HRSG Inspection Tasks. HRSG Inspection

Transcription

1 HRSG Inspection Tasks Presented By: Bryan F. Craig, P.E HRST Inc. 1 Goals: HRSG Inspection 1. Document condition of equipment 2. Identify items that need immediate maintenance 3. Identify items that need budgeting and planning for maintenance next year 4. Identify problems early, allowing time for scrutiny and analysis 5. Due diligence..show stakeholders you have proactive approach. 2 1

2 HRSG Inspection Key Elements 1. Dedicated inspectors 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 3 HRSG Inspection Gas Side Inspection Areas Access Lanes (inlet duct, firing duct, SCR, lanes between bt tube bundles, stack) Crawl spaces under and above tube headers Important to document locations clearly for future reference Best to prepare in advance, rather than identify problem locations on the fly 4 2

3 5 Inlet Duct Items:* 1. Liner System Gas Side Tasks Loose plates, spinning washers, exposed insulation, failed studs. 2. Flow distribution plates or vanes 3. Tubes & Fins corrosion, warping, vibration wear 4. Baffles & Tube Ties vibration damage, wear, expansion interferences, weld cracks. 6 3

4 Inlet Duct Liner Loose & broken components 7 Inlet Duct Liner Spinning Washers 8 4

5 Inlet Duct Liner Liner Gaps, Exposed Insulation 9 Flow Distribution Grid 10 5

6 Tube Ties Tube & fin wear at tube tie 11 Failed Tube Ties 12 6

7 Gas Side Tasks Firing Duct Checklist 1. Liner System (same as inlet duct, plus look for oxidized components) 2. Duct Burner: Sag in elements or baffles Nozzle plugging Coke buildup Burner wing condition 3. Tubes & Fins (same as inlet duct, plus) Evidence of flame impingement or local hotspots 4. Baffles & Supports 5. Location of firing duct thermocouples 13 Reheater upstream of duct burner 14 7

8 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

9 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. 17 Oxidized Liner Components 18 9

10 Local Burner Hotspots 19 Gas Side Tasks Tube Bundle Access Lane Checklist: 1. Liner System (same checks as inlet & firing ducts, problems less prevalent) 2. Tubes & Fins: corrosion, warping 3. Baffles & Supports (same as previous) 4. Catalyst Fouling Gas bypass around perimeter Packing between blocks 20 10

11 Tube & Fin Fouling 21 Tubes & Fins Tube Buckling Superheaters & Economizers 22 11

12 Tubes & Fins Cracking HPSH Tube 23 Gas Baffles Exhaust flow into page Sidewall Baffles Center (Laning) Baffles Upper Header Tubes Header (Bulkhead) Baffles Lower Header 24 12

13 Baffle Failures 25 Baffle Gaps Decrease Performance 26 13

14 Catalyst Fouling Catalyst Gas Bypass 28 14

15 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 7. Header corrosion 8. Tube/header joint condition (if visible) 29 Spray pattern is a leak indication 15

16 Fin scale debris on crawlspace floor Oxidized carbon steel debris on crawlspace floor 16

17 Accelerated corrosion near penetrations, probably caused by rain water leaking past penetration seal. Roof debris blocks drainage holes, trapping rainwater

18 Bulkhead Gas Bypass Hot Exh 35 Gap between baffle and floor is too large, allows gas bypass, decreasing performance

19 Bent Drains Indicate Stress 37 Exterior Tasks Exterior Inspection Checklist 1. Casing hotspots, cracks 2. Piping penetration seals 3. Access door condition 4. Foundations 38 19

20 Casing Access Doors Hot Spot 39 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

21 These bellow cracks were easy to see! However, it took some extra effort to climb up on the roof casing to inspect. 41 HRST Upgraded Pipe Penetration Seal PROBLEM: Tears in Fabric Cracks in Bellows Delay box SOLUTION: HRST Pipe Penetration Seals 42 21

22 Casing Stress & Cracks Expansion Stress Points (Typ) 43 Casing Stress & Cracks 22

23 Casing Crack Hotspots 23

24 HRSG Inspection Water/Steam Side Tasks Steam Drums are the only non intrusive access to the water/steam side in a modern HRSG. Drums are often also inspected by the water chemistry dept and insurance inspector. 47 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 5. Approximate waterline vs. drawing 6. Debris 48 24

25 Drum Surface Condition 1. Drum surface details (color, condition, pits) Color Red is good in an oxidizing environment Red is bad in a reducing environment Condition Keep track of surface defects from manufacture Track whether smoothness (roughness) is changing Pits Do you have them? What do they look like underneath? 49 Oxygen Attack in Steam Drum Offline 25

26 HP Drum Condition Surface defects in an HP drum from rolling steel NOT a significant issue 51 Signs of Distress 2. Signs of distress on steam separation 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 52 26

27 Cracks? Signs of Distress Baffle Cracks? 53 HP Belly Pan Cracks (or baffle plate) 54 27

28 Downcomer Indications 55 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) 56 28

29 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: shear wave, phased array

30 Cyclones worn through from FAC 59 Belly Pan Thinning UT in LP & IP Check here! 60 30

31 LP Belly Pan Hole (FAC) 61 Mechanical Integrity 4. Integrity of Internals Piping Broken U Bolts Missing nuts Plugged Chem Feed Lines Separators Failure Plugging Missing hardware 62 31

32 HP Fallen Chem Feed Line U bolt broke off 63 HP Drum Chem Feed Line 64 32

33 HP Drum broken cyclone attachment 65 Deltak Perforated Plate Above Mesh Separator 66 33

34 Deltak Mesh Separator Failure 67 Approximate Water Line vs. Drawing 5. Water Line Readings 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 68 34

35 LP water level 69 LP level transmitter proximity to pump suction 70 35

36 Debris in level tap Lower level tap magnetic debris 71 Debris in Drums 6. Debris bi Amount Color Magnetite vs. Hematite? Flakes vs. Powder? 72 36

37 Debris in drum 73 Summary Gas Side AccessLanes (inlet duct, firingduct, SCR, between tube bundles, stack) Crawl spaces under and above tube headers Exterior 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 74 37

38 HRSG Inspection Further Work Online or Hot Inspection HRSG inspection while unit is operating Ideal for finding hotspots, casing cracks, penetration seal failures 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. UT tubes and piping beyond spot checks (A Scan, Phased Array, or Shear Wave) 2. Dye Penetrant or Magnetic particle testing of suspect areas 3. Conventional and Digital X Ray (Radiography) 4. Eddy Current Testing 5. Piping Assessment 6. Hardness and Replication (P91) 7. Desuperheater removal & inspection 8. Borescoping 9. Tube samples 75 Any Questions? Bryan F. Craig, P.E HRST Inc. bcraig@hrstinc.com (office) (cell 76 38