Signal 1: Fault frequency is increasing

A generator that requires repair twice a year or less is within the range of normal wear-and-tear maintenance. If it requires repair four or five times a year, where the same problem recurs shortly after each repair, or where different components fail each time, 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. The way to determine this is to review the past year's maintenance records and look at the interval between each failure. If the intervals are getting shorter, the equipment is aging overall, and various components are reaching the end of their service lives one after another. 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. Understanding these patterns is an important part of diesel engine remanufacturing decision-making, as it helps determine whether an engine is a candidate for comprehensive restoration or should be retired.

Signal 2: Replacement parts are becoming increasingly difficult to obtain

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. If two consecutive repairs are delayed due to inability to find parts, or if the parts that are found cost more than double the normal price, the parts supply has become problematic. A typical signal is when a repair technician says, "This part is hard to find now; I'll try to find a salvaged one." Salvaged parts come with uncertain service life—they may fail again soon after installation. If parts cannot be obtained, the equipment should be retired. Under Hainan's bonded maintenance policy, the procurement cycle for imported parts has been shortened, but this assumes the manufacturer is still producing the parts. For models that the manufacturer has discontinued, even the best policy cannot help. In such cases, diesel engine abnormal noise repair may become impossible simply because the necessary replacement parts are no longer available.

Signal 3: The repair cost percentage is too high

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 Hainan's bonded maintenance policy, tariffs on imported parts are exempt, which lowers the cost of each individual repair. However, the logic of cumulative repair costs remains unchanged. Add up the repair invoices from the past year, calculate the total, and you will have a clear picture. Regular generator performance testing and repair can help catch problems early, potentially avoiding costly repairs and extending equipment life.

Signal 4: Energy consumption is significantly higher

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 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. Calculate the additional fuel cost and compare it with the repair cost—this will tell you whether the equipment is worth keeping. Before making a final decision, a thorough generator performance testing and repair assessment can provide the data needed to determine whether the equipment still meets operational requirements.

Signal 5: Downtime losses are too great

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. A common issue that leads to downtime is generator failure to energize repair situations, where the generator runs but produces no voltage—these can often be resolved quickly with proper troubleshooting, but repeated occurrences may indicate deeper problems.

Signal 6: Safety risks are difficult to control

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. If the equipment has safety hazards that cannot be completely eliminated through multiple repairs, retirement and replacement is the safest choice. One specific area of concern is generator oil pressure low causes—if low oil pressure persists despite multiple repairs and component replacements, the engine may have internal wear that makes continued operation risky.

Summary

To determine whether an old generator should be kept or replaced, look at six signals: fault frequency, parts availability, repair costs, energy consumption performance, downtime losses, and safety risks. If two of the six signals 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 making the "repair" path cheaper and faster, but it 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. Equipment that should be retired still needs to be retired. Therefore, the criteria for retirement remain unchanged. 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.

Hainan Longpan Oilfield Technology Co., Ltd. is Hainan Province's first pilot enterprise for bonded maintenance outside the free trade port area. Its business scope covers diesel engine remanufacturing, diesel engine abnormal noise repair, generator performance testing and repair, generator failure to energize repair, analysis of generator oil pressure low causes, and gas engine overhaul.

If you are struggling with the decision of whether to keep or replace your old equipment, we can help you conduct a comprehensive assessment and provide recommendations on whether to keep or replace. From fault frequency to parts availability, from repair costs to energy consumption performance, from downtime losses to safety risks—once the numbers are clear, the decision becomes easy.