1. Connecting rod bolt bears great alternating impact load during engine operation. It is an important part of small mixer engine. It is made of high-quality alloy steel through quenching and tempering treatment and precision machining. It has high strength and impact toughness. It can not be replaced by ordinary bolts or low-quality parts. If the bolt material, heat treatment and machining accuracy do not meet the technical requirements, it will lead to insufficient mechanical strength and deformation and fracture accidents.

2、装配前应仔细检查。当发现螺栓上有划伤、滑扣、裂口、凹痕、缩颈或裂纹(应用浸油法检查或磁力探伤检查)，或螺栓、螺母配合松弛，或螺栓不能与螺栓孔紧密配合，或利用对比法观察，螺栓长度比新的标准螺栓长度长2%的，都应予更换。

2. Check carefully before assembly. If the bolt is found to be scratched, buckled, cracked, dented, necked or cracked (inspected by oil immersion method or magnetic flaw detection), or the bolt and nut fit is loose, or the bolt cannot fit closely with the bolt hole, or the bolt length is 2% longer than the new standard bolt length by comparison method, it shall be replaced.

3、检查连杆轴承与连杆轴颈的配合间隙，若间隙过大，易于导致连杆螺栓的断裂事故。此时应更换新的连杆轴承或加大轴承，并予选配或刮配。

3. Check the fit clearance between connecting rod bearing and connecting rod journal. If the clearance is too large, it is easy to cause the fracture accident of connecting rod bolt. At this time, the connecting rod bearing shall be replaced with a new one or enlarged one, and shall be selected or scraped.

4、检查连杆螺栓或螺母与连杆端盖台肩支承面的贴合情况，若有毛刺或不平，应予修磨，否则连杆螺栓受附加力矩作用，极易折断。

4. Check the fit between the connecting rod bolt or nut and the shoulder bearing surface of the connecting rod end cap. If there is burr or unevenness, it shall be polished, otherwise the connecting rod bolt is easy to break under the action of additional torque.

5、装配时应用扭力扳手将连杆螺栓交替分次(一般分3—4次)逐步均匀拧规定钮矩。若拧紧钮矩不足，工作中连杆结合面产生缝隙，螺栓受冲击力时易被拉断或剪断；拧得过紧，螺栓伸长变形，强度降低，受力后易折断损坏。各种机型发动机的连杆螺栓规定扭矩不尽相同，在缺乏技术资料的情况下，可根据螺栓直径估算其权矩范围，如MU连杆螺栓，其扭矩为60—80Nm；M12螺栓，其扭矩为80—100Nm；M14螺栓，其扭矩为100—120Nmo。

5. During assembly, the connecting rod bolts shall be tightened to the specified torque with a torque wrench in alternating times (generally 3-4 times). If the tightening button torque is insufficient, there is a gap on the connecting rod joint surface during operation, and the bolt is easy to be pulled or cut off when subjected to impact force; If it is tightened too tightly, the bolt will stretch and deform, the strength will be reduced, and it is easy to break and damage after being stressed. The specified torque of connecting rod bolts of various engines is different. In the absence of technical data, the safety torque range can be estimated according to the bolt diameter. For example, the safety torque of Mu connecting rod bolt is 60-80nm; M12 bolt, with torque of 80-100nm; M14 bolt with torque of 100-120nmo.

6、打螺栓时若发现同一连杆上某一螺栓扭矩超过规定值过多时，应将该连杆上的两只连杆螺栓全部拧松后重新分次交替拧紧，并使两只螺栓松紧一致。不允许仅仅松退拧得过紧的那只螺栓，否则螺栓产生附加弯曲应力，易疲劳断裂。

6. If it is found that the torque of a bolt on the same connecting rod exceeds the specified value too much during bolt driving, loosen all the two connecting rod bolts on the connecting rod and tighten them alternately in several times, and make the tightness of the two bolts consistent. It is not allowed to only loosen the over tightened bolt, otherwise the bolt will produce additional bending stress and be prone to fatigue fracture.

7、在拧紧连杆螺栓过程中，应设法转动曲轴，检查其转动是否自如，若螺栓拧紧后曲轴转动困难应查找原因，切不可将连杆螺栓拧松来转动曲轴。

7. During tightening the connecting rod bolts, try to rotate the crankshaft to check whether it rotates freely. If it is difficult for the crankshaft to rotate after the bolts are tightened, find out the reason. Do not loosen the connecting rod bolts to rotate the crankshaft.

8、为预防小型搅拌车连杆螺栓或螺母工作中松动，应采用崭新的开口销、铁丝或锁片等防松装置锁紧；若螺母上的槽口与螺栓上的孔末对正，原则上只能往里旋去对准；用过的开口销、铁丝或锁片不得再用。

8. In order to prevent the connecting rod bolts or nuts of small mixer from loosening during operation, new locking devices such as cotter pin, iron wire or locking plate shall be used for locking; If the notch on the nut is aligned with the end of the hole on the bolt, in principle, it can only be screwed inward for alignment; Used cotter pins, wires or locking tabs shall not be reused.

9、使用中应定期检查连杆螺栓紧卧情况，发现松退时应查找原因，检查螺栓有无损伤，再用权力扳手按规定钮矩分次拧规定值。

9. During use, the tightening and lying of connecting rod bolts shall be checked regularly. When it is found that the connecting rod bolts are loosened, the cause shall be found, the bolts shall be checked for damage, and then the power wrench shall be used to screw them to the specified value according to the specified button torque.

10、工作中当连杆螺栓松退或被拉长时，在完全松脱、断裂之前，因连杆轴承松旷，会发出较大的敲击声和振动，此时应立即停车，以免发生更大事故。

10. During operation, when the connecting rod bolt is loosened or stretched, before it is completely loosened and broken, there will be a large knocking sound and vibration due to the looseness of the connecting rod bearing. At this time, stop immediately to avoid greater accidents.

11、当某根连杆螺栓有滑扣、裂损或断裂时，应将同一连杆上的两根连杆螺栓成对更换，不得新旧搭配使用。

11. When a connecting rod bolt is buckled, cracked or broken, the two connecting rod bolts on the same connecting rod shall be replaced in pairs, and the old and new shall not be used together.

12、当发动机多次烧瓦或一次烧瓦严重时，连杆螺栓材料受高温退火作用，金相组织发生变化，机械强度下降，承载能力下降，应予换新。

12. When the engine burns the Bush for many times or once, the connecting rod bolt material is subject to high-temperature annealing, the metallographic structure changes, the mechanical strength decreases and the bearing capacity decreases, so it should be replaced.

13、当发动机出现飞车、咬缸或翻车事故后，切不可忽视对连杆螺栓的仔细检查，当发现螺栓变形、裂损后，应及时更换。

13. In case of flying, cylinder biting or rollover accidents of the engine, the careful inspection of the connecting rod bolts must not be ignored. When the bolts are found to be deformed and cracked, they should be replaced in time.

14、为预防连杆螺栓疲劳断裂损坏，在小型搅拌车发动机工作累计6000—7000小时后，即使螺栓外表元明显损伤，也应换新。

14. In order to prevent fatigue fracture and damage of connecting rod bolts, even if the bolt surface is obviously damaged after 6000-7000 hours of operation of small mixer engine, it shall be replaced.