HRSG Inspection Basic Tasks

1

HRSG Inspection Tasks

Presented By:Bryan F. Craig, P.EHRST Inc.

AEP / BRO Forum8/10/2009 Columbus, OH 1

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

4. Identify problems early, allowing time for y p y, gscrutiny and analysis

5. Due diligence…..show stakeholders you have proactive approach.


2

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

• ExteriorAEP / BRO Forum8/10/2009 Columbus, OH 3

HRSG InspectionGas‐Side Inspection Areas

• Access Lanes (inlet duct, firing duct, SCR, l b t t b b dl t k)lanes between tube bundles, stack)

• Crawl spaces under and above tube headers

• Important to document locations clearly for future referencefuture reference

• Best to prepare in advance, rather than identify problem locations “on the fly”


3


Gas‐Side Tasks

Inlet Duct Items:*

1 Liner System1. 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.


4

Inlet Duct LinerLoose & broken components


Inlet Duct LinerSpinning Washers


5

Inlet Duct LinerLiner Gaps, Exposed Insulation


Flow Distribution Grid


6

Tube Ties

Tube & fin wearTube & fin wear at tube tie


Failed Tube Ties


7

Gas‐Side Tasks

Firing Duct Checklist1. Liner System (same as inlet duct, plus look for oxidized

components)p )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 hotspotsEvidence of flame impingement or local hotspots

4. Baffles & Supports5. Location of firing duct thermocouples


Reheater upstream of duct burner


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

Coking: Usually due to olefins in refinery gas. Sometimes coking occurs with natural gas due to poor air/fuel mixing at burner.

gas pipe.


Oxidized Liner Components


10

Local Burner Hotspots


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, warping3. Baffles & Supports (same as previous)4. Catalyst

– Foulingg– Gas bypass around perimeter– Packing between blocks


11

Tube & Fin Fouling


Tubes & FinsTube Buckling – Superheaters & Economizers


12

Tubes & FinsCracking – HPSH Tube


Gas Baffles Exhaust flow into page

Sidewall Baffles

Tubes

Upper Header

Sidewall Baffles

Center (Laning) Baffles

Lower Header

Header (Bulkhead)

Baffles


13

Baffle Failures


Baffle Gaps Decrease Performance


14

Catalyst Fouling

Catalyst Gas Bypass


15

Gas‐Side Tasks

Crawl Space Checklist:1. Water from tube leaks?2. Floor debris3. Liner condition4. Liner fit‐up around piping and hanger

penetrations5. Baffles6 Bent piping6. Bent piping7. Header corrosion8. Tube/header joint condition (if visible)


Spray pattern is a leak indication

16

Fin scale debris on crawlspace floor

Oxidized carbon steel debris on crawlspace floor

17

Roof debris blocks drainage holes, trapping rainwater.

Accelerated corrosion near penetrations, probably caused by rain water leaking past penetration seal.


18

Bulkhead Gas Bypass

HotExh


Gap between baffle and floor is too large, allows

gas bypass, decreasing

performance.


19

Bent Drains Indicate Stress


Exterior Tasks

Exterior Inspection ChecklistExterior Inspection Checklist

1. Casing hotspots, cracks

2. Piping penetration seals

3. Access door condition

4 Foundations4. Foundations


20

CasingAccess Doors – Hot Spot


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.


PROBLEM:

T i F b i

HRST Upgraded Pipe Penetration Seal

Tears in Fabric

Cracks in Bellows

SOLUTION:

Delay box

SOLUTION:

HRST Pipe Penetration Seals


22

Casing Stress & Cracks

Expansion

Stress Points (Typ)


Casing Stress & Cracks

23

Casing Crack

Hotspots

24

HRSG InspectionWater/Steam‐Side Tasks

Steam Drums are the only non‐intrusive access yto the water/steam side in a modern HRSG.

Drums are often also inspected by the water chemistry dept and insurance inspector.


Water/Steam‐Side Inspection Tasks

Steam Drum Checklist1. Drum surface condition2. Signs of distress on steam separation

equipment & belly pan3. Thickness of belly plates and steam

separators4. Mechanical Integrityg y5. Approximate waterline vs. drawing6. Debris


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

– PitsPits – Do you have them?

– What do they look like underneath?


Oxygen Attack in Steam Drum ‐Offline

26

HP Drum Condition

Surface defects in an HP drum from rolling steel NOT a significant issue


Signs of Distress

2. Signs of distress on steam separation equipment & belly panequipment & belly pan

– Cracks in the belly pan

– Cracks in the final separator corners

– Weld seams in the shell and shell to head

– Downcomer indications


27

Cracks?

Signs of Distress

Baffle Cracks?


HP – Belly Pan Cracks (or baffle plate)


28

Downcomer Indications


Thickness of Belly Pans and Steam Separation Equipment

33. 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)


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

h d d f k d– More sophisticated UT used for crack detection: shear wave, phased array



30

Cyclones worn through from FAC


Belly Pan Thinning –UT in LP & IP

Check here!


31

LP Belly Pan Hole (FAC)


Mechanical Integrity

i f l4. Integrity of Internals

– Piping– Broken ‘U’ Bolts

– Missing nuts

– Plugged Chem Feed Lines

– Separators– Failure

– Plugging

– Missing hardware


32

HP – Fallen Chem Feed Line

U bolt broke off


HP Drum – Chem Feed Line


33

HP Drum – broken cyclone attachment


Deltak – Perforated Plate Above Mesh Separator


34

Deltak ‐Mesh Separator Failure


Approximate Water Line vs. Drawing

i di5. 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


35

LP – water level


LP – level transmitter proximity to pump suction


36

Debris in level tap

Lower level tap magnetic debris


Debris in Drums

6 b i6. Debris

– Amount

– Color

– Magnetite vs. Hematite?

– Flakes vs. Powder?


37

Debris in drum


• Gas Side – Access Lanes (inlet duct, firing duct, SCR, between tube

Summary

Access Lanes (inlet duct, firing duct, SCR, between tube bundles, stack)

– Crawl spaces under and above tube headers

• Exterior– Casing hotspots, cracks– Piping penetration seals– Access door condition– Foundations– Foundations

• Steam/Water Side– Steam Drums are the only non‐intrusive access to the

water/steam side in most HRSGs


38

HRSG InspectionFurther Work

• Online or “Hot” Inspection– HRSG inspection while unit is operating– Ideal for finding hotspots, casing cracks, penetration seal failuresg 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. UT tubes and piping beyond spot checks (A Scan, Phased Array, or Shear Wave)2. Dye Penetrant or Magnetic particle testing of suspect areas3. Conventional and Digital X‐Ray (Radiography)4. Eddy Current Testing5. Piping Assessment6. Hardness and Replication (P91)7. Desuperheater removal & inspection8. Borescoping9. Tube samples


Any Questions?

Bryan F. Craig, P.EHRST [email protected]‐855‐4688 (office)612‐743‐1009 (cell


Documents

HRSG Inspection Basic Tasks