HRSG Inspection Tasks
Presented By: Bryan F. Craig, P.E HRST Inc.
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HRSG Inspection Goals: 1. Document condition of equipment 2. Identify items that need immediate maintenance 3. Identify items that need budgeting and planning for maintenance next year yp y, g 4. Identify problems early, allowing time for scrutiny and analysis 5. Due diligence…..show stakeholders you have proactive approach. 8/10/2009 Columbus, OH
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HRSG Inspection Key Elements 1. Dedicated inspectors •
Good inspections take days not hours! Good inspections take days not hours!
2. Recording observations (facts) •
Photos, measurements, notes
3. Organize facts logically •
Every fact should be accurately linked to a specific location.
4. Measurements at critical areas •
Thickness (UT), Gap distance, crack length
5. Three location types • • •
Gas Path Steam/Water Side Exterior
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HRSG Inspection Gas‐Side Inspection Areas
• Access Lanes (inlet duct, firing duct, SCR, l lanes between tube bundles, stack) b t t b b dl t k) • Crawl spaces under and above tube headers • Important to document locations clearly for future reference future reference • Best to prepare in advance, rather than identify problem locations “on the fly” 8/10/2009 Columbus, OH
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Gas‐Side Tasks Inlet Duct Items:* 1 Liner System 1. Liner System –
Loose plates, spinning washers, exposed insulation, failed studs.
2. Flow distribution plates or vanes 3. Tubes & Fins –
corrosion warping vibration wear corrosion, warping, vibration wear
4. Baffles & Tube Ties –
vibration damage, wear, expansion interferences, weld cracks.
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Inlet Duct Liner Loose & broken components
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Inlet Duct Liner Spinning Washers
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Inlet Duct Liner Liner Gaps, Exposed Insulation
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Flow Distribution Grid
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Tube Ties
Tube & fin wear at tube tie
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Failed Tube Ties
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Gas‐Side Tasks Firing Duct Checklist 1. Liner System (same as inlet duct, plus look for oxidized components) p ) 2. Duct Burner: – – – –
3.
Tubes & Fins (same as inlet duct, plus) –
4. 5.
Sag in elements or baffles Nozzle plugging Coke buildup Burner “wing” condition Evidence of flame impingement or local hotspots Evidence of flame impingement or local hotspots
Baffles & Supports Location of firing duct thermocouples
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Reheater upstream of duct burner 8/10/2009 Columbus, OH
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Burner Baffle Failures Coen baffle weld seam cracks & failures
Coen fix for baffle weld seam cracks & failures. May not be enough, some cracking still being found. 8/10/2009 Columbus, OH
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Carbon Buildup
Carbon inside gas pipe. Build up has fractured the gas pipe.
Coking: Usually due to olefins in refinery gas. Sometimes coking occurs with natural gas due to poor air/fuel mixing at burner. 8/10/2009 Columbus, OH
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Oxidized Liner Components
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Local Burner Hotspots
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Gas‐Side Tasks Tube Bundle Access Lane Checklist: 1. Liner System (same checks as inlet & firing y ( g ducts, problems less prevalent) 2. Tubes & Fins: corrosion, warping 3. Baffles & Supports (same as previous) 4. Catalyst – Foulingg – Gas bypass around perimeter – Packing between blocks
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Tube & Fin Fouling
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Tubes & Fins Tube Buckling – Superheaters & Economizers
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Tubes & Fins Cracking – HPSH Tube
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Gas Baffles
Exhaust flow into page
Sidewall Baffles Upper Header Center (Laning) Baffles
Tubes
Lower Header Header (Bulkhead) Baffles
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Baffle Failures
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Baffle Gaps Decrease Performance
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Catalyst Fouling
Catalyst Gas Bypass
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Gas‐Side Tasks Crawl Space Checklist: 1. Water from tube leaks? 2. Floor debris 3. Liner condition 4. Liner fit‐up around piping and hanger penetrations 5. Baffles 6 Bent piping 6. Bent piping 7. Header corrosion 8. Tube/header joint condition (if visible)
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Spray pattern is a leak indication
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Fin scale debris on crawlspace floor
Oxidized carbon steel debris on crawlspace floor
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Accelerated corrosion near penetrations, probably caused by rain water leaking past penetration seal. 8/10/2009 Columbus, OH
Roof debris blocks drainage holes, trapping rainwater.
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Bulkhead Gas Bypass
Hot Exh
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Gap between baffle and floor is too large, allows gas bypass, decreasing performance.
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Bent Drains Indicate Stress
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Exterior Tasks Exterior Inspection Checklist Exterior Inspection Checklist 1. Casing hotspots, cracks 2. Piping penetration seals 3. Access door condition 4 Foundations 4.
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Casing Access Doors – Hot Spot
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Penetration Seals
Bellows cracks can be difficult to see. Tight cracks, bellows are compressed when off line. Look for hot spots, and nearby insulation “fur.” 8/10/2009 Columbus, OH
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These bellow cracks were easy to see! However, it took some extra effort to climb up on the roof casing to inspect. 8/10/2009 Columbus, OH
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HRST Upgraded Pipe Penetration Seal
PROBLEM: T Tears in i Fabric F bi Cracks in Bellows Delay box
SOLUTION: HRST Pipe Penetration Seals
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Casing Stress & Cracks
Expansion
Stress Points (Typ) 8/10/2009 Columbus, OH
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Casing Stress & Cracks
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Casing Crack
Hotspots
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HRSG Inspection Water/Steam‐Side Tasks
Steam Drums are the only non‐intrusive access y to the water/steam side in a modern HRSG. Drums are often also inspected by the water chemistry dept and insurance inspector.
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Water/Steam‐Side Inspection Tasks Steam Drum Checklist 1. Drum surface condition 2. Signs of distress on steam separation equipment & belly pan 3. Thickness of belly plates and steam separators 4. Mechanical Integrity g y 5. Approximate waterline vs. drawing 6. Debris 8/10/2009 Columbus, OH
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Drum Surface Condition 1. Drum surface details (color, condition, pits) –
Color – –
–
Condition – –
–
Red is good in an oxidizing environment Red is bad in a reducing environment Keep track of surface defects from manufacture Track whether smoothness (roughness) is changing
Pits Pits – –
Do you have them? What do they look like underneath?
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Oxygen Attack in Steam Drum ‐ Offline
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HP Drum Condition
Surface defects in an HP drum from rolling steel NOT a significant issue 8/10/2009 Columbus, OH AEP / BRO Forum
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Signs of Distress 2. Signs of distress on steam separation equipment & belly pan equipment & belly pan – – – –
Cracks in the belly pan Cracks in the final separator corners Weld seams in the shell and shell to head Downcomer indications
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Signs of Distress Cracks?
Baffle Cracks?
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HP – Belly Pan Cracks (or baffle plate)
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Downcomer Indications
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Thickness of Belly Pans and Steam Separation Equipment 3. UT test –
F/W, Deltak, Vogt, NEM, Aalborg, Alstom, etc – Belly Pans – Cyclones (F/W = horizontal, others = vertical)
–
N/E and Cerrey – Belly Pans (no cyclones)
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Ultrasonic Thickness Measurements – – – –
Thickness measurements are a useful tool to document condition of drum internals, tubes and , piping. Be specific about locations & documentation Most measurements are simple thickness for general documentation or to track Flow Accelerated Corrosion More sophisticated UT used for crack detection: h d df kd shear wave, phased array
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Cyclones worn through from FAC
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Belly Pan Thinning – UT in LP & IP Check here!
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LP Belly Pan Hole (FAC)
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Mechanical Integrity 4. Integrity of Internals i f l –
Piping – Broken ‘U’ Bolts – Missing nuts – Plugged Chem Feed Lines
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Separators – Failure – Plugging – Missing hardware
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HP – Fallen Chem Feed Line
U bolt broke off
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HP Drum – Chem Feed Line
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HP Drum – broken cyclone attachment
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Deltak – Perforated Plate Above Mesh Separator
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Deltak ‐ Mesh Separator Failure
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Approximate Water Line vs. Drawing 5. Water Line Readings i di – The water line is often falsely reading low due to – proximity of the downcomer or pump suction to the level transmitters. The suction effect of those large lines ‘pulls’ on the level sensing lines. – Plugging of the lines is problematic if they are positioned off the bottom of the shell. – The number one cause of faulty level indication or control is calibration or compensation 8/10/2009 Columbus, OH
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LP – water level
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LP – level transmitter proximity to pump suction
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Debris in level tap
Lower level tap magnetic debris 8/10/2009 Columbus, OH
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Debris in Drums 6 Debris 6. bi – – – –
Amount Color Magnetite vs. Hematite? Flakes vs. Powder?
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Debris in drum
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Summary •
Gas Side – –
•
Exterior – – – –
•
Access Lanes (inlet duct, firing duct, SCR, between tube Access Lanes (inlet duct, firing duct, SCR, between tube bundles, stack) Crawl spaces under and above tube headers Casing hotspots, cracks Piping penetration seals Access door condition Foundations
Steam/Water Side –
Steam Drums are the only non‐intrusive access to the water/steam side in most HRSGs
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HRSG Inspection Further Work • Online or “Hot” Inspection – HRSG inspection while unit is operating – Ideal for finding hotspots, casing cracks, penetration seal failures g p , g ,p – Can check hot position of spring hangers
• “Extended Scope” offline inspection – Depending on the age, quantity & severity of cycles and history of issues, more intrusive inspection techniques may be best to quantify condition. – Common techniques: 1. 2. 3. 4. 5. 6. 7. 8. 9.
UT tubes and piping beyond spot checks (A Scan, Phased Array, or Shear Wave) Dye Penetrant or Magnetic particle testing of suspect areas Conventional and Digital X‐Ray (Radiography) Eddy Current Testing Piping Assessment Hardness and Replication (P91) Desuperheater removal & inspection Borescoping Tube samples
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Any Questions? Bryan F. Craig, P.E HRST Inc.
[email protected] 813‐855‐4688 (office) 612‐743‐1009 (cell
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