mechanical kiln inspection

Improves and ensures kiln availability by optimisation of:

■ Kiln axis

■ Kiln shell ovality

■ Axial balance

■ Kiln crank

Mechanical kiln inspection

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MAIN FEATURES

• Ensures high kiln availability

• Reduces maintenance costs

• Short payback time

• Performed during normal kiln operation

• Extended lifetime of refractory liningand other key kilncomponents

• Backed up by F.L.Smidth´s in-house engineering departments

• Based on more than 120 years ofexperience in kilndesign

• Performed by highly experienced F.L.Smidth kiln specialists

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Introduction

Kiln inspections Regular kiln inspection is required to ensureoptimum availability of the kiln installationand to verify that the kiln operates withinthe load and stress parameters laid down bythe kiln designer.Today’s state of the art methods of inspectionperformed during normal operation of thekiln are based on advanced measuring techniques and evaluated by highly experienced kiln specialists.Although the vast majority of cement plantsemploy a very experienced maintenancestaff, it is not economically and technicallyviable for the individual plant to invest inthe measuring instruments and develop thecomputer software required, acquire andmaintain the skills necessary to performthese advanced inspections, process thedata and evaluate the results.Therefore it is an accepted practice in thecement industry worldwide to call on anoutside company to carry out these comprehensive kiln inspections at regularintervals.

F.L.Smidth F.L.Smidth is the world's largest supplier ofrotary kilns, spare parts and services to thecement industry. With more that 120 yearsof experience as kiln designers, F.L.Smidthpossesses a huge technical know-how onrotary kilns and employs a group of highlyexperienced field engineers, who work dailyas kiln specialists at cement plants all overthe world backed up by the entireF.L.Smidth organisation. The Hot Kiln Alignment method was introduced into the cement industry in1981 allowing a full inspection of the kilnto be performed during normal operation.Since then, F.L.Smidth has continuouslyupdated and improved the method, measuring instruments and computer software to provide our clients with thebest possible tools to evaluate the consequences of the kiln’s present operating condition in respect of the availability.


The F.L.Smidth conceptThe inspection concept innovated by F.L.Smidth focuses on the following four elements:• Kiln axis• Kiln shell ovality• Axial balance• Kiln crankThe root causes of the vast majority of the failures of kiln installa-tions originate from one or more of these elements, thus posing aserious threat to the availability of the kiln.In addition, the F.L.Smidth concept includes a thorough inspection ofthe drive station, kiln shell profile analysis, and a general inspection ofthe mechanical condition of the other key kiln components. Very oftenthe load condition of a kiln changes over the years due to e.g. increasedcapacity, change of fuel and/or changes of refractory lining quality.To compensate for such changes, F.L.Smidth recommends that thekiln be recalculated based on the present load conditions and that the optimum kiln axis be determined taking the load distributionbetween the individual supports and the stress levels in kiln shell,tyres and rollers, as well as the bearing loads into consideration.

F.L.Smidth inspection typesF.L.Smidth markets the following three standard inspections coveringall types of rotary kilns:• Comprehensive kiln inspection• Two-support kiln inspection• Hot kiln alignment checkThe F.L.Smidth standard inspections consist of individual modules,most of which are optional, enabling the client in co-operation with

F.L.Smidth to tailor an inspection to meet hisspecific needs.The results of the F.L.Smidth inspection are presented in a written report and/or on a CD-Rom, with recommendations of measuresto be taken.Additionally, any adjustments to the kiln recommended by F.L.Smidth can, at theclient’s request, be supervised and verified byan F.L.Smidth field engineer in continuationof the inspection.

BenefitsThe comprehensive kiln inspection performedon a regular basis in co-operation withF.L.Smidth provides the client with the knowledge necessary to prolong the lifetimeof the refractory lining and expensive kilncomponents and reduces the risk of unscheduled stoppages, thus ensuring highkiln availability.Empirically, the payback time of a comprehensive kiln inspection is very short as the expenditure on this inspection is very marginal as compared with the cost of refractory lining and components to be replaced as a result of avoidablemechanical failures as well as the cost of the consequential production losses incurred.

Hot bearings Cracks Wear Lining loss

Root causes

On bearingjournal

On thrustcollar

In kilnshell

In supportingroller shaft

On suppt.rollerand tyre

Betweentyre andkiln shell

Betweenthe tyres

Underthe tyres

Kiln shellovality

Kiln shellovality

Kiln shellovality

Kiln axis Kiln axis Kiln axis Kiln axis Kiln axis

Kiln crank Kiln crank Kiln crank Kiln crank

Axialbalance

Axialbalance

Lubri-cation Corrosion Operation

Liningqualities

SymptomsSymptoms and root causes


ElementsKiln axisThe kiln axis is defined by the position of the supporting rollers. It determines the distribution of the kiln weight load between the supports and thus the distribution of the longitudinal bending stresses in the kiln shell.Misalignment of the kiln axis may result in overloading of supports, excessive stresses in kiln shell, tyres and supporting rollers as well as bearing overload.The kiln axis is measured during normal kiln operation using two electronic theodolites, connected to a computer calculating the horizontal and vertical kiln axis by specially developed software.Additionally, the “Comprehensive kiln inspection” includes a completerecalculation of the kiln, based on the axis measured and the presentload conditions, to determine the optimum kiln axis, taking both load distribution on the supports, the stress levels in kiln shell and tyres, and the kiln axis into consideration.

Kiln shell ovalityThe dynamic ovality is defined by the degree ofdeformation of the kiln shell and determinesthe distribution of the cyclic, circumferentialbending stresses in the kiln shell.Excessive ovality can result in circumferentialbending fatigue in the kiln shell and refractorylining failures.The ovality is either calculated on the basis ofthe tyre migration or measured via the ShellTest method.

Axial balanceAlthough a rotary kiln is always in axial balance, the axial balancecan be established either between large forces or preferably, inorder to ensure the availability, between small forces.The state of axial balance is defined by the degree of parallelismbetween the kiln axis and the axes of the individual supportingrollers determining the magnitude and directions of the axial frictional forces between the tyres and supporting rollers and on the thrust roller(s).Large axial forces may result in hot supporting roller bearings, failure of the thrust device(s) or damaged end seals.


ElementsKiln crankA kiln crank, whether mechanical or thermal, can cause excessive, extra, cyclic loads between supporting rollersand tyres and stresses in the kiln shell.A mechanical crank is caused by a permanent deformationin the kiln shell, whereas a thermal crank is caused by tem-perature variations along the circumference of the kiln shell,and so it is present only during operation of the hot kiln.Excessive crank formation can lead to failure of contact sur-faces, supporting roller shafts, tyres, kiln shell and lining.The kiln shell is checked for crank formation by measuringthe variations in the deflection of the supporting rollershafts, which has to stay within certain limits.

Kiln driveAn examination of the kiln drive constitutes anotherimportant element of a kiln inspection. The condition ofthe kiln drive is determined by measurering of the axialand radial wobbling of the girth gear as well as evaluationof the mesh and root clearance between the girth gearand pinion(s).Further, the condition of the tooth profiles, the lubricationof the gears, as well as the stud bolt connections betweenthe girth gear and the spring plates and the welds betweenthe spring plates and the kiln shell are examined. To completethe examination of the kiln drive, the operating temperatureand vibration levels of the main gear unit are checked.

Kiln shell profile analysisA kiln shell profile analysis is made to investigate thedegree of deformation of the kiln shell. Such deformationmay have no influence on the loads on the supportingrollers but can contribute to refractory lining and kiln shellfailures.The kiln shell profile analysis is based on an evalua-tion of the kiln cross-section geometry measured at regularintervals along the length of the kiln. The analysis is pre-sented graphically.

General inspectionThe general inspection of the kiln comprises a visual exami-nation of the condition of other key kiln components notincluded in any of the above activities, but the possiblepoor condition of these components can also pose a threatto the availability of the kiln.


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Comprehensive kiln inspectionInspection of two-support kiln

Hot kiln alignment check

Inspectionmodules

Inspectiontypes

Data in this brochure is intended for preliminary project planning only. Manufacturer reserves the right to modify equipment details and/or specifications without notice.

DENMARKF.L.Smidth A/SVigerslev Allé 77 DK-2500 ValbyCopenhagenTel: +45 36 18 10 00Fax: +45 36 30 18 20E-mail: [email protected]

USAF.L.Smidth Inc.2040 Avenue CBethlehem, PA 18017-2188Tel: +1 610-264-6011Tel: +1 800-523-9482Fax: +1 610-264-6170E-mail: [email protected]

INDIAF.L.Smidth Ltd.Capital Towers180, Kodambakkam High RoadNungambakkamChennai 600 034Tel: +91 – 44-52 191234Fax: +91 – 44-2827 9393E-mail: [email protected]

www.flsmidth.com

Up-to-date addresses of worldwidesubsidiaries and sales offices are available from our website

��) Included in the standard inspection

*) Optional

Standard kiln inspections


mechanical kiln inspection

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