Carbon brushes are very small components on a generator, and many people do not take them seriously. But when they wear short, spring pressure decreases, the contact between the brushes and slip rings becomes unstable, excitation current fluctuates, and output voltage becomes unstable. Many cases of voltage instability end up with technicians disassembling windings for hours, only to discover the problem was the carbon brushes. How long should carbon brushes be before replacement? Less than ten millimeters—they must be replaced. But many people wait until five millimeters, by which time the slip rings may already have grooves worn into them. Replacing carbon brushes costs a few dozen currency units. Replacing slip rings requires disassembling the generator and costs thousands. Even worse, after slip rings become grooved, new carbon brushes have a smaller contact area and will wear down quickly again, creating a vicious cycle. Therefore, carbon brush inspection cannot wait. Every time the equipment is shut down for maintenance, the cover should be opened and the brushes checked. This is especially important when diagnosing generator voltage fluctuation causes, as worn brushes are one of the most common sources of voltage instability. Under Hainan's bonded maintenance policy, imported carbon brushes can be procured duty-free and quickly, so there is no reason to delay replacement due to waiting for parts.

Coolant is also easily overlooked. Many people add coolant to an engine once and never replace it. Coolant has a shelf life, generally two years. After the expiration date, the rust inhibitor fails, the anti-corrosion agent fails, and the pH value changes. If it becomes acidic, it corrodes the radiator and cylinder block. If it becomes alkaline, it produces scale that blocks water passages. By the time the coolant becomes turbid or has sediment, the water passages may already be significantly corroded. A corroded cylinder block surface develops small pits like a honeycomb. These pits destroy the cylinder head gasket seal, causing coolant to leak into the combustion chamber or combustion gases to enter the cooling system. Replacing coolant is inexpensive, but flushing water passages, replacing the cylinder head gasket, and replacing the water pump are not cheap. In more severe cases, the cylinder block corrosion is too deep to repair, and the entire block must be replaced. Therefore, coolant must not only be added but also replaced regularly—once every two years, and this cannot be skipped.

Air filter maintenance also tends to go to extremes. One extreme is never cleaning the filter—using it until it is completely clogged, causing insufficient air intake, power loss, and black smoke. When the air filter becomes clogged, intake resistance increases, the engine struggles to draw air, fuel combustion is incomplete, power drops, and fuel consumption rises. Even worse, when a filter is severely clogged, negative pressure can collapse the filter element, causing dust to enter the engine directly. The other extreme is using high-pressure compressed air to blow out the filter too frequently, which can rupture the filter paper. A ruptured filter cannot block dust, and dust entering the engine wears out cylinder liners and piston rings. The correct practice is to follow the hour schedule—typically every 500 hours in normal environments, every 250 hours in dusty environments. When cleaning a filter, use low-pressure air, blow from the inside out, and keep pressure below 0.3 MPa. Keep the nozzle a distance away from the filter element—do not blow directly against it. Under Hainan's bonded maintenance policy, imported filters can be procured duty-free, so there is no reason to avoid replacement due to cost.

An engine has hundreds of bolts, and each has a specified torque value. How tight to torque cylinder head bolts, connecting rod bolts, and main bearing cap bolts—all are different. If torque is too low, bolts will loosen. If torque is too high, bolts will stretch, deform, or even fracture. Some people rely on "feel" and think more force is better. As a result, cylinder head bolt torque is uneven, the cylinder head gasket does not seal properly, and coolant leaks into the combustion chamber. If connecting rod bolt torque is too high, the bolt stretches, its strength decreases, and it fractures during operation, causing the connecting rod to punch through the cylinder block. Many engines fail soon after an overhaul precisely because bolts were not tightened to specification. Torque wrenches must be used, and bolts must be tightened step by step in the specified sequence. This is basic, but many people fail to do it. Some technicians have torque wrenches but never calibrate them—after years of use, their accuracy has drifted, and the torque they apply is still incorrect. Torque wrenches need to be calibrated once a year; this is also easily overlooked.

There is water in diesel fuel, and water damages fuel injectors. One function of the fuel filter is to separate water from the fuel. There is a drain valve at the bottom of the filter, and it needs to be drained regularly. But many people do not know to drain it, or they know but never do it. Water accumulates until it is drawn into the fuel injectors, causing the injector plungers to rust and seize. A single fuel injector costs thousands, and six cylinders means tens of thousands. Moreover, when an injector seizes, fuel atomization is poor, combustion is incomplete, the exhaust pipe emits black smoke, carbon builds up on the piston crowns, and in severe cases, the piston can burn out. The action of draining water takes one minute per week and requires no tools. Open the drain valve, release a small amount of fuel, and check for water. If water is present, continue draining until it is clear. Under Hainan's bonded maintenance policy, imported fuel injectors can be procured duty-free, but even at a lower cost, it is still better not to have them fail at all.

In many power plant operation logs, only the word "normal" is written. Normal today, normal tomorrow, normal the day after—no changes are visible. When equipment finally fails, reviewing the log provides no clues, and no one knows when the problem started. A good log should record specific values: voltage in volts, current in amperes, oil pressure in megapascals, coolant temperature in degrees Celsius, and exhaust color. Comparing each set of data with the previous set reveals trends. Continuously decreasing voltage indicates a problem with the excitation system. Continuously decreasing oil pressure indicates accelerating bearing wear. Continuously increasing coolant temperature indicates the cooling system is deteriorating. Writing a few numbers does not take much time, but not writing them can cost a lot of money. Some power plants use spreadsheets for logging, with data automatically generating trend charts, making changes immediately visible. Whether equipment is in good condition—looking at trend charts is far more reliable than listening to sounds.

From carbon brush length to coolant replacement intervals, from air filter maintenance to bolt torque specifications, from draining fuel filters to maintaining complete operation logs—none of these items individually seems major, but each can determine whether equipment lasts ten years or only five. If carbon brushes are not replaced, slip rings wear out. If coolant is not replaced, the cylinder block corrodes. If air filters are not maintained properly, cylinder liners wear out. If bolts are not torqued to specification, the engine is destroyed. If fuel filters are not drained, injectors seize. If logs are not kept, problems are discovered too late. Any lapse in these six details can cause perfectly good equipment to fail prematurely. Conversely, if these six details are done correctly, equipment life can be extended by a significant margin.

The bonded maintenance policy in China's Hainan Free Trade Port makes the imported parts involved in these tasks cheaper and faster to obtain, so enterprises have no excuse to delay. Replace carbon brushes when they reach the end of their life. Replace filters when they reach their hour limit. Replace coolant when it reaches its age limit. Tighten bolts to the specified torque. Drain water regularly. Keep records carefully. These tasks do not require advanced technical skills; they require attention to detail and consistency.

Hainan Longpan Oilfield Technology Co., Ltd. is Hainan Province's first pilot enterprise for bonded maintenance outside the free trade port area. With a technical team of over 300 members and specialized equipment including cylinder boring machines, crankshaft grinding machines, and load bank test systems, 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 voltage fluctuation causes, and technical support for power plant maintenance engineers. If you are seeking solutions to various problems in equipment maintenance, professional technical support can help you get these details right, reduce maintenance costs, shorten equipment downtime, and ensure the long-term reliability of your equipment.