How To Prevent cement rotary kiln cracks

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With the mature of kiln outside the decomposition technology, cement continuously research and development and the improvement of machinery manufacturing of large equipment, provides conditions for single cement production capacity expansion, a lot of rotary kiln in the rotor is not a long time, there is a barrel crack, especially in transitional zone of rotary kiln shell crack, caused a big loss to production enterprises, the causes of cracks in the rotary kiln shell and preparedness plan

1. The part of rotary kiln prone to crack

There are many cracks in rotary kiln.At present, the most cracks occur on the cylinder of the transition belt of rotary kiln. Once cracked, the economy and reliability of repair are poor, that is, the cylinder must be replaced.

2. Cause analysis of cracks in rotary kiln barrel

Rotary kiln is a kind of thermal equipment with multi-point support and heavy load and low speed.The main cause of crack is analyzed.

2.1 causes of longitudinal crack formation

The longitudinal crack occurs in the weld of the cylinder and the plate or the block under the wheel belt.The reasons are mainly caused by four aspects.The first is the design with thin shell plate thickness selection, we know that rotary kiln for horizontal longitudinal soft, if the sheet thickness, it is difficult to ensure the lateral stiffness, so the cylinder in the self-respect and roller support reaction force of the alternating stress and stress under the action of pulse, easy to make the material produces fatigue, after reaching a certain conditions, the crack will be relatively weak at the weld heat affected zone of the form

In terms of installation, often only pay attention to the precision of cold kiln, and ignore the long-term running under hot precision, such as the production of belting leather, barrel, wheel gear temperature is different, its center high rise also inconsistent, causing rotary kiln operation when the gear center is not in a straight line, hard to avoid the stress change of each gear belting leather center high rise high demanding is large;

2.2 causes of annular crack formation

Circumferential cracks mostly occur at the weld of the excessive cylinder on both sides of the belt, at the weld of the spring plate of the big gear ring and the cylinder, and at the cylinder of the transition zone of the rotary kiln.Belting leather shell thickness under much more than twice as high in the middle section of the cylinder thickness, if the cylinder under the belting leather with the middle section of the improper selection of excessive cylinder thickness between the roller by belting leather to support reaction force on the cylinder, the cylinder of deformation is hard to smooth transition to general cylinder, caused by rotary kiln belting leather on both sides of the barrel crack.Big gear ring on the spring plate and the rotary kiln shell welds are also prone to produce circular crack, big ring gear in the cylinder body slants thin, and the spring plate thick, cause cylinder stiffness is small, the spring plate stiffness big, as a result, the equipment operation, the spring plate cannot digest by deformation ease external stress, when the rotary bending serious damage gear to the size of the contact state, still can cause vibration of the rotary kiln body bending generate additional load, promote the generation of cracks.

2.3 cylinder body cracking caused by high temperature

Rotary kiln as a thermal technology equipment, internal flame temperature can reach 1700 degrees, although the cylinder by a brick kiln and insulation protection, to the cylinder on the surface of the body surface temperature is high, in the absence of kiln calcining zone barrel skin, even the new brick, barrel temperature can reach 450 degrees, also it is greatly weakened the strength of cylinder, if the kiln at high temperatures would be a long-running cylinder does not crack, especially in the case of off red brick kiln, local tube feel lose strength, lose the ability to resist external force, improper measures at this point, such as forced ventilation in high temperature water cooling, even can make cylinder contraction and cracks

3. Preventive measures for cracking in rotary kiln

3.1 preventive measures for longitudinal cracks

Longitudinal cracks tend to occur in the rotary kiln belting leather plate or block of the welds, cylinder block and cylinder stiffness of the main causes of crack is the lack of, a higher temperature stress and additional stress and other factors, so in the process of design and manufacture of rotary kiln, should be appropriate increase the thickness of the cylinder, according to relevant data, belting leather cylinder body shell thickness should be not less than one point five percent of nominal diameter, floating plate thickness of the block is not greater than fifty percent of the cylinder thickness, the width of the block is not greater than 200 mm, in order to reduce the support reaction force caused by uneven cylinder deformation and additional stress and temperature stress.

3.2 preventive measures for circumferential cracks

Rotary kiln ring to the crack easily occurs in belting leather on both sides of the excessive cylinder shell, the big gear ring spring plate and shell welds, in order to prevent the crack, should fully consider when design and manufacture of the cylinder thickness, belting leather on both sides of the cylinder thickness of the transition section of up to belting leather under the shell thickness and the average of the middle section of cylinder thickness, facilitate cylinder deformation caused by the support reaction, too gentle and natural, to facilitate the diffusion of stress, reduce stress concentration.

The center line and thickness of rotary kiln barrel should be checked every year to ensure the life of the barrel.Try to reduce the additional load on the cylinder due to adjustment, this paper only introduces the cause of rotary kiln cylinder crack and solution ideas, there are a lot of details, if you have a need can leave a message with us online

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