In jaw crusher, flywheel and grooved wheel are respectively installed on both sides of eccentric shaft. Flywheel has two important functions in jaw broken work: one is to balance the weight of the Geneva wheel; the other is to store energy. In the work of jaw crusher, once the flywheel fails, it will directly affect the production of the equipment. Crack is a common fault in jaw crusher flywheel. This paper mainly introduces the causes of flywheel cracks and specific solutions.

Causes of flywheel crack

In view of the frequent cracks on the flywheel of jaw crusher, the main reasons are as follows:

1. Material problem

The material of flywheel and pulley is generally gray cast iron, because of its low cost and easy processing. But the disadvantage of gray cast iron is brittleness, poor mechanical properties, easy to crack under external force.

2. The particle size is too large

If the ore block entering the crusher is large, it is easy to break the jaw or "stuffy" of the feeder, and sometimes it has to be treated with explosives, which will inevitably impact the crusher and even the flywheel, and cracks will appear after a long time.

3 design and manufacturing process issues

• The crack is located at the transition of casting fillet, the wall thickness difference is large, the transition fillet is small, the stress concentration is easy to occur after pouring, and the crack is easy to appear after the load is applied.

• Improper selection of casting fillet will cause shrinkage cavity and crack during casting, resulting in stress concentration.

All of the above problems will appear cracks because of the stress problems.

Countermeasures

Due to the tight production task and lack of spare flywheel, some manufacturers adopt temporary treatment to cope with production. Generally used The advantage of repair welding treatment is that it can gain casting time of spare parts and maintain production temporarily; the disadvantage is that the welding performance of gray cast iron is poor Due to the lack of on-site thermal insulation measures and the influence of welding level, cracks often occur in the welding process. Even after welding, the service life is not long, and cracks will appear again after 3-6 months.

In order to prolong the service life of the treated flywheel, the treatment scheme can be replaced. The specific methods are as follows:

1) In order to avoid machining stress on the outer circle of the wheel hub of flywheel, the chamfering of 20 mm should be reserved during machining. The original wheel hub diameter is 520 mm, and the diameter is 516 mm ± 31, so as to ensure the surface processing accuracy, machining dimension and tolerance.

2) The processing of the two sides of the flywheel web is to ensure sufficient contact area between the splint and the web. The processing depth is about 2mm, and the diameter is 900mm. The machined surface and the raw surface of the web plate are transited by chamfering.

3) To process a pair of flange with boss, the material is 45 steel which has good plasticity and toughness and is easy to machine. The flange hole size is 516 ± 31.

4) The dimension and tolerance of the inner hole of the flange sleeve is a transition fit with the outer circle of the wheel hub after machining, which is convenient for clamping the flywheel with cracks.

5) High strength bolts with reamed holes are used for fixation. Because the diameter of the reamed bolt is almost the same as the diameter of the hole, the bolt is mainly affected by the extrusion and shear stress in addition to the tensile force. When there is relative sliding between the connected parts, it depends on the shear action of the bolt itself to prevent its movement, so only a small pre tightening force is needed. Under the condition of vibration load in the field, the reamed bolt should be used for the structure with flange tightening friction and force transmission.

6) Install a pair of processed flange sleeves on both sides of the flywheel to ensure the installation in place.

7) 18 bolt holes are reamed evenly with reamer, and the flange and flywheel web are fixed with high-strength bolts of grade 8.8 to ensure the clamping strength of the two flanges to the flywheel web.

8) Check regularly to prevent further crack propagation and deformation of flywheel.

Due to the bad working environment and medium conditions of jaw crusher, some problems can't be avoided in use. Therefore, engineers and technicians are required to deal with the equipment problems on site to avoid delay in production.