The accident was due to the action of acid o the checknut.
事故是由于酸对防松螺母的作用而发生的。
2
Make sure check the bolt and nut before testing run. and if they become less crowded, fastening again.
试车前务必检查所有螺栓、螺母是否有松动，若有松动的螺栓、螺母必须重新紧固。
3
Maintenance should first check the tire pressure, wear, nut loose or fall off, remove the twins or tread on the inserts and nails and other sharp objects.