Reffailue nosering pradeep kumar

Refractory failure at
nose ring and cooling zone
of kiln
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uncontrollable
axial thrust due
uneven expansion
etc
Shell warpage
or ovality
bell mouth
formation
( mechanical
stresses)
Wear on refractory due to
incorrect selection and
wrong installation
In- correct design
of retainer rings or
wrong location
In adequate
space for
expansion
Causes for refractory failure
Thermo-chemical
stresses and thermo
mechanical stresses
Burning of
castings
Failure of
castables

Axial thrust and inadequate expansion
Axial thrust is always there on the nose ring refractories . This is due
to the inclination of kiln and the expansion of bricks. If refractories
cannot withstand they crumble.Though FLS kilns have outlet cone
to arrest the thrust in some of the kilns the thrust is still on the nos ering
area.
The thrust, due to expansion, can be compensated only giving
extra expansion at the nose ring area.ie between the bricks from nose ring
base to retainer ring. If we install bricks in a following way it will reduce the
thrust. Some plants placed SS shim on the retainer ring in between two rings of
bricks . RHI recommends this method.
4 mm ceramic board on the casting
this is applicable to brick lining too
when it is used on tip casting
2 mm SS shim on retainer ring
10 to 30 mm
ceramic pads
2 mm expansion card board
For alumina bricks no expansion
To be filled with castable.

Castings burn away now a days, after kiln up gradation and cooler
up gradation, because of high secondary temperature, velocity and
clinker dust entrainment. If we give castable lining on the hot face
side of castings we can increase the life of the castings. Most of the
plants face this problems with brick lining on nose ring..
castable
2 mm expansion
cardboard joints
4mm ceramic board5 mm ceramic board
on the retainer
ring
Very important is nose ring velocity per nozzle is > 60 m/ s
and it should be focused on the casting block not on the kiln shell.
Nose ring cooling can be enhanced by intensifying the cooling air jet.
Less tip casting casting life
2 mm Ceramic
boards

to arrest the axial thrust due to extra expansion with ceramic
fiber boards can be given.
4mm ceramic fiber boards
( which can withstand
1200 deg c) on the casting
5 mm ceramic board
on the retainer ring
2 mm card board
Anchors are of SS310 steal grade with correct spacing

Axial thrust
1000 mm
198mm198198198178
The brick which is under maximum thrust
and stress
300L230230230
If we increase the length it may
withstand some more thrust.
Tip shall be always
curve shaped

Nose ring cooling air = 70 m / s
Well directed to cool the blocks
5mm ceramic fiber board
Latest tip casting

Nose ring cooling air is directed on kiln shell
the air is preheated and will not cool the castings
- incorrect practice

Wear on refractory due to incorrect
selection and installation
Refractories are to be selected to suit the operational
and process conditions . LC castables on Andalusite
based castables are suitable.Corundum based castables
are good wear resistant but they are easily attacked by
free lime and excessive liquid.They are very sensitive to steam
formation. Magnesia spinel bricks can take more thermo-
Mechanical and thermo-chemical stresses at the
nose ring area. Proper expansion is a must to reduce spalling
due to expansion. The function of ceramic board is to
accommodate the thrust coming from expansion.

Lack of expansion
causes spalling
GCW

Inadequate expansion
between two monolithic blocks
causes this spalling GCW

Crack formation
after one month
operation.This is
due to inadequate
expansion
APCW

Castable dislodged from the shell
due to wrong installation .Inadequate
expansion joints caused spalling.The
life is only 3 months
Initial cracks
after 1 month
of operation
APCW

In sufficient expansion
joint at the junction of
two blocks. Minimum
5 mm expansion joint
Is necessary
APCW

Expansion not given
properly
Spalling has started
after one month’s operation
APCW

Dense surface
due to more compaction due to
excessive vibration which does not
allow the steam escape.
(ACW)

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

Castable bursts due to
uncontrolled steam pressure . This
is due to 1) rapid heating as the
flame is much shorter 2) too much
vibration hence the fines got
segregated and close the capillaries
3) absence of organic fibers which
burns out to form capillaries 4) It is
corundum based castable , needs
more water addition and hence very
sensitive to the above mentioned
reasons. 5) Absence of
deflocculants reduce the workability
and needs more vibration than
needed. Ageing can reduce the
effectiveness of deflocculants.
Steam explosion

Mechanical stresses
on the refractories

Shear cracks due to excessive
thrust on bricks adjacent to tip casting

Liquid infiltration into the brick
and damage the bricks.This thermo-chemical
and the consequent thermo-mechanical stresses
destruct the texture of the bricks, even the
high quality spinel bricks

bricks bricks adjacent to
tipcasting under gone severe
thermal stresses The horizontal
Cracks are quite visible
Stresses on spinel bricks

Pinch at
retainer rings
Phenomena
collapse of brick rings
against retainer rings and
outlet segments from
pinch spalling
Symptoms
Horizontal cuts and crack
of bricks at the upper edge
of retainer and
transposing nose ring
segments
Reasons
• Thrust and oscillations
generate shear cracks and
grinding
• Flexing kin or ovality
accelerate the damage
Improvements
Stiff kiln shell
no nose shaped bricks
Use double retainer rings
or conical retainer rings..

Stresses on the bricks at and on the retainer ring

Crushing of bricks near the ring area
Shear cracks on the bricks adjacent to retainer ring
due to excessive axial thrust
Retainer ring

Bricks crushed, twisted and sheared at the retainer ring
by excessive axial thrust

Even the tip casting blocks got uprooted
due to excessive thrust. Tip of the shell is totally damaged.
Excessive thrust on the tip

The old type retainer ring is unable to arrest the thrust.
thrust

Excessive thrust at the junction of the cone and
cylinder in a FLS kiln(APCW). Even the cone fails to reduce
the thrust. The bricks are Spinel bricks.

Excessive thrust shear the bricks
even the top -grade spinel grade.
The bricks before the retainer ring got lifted.
Application of adequate mortar is a must for
brick lining at the nose ring area.
APCW)

Bricks got uprooted
at retainer ring
(APCW)

Bottom half of the
Bricks are missing.
They got ground due
to excessive friction
Bricks must have
full contact with
retainer ring
Mortar is a must to
overcome ovality
and bell mouth.

Retainer rings
The reasons for creating hotspots are as follows :
1. All magnesia – containing bricks tend , because of their
expansion ranging from 1.6 to 1.8 % ,to expand in the
direction of kiln inlet when the kiln is actually heated up.
In these conditions the brick rings situated beneath the
retainer ring are already pushed into or in some cases
over the retainer ring and are thus damaged.
2. If some coating is slowly built up in the sintering zone ,
the temperature of the brickwork decreases leading to
re expansion during which the retainer rings have to
compensate the forces from the brickwork of the whole
sintering zone
3. Bricks must have full contact with retainer ring .Other wise
the bricks undergo severe stresses and get crushed.

Here the v –joint created is due to either the blocks are over heated
and so the collar got distorted or; the collar does not have smooth surface
and so the brick does not have full face contact which makes the brick
slant.Another strong reason is shell tip has bell mouth. The brick
ring before the retainer ring got lifted from the shell by 30 to 40 mm
At the retainer ring the bricks are crushed as most of the
bricks did not have full face contact with retainer ring because of
welding seams. This has to be ground to smooth surface..
In many areas retainer ring was
exposed
1200 mm
Nose ring area at AC
Almag -85 Almag AF

HA-70 bricks twisted at 47 m
Castings got oxidised
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.
Bricks adjacent
to retainer ring
got crushed
AC

Welding joints
This welding joint will not allow the brick to have
full face contact and the brick undergoes stresses under
dynamic conditions ,gets twisted and crumbled. This needs
grinding to smooth surface to have 100% contact.Almag AF is
highest class spinel brick which too failed in this area.
This point has highly
concentrated stress.Retainer ring
thrust Crack propagation
AC

Retainer ring
thrust
After grinding the brick has full contact with the retainer ring.
Kiln shell

1200 mm
Recommended lining for tip casting
and at retainer ring ( AC)
High grade spinel brick
300 mm L Almag –85 or
Almag AF
High grade spinel brick with 300mm L is also recommended
to achieve better life.
Normal spinel brick CCS(cold crushing strength) = 400 Kgs / sq cm
high grade spinel brick = 700 Kgs/ sq cm

Modification of retainer ring
Increase the
hollow space to have
more welded surface
Here the welding joint
can be avoided or
the welding can be
ground to
smooth surface
Hollow
space to weld
retainer ring
to the kiln shell
and filled with
castable
Retainer ring should have a full contact with the brick
In correct
correct

Nose ring block, designed by PSB
for spinel brick lining
Please note that the bricks
have full contact with face
Of the casting.

PSB ‘S design
Please note that the bricks
have full contact with face
Of the casting.

SIFCA
It is an excellant
Compromise between
metallic alloy
and refractories
It is as tough as
metal and as wear
and heat resistant as
refractories.

This kind of cowl shell of PSB design will provide
effective cooling
PSB ‘S design

RHI design – Tip casting

The surface
is coated by
Tungsten
carbide
Tip casting designed by Brok-Hausen
Castable

FLS design
Out let sectors
The nose is lined with
low cement castable
which protects the
castings from heat
and clinker dust
abrasion

Here the castings get oxidised
due to high secondary air temperature
And hence it needs extra cooling.
Refratecknik design

Retainer ring -Refratechnik

RHI lining with FLS tip casting

RHI design – Tip casting
Abrasion
Resistant castable

Nose ring – Harbison walker

Refratecknik ‘s lining recommendation for a FLS kiln

Conical retainer rings to reduce the thrust on the
bricks designed by Magattoux and RHI

Conical retainer ring

Double retainer ring
Some plants use two retainer rings but it has not reduced
axial thrust.

1.6 m
10 mm ceramic blanket
on the cone which is not
Correct . It should be on the
cylinder
This is a high stress zone as there is
point contact
The lining at the junction of the cone and cylinder
FLS kilns(GCW)
198 mm
2 mm expansion joint
198 mm
Please note that the diamond bricks should never cross
the cone either way as it creates a v-joint

30 mm
Recommended for better thrust relief
168 mm
198 mm 198 mm
For this the end brick needs cutting
ie., reduction in L from 198 to 168 mm.
To avoid cutting of bricks the
retainer ring can also be shifted by
30 mm. The exp.joint is on the cylinder.
There should be face contact not point contact

1.0 m
0.97 m
30 mm
Ceramic board
Recommended expansion joint
5 mm ceramic board
300 mm 300mm 198mm 172
Ceramic board placed on the retainer ring

400 mm
1200mm
267 mm
933 mm
Anchors are
staggered. As per
the chart the spacing
is 217 mm. As the width
is only 400 mm
it is not possible to fix
the anchors with 217 mm
spacing . We can have
170mm or 160 mm
spacing and
see the anchor head
does not cross the other
anchor nor of
the other block. Anchors
are to be coated by
bitumen or wax
170 mm
170 mm
5mmCeramic board
as expansion joint.
Anchor spacing for casting at nose ring area

Maximum anchor spacing
Anchor diamter (mm)
Lining thickness (mm)
6 φ 8 φ 10 φ 13 φ
75
100
125
150
200
250
300
354 472 590 767
306 409 511 664
274 365 457 594
250 334 417 542
217 289 361 470
194 258 323 420
177 236 295 383

Straight expansion
joints

Nose ring casting
Note the expansion joint is straight
and distinct. No over lapping

Castable at nose ring
Please note
that expansion joints are distinct and
straight

Nose ring casting by Hasle

Pre cast nose ring
blocks

Clear expansion joints expansion
must be be distinctly visible after
casting at nose ring area

Pre cast blocks
fixed on retainer rings

Lining at retainer
ring area

Reffailue nosering pradeep kumar

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