1. Refractory failure analysis
-K.P.PRADEEP KUMAR

2. Refractory failure at
Tip casting area

3. Castable should be heated
very carefully to control the
steam presure
ACW 1&2 - Picture before bursting

4. Castable bursted due to
un controlled steam pressure ,
11 hr after initial heat-up
(ACW)

5. Castable bursted due to
uncontrolled steam pressure . This
was due to 1) rapid heating as the
flame was much shorter . Pilot
burner- oil flame was close to the
outlet and the castable.
2) Oil spilled on the castable and
caused local heating.
Castable bursted
at nose ring area
ACW 1 & 2
It is observed that only castable
blocks at the bottom half got
damaged more.

6. Castable failure at the tip casting area at ACW
Causes:
(at the time of heating up kiln ,after major lining)
• too short oil flame close to the castable caused
uncontrolled steam pressure resulted in bursting of castable.
• oil spillage on the castable caused local heating
Remedies
• Elongate the flame and push the burner farther inside the kiln so
that radiation Is reduced on the castable.
• Spread clinker nodules on the refractories from tip to 10 M length
• Changed over to andalusite based castable.

7. APCW
cracks begin , after one month
Operation at the junction of two
monolithic blocks

8. This crack formation is due to
Inadequate expansion joint after
two months of kiln operation. There
is no wear but observed cracks on the
Surface and deep cracks at the junction
Of two castings.
APCW

9. Castable failure after 4 months operation
due to inadequate expansion joint and
Thermal shocks
APCW

10. Castable failure due to
Inadequate expansion joint causes
deep crack formation and spalling
after 4 months of operation.
APCW
Deep penetration of clinker liquid
Into the brick.

11. One monolithic casting has crossed
to the other casting and the blocks expanded
taking the casting along with, which
ended in spalling.There should be
a clear expansion joint of 10 mm between
the blocks.
APCW

12. Remedies
• Tip casting plates( with male and female joint) have been modified to
straight blocks .
• Castable was changed from andalusite based to
Corundum based to withstand abrasion.
• Expansion gap was increased from 5 mm 15 mm with ceramic
boards
Refractory failure on the tip casting at APCW
Causes
• Thermal shocks
• Cracking due to inadequate expansion joint . ( expansion joint closed
during vibration) Very often it is observed that the expansion gap
between the castings are filled with Castable.

13. This L –joint
will not allow
to give expansion
joint properlly
( overlapping due
to male
and female joint
Before modification

14. This straight expansion joint
allows proper expansion.
After
modification

15. Castable on the modified blocks APCW
Expansion joint is straight in the
Modified castings.

16. Tip casting blocks are not in line
This V-joint will make make the brick
ring mis aligned. The suppliers engrave the
letters on the castings on the collar which makes point contact
with the bricks. It can be engraved on the on the hot face side.
Dimension tolerance must not deviate from limit specified by OEM.
AC kiln

17. Tip casting
Retainer ring
a
b
c
d
e
a
b
c
d
e
Tip casting Retainer ring
A=b=c=d=e and so on a,<b =c < d=> e
Installation of castings at the kiln tip area.
Casting’s periphery at its base side must be in line.

18. .
.
Nose ring Blocks
Suppliers must be advised not to engrave the letters on the base
and the collar where bricks have contact with castings.
Letters can be engraved on the hot face of
the castings
Bolts must never be
protruded .This acts
like a pivot and castings
will not have contact with
the bricks. Casting must
have machined surface
and the blurs must be
ground to get fine surface
on the castings..

19. Engraved letters and blurs can create
point contact between the bricks and the
castings which will pinch the brick surface
and causes refractory failure at the tip.
Ensure 100 % contact between
The brick and the castings
Nose ring castings

20. Engraved letters and blurs can create
point contact between the bricks and the
castings which will pinch the brick surface
and causes refractory failure at the tip.
Ensure 100 % contact between
The brick and the castings
Nose ring castings

21. HA-70 bricks twisted at 47 m
Castings got oxidised
as well as corroded
V-joint gap due to bell mouth
Or casting got sunk. If casting
face is not smooth it can create
this gap. This need a machined
Surface. Point contact is not
acceptable. Letters engraved on the
face can also create gap because
of point contact.
AC

22. Bell mouth formation at
Kiln outlet
AC
Casting are oxidised too
After 3 months of operation
Thinned down to almost half.

23. This V gap formation is due to
bell mouth formation.
AC

24. AC
Bricks got crushed
The bricks on the retainer
ring were pushed by
20 – 30 mm. That time
the kiln had severe
Upset run. Huge variation
in chemistry , due to
Low silo level and flux
variation due to wetness
of red ochre.

25. 0 –1.2 M area
The bricks are crushed
Due to excessive thrust.
Bell mouth formation is also there.
VC-3 Kiln

26. The castings are oxidized as well as corroded
after 3 months of operation. When we fire pet coke Nickel/ chromium Ratio needs
change .Also found that there is wear though the hard face welding is done. High
Efficiency cooler increases the secondary temperature and may burn the castings .
The dust erosion and clinker falling on the Castings can also increase the wear .Nose
ring cooling must be enhanced. Cooling air volume =400 Cum/min , and velocity
of air at nozzle t >45 M/s and the no.of nozzles , minimum is 6.
RC-3 Kiln

27. The gap created must be due to bell
mouth Formation or nose ring castings
got sunk because of intolerable heat.
Nose ring cooling must be enhanced
RC3 Kiln

28. Out let blocks are cracked
Due to over heating after the
Installation of high efficiency
Static grates cooler.
GS Kiln

29. Now the hot face is covered by
Castble.The life has increased to
more than one year.
GS Kiln

30. Nose ring cooling
For kiln Dia < 4.0 M,
cooling air volume 400 cum/min
For kiln dia > 4.0 M,
cooling air volume 500 cu m/ min
Nozzle velocity = 40 – 45 m/s
Minimum no.of nozzles =6
< 1.5 M

31. 0 –2.2 M
VC-3 Kiln
2 nd row after tip casting
Unstable coating due to high sulfur recycle variation
Low alumina modulus. High liquid forms the coating upto
the tip. Sufur volatile factor some times reach > 3.5 and
Varied from 2 to 3.5.Petcoke sulfur exceeds 7.5%.

32. Refractory failures at the tip casting
in AC and VC
Causes
• bell mouth formation
• Casting loose their mechanical stability due to corrosion and
oxidised
• Insufficient cooling of nose ring
• Frequent ring formation and doslodgement at the tip and
consequent thermal shocks
• High liquid content and variation in clinker liquid quality due to
variation in sulfur cycle.Often it crossed > 3.0 .
Remedies
• change the outlet shell
• Improve the nose ring cooling air volume and cooling nozzle velocity
• Control the chemistry and sulfur cycle.
• Nickel / Chromium has to be adjusted as Nickel is vulnerable to sulfur
attack and chromium to alkali attack.

33. This is due to bell mouth formation.
Even the spinel bricks had failed. Mortar
application is must to have more flexibility.
VC-3 Kiln

34. 0 –2.0 M
Bricks on the retainer ring
got crushed
VC-3 Kiln

35. Even the bricks on the retainer ring
got shifted due to excessive axial thrust
Sudden increase in temperature on brick surface
Due to coating collapse. kiln had severe upset run
When this failure occurred.
AC kiln

36. Refractory failure at retainer ring area in AC and VC.
Causes
• instability of coating in this area due to change in chemistry and variation in sulfur
cycle because of petcoke firing
• Excessive axial thrust due to higher vrpm
• Flame needs tuning
• Rhino horn formation on burner tip distorts the flame.
Remedies
• Variation in chemistry needs control
• Higher grade spinel bricks will improve the life
• flame should be shaped to short , convergent and hot flame.
• Install shock blasters to dislodge the Rhino horn on the burner tip.

37. 30 % of the brick is penetrated .
Aggressive liquid attack on brick ( 33 % liquid in
clinker)
These cracks show that the bricks
undergone severe thermo-mechanical
Stresses.
APCW
Location : 1st row after tip casting block.
The gap between the castings is much higher
than the OEM specifications.

38. Deep penetration of liquid into the bricks
Theses crack show that there is severe stresses on
the bricks Thermo-mechanical as well as thermo chemical
( bell mouth formation and aggressive liquid attack on the brick)
APCW

39. Refractory failure at kiln outlet – APCW
Causes;
• Too high liquid % which penetrate deep into even the spinel bricks and
degenerate spinels and destruct the bricks. Coating is also unstable
• Bell mouth formation causes thermo-mechanical stresses
• Casting are not in line as their dimensions have deviation than the
tolerance limits than specified by OEM.
• axial thrust
Remedies
• Optimize the liquid to reduce coating
• Castings must have tolerance limit as recommended by OEM
• Change the outlet cone shell to straight shell to reduce the axial thrust with
• installation of conical retainer rings of Magattoux.

40. GCW
Even the spinel bricks had been
Impenetrated by aggressive liquid
Degenerate the spinels . The bricks
losses Its strength.

41. GCW

42. GCW

43. GCW

44. GCW

45. Hasle D-59 A castable
Bricks are twisted
and crushed due to
high axial thrust
GCW-1
If bricks are attacked by
aggressive liquid they are
vulnerable to any stresses

46. Failed area
adjacent to retainer ring
GCW-1

47. Shell surface is rough
We have to apply mortar
Underneath the bricks .to have
full contact with the shell
and cold face of the brick.
GCW-1

48. GCW-1
The spinel bricks are crushed
and destructed

49. up to half of the brick thickness is
attacked by aggressive liquid attack.
GCW-1

50. Deep melt infiltration inside
The brick. The bricks had undergone
Very high thermo- chemical
And thermo mechanical load.
Almost 50 % brick is attacked by liquid
Which can destroy the ingrediants of the
brick . This is a hercynite Spinel brick , Ankral Z1.
GCW-1

51. Huge cracks show
the bricks undergone
Severer thermo-mechanical
stresses. The Thermochemical attack
on the bricks make more vulnerable
for thermo-mechanical stresses
GCW

52. Refractory failure at kiln outlet – GCW
Remedies
• High grade spinel bricks which only increases the life by giving
resistance to aggressive liquid attack. Variation in quartz has to be
reduced.
• Replacement of conical shell to straight shell to reduce axial thrust.
Conical retainer ring is the second option to arrest the thrust.
• Live ring migration at first tyre must not be more than
12mm/revolution.Proper shimming has to be done accordingly.
• Surge hopper has to be installed to collect the bag house dust to reduce
chemistry variation in kiln feed.
Causes
Very high burning zone temperature due to presence of quartz and to maintain
free lime < 1.1 %. The liquid has less viscosity and penetrate the bricks deep.
changes in chemistry when raw meal stops , variation in kiln feed LSF by 2-4
Flame gets distorted often due to rhino-horn formation on burner tip
very high variation in I tyre migration due to coating instability , ie 0 mm to 30 mm

53. Refractory failure at
retainer ring area - APCW
and GCW kiln

54. APCW Bricks got crushed at the
retainer ring

55. Bricks at the retainer ring got
Crushed due to excessive axial
thrust. Very high thermo-chemical
Stresses on the bricks. Liquid
had deep penetration and destructed
the spinels and The texture.of the bricks.

56. Crushing of the bricks
APCW

57. Bricks crushed at the
Retainer ring

58. Refractory failure at kiln outlet and near
the retainer ring – APCW and GCW.
Reasons
Frequent coating failure due chemistry variation
Too high liquid % in clinker ie.,33%
Flame and reduced conditions
Severe thermal shocks due to coating dislodgement which takes away
part of the bricks.
Remedies
Optimise the liquid
Change over to high grade spinel bricks like Almag AF or Ankral R1
Due to dusty conditions flame gets disturbed and reduced conditions
prevail . This causes the coating very unstable and causing thermal
Shocks.

59. Too many retainer rings are unneceassry
They act like stiffeners and when kiln shell gets
Heated up this will, shear the shell . 75 mm thick
Retainer ring is tougher than kiln shell. Therer are
4 rows of Magattoux retainer rings from 1.2 – 1.8 Meter ,
double retainer ring at 1 M
and Single retainer ring.at 0.4 M
Shell is warped at many places

60. Bricks are under stress
Alumina bricks is a not good selection
The conical retainer ring are meant for
Spinel bricks
HCW

61. Bricks have cracks
Shows that bricks are under
Thermo mechanical stress.
First row bricks are totally crushed
and washed out. The castable also
got dislodged as the brick ring moved
and created axial thrust on the castable
too. The second and other rings
moved forward by 45 mm.

62. Shell crack axial

63. Retainer ring surface is wavy
Retainer ring is burnt.

64. Shell crack ,
Retainer ring crack

65. Shell crack
crack on
retainer
Conical retainer ring of
RHI & Magattoux
Surface is wavy

66. Castable casted on
the tipcasting face ,done
at site
First retainer ring warped. This makes the
bricks twisting .

67. As the shell is having wavy surface the conical retainer ring
donot have contact surface with bricks and hence bricks
need cutting at the bottom by 12- 18 mm in many places and
mortar application underneath the bricks to fill up the gaps.
Mortar application is done at radial joints too.

68. After conical rings no extra
retainer ring is needed

69. Refractory failure at retainer ring area HCW
Remedies
Damaged outlet shell is to be replaced by new shell
Spinel bricks will be used on the conical retainer ring instead of High
alumina bricks to have better locking and arching which avoids shifting.
Retainer ring must have smooth surface and have the same curvature
of kiln.
After conical retainer ring no retainer ring is needed as recommended
by refractory suppliers
Causes
wrong selection of bricks
too may retainer rings
shell surface is wavy and warped also.
conical retainer rings are not fixed properly as it is observed that it falls at
12 O’ clock position while rotating the kiln

70. Thanks a lot
PRADEEP KUMAR