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Cement pipe mold assembly which should be the connecting bolts?

Cement pipes in the centrifugal molding process, often due to mold cement pipe bolt fracture accidents, resulting in centrifugal molding machine and mold damage, serious threat to personal safety. So find out bolt break cause and remedy is necessary.

Cement pipe mold causes bolt fracture are:

1. Equipment manufacturing error, installation error and cement pipe mold deformation after use for some time, will lead to mold the axial and radial runout string action, the bolt Loaded surge, even more than the allowable strength.

2. The material properties bolts reach the design requirements (if the production equipment manufacturers to A3 instead of 45 steel or 40Cr); improper bolt shank head structure design, stress concentration, resulting in fatigue failure.

By the bolt stress analysis and Failure Analysis shows that the main factor causing the bolt bolt fracture material properties and design the improper selection of bolt structure is irrational. Suggest:

1. The manufacture of bolts should consider hex head bolt stress is maximum configuration shown in Fig. 1a, this structure can effectively reduce the stress concentration bolt head. By the use of better, bolt life can be increased by 30%.

2. In the nut below the disc spring loaded pad (Fig. 1b), this spring there are energy consumption during operation, vibration absorption effect, strong buffer and damping capacity, so that the coupling member is a bolt that is at work have more tension big stretch, reducing the maximum stress caused by vibration, is one of the effective measures to prevent the threaded bolt parts breakage.

Figure 1 Figure improve strength structural bolts

Figure 1 Figure improve strength structural bolts

3. In the cement pipe mold design and manufacturing, taking into account the impact, vibration and other factors, will be changed to M27 or M24 bolt M30, bolts increase the allowable stress values. Using 45 steel and 40Cr steel bolt material, not the best A3 steel. The manufacture of rolling ring coupling bolt hole surface finish should not be too low (roughness not too high).

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