Abstract: Indexes in natural life.economic life and technical life to weigh service life of operating equipments at stations of oil and gas pipelines are presented.Two calculation methods to determine economic life of equipments at the stations are introduced.Minimum mean expense method is used to calculate yearly mean service costs through yearly mean operating and maintenance charges and yearly mean depreciation charges; degeneracy value method of equipments covers over the factors in yearly interests of occupied capital for equipments based on yearly degeneracy values.The optimized renewal period of equipments is calculated with different methods by a case.