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Chinese cement kiln suddenly broke and the kiln body was torn into three sections

The scene

It is understood that Datong Jidong Cement Co., Ltd. was established in 2008 with a total investment of 1.5 billion yuan. The company has two 4,500 tons of modern new dry process cement clinker production lines and two 7.6MW pure low temperature waste heat power generation projects. Annual output of clinker 3 million tons, cement 4 million tons. The accident that occurred this time was No. 1 kiln. The specific cause of the accident was still under investigation.

Cement rotary kiln is one of the key equipment in the cement plant and is the core link of the entire cement plant. Due to the large volume, coupled with the alternating hot and cold, high temperature operating environment, the cylinder fracture and weld cracking accidents also occur from time to time.
Rotary kiln shell fracture usually has the following situations:

1 In the cylinder under the wheel belt, a phenomenon of “neck-nakedness” of different degrees occurs, and the continuous operation can easily cause the cylinder to break (crack or break).

2 The cylinder body at the intersection of the cooling machine and the material outlet of the rotary kiln is prone to cracking.

When the rotary kiln shell breaks, there are usually many forms:

1 The crack is distributed along the circumference of the section of the cylinder and is accompanied by the phenomenon of bending of the cylinder.

2 Once the crack exceeds 1/3 of the circumference of the kiln, there is a risk that the cylinder may break.

The analysis of the causes of the breakage of the rotary kiln shell causes many reasons for the breakage of the rotary kiln shell. The following points are summarized:

(1) The overall strength is low, and the cylinder breaks after being put into normal production

For example, in a rotary kiln with a multi-cylinder cooler, several multi-cylinder cooling machine discharge holes are arranged on the circumference of the cylinder at the junction of the cooling cylinder and the kiln feed port, so that the length of the actual iron plate is only 1/2 of the circumference. Around, the overall strength has dropped significantly, so it is very easy to break here.

(2) Material fatigue at high temperature, causing cylinder fracture

Rotary kiln shells are subject to alternating loads and changes in cold and heat for a long period of time. When the kiln is stopped due to production reasons and non-productive reasons, radial deformation may occur in the section of the cylinder. The thermal calibration of rotary kiln shows that the surface temperature of the cylinder is often above 300°C. In such a high-temperature working environment, especially the alternating of cold and hot, it is easy to cause the material of the steel plate of the cylinder body to be fatigued, the rigidity is reduced, and then the fracture occurs.

(3) Inappropriate maintenance resulted in the breakage of the cylinder

After the crack in the rotary kiln shell, repairs must be carried out. However, in the course of repairs, if the welder’s welding technology fails, or the welding filler metal is not properly selected, the welded part will be easily cracked again, and will expand and expand, resulting in the occurrence of a tube fracture accident.

(4) Rotary kiln shells inadvertently formed groove marks in the process of manufacture, transportation, installation, etc.,

resulting in fine cracks, fine cracks extending after load, and development of barrel fracture. Or the tube may have residual welding stress during the manufacturing process. Even defects such as pores and sand holes may occur in the weld. Under alternating stress and high temperature, the defects form cracks, and the weld seam becomes a crack, which causes the cylinder to break.

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