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Calculate the shim thickness for kiln tires? (Engr.Tarique)

Cold gap calculation:

If historical temperature information is available long term averages of shell to tire temperature

differences are a good !a" to calculate the cold gap#filler bar thicknesses. If so the filler bar

thicknesses determined b" creep reduction can be verified.

$iln %hell &iameter ' Temperature &ifference bet!een Tire and %hell ' E'pansion Coefficient

eduction of the *iller +ar to Tire I& ,ap (E'pansion)

E'tra gap (safet" factor) -ve. recorded creep#?

Total gap E'pansion E'tra gap

-verage shim thickness /(Tire I.&. 0 %hell 1.&.) 0 Total gap2#3

T"picall" for an" tires and shell chairs that are in good condition the tire creep !ill be in the range

of 4 to 53mm (6igration of tires (Creep) is specific for each tire and is specified in the 1E6

documents).

(-hmad 7ilforoushan)

1E6s design the a diameter difference of 8 mm bet!een the live ring dia and the kiln shell 1&

!hich corresponds to relative movement of 8'?. elative movement determined during the kiln

operation in relation to the kiln rotation does not provide shim plate thickness !hich needs to be

inserted to check the creep especiall" if it is on higher side. It has been seen that insertion of shim

based on relative moment calculations ma" lead to a sei9ure or ver" restricted relative movement.

6uch accurate method of calculating the shim thickness to be inserted is based on calculation of

t"re e'pansion and air gaps. T"re e'pansion at the inner t"re surface pertains to t"re inner surface

temperature !hich cannot be measured. This can be back calculated from the t"re outer surface

temperature. The air gap in cold condition is determined b" correcting for the t"re e'pansion and

kiln shell e'pansion.

(-shim +hattachar"a)

the simplest !a" to calculate shim thickness that "ou have recorded the migration for last three

months and if the migration e'ceed the limit then "ou can simpl" calculate the thickness b" thefollo!ing formula.

TThickness of shim required

-verage of migration recorded during last three months

5;-mount b" !hich !e are going to reduce the migration

so T05;#4.3<

*or e.g

if migration recorded is 8=

so T8.><mm

so !e have to insert 3mm shim under all chair plates.

?-ftab -hmad?

ou can determine correcting of old shims according to creep (@ot kiln) in this !a" i tell "ou in ane'ample:

our information:

-ve. recorded creep A;mm#rev ecommended Creep base on 1E6 document 4mm

7eeded reduction of creep (A; 0 4) 8Amm#rev

7eeded reduction of Tire clearance (@ot kiln) (8A # ?) 5;.<mm

7eeded increased thickness for each shim (5;.< # 3) =.Amm

Then indicate each one of old shims and its position on shell and then:

each composition of each old B ne! shims in specified position !ill be: (thickness of old shim

=.Amm) then install composition of each old B calculated ne! shim !ith together on specified

position.

(-hmad 7ilforoushan)

It is important that the creep is neither too lo! (= mm) nor too high (D3= mm). Ideall" the creep

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or migration for an" roller stations or pier

of the kiln should be around <05; mm suggesting presence of ideal hot air gap (creep#I8 mm).

If the creep is not !ithin the range of =03= mm (Fust as a guide onl") it !ill lead to either shell

constraction or e'cessive fle'ing of the shell depending on creep value. This in turn leads to pre0

mature failure of refractories and in e'treme conditions it can even cause shell cracks.

The follo!ing steps must be taken to ensure that the creep falls bet!een the above mentioned

limits:

5. The hot air0gap is not less or in e'cess of 8 mm. If less reduce the chair pad thickness

appropriatel". If high carr" out chair pad shimming or replacement.

3. Ensure the shell and t"re temperatures are close to those considered during chair pad designing.

&ail" check the average shell temperatures on either side of t"re as !ell as t"re temperature. If

necessar"adFust process parameters.

8. Gse of proper lubrication for t"re bore (I&) !ith Hube +ars (!a' based graphite bars) onl". Gse

of grease or other liquid based lubricant attracts dust aggravating chair pad !ear causing high

creep.

A. Ensure that the kiln is in !ell aligned condition. 6is0aligned kiln ma" e'hibit false creep values.

=. Ensure that shell is not allo!ed to bend and distort due to occurrence of red spot etc. +ent shell

!ill not allo! the t"re to rest properl" on the rollers causing false creep.

?Carlito Tolentino?