The annual maintenance cost calculation of a nitrogen generator system is a systematic and refined accounting work that covers fixed routine maintenance costs, variable fault repair costs, consumable replacement costs, labor costs, and auxiliary operating costs, which is applicable to industrial, food, laboratory and all types of nitrogen generation equipment. The core of the calculation method is to classify and quantify all measurable maintenance expenditures throughout the year, eliminate ambiguous cost items, and form accurate data support for equipment operation budget formulation and equipment life cycle management. Different types of nitrogen generators (membrane separation, PSA, high-purity laboratory type) have differentiated maintenance cost ratios, so targeted itemized statistics are required in the calculation process to avoid one-size-fits-all data errors.

First, fixed routine maintenance costs are the most basic and stable expenditure, accounting for 40%–50% of the total annual maintenance cost. This part includes regular equipment inspection, system calibration, pipeline pressure testing, and daily operation monitoring fees. For industrial large-scale nitrogen generators, fixed maintenance items cover monthly air compressor operation check, quarterly nitrogen purity calibration, and annual overall system debugging. The calculation standard is based on the equipment model, operating hours and manufacturer’s maintenance specifications. The annual fixed maintenance cost can be obtained by multiplying the single routine maintenance fee by the annual maintenance frequency plus the annual system calibration service fee. For small mobile equipment, the fixed cost is relatively low, mainly reflected in daily appearance inspection and parameter debugging.

Second, consumable replacement costs are variable core expenditures, including filter elements, membrane modules, activated carbon, drying agents and other vulnerable parts. Each consumable has a fixed service life and replacement cycle. The calculation method is to divide the annual operating hours by the service life hours of a single consumable to get the annual replacement quantity, then multiply by the unit price of the consumable. Among them, membrane separation membrane modules have a service life of 3–5 years, with average annual amortized cost; precision filter elements need to be replaced 2–4 times a year according to air quality, which is a high-frequency consumable cost. In addition, the loss of sealing rings, valves and other small accessories should be included in the consumable cost statistics to ensure full coverage of expenses.

Third, labor and fault maintenance costs are supplementary variable expenditures. Labor costs include the salary and technical service fees of professional maintenance personnel responsible for daily inspection and maintenance of the equipment, which can be calculated according to the annual working hours of personnel and unit labor price. Fault maintenance costs are uncertain expenditures, which can be calculated by averaging the annual fault repair costs of the same type of equipment in the industry, including component repair, fault troubleshooting, and emergency maintenance service fees. Finally, the total annual maintenance cost is the sum of fixed maintenance cost, amortized consumable cost, annual fault maintenance cost and auxiliary management cost, and the cost proportion of each item can be analyzed to optimize subsequent equipment operation and maintenance strategies.