Repair, adjustment and mechanical check-out of clinker burning kilns
Equipment for cement plants: check-out of rotary calcination kilns
Performance and efficiency of cement plant equipment depend directly on precision of its installation, repair and correctness of maintenance which are the major factors contributing to technical and economical effect of the up-to-date equipment application. The success depends largely on the level of organization and mechanization of labour associated with repair of equipment, improvement of its design, manufacture of durable spare part for it, selection and application of up-to-date wear-resisting materials with high-performance mechanical properties. The Samara Strommashina plant manufactures and supplies all necessary industrial equipment for cement plants and carries out installation supervision and provides technical support. We are also ready to provide assistance in the form of consultations on issues of repair, adjustment and mechanical check-out of rotary calcination kilns.
Rotary kilns: how bands are checked
Bands of a large-dimensioned rotary kiln are delivered to the cement plant as two half-rings which are then connected at the plant using electroclad welding without any further machining. It requires fairly precise check-out of the half-rings during assembly and strict compliance with prescribed welding conditions, as deformation occurs in this process – approximation and rotation of the half-rings which shall be compensated by rigid attachment or respective skew during assembly.
Ellipticity of the bands is checked using an end gauge with a micrometer screw or an indicator, and and "rider" device or an instrument to measure radii. Coplanar alignment of welded half-rings is checked using a levelling instrument and a levelling rod with millimetre graduations and using a microlevel.
Check-out of the band during its installation into the casing means correct spacing of radial gaps and position of the band in the plane perpendicular to the casing plane.
When the band is installed along the casing axis, it can be checked out using the circumferential gauge mark when the band shell is supplied complete with shoes attached to it. In this case thickness of each shoe and the distance from the circumferential mark to the band end plane are checked.
The shim thickness (if no grooved shims and gauge mark are available) are determined from the formula
S= (Dб-D0)/2 - K
where S is the shim thickness, Dб and D0 are the inner band diameter and outer shell diameter (determined by dividing their actual circumference lengths by pi character), К is the set expansion gap.
The run-out meters and automatic gap gauge are used to check correctness of installation of the band on the rotary kiln casing.
Check-out of rotary calcination kiln foundation frames
The rotary kiln check-out shall begin with checking the foundation frames – the main support structures of roller supports.
The kiln roller support foundation frames shall be installed taking into consideration parallelism of their planed top surface of axial kiln plane tilted to horizon at set angle to rotation axis; at the set distance from the adjacent frames and position of longitudinal axis in the vertical axial plane of the kiln. The longitudinal and transversal axes shall be marked on the frame surface, and the support foundations shall be equipped with metal plates with marks showing position of longitudinal and transversal axes of the foundations determined with the transit instrument.
Before installing the foundation frames and during replacement of the roller supports the reference measurements of the band diameters, support roller diameters and roller support heights shall be carried out.
Position of longitudinal axes of the frames in the vertical plane of the kiln shall be checked out by plumbing and stringing a 3.3 to 4.8 mm diam. cable or 4.5 mm diam. steel wire and hanging them up on several U-shaped supports by aligning the longitudinal frame axis with the plane formed by the string and plumb bobs. A ruler and a wedge shall be used for checking the plates in the plane parallel to the axial kiln plane (at an angle).
Check-out of the rotary kiln roller supports
The main condition of the correct roller support installation is parallelism of the kiln rotation axis support rollers axes.
The support roller check-out shall begin with checking the roller support inclination angles. It shall be performed using a special wedge having the same inclination angle as the kiln axis by installing it (with the level) onto the support roller.
Position of the support frame shall be adjusted using shims. Position of the support roller ends shall be checked using a metal ruler. Then an end gauge and a plumb bob lowered using a string are used to check the distance from the generating line roller to the kiln axis, i.e. the distance to the vertical axial plane of the kiln.
Axes of the support rollers on all supports, except 1–2 pairs of rollers (downstream the driving gear in the cold part of the kiln) shall be installed in parallel with the kiln axis. The necessary skew of the said roller pairs shall be determined depending on pressure on the top or bottom support roller (based on the bearing heat build-up): the roller axes skew direction depends on the kiln rotation direction.
The height of the support rollers shall be checked using a levelling instrument and a levelling rod which shall be installed successively on the right and on the left rollers of each support. If necessary, the foundation frame position may be adjusted.
If the band diameters are equal, the reference check of the roller support position shall be checked using a transit instrument. To that end, the transit instrument shall be installed on one of the end supports in alignment with the roller.
The rotary kiln casing check-out
The kiln casing check-out is a very important checking procedure. The uninterrupted operation of the whole kiln depends on straightness, rigidity and strength of the casing.
The Figure illustrates the diagram of the check stand reference assembly of the rotary kiln casing.
Each field joint shall be equipped with at least four plates connected with unit by means of welding and connected with the adjacent unit using finishing bolts. After fitting and connecting several mounting units on about 50 m long roller stand using this method, the whole section shall be moved to the right by the length of the unit which shall be disconnected. The units shall be fitted to each other and connected, then the cycle is repeated.
To check the correctness of position of the shell end edges, a tool with a special optical head is used.
The shells in the unit shall be checked using light method, and the completely installed casing shall be checked either using strings stretched along the casing or using a transit instrument installed in parallel with the upper generatrix of the casing and a levelling rod.
To straighten the unit axis on the shell joints, it is necessary to remove a part of the casing – cut out the wedges the dimensions and position of which shall be determined by analytical or graphic method.
The rotary kiln drive check-out
The girth gear shall be installed so that its axis were aligned with the support band axis, i.e. with the longitudinal axis of the kiln. Consequently, the following conditions shall be met during the girth gear alignment:
a1=a2=a3=a4; b1=b2; c1=c2.
In case of abnormal radial run-out the gear shall be turned so that the maximum run-out location faced upwards. The radial run-out of the gear fixed on the kiln casing with springs parallel to the kiln axis shall be removed by adjusting the thickness of shims under the springs.
The kiln bands located near the girth gear shall be used as a reference for checking out the latter. The girth gear shall be checked out by measuring the distance between the fixed shifting gauges and the respective gear surfaces during casing rotation (without axial displacements). The gear shall be checked out using four wire strings stretched after each 90º along generatrices of the base bands, and by installing it in the plane parallel to end planes of the base bands. It shall be checked by measuring the distances from the the gear pitchline to the wire strings and between the gear end planes and the band.
It is also recommended to use the gear check-out method where the kiln rotation axis is used as a reference. ИГЦО-3 tools are used for this purpose.
The spur pinion with the shaft shall be checked out on radial and lateral clearance and engagement measured after each 90º of the girth gear turn.
In this case it is necessary to take into consideration the girth gear diameter increase due to the temperature differential in the radial clearance in engagement. After adjustment of the spur pinion and the girth gear based on clearances the engagement shall be checked using the paint method.
Check-out of the calcination kiln rotation axis straightness
There are many methods to check out the straightness of the kiln rotation axis where standard geodetic instruments are used: wire string, water level, movable female centre, etc., and a light beam.
Position of the rotation axis shall be checked out in two mutually perpendicular axial kiln planes one of which is vertical.
The procedure to determine position of axis in the vertical plane using a levelling instrument or a transit instrument and a levelling rod is as follows:
1. The levelling instrument or the transit instrument shall be installed so that the aiming axis could be the reference for determination of position of the upper band points.
2. The levelling rod shall be used to measure h1, h2, h3, h4 and h5 values.
3. A tape measure is used to measure band diameters D1, D2, D3, D4, D5 and horizontal distance between them L1, L2, L3, L4.
4. The values shall be calculated. The obtained points С1, С2, С3, С4 and А are on the same line.
5. Comparing the calculated values with those obtained in measurements, the kiln rotation axis distortion value δ and the distortion direction shall be determined:
The straightness of the geometric kiln axis in the plane inclined at the same angle as the kiln rotation axis shall be checked using a thin steel wire stretched and fixed along the kiln parallel to its axis passing through centres of the first and the last bands, possibly closer to them and somewhat below their centres. Values a shall be determined by measuring the distance between the plumb bobs lowered from the string and the plumb bobs thrown over the bands. In this case А1 is assumed to be equal to А5, supposing that А1=(D1)/2+ а1, etc. Comparing the obtained values with А1, position of the kiln axis in this plane is determined.
When the kiln axis is checked out by checking position of the support rollers, the steel wire shall be stretched along the kiln on the level of support rollers axis centres, in the plane passing through the centres of the end bands.
You can ask our plant's specialists any questions concerning the rotary clinker calcination kiln operation. The Strommashina has been developing and manufacturing rotary kilns for over 70 years already – we have vast experience in operating industrial equipment and will surely find a solution of your problem.