170089832-D3-2-100701-Kiln-Mec-Behav-Patroller.pdf

7/27/2019 170089832-D3-2-100701-Kiln-Mec-Behav-Patroller.pdf

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Kiln Mechanical behavior for Patrollers


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100701 Kiln Mec Behav patroller.ppt2

Content

Thermal Expansion

Thermal Expansion effects on the shell

Thermal Expansion effects

Mechanical crankshaft

1

2

3

4


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> 110C

> 145C

> 180C

> 215C

> 250C

> 285C

> 320C

> 355C

> 390C

> 425 C

Kiln temperature profile

100

150

200

250

300

350

400

450

500

Temp: C Max

AvgMin

m

0 10 20 30 40 50 60 70 80

Average

250C


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How to evaluate Expansion?

)()100

(2.1 minitial

C

Initial

C

Finalmm Length

TTExpansion

At 250C, a 70 m kiln is 190 mm longer than at 25C

Temperature must always be taken into account on kilns

On repair/replacement operations

On adjustments when done in cold conditions


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Thermal Expansion

Thermal Expansion effects on the shellShrinkage of the tyre on shell

Thermal bending



1

2

3

4


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Shrinkage of the shell into the tyre

Under tyre shell temperature is greater than tyre average temp.

In normal operation

.. and more in start-up phase

High risk to shrink the shell at start-up

too quick preheating

too small cold clearance value

Consequences

Shell will be deformed permanently

Will possibly lose some bricks

Will probably have some problems of fixation

Will lead to potential shell cracks in the future


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Variation of Temperature along kiln

0

50

100

150

200250

300

350

400

0 8 16 24 31 39 47 55 63 71

Pier Pier Pier

GG

door

What is the effect of

this profile of

temperature?

Max

Average

Min

Thermal bending

Why this variation

(max/min) of

temperature in a

section?


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0

50

100

150

200

250

300

350

400

0 8 16 24 31 39 47 55 63 71

Avg. 300 C

Avg. 220 C

Length = 12 m

Expansion at 300 C

= 1.2 x (300-20)/ 100 x 12 = 40 mm

Expansion at 220 C

= 1.2 x (220-20)/ 100 x 12 = 29 mm

Differential = 11 mm

Thermal bending


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0

50

100

150

200

250

300

350

400

0 8 16 24 31 39 47 55 63 71

Thermal bending

12m + 40mm

12m + 29mm

Due to the mass of the kiln, there is still a contact on each pier .. but load is lighter at central pier and higher at the other one

.. and opposite after half a rotation !

If the thermal bending is very high some tyres could even not

touch the rollers!


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Thermal bending causes

A defect in coating can lead

To different temperatures on the same section

Then to differential expansion

Then to kiln thermal bending

When the kiln is not properly rotated

During start-up

During kiln stoppage

When the kiln is not rotated after one incident

Importance of barring drive!


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Thermal bending corrective actions

Modify process parameters

to get proper equal coating

Barring drive always to be ready to operate

If too late, shell replacement: Figuil (Cameroon) Example Production incident, no barring during 10 min.

Tropical rain (which cools only top of shell)

Kiln bent forever (tyre/roller clearance 25mm)

Need for cut or shell replacement

Cost > 100.000 USD

Stoppage time needed > 10 days


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Thermal Expansion


Thermal Expansion effectsGirth gear

Kiln bearing liner


1

2

3

4


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Girth-gear root clearance increase

Girth-gear fixed on the shell

Example of a 3-pier 4.6 m diameter kiln with pre-heater: Root

clearance increases about 6 mm

Clearance


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Kiln roller bearing

Kilns are generally rotating on roller shaft with liners

Few roller bearings because

very high loads and low rotating speed

expensive to design and use

Are there any limits?

Yes, there is a limit of pressure on a liner

Special mode of friction, low speed, negative influence


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Kiln roller bearing liner Temperature

Depends on friction -> related to rotation

Most of the torque used to lift the material inside the kiln / Very little

converted to heat through the shaft/liner contact

Torque liner about Torque motor x (0.03 to 0.05)

Depends on the load -> related to Design. (FLS, POLYSIUS, CLE, FCB using approx. same design limit)

Quality of geometry and lubrication

Alignment of kiln tires

Shell axis deformation (permanent or thermal)

In case of severe liner overheating, this torque can suddenly increase


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Expansion effect on Kiln bearing liner

When the kiln starts, tyre will heat the roller, then the shaft

After 48 hrs, the shaft diameter will be bigger but the liner support

will remain cool (water cooling)

The expansion of the shaft will reduce the oil film thickness and

the contact will increase

Contact

Surface

SHAFT (HOT)

SHAFT (COLD)


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Kiln bearing liner overheating cycle

Overheating

Shaft diam.increases

Less

clearanceLess oil

More wear

Viscositydecreases


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Kiln bearing liner -> Emergency procedures

Best method = Oil re-circulation with cooling and cleaning

Small units available on the market with installation on request

In case of small problem, putting the kiln on barring can save you!

Time to decrease shaft temperature, get proper viscosity back, comeout of the vicious cycle

Cool by air roller flank to limit kiln heat transmission to shaft

Oil usage

The best oil cannot solve contact pattern problems

Very thick oil or synthetic oil cannot solve too low clearance betweenshaft and liner

Check if this synthetic oil can be mixed with mineral

Check if this synthetic oil does not chemically attack any bearingpart

put the highest viscosity you can, assuming the real viscosity willdrop very quickly because of temperature (oil viscosity diagram

versus temperature must be known)


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Kiln bearing liner -> Musnt

Fan cooling: dangerous on bearing

Housing open = Dust contamination = Be careful!

Are you sure you are cooling the shaft or the housing? (think of

expansion)

Cool the roller flank with water

Water on roller is dangerous

Permanent application or heat shock leads to spalling

Use grease or molycot is forbidden

very dangerous

can block the oil pocket, preventing any oil from entering to lubricate

liner and shaft


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Expansion Conclusion

Heat is a very important parameter for kiln shell

Attention should be always given to temperatures

Maximum temperature

But also differential

Mechanical staff must take extreme care in case of kiln thermal

bending


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Content

Thermal Expansion



Mechanical crankshaftMisalignmentBrick Failure

1

2

3

4


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Kiln Misalignment

As an example on 3 piers, a mechanical bend is one tube which is deformedso the 2nd section is rotating when sections 1 and 3 are perfectly set-up in

line


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Wrong Kiln Alignment

Wrong alignment of shell at erection due to

Subcontractors lack of know-how

Deformed new or old shells

Not properly chosen shells to be replaced

SHELL ECCENTRICITY

OR "CRANKSHAFT"

KILN SHELL

AXIS UNDER

TYRE

POOR

ALIGNMENT

OF SHELLS


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Wrong Kiln Alignment effects

On a poorly aligned 3-station kiln, tire 2 too high by about 10 mm

Overload = 8 t/mm x 10 mm = 80 t (TC calculation)

Permanent load supported by this tire = 80 t higher than normal

Possible problems (depending on design safety coefficient) on

Bearing liners overheating

Tyre (wear, holes, crack, )

Rollers (wear, holes, crack, )

Shaft crack

Brick failures Too high load => too high ovality => problem of bricks

Frame cracks

Shell cracks


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Brick Failure

If not followed by stoppage (major cause)

Too long run with missing bricks / Too high temperature on the

shell with bricks

Some indicators

If the circumference of hot-spot is > 90 of the total, it becomes

dangerous for the kiln shape, otherwise it will create only local

deformations (but still bad)

Axial hot-spots are less dangerous than radial


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Brick Failure effect


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Mechanical crankshaft without visual indications

Possible

Since kilns are generally very flexible, you may have a crankshaft

but as the kiln deforms during rotation, the deformation is not

visible

Sometimes kilns are affected by several crankshafts in oppositephases


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100701 Kiln Mec Behav patroller ppt

How to check there is a crankshaft?

By looking for

Periodical noise at the speed of kiln rotation

Periodical motor amperage fluctuation

Periodical deflection of roller shaft

If you see a significant radial run-out on kiln seals or on the shellbetween two piers

IMPORTANT : To detect a potential problem you must wait for 5 or

6 rotations!!!

Date post:	14-Apr-2018
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170089832-D3-2-100701-Kiln-Mec-Behav-Patroller.pdf

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