCFA) 5 Actions 6 Conclusion 5 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 Findings 6 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  Rotor: Major damages on stages 16 to 19 Findings 7 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  Stator:  Major damages on stages 16 to 19   minor damages on blade carrier & lever system 1 Background 2 Description of the machine 3 Findings 4 Root Cause Failure Analysis (RCFA) 5 Actions 6 Conclusion 8 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 Root Cause Failure Analysis 9 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  In order to clear up the compressor break down cause,  following investigations were performed: on-site inspection RCFA  laboratory analysis  timeline and operation data evaluations aerodynamic investigations Root Cause Failure Analysis - Overview 10 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 Blade bushes  Manufacturing report  Blade Machining  Geometry of blades Foreign object   Operation below choke line/stall  !  Metallurgical Investigation  Material Properties Vibration Trends   Response line Campbell diagram Gas bending  stress (normal operation)  Low flow operation  Blade natural frequency          Design clearances Normal operation   Adjusting cylinder Rotating stall  Hardness test Fatigue fracture  Raster lines ?! Surge Protect°      Coating report Coating Coating  Corroded / Eroded blades Alignment review Start / stop      References  Material suitable for actual conditions     Field Service works    7. Site Layout Process layout  Layout changes    Instrument arrangemt    3. Blade design 2. Manufacturing & Assembly 1. Site & Work- shop Inspection Corrosion  4. Material Inspection 5. Compressor Controls 6. Operation  Assembly report Blade Failure   Surge   no contribution  ?! possible contribution ! important contribution Perform. control   Set Point changes  Compressor envelope ?!  Cracks in other Blades Axial displacemt    silencer incident !                                 RCFA – Laboratory analysis 11 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  Blades failed/fractured  in stage 18 & 19 (blades of stage 18 failed by material fatigue)  Fracture initiation and propagation always on/from the back-side of the blades (transition area airfoil-blade root)  RCFA – Laboratory analysis 12 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  Deposits with corrosive potential  In all deposits,       remarkable sulphur and      chloride - enrichments in      various concentrations.   Deposits contain dilutable      elements         corrosion of blade material          (with moisture)  Local corrosion reduces material fatigue        resistance        corrosion fatigue caused by cracks with            simultaneous influence of mechanical               alternating load and of attacking medium. RCFA – Timeline Evaluation, Operation Data Analysis 13 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 February: completion of compressor installation  (new blading installed) May : termination of commissioning July 11th : silencer failure July 31st : compressor breakdown ASV Operation data during  compressor breakdown RCFA – Operation Data Evaluation 14 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 May – June :    operation at   chokepoint 1     for several hundred     hours     standstill of   compressor  Reason : warm-up of compressor RCFA – Operation Data Evaluation 15 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 ASV silencer  July 11th  :  silencer failure  RCFA – Operation Data Evaluation 16 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 discharge pressure 4.2 barg 0.2 barg Silencer failure leads to a sudden pressure drop and a resulting negative pressure wave hits the compressor blading.  RCFA – Operation Data Evaluation 17 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 Result of silencer failure:    operation at  chokepoint 2  for approx. 8 hours     (cumulative) from  June 12th until   July 31st Choke Point 2     - 100% Speed (1.5h)  - Increasing of backpressure (1s)  - Opening of IGV (4 min)      -  Silencer incident   - Dropping of backpressure to 0.2 barg RCFA – Aerodynamic Investigations 18 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 choke operation: explanation actual inlet volume flow actual discharge volume flow static inlet pressure static discharge pressure 1 bara 140 m3/s 4 bara 1.2 bara 120 m3/s 50 m3/s exemplary values only (qualitative) pressure volume flow RCFA – Aerodynamic Investigations 19 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 choke operation: explanation R17                    S17                R18                 S18          R19               S19  specific flow conditions (stall), which can stimulate the natural frequencies of the blades RCFA – Aerodynamic Investigations 20 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 choke operation: first bending mode (B1)  RCFA – Aerodynamic Investigations 21 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 airfoil cross section with highest bending moment choke operation: first bending mode (B1)  RCFA – Breakdown causes 22 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  long standstill / operation @ warmup speed 1  punctual corrosion  - reduction of material  fatigue resistance  - fracture starting points failure of silencer choke operation High dynamic blade loading with excitation of B1-mode during choke   fractures in rotor blades #18 switching compressor to BF increase of blade load blade overload #18 blade failure #18 DOD #16 - 19 1 Background 2 Description of the machine 3 Findings 4 Root Cause Analysis (RCFA) 5 Actions 6 Conclusion 23 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 RCFA – Countermeasures 24 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 In order to avoid any further compressor breakdown due to above mentioned reasons, 3 countermeasures were implemented: 1. realization of a choke control system (see next slide) RCFA – Countermeasures 25 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 ISO-Valve 1. realization of a choke control system: Choke line Alarm line RCFA – Countermeasures 26 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 2. improved resistance against overload and fatigue fractures with modified rotor blade design 3. avoidance of corrosion attacks by application of an inorganic aluminum coating with chromate/phosphate inert sealant (rotor blades only) 1 Background 2 Description of the machine 3 Findings 4 Root Cause Analysis (RCFA) 5 Actions 6 Conclusion 27 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014 Conclusion 28 < > Y. Bidaut / Ch. Müller METS III – Case Study – Blade Failure 01.12.2014  The encountered case was the consequence of the     concatenation of many factors:  Choke operation o  High load on blades  Corrosion   Not only the surge but also the operation in (deep) choke is      an issue for the reliability of an axial compressor   To prevent any future damage appropriate countermeasures     are necessary:  Choke control system o  Increased blade thickness  Application of coating All data provided in this document is non-binding.  This data serves informational purposes only and is especially not guaranteed in any way. Depending on the subsequent specific individual projects, the relevant data may be subject  to changes and will be assessed and determined individually for each project. This will depend on the particular characteristics of each individual project, especially specific site and operational conditions. Disclaimer Thank you very much  for your attention  Questions ? 

Blade Failure on an Axial Compressor Caused by Unexpected Operating at Choke

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Blade Failure on an Axial Compressor Caused by Unexpected Operating at Choke

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Texas A&M Repository

Blade Failure on an Axial Compressor Caused by Unexpected Operating at Choke

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Texas A&amp;M Repository

Texas A&M Repository