10a-Field Evaluation of Heaters Mod

Training Services

Troubleshooting Field Evaluation of Heaters

FH/10-1

Section Outline

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Process Considerations

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Data Collection

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Visual Visual Observations Observations - Combustion Combustion

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Visual Visual Observations Observations - Firebox Firebox

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Process Heat Balance

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Flue Gas Heat Balance

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Radiant Flux Rate

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Bridgewal Bridgewalll Temperatur Temperaturee Evaluation Evaluation

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Efficiency

FH/10-2

Data Collection- Control Room

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BWT- (Radiant (Radiant Flux Flux Rate) Rate)

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Stack Temperature-(Cold End Approach, Efficiency)

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Flue Gas O2- (Firing (Firing Quality, Quality, 2% minimum) minimum)

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Burner Pressure-(High Pressure=High Firing Rate)

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Process Flow Rate-(Over Design=High Duty)

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Process Delta Temperature-(Process Duty, Flux Rate)

FH/10-3

Typical Furnace Temperatures Stack Temperature 400°F400°F- 204 °C 

Flame Temperature –

Bridgewall Temperature 1450°F 1450°F - 788 788 °C Flame Temperature 3300°F 1816°C

HTR-R00-22

Depends on Fuel Composition



Radiant exit or Bridgewall Temperature

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Depends on Tube Temperatures and Heat Flux

FH/10-4

Bridgewall Temperature Evaluation 

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How hard is the heater operating? –

1400-1500 F (760-815 C is normal

–

1600-1650 F (871-900 C is approaching maximum limits

Fouling of tubes –

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Every 100º fouling raises the BWT 50º

It is rare to find heater problems with BWTs below 1300°F (705°C)

FH/10-5

Low BWT

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Dark Box

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BWT below 1300°F (705°C)

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Low Firing Rate

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Rare to find problems

FH/10-6

UOP Method Crude Heater 1700 1600

F , e r u1500 t a r e p m1400 e T l l a w1300 e g d i r B

°

1/16” Scale 1/32” Scale

Clean Tubes

1200 1100 5000

7000 9000 11000 13000 15000 Radiant Flux Rate, Btu/hr-ft 2 FH/10-7

HTR-R00-29

Typical Furnace Temperatures Stack Temperature 400°F- 204 °C

Bridgewall Temperature 1450°F - 788 °C

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Use the UOP fuels program to determine radiantconvection split

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Use the fuel meter to determine the heat release and radiant flux rate

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Compare actual BWT to predicted from the flux chart

Flame Temperature 3300°F 1816°C

HTR-R00-22

FH/10-8

Bridgewall Temperature Evaluation 



If actual BWT higher than predicted? –

Fouling of tubes (insideor outside)?

–

Flame height is too high?

–

Short Firebox Height?

–

Combustion Problems?

If actual BWT lower than predicted? –

Heater is performing very well

FH/10-9

Typical Furnace Temperatures Stack Temperature 400°F- 204 °C

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Use Cold End Approach=(Flue Gas OutProcess Inlet)

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Use convection charts to determine predicted cold end approach

Bridgewall Temperature 1450°F - 788 °C Flame Temperature 3300°F 1816°C

HTR-R00-22

FH/10-10

Cold End Approach 450 F Process Inlet - Fuel Oil - NPS 6 450 400

F , h350 c a o r p300 p A e r 250 u t a r e200 p m e T150 d n E100 d l o C 50

°

0

3” fins/inch, 0.75” high, 0.10” thick

0.4 lb/ft2-sec.

0.3 lb/ft2-sec.

0.2 lb/ft 2-sec.

6

7 8 9 10 11 Number of Tube Rows

12 FH/10-11

HTR-R00-53

Convection Tubes

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Sootblowing LaneHeater is in operation with gas temperature at 800°F (427°C)

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Light brown material is ash

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Ash reduces heat transfer and results in high cold end approach

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Grey tube areas are clean

FH/10-12

High BWT

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High Radiant Flux Rates

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High TWTs

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High Corrosion Rates

FH/10-13

High BWT 

Refractory Damage

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FCC Catalyst Fines Cover Tubes

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TWT is 200°F Hotter

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Higher Firing Rate

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Bright color indicates hot firebox

FH/10-14

Visual Observations - Firebox

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Coloring of Refractory and Tube Supports

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Appearance of Tubes –

Bowing

–

Scale

–

Hot Spots

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Appearance of Refractory

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Smoke from Stack

FH/10-15

Color in Relation to Temperature of Steel Temperature

Color

990°F

(532°C)

Black red, dark blood red

1050

(566)

Dark red, blood red, low red

1175

(635)

Dark cherry red

1375

(750)

Cherry red

1550

(850)

Light cherry, light red

1650

(900)

Orange

1725

(950)

Light orange

1825

(1000)

Yellow

1975

(1080)

Light yellow

2200

(1200)

White FH/10-16

Visual Observations - Combustion

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Color of Flame

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Evidence of Incomplete Combustion

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Flame Impingement

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Flame Shape and Stability

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Burner Air Register Settings

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Fuel Pressure

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Draft

FH/10-17

Color of Refractory 

Vertical Cylindrical Floor

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Bright Refractory Color

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Heater is Overfired

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Floor is normally 1200°1600°F (650°C-870°C)

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Actual Floor is 2000 F (1100°C)

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High Maintenance

FH/10-18


Hydrogen Reformer (Terrace Wall)




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Tube is 1697°F(925°C)

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Floor is 1790°F (977°C)

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Sidewall is 1840 °F (1005°C)

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One of the hottest heaters

FH/10-19


Hydrogen Reformer (Side Fired)




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Tube is 1770°F(966°C)

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Floor is 1890°F (1032°C)

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Sidewall is 1909 °F (1043°C)

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One of the hottest heaters

FH/10-20

Color of Tubes 

Hydrogen Reformer (DownFired)

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Hot Spots on Tube 1706-1742°F(930-950°C)

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Coke due to naphtha feed with poor steam/HC control

FH/10-21

Troubleshooting 

Tube Support Temperature indicates Gas temperature and Flux rate at that point

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Bright Refractory Color indicates low excess air(2% O2)



High excess air would have stiff blue flames and no refractory color

FH/10-22

Color of Tube Supports 

Look for hot spots and heat maldistribution on tube supports

Colder tubes near the floor

Hot tubes in the middle

FH/10-23

On-Line Inspection 

Tube Guide Temperature indicates Gas temperature and Flux rate at that point

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Colder Color at wall on guide

FH/10-24

Portable Instruments

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Infrared Pyrometer-(Minolta-Land Model 339)

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Portable O2 Analyzer( O2 and CO)

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UOP uses Testo Model 342-3 (O2 ,NOx, CO, Temperature)

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Temperature Probe

FH/10-25

Infrared Pyrometer 

Minolta-Land Model 339(Furnace Pro)

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Obtain Tube Surface Temperatures

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Obtain Firebox Temperatures

FH/10-26


Shock Tube Support Temperature indicates BWT (flue gas exit)

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Obtain Radiant Flux Rate

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Shot from side view port on Vertical Cylindrical Crude Heater

FH/10-27

Floor Viewports 

Floor Observation (6”) recommended on vertical tube heaters



Needed to view all tube surfaces

FH/10-28


Floor Observation (3”-75mm) Opening on Vertical Cylindrical Crude Heater

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Shoot roof refractory temperature, if no tube support available

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Obtain BWT and Flux Rate

FH/10-29


Oil fired Crude Heater tubes

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White tubes covered with ash were 1000°F

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Dark tubes were 1240 °F with 7-10 mm coke

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Very dark front face is where oil ash has melted due to high temperature

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Dark tubes are bowed

FH/10-30

Infrared Scan to Detect Hot Spot 

Monitor at least every 3 month

1111.8°F

SP01

1000 SP02: 942.7°F

800

600

538.7°F

FH/10-31

Infrared Scans Plot TWT , firebox temperature, feedrate

1400 1200 F ° 1000 e r u 800 t a r e 600 p m e 400 T

1325 1325 1290 1285 1285 1275 1225 1165 1230 1300 1280 1150 1250 1250 1250 1150 1175 1150 1180 1225 1220 1225 1220 1210 1200 1275 1185 1190 1300 1 270 1270 1150 1270 1 225 1135 1110 1110 1185 10101075 1080 1120 11201090 951950 950950925925925 900900900 825847 800851850 810 800761800 750 675 650

FIREBOX MAX TUBE

./

R/A CHG. (BPH)

200 0 0 0 / 6 / 1 1

1 0 / 7 / 5

1 0 / 6 2 / 7

2 0 / 5 1 / 4

2 0 / 9 / 0 1

2 0 / 1 1 / 0 1

m p 2 0 / 4 1 / 0 1

2 0 / 6 1 / 0 1

2 0 / 8 2 / 0 1

3 0 / 9 / 1

3 0 / 7 1 / 7

Date of Scan

F-1 Furnace FH/10-32

On-line Inspection

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Flames Are Too Long

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Flame Height Should be 50% of Firebox Height

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High BWT

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Hot Roof Supports

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Poor Revamp

FH/10-33

Tube Supports 

API 560



Increasing temp. From 1500F to 1600F decreases strength 31%

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Increasing temp. From 1600F to 1700F decreases strength 41%

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Older heaters usually designed for 1600F

FH/10-34

Damaged Shock Tube Support Severe creep and yielding of pin and support Small web thickness 5/8” (13 mm) Need 19-25mm web Sigma phase embrittlement of 25Cr-12Ni Material

FH/10-35

Tube Supports 

Unifrax Fiberfrax LDS Moldable Ceramic Fiber



Air Hardens



Protects Tube Supports

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Good for Oil Firing Protection



Sacrificial Coating



Phone 716-278-3800



Fax 716-278-3900

FH/10-36

Tube Support Inspection

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Broken Supports

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Bowing or Yielding

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Cracks

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Oxidation

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Corrosion

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Replication Test (normally not performed)

FH/10-37

Broken Tubesheet Crack in tubesheet Is support binding on refractory ?

FH/10-38

Combustion Monitoring

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Flue Gas O2 ›2-4%on Gas Firing



Operating Excess Air = 12%-26%



New Unit Design = 15%



Flue Gas O2 ›4-6%on Oil Firing



Operating Excess Air = 26%-44%

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New Unit Design = 25%

FH/10-39

Combustion Monitoring

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Low O2 = Bad Combustion



Afterburning

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Flame Impingment

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Tube Failures

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Refractory Damage

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Tube Support Failures

FH/10-40

Burner Problems 

Poor Oil Flame



Burners Need Air



Oil Haze impinging on roof tubes



Unburned Fuel burning in convection section



Burned off extended surface

FH/10-41


Brickwall- Improper interlaced expansion joint

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Brickwall- expansion joint gaps are too small



High Maintenance problems

FH/10-42


Brickwall- Improper interlaced expansion joint



Marked for removal at 10° Lean

FH/10-43

Troubleshooting 

Platforming Heater- 9 Cr tubes



Heavy Scale



Increased fuel firing



Yellow scale 1750 F



Average surface 1350 F

FH/10-44

UOP Method Platforming Double Fired U Tube Heater 2000 1900 F , e r 1800 u t a r e p1700 m e T l l 1500 a w e g d 1600 i r B

°

1/16” Scale 1/32” Scale Clean Tubes

1400 1300 10000 14000 18000 22000 26000 Radiant Flux Rate, Btu/h-ft 2

HTR-R00-32

FH/10-45

Troubleshooting



Use walnut shells to blast loose scale off tubes on line



Reduced fuel firing



Only recommended for loose scale



Cetek does this service

FH/10-46

Establish Work Scope of Turnaround

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On-line Inspection

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Operational Data



Past Inspection Reports



Code or Jurisdictional Requirements



Projected Service

FH/10-47

Troubleshooting 

Most Heater Accidents Occur During Lightoff



15-20 Minute Purge



Test for Combustibles?



Good Operating Instructions



Burner Management Systems

FH/10-48

10a-Field Evaluation of Heaters Mod

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