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Selection and Maintenance of Diesel Generator Set

Selection and Maintenance of Diesel Generator Set

With the rapid development of the diesel generator industry, its service content has become increasingly extensive. At present, many domestic owners such as Netcom, China Telecom, China Mobile, China Unicom, and China Railcom have competed to serve the society. After nearly 15 years of hard work, my country’s accession to the WTO will soon become a reality. All this means the service connotation and service quality of the information service industry. As people’s work and life are becoming more and more prominent, the power supply that guarantees the normal and reliable operation of the entire system becomes more and more important and cannot be ignored.

Currently, the backup power sources used in the information industry mainly include: ① Direct current (DC) 48V battery packs (including phase-controlled rectification and switching power supply equipment). It can provide backup power for DC equipment. Although the backup time provided is limited, the power supply to the equipment will not be interrupted when the mains power is interrupted. ②UPS uninterruptible power supply system (true online type). It can provide high-quality and pure sine wave backup AC power for AC equipment. Although the backup time provided is limited, the power supply to the equipment will not be interrupted when the mains is interrupted, and it will always provide protection for the equipment. Use electrical equipment hardware and data It will not be affected in any way by the abnormality of the power grid. ③Back-up diesel generator set. It can provide backup power for AC equipment. Although the power supply to the equipment will be interrupted for a while (at least 10 seconds) when the utility power is interrupted, it can supply power to the load for a long time. It is the backup power supply with the best cost performance. .

The selection of diesel generator set in the backup power solution:

  1. The selection of the use scheme of the standby diesel generator set. According to the different requirements of the user, the diesel generator set usually has the following three configuration schemes: ① A single manual diesel generator set is used as a backup for the mains power supply and is not equipped with an automatic transfer switch (ATS). . This scheme is the simplest. When the mains power is interrupted, it provides backup power for all or part of the load. The operation of the unit and the conversion of dual power sources in this system are completely manual. ②A single automatic diesel generator set is used as a backup power source for the mains power supply and is equipped with an automatic transfer switch (ATS). This solution automatically supplies power to all or part of the load when the mains power is interrupted. While serving as an unmanned station, it can realize remote start-up and shutdown operations. ③Multiple units are paralleled. ④Multiple units operate independently and stand by each other. ⑤Mobile power station, that is, on-board unit or trailer unit. The first configuration scheme is mostly suitable for occasions where power supply requirements are not high and operators are required. To a certain extent, this configuration is difficult to meet the needs of the current information industry development, and it is mostly in the ranks of elimination or transformation. The second scheme is currently the first choice for construction units, and it can be said to be in place in one step, and is most suitable for the needs of the modern information industry revolution. The third option is mostly used in self-supplied power plants or power stations. This operation mode has higher speed and voltage regulation functions for multiple units, and the entire control system is burdened with high maintenance requirements, so there are fewer cases in the communication industry backup power system , And gradually phased out and replaced by high-power units. The fourth scheme has two types: 1 for 1 or N+1. From the perspective of operation, this scheme is flexible and economical to use, but it has the following problems: (1) Large area; (2) 1+1≠ 2 ; (3) The low-voltage power distribution system and power supply lines are complicated. Each unit and the power distribution system must be equipped with a transfer switch, which requires a lot of economic investment; the entire backup power system is automatic or manual. (4) Large amount of maintenance. The fifth method has been practically verified in recent years and should be one of the development directions for the use of reserve units in the next few years, because the number of units is small, the mobility is strong, it is convenient for centralized maintenance, and it is more economical.
  2. Selection of diesel generator set.

At present, there are many brands of diesel generator sets. After the standby diesel generator set project is completed and put into operation, its service life is longer (not less than 15 years). Therefore, the following factors should be fully considered when selecting: (1) Unit capacity The prime mover of the diesel generator set is a compression-ignition internal combustion engine, running at no load or light load, which not only affects the power index and economic index of the unit, but also various abnormal phenomena may occur for the prime mover of different brands. Engine manufacturers generally require that its load rate is not less than 30%. Therefore, while considering the minimum load rate, the corresponding spare capacity should be set aside for future development according to the construction plan. When determining the capacity of the unit, it is necessary to fully understand the nature of the load of the power supply equipment. At present, the information service industry is mostly equipped with UPS power supplies, switching power supplies, and thyristor rectifiers that have not been eliminated. They pollute the power supply for them and have special requirements for frequency, voltage stability and power supply capacity. The adjustment rate of the electronic governor of the general unit is ±1%, and the adjustment rate of the mechanical governor is ±3%. The output voltage characteristic is directly related to the selected generator. (2) Model selection; diesel generators are generally divided into two types: open frame type and silent type. The construction unit should make a selection of models according to the comprehensive consideration of local environmental protection requirements, its own financial status, and site conditions. (3) Selection of ATS; automatic transfer switch (ATS) is an important part of the intelligent (including automatic) diesel generator set system. It is required to be safe, reliable, easy to install, operate and maintain, and can be based on the requirements of the construction unit Realize the conversion of more than two power sources. At present, the conversion components in ATS include contactor components, low-voltage circuit breakers or load switches, electric disconnect switches that can be operated with load, etc. for selection. In addition, the ATS should cooperate with the unit (because the automatic control and monitoring functions of the unit itself are different in different assembly plants) to form a complete automated backup power system. Under normal circumstances, the capacity of the ATS provided by the generator set supplier matches the capacity of the generator set. It is a standard configuration. If the construction unit has special requirements, it should be specified when ordering.

Maintenance of diesel generator sets in backup power solutions: As a backup power solution, diesel generator sets require stable performance, especially self-starting function, stable operation with load, automatic adjustment function, etc. The above functions are directly related to the daily maintenance of the unit. Therefore, the daily maintenance and maintenance of the unit according to the technical specifications cannot be ignored. The following maintenance contents at all levels are for users’ reference.

Maintenance includes the following:

  1. Routine maintenance (inspection, testing, simple treatment, can be completed by the operation staff): (1) Check the fuel storage in the fuel tank and fill it up. (2) Check the oil level in the oil pan. (3) Clean diesel engine, water pump, generator and other ancillary equipment. The focus is on the radiator. (4) Check the cooling water level. (5) Check whether the transmission belts are in good condition. (6) Check whether the water preheating system of the unit works normally. (7) Check the electrolyte level and floating charge condition in the starting battery. (8) Check whether the ATS is working abnormally. 
  2. Primary technical maintenance (maintenance work can be performed by user maintenance staff):             Basic technical maintenance based on the completion of daily maintenance work, the following tasks also need to be completed: (1) Clean the fuel tank and oil pan, and drain it Oily. (2) Replace the diesel filter, machine filter, air filter, water filter, and side filter when appropriate. (3) Change the oil. (4) Check and tighten the seals (oil, water, gas). (5) Check whether the electrical and cable connections are reliable. (6) Drain the accumulated water in the oil-water separator. (7) Check and adjust the charger and charger. (8) Check, test, and adjust various functions of the entire system.

3. Intermediate technical maintenance and advanced technical maintenance (should be completed by specially trained engineers and technicians, and the maintenance includes primary maintenance): (1) Thoroughly clean the fuel injection system. (2) Thoroughly inspect and clean the lubrication system. (3) Remove and wash the cylinder head, clear the carbon deposits, and remove the exhaust pipe to remove soot. (4) Check whether each transmission is flexible, oily, rusty, and damaged. (5) Check the sealing condition of the seals. (6) Check and adjust the valve clearance. (7) Check the turbocharger. (8) Check and adjust the speed sensor. (9) Clean the generator and check its insulation and connection. (10) Load test, calibrate the fuel supply pump.

Diesel generator set maintenance manuals or industry operation and maintenance procedures will put forward specific requirements for operation and maintenance personnel, but for each set in actual use, some adjustments should be made according to the specific situation. Therefore, the maintenance of diesel generator sets must pay attention to the following issues:

  1. Fuel

For maintenance personnel, the fuel quality should be ensured, and fuel that meets the labeling requirements, is reasonably viscous, clean and free of impurities, and is filtered and deposited. Its main performance indicators include cetane number, viscosity, freezing point, ash content and impurities, actual gum quality, etc. Wrong choice of fuel label (condensation point deviation) will cause temporary blockage of the fuel supply system including filters, fuel pumps, and injectors, which will not only make the unit paralyzed, but also cause certain difficulties in emergency treatment. This problem occurs frequently in the cold season and cannot be ignored. The high content of fuel impurities (such as residual carbon, ash, actual colloid, moisture, and other particulate matter) will shorten the replacement cycle of the fuel supply system filter and cause the unit to fail to work normally. The most representative phenomenon is no-load or The unit operates normally under light load, and the unit frequency drops sharply or even shuts down under light or heavy load. In view of this situation, if the filter is not replaced for a long time, it may also cause blockage and early wear of the high-pressure fuel supply circuit and the fuel injector, shorten the service life of the unit, and cause more difficult to solve faults. At this time, it must be ruled out by professionals. Therefore, under normal circumstances, the fuel supplemented by the unit must undergo precipitation and filtration treatment to ensure that the fuel is clean. PT fuel supply pumps have higher requirements for this.

  1. The lubrication of the unit is well known to everyone that the lubrication system of the unit is very important, otherwise it will not only affect the normal operation of the unit, but if it is serious, it will cause damage to the unit’s parts and even the unit to be scrapped. In summary, there are five functions of the lubrication system:  (1)  Use a lubricating film to separate the friction surface of the parts to reduce wear and power consumption. (2)  The flowing lubricating oil takes away the heat generated by the friction surface and cools the surface of the friction part. (3)  The flowing lubricating oil cleans the friction surface, and takes away the metal chips and dirt that are worn off to reduce the wear of the parts. (4)  There is lubricating oil between the cylinder liner and the piston and piston ring to help seal and facilitate the establishment of compression and starting. (5)  A layer of lubricating oil on the surface of the machine parts can prevent surface oxidation and corrosion. Therefore, in addition to the selection of high-quality lubricating oil, the main performance indicators include viscosity, kinematic viscosity ratio, freezing point, flash point, acid value, etc. The maintenance work of the lubrication system should be completed regularly according to the specific situation, mainly including the following: oil level inspection , Check and adjust the oil pressure, check the oil temperature (82-107 degrees), replace the filter element, clean the filter, seal the oil pump, etc. PS: The practical judgment method of engine oil performance is to check the viscosity and consistency.
  2. Maintenance of the cooling system (water cooling) of the unit: It is extremely important that the cooling system of the unit is working properly, because the cooling system is not effective or not cooling will cause the following consequences: ●The parts are overheated, and the strength and rigidity of the metal materials are significantly reduced. ●Excessive heating temperature of parts causes volume expansion, destroys the normal cooperation between parts, and even jams and damages. If the temperature is too high, the viscosity of the lubricating oil will decrease, even oxidizing and coking, and losing its lubricating effect. ●If the temperature of the parts in the cylinder is too high, the fresh air entering the cylinder will be heated by the high-temperature parts, the specific volume will increase, and the actual air intake will decrease. The low temperature of the cooling system will cause the following consequences: ●The viscosity of the lubricating oil will increase, the fluidity will be poor, and the friction resistance of the moving parts will increase. ●The temperature of the parts in the cylinder is too low, which prolongs the fuel ignition delay period and makes the work rough. ●The loss of heat energy taken away by cooling increases, and the effective power decreases.

It is not difficult to see from the above that whether the cooling system works normally or not will directly affect the power, economy, reliability and service life of the internal combustion engine. Therefore, it must be carefully maintained: ① Check the cooling water level and water quality. ② Regularly clean the cooling system. ③Check and adjust the tension of the fan belt. ④Check the thermostat (74-91 degrees). ⑤ Take effective measures to prevent freezing of the unit in the cold season. If necessary, the water in the cooling system must be completely emptied.

  1. Maintenance of the ventilation system of the computer room: Although the ventilation of the computer room does not belong to the unit itself, it is the basic prerequisite for the normal operation of the unit. Without good ventilation in the computer room, the power, economy, reliability and service life of the unit will be seriously affected. . The most intuitive and common phenomenon is:  (1) The replacement cycle of air filter, oil filter, and fuel filter is shortened, and the wear of mechanical parts is accelerated. (2) Because the unit cannot get enough fresh air, its prime mover’s power performance (load capacity) is severely restricted. The cooling of the unit cannot be guaranteed, causing the generator and prime mover to overheat, the entire system shuts down due to protection, and even the generator is burned. (3) The ventilation and heat preservation of the machine room are contradictory to a certain extent, otherwise the prime mover may be damaged in the cold season, resulting in undue economic losses.
  2. Maintenance of control and other ancillary systems: Although the control and other ancillary systems are not the main body of the unit, they must complete the intelligent control of the unit, automatic protection, data detection and transmission, interlocking control of the transfer switch, and charging of the starting battery. The preheating of the unit is related to the normal and safe operation of the entire system. Therefore, its regular maintenance is indispensable, mainly including the following:  (1) Whether the automatic start-up, stop and ATS chain control functions are normal. (2) Simulation test of the protection function of the unit (high water temperature, low oil pressure, overspeed, etc.). (3) Whether the battery charger and unit warm-up work normally. (4) Whether the sampling and display of each parameter of the unit are normal.