The causes and the prophylactic measures of tube mill fracture of the bolt

Tube mill 2019 - bolt fracture reason and preventive measures 07 - 21 Wang Zhanguang ( Jiaozuo strong cement) Use common tube mill in the cement industry, used for grinding, end cover bolt fracture often bring trouble to the production, now in its fracture personal opinions about the causes and prevention measures, can play the reference role. A, grinding body fracture reasons and prevention of mill liner bolts and bolt fracture reason is more, in the aggregate, mainly has several aspects. First is the quality problem, when the bolt in machining defects exist too deeply, such as thread screw knife grain, the head and the screw is not vertical, etc. , when the thread deep section stress increase; Mark can cause stress concentration; Vertical screw and end face can create bolt unilateral stress, increasing the local stress and so on, these defects virtually partial overload can make bolt, when its over its ultimate strength, bolt can produce crack fracture. Second, improper installation also can produce the bolt fracture, such as the bolt head and liner pits contact is bad, do not paste, can make the bolts one or the local stress, local stress increases, easy to make the bolt fracture; Nut and grinding body contact is not good, also can make the bolt unilateral stress, fracture, irregular uneven pad, of course, also is such. Third, excessive pre-tightening force will also promote the bolt fracture, especially when local stress in the bolt. Fourth, plate hole and ground bolt hole concentricity is bad, serious deviation, when installation of bolts have to knock hard hit, shell or plate will cause harm to the screw, such as scratches and wear, the bolt fracture easily. In order to avoid or reduce grinding body bolt fracture, can prevent from the following several aspects: first, to strictly the quality pass, bolt of acceptance defects were found, such as the material is wrong, rough machining, crack, bolt head not neat blatantly defective bolt stored separately, it is strictly prohibited to enter the production line. Second, when installation must ensure that the whole nut with barrel paste; Bolt head and liner pit writings, affecting the writings of parts for repair, and help ensure that pits in the form of hammer with the bolt head writings; At the same time focus on grinding body screw hole and lining board screw hole of the contact ratio, prevent damage bolt; According to the standard requirement of bolt pre-tightening, prevent preloaded overdone. Second, the cylinder head bolt fracture reason and prevention of cylinder head bolt with end plate bolt connecting bolts and hollow shaft and the end cover, the end plate bolt fracture reason is roughly same, the following main analysis of hollow shaft connection bolt fracture reason and prevention. First, hollow shaft and end cover joint bolt intensity is higher, the machining accuracy is high, part positioning function, need and articulation hole with hole, so the demand is higher. The fracture reason mainly has several aspects. First is improper material selection, insufficient strength. Second, the machining accuracy is insufficient, defects, such as processing and rough, insufficient size, the screw and the bolt head is not vertical, etc. , in the operation of tend to produce stress concentration, caused the fracture. Third, installation, installation bolt head or nut and end cover or hollow shaft do not paste, bolt unilateral, cause local stress cracks. Fourth, hollow shaft end or stop end cover mouth ends, perpendicular to the bolt hole does not cause the nut and bolt head face don't paste, bolt caused by local stress too much. Fifthly, cover and hollow shaft machining precision is poor, do not in themselves paste, in the operation of increasing the bolt stress. Its six, when installation, loads during operation when the bolts in tension, excessive pre-tightening force and pulling force, more than the bolt strength limit, will break, and so on. More bad situation will make the bolt produces local stress is too large, easy to produce cracks and fracture. Precautions: 1. Acceptance to check material, see whether material conform to the requirements of the drawings. Checks to see if there are any defects, it is forbidden to unqualified parts into the production line. 2. When installation to ensure nut, bolt head with hollow shaft, tight end cover, if there is a problem to properly repair, and moderate prestressing force. 3. Hollow shaft and end cover must be tight fit, if necessary, can carry on the processing, to achieve optimum conditions, the local clearance is less than 0. 5 mm. Three, the conclusion about the mill the cause of the bolt fracture is more, this article is based on personal experiences some of the main reasons for and preventive measures, deficiencies please comment. In addition to make new mill in bolt fastening, must check every day until not loose, must prevent rupture caused by loosening the harm of bolt. About the bolt pre-tightening force, can be ordered according to the instruction or manual. （ Wisdom cement)