I. Judgment Based on Fault Frequency

A generator that requires repair twice a year or less is within the range of normal wear-and-tear maintenance. A generator that requires repair four or five times a year, where the same problem recurs shortly after each repair, or where different components fail each time, indicates that the equipment has entered a "fault-prone period."

The typical characteristic of a fault-prone period is that the interval between repairs becomes increasingly shorter. Previously, one repair lasted two years; now, one repair lasts only two months. At this point, the question is no longer "how to repair it this time," but "whether to keep it at all." If failures are concentrated on the same component—for example, the same phase winding keeps burning out—the issue may be a design flaw or an operational habit, and can be addressed specifically. If different components fail each time—bearings this time, rectifier diodes next time, the AVR another time—this indicates overall equipment aging, with various components reaching the end of their service lives one after another. At this point, retirement should be considered.

II. Judgment Based on Parts Availability

For some older equipment models, the original manufacturer has been out of production for many years, and replacement parts are increasingly difficult to find. Using salvaged parts offers no quality guarantee—no one knows how long they will last. Using substitute parts often involves dimensional mismatches that require on-site modification, which is time-consuming, labor-intensive, and not always successful.

Under the current bonded maintenance policy in Hainan, China, the procurement cycle for imported parts has been compressed from two to three months to one to two weeks—but this assumes the manufacturer is still producing the parts. For models that the manufacturer has discontinued, parts supply will only become scarcer. One signal is when two consecutive repairs are delayed due to inability to find parts, or when the parts that are found cost more than double the normal price. If parts cannot be obtained, the equipment should be retired.

III. Judgment Based on Repair Costs

The cost of a single repair, expressed as a percentage of the price of a new unit, is a useful reference indicator. An industry rule of thumb is: if a single repair cost exceeds 30% of the price of a new unit, retirement should be considered. This is because the cost of this one repair already equals one-third of a new machine, and other components may continue to fail after the repair.

Another criterion is the total annual repair cost. If multiple repairs are performed in a year and the cumulative cost exceeds 50% of the price of a new unit, replacement should also be considered. This is because the money spent on repairs in that one year already equals half the cost of a new machine, yet the equipment remains the same old unit. Under the bonded maintenance policy in Hainan, China, tariffs on imported parts are exempt, which lowers the cost of each individual repair. However, the logic of cumulative repair costs remains unchanged.

IV. Judgment Based on Energy Consumption Performance

A typical characteristic of old equipment is high energy consumption. For the same load, fuel consumption is 20–30% higher than that of a new unit. The extra fuel burned over a year may be enough to pay for several repairs.

Here is how to calculate it: record the fuel consumption of the existing equipment over 100 operating hours, and compare it with the fuel consumption data listed in the instruction manual for a new unit of the same model. If the difference exceeds 20%, the equipment's thermal efficiency has significantly declined. High fuel consumption not only costs money, but also indicates incomplete combustion and high exhaust temperatures, which affect other components as well. For equipment that runs 2,000 hours per year, the additional fuel cost can be substantial.

V. Judgment Based on Downtime Losses

The frequency and duration of equipment failure-related downtime directly affect production. If equipment fails ten times a year, with each failure causing three to five days of downtime, the cumulative downtime exceeds one month. For facilities with backup power, the loss may be limited to repair costs and labor. For facilities without backup power, the loss from one day of production stoppage may far exceed the repair cost itself.

The judgment method is: record the downtime duration for each failure, multiply it by the production loss per unit of time, and calculate the total. If this figure has been increasing for two consecutive years, and the rate of increase is rapid, the equipment's aging is increasingly affecting production. At this point, even if repair costs are low, replacement should be considered.

VI. Judgment Based on Safety Risks

Some hazards of old equipment cannot be measured in monetary terms. For example, a fine crack in the engine cylinder block could cause coolant or oil leakage at any time. Aging generator insulation could cause electrical leakage or arcing at any time. These conditions may not be detectable through routine testing, but their consequences would be severe.

Signal: maintenance personnel discover anomalies during disassembly and inspection but cannot identify the root cause, or the same area repeatedly fails without explanation. When safety risks are present, it is better to err on the side of caution.

VII. The Role of the Bonded Maintenance Policy

It should be noted that the bonded maintenance policy in Hainan, China, makes repairs faster and cheaper. Equipment that was originally scheduled for retirement may be able to run for another two years because repair costs have decreased and parts arrive more quickly.

However, the policy does not change the physical condition of the equipment. A cracked cylinder block, a bent crankshaft, burned windings, or aged insulation—no policy can restore these. Therefore, the criteria for retirement remain unchanged—fault frequency, parts availability, repair costs, energy consumption, downtime losses, and safety risks are still the same six indicators. What has changed is the cost of taking the repair path. Equipment that was previously unaffordable to repair is now affordable. Equipment that previously could not tolerate the waiting time can now tolerate it. But equipment that should be retired still needs to be retired.

VIII. Summary

To determine whether an old generator should be retired, look at six indicators: fault frequency, parts availability, repair costs, energy consumption performance, downtime losses, and safety risks. If two of the six indicators show red flags, retirement should be seriously considered. If three or more show red flags, the decision is essentially made.

The value of the bonded maintenance policy in Hainan, China, lies in this: for equipment that "can still be saved," it makes the cost of saving it lower and the turnaround time shorter. For equipment that "cannot be saved," it does not change the conclusion.

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