According to the characteristics of the work:
1. Dynamic load(the force suddenly extend and suddenly shrink, a lot of times) spring, it will cause the whole body to malfunction when the spring is damaged, such as: Valve spring of engine, friction clutch spring, electromagnetic brake spring, etc..
2. Spring loaded with static load or uniform load, such as: the safety valve and pressure relief valve spring, brake and transmission of the spring, etc..
3. Unimportant springs, such as check valves, springs, door springs, and springs, etc..
According to manufacturing precision:
1. First level precision: the force deformation of the deviation of 5% of the spring, such as the governor and the instrument need to accurately adjust the spring.
2. Second level precision: the deviation of the force deformation is about 10% of the spring, For example, safety valve, pressure relief valve and check valve spring, internal combustion engine intake valve and exhaust valve spring.
3. Third level precision: the deviation of the force deformation is about 15% of the spring, do not require accurate adjustment of the load of the spring, such as: the lifting hook and buffer springs, brake or coupling compression springs, etc..