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Analysis of Common Safety Hazards of Domestic Diesel Generators

Time: 2019/04/08

Based on our long-term research studies, the following points need special attention:

I. Acceptance after completion of domestic diesel generator set
Because there is no special instrument for loading test machine, it is impossible to check whether the output rated power and load capacity can meet the design requirements after the completion of the project, which directly affects the acceptance of the project; some units have reduced the environmental noise after the installation of noise reduction equipment. However, there is a certain impact on the output power of the unit. It is impossible to detect how much the output power of the unit is lost, whether the quality of the noise reduction project meets the contract requirements according to the original design, and to ensure that the unit ’s reasonable power loss is reasonable.
How to extend the service life of the generator and let the generator play its due energy, the early installation of the diesel generator set is very important. The following are the precautions for installation:
1. The installation site should be well ventilated. There should be sufficient air inlets on the generator side and good air outlets on the diesel engine side. The area of the air outlet should be more than 1.5 times the area of the water tank; the air inlet is not smooth or does not meet the requirements, and less air enters the cylinder, which will cause insufficient fuel in the cylinder, cause carbon deposits, and affect the load capacity of the diesel generator set ; Similarly, the exhaust pipe does not meet the requirements, and the oxygen content of the air in the engine room will be reduced, which will also cause insufficient fuel in the cylinder, generate carbon deposits, and affect the load capacity of the diesel generator set.
2. The surroundings of the installation site should be kept clean, and articles that can generate corrosive gases such as acid and alkali can be avoided in the vicinity. Conditional should be equipped with fire extinguishing devices.
3. For indoor use, the smoke exhaust pipe should be led to the outdoor, the pipe diameter should be the diameter of the smoke pipe of the muffler, and the elbow of the connected pipe should not exceed 3, in order to ensure the smooth exhaust of the smoke, and the The pipe is inclined 5-10 degrees downwards to avoid rainwater injection; if the exhaust pipe is installed vertically upwards, a rain cover should be installed. In order to increase the output power of diesel generator sets, in the case of a certain cylinder capacity and number, only by forcing more air into the cylinder to fully burn the fuel in the cylinder, can the average effective pressure of the unit be increased. At present, diesel generator sets use turbine boosters. Compressor, which has stricter requirements on the exhaust of diesel generators. Once the exhaust is not smooth or the exhaust gas speed cannot meet the requirements, the air entering the cylinder is reduced, which will cause the load capacity of the diesel generator to decrease.
4. When concrete is used for the foundation, the level must be measured with a spirit level during installation so that the unit is fixed on a level foundation. There should be special anti-shock pads or foot bolts between the unit and the foundation.
5. The unit casing should have reliable protective grounding. For generators that need a neutral point to be directly grounded, a professional should perform neutral grounding and configure lightning protection devices. It is strictly forbidden to use the grounding device of the mains to carry out the neutral point. Connect directly to ground.
6. The two-way switch between generator and city power should be very reliable to prevent reverse power transmission. The wiring reliability of the two-way switch needs to be verified by the local power supply department.
7. The wiring of the starter battery should be firm.
In summary, after the installation of the diesel generator set is completed, it should be checked and accepted, mainly the load capacity test and electrical characteristics test, whether it can reach the power level required by the original bidding or whether it meets the original designed capacity requirements, so that it can be achieved in mind. There are several to avoid the occurrence of security accidents.

Limitations in daily maintenance of domestic diesel generators
At present, the implementation of the maintenance operation plan of the unit is limited to the following maintenance methods:
1. Inspection of the four leakage phenomena, surface, starting battery, oil and fuel of the unit;
2. Clean and improve the environment of the equipment room, and regularly replace the three filters;
3. Carry out no-load every month and perform maintenance such as loading test machine every six months;
4. Use power monitoring to observe power quality parameters in real time.
Limitations of maintenance methods:
1. The loading test in the existing maintenance is only the on-load test of the existing back-end electrical equipment;
2. The diesel generators are tested at full load and full load for a specified period of time. 3. The no-load test machine and a large amount of carbon deposits generated by low-power loading.
Note: Domestic diesel generator sets will have different degrees of power reduction according to the environment of the machine room, service life, inadequate daily maintenance, replacement of equipment and components, etc. This poses a significant safety hazard and the diesel generator set is unloaded for a long time. Or idling, carbon deposits will be generated, which will reduce the engine output power, affect the power output of the entire unit, and even cause the illusion of normal operation. Once the load is actually loaded, a major failure of the diesel generator can not operate normally.
Formation of carbon deposits: Because the temperature of the combustion chamber is too low, it is impossible for the fuel to completely burn, which will cause carbon deposits, which will block the nozzle holes and piston rings of the fuel injectors, and there will be "black oil" overflow from the exhaust pipe It may also cause the valve to get stuck. Some unburned diesel will wash the lubricating oil on the cylinder wall and dilute the oil in the crankcase, causing all the running parts in the engine to suffer from poor lubrication.
The domestic diesel generator set runs under a small load. As the running time continues, the following faults will occur:
1. The piston & mdash; cylinder liner is not well sealed, the engine oil flies up, enters the combustion chamber to burn, and the exhaust gas emits blue smoke;
2. For supercharged diesel engines, the supercharging pressure is low due to low load and no load. It is easy to cause the sealing effect of the oil seal (non-contact) of the supercharger to decline, and the oil penetrates into the plenum and enters the cylinder with the intake air;
3. A part of the oil flowing up to the cylinder participates in the combustion, and some of the oil cannot be completely burned, and carbon deposits are formed at the valve, the intake port, the piston crown, and the piston ring, and a part is discharged with the exhaust gas. In this way, engine oil will gradually accumulate in the exhaust duct of the cylinder liner, and carbon deposits will also form;
4. The supercharger's supercharged indoor engine oil accumulates to a certain extent, and will leak out from the joint surface of the supercharger;
5. Long-term low-load operation will lead to more serious wear and tear of moving parts, and deterioration of the combustion environment of the engine, leading to the consequences of an early overhaul period.
Therefore, foreign diesel engine manufacturers, regardless of the use of naturally aspirated or supercharged models, have emphasized that the low-load / no-load operating time should be minimized, and the unit load must not be lower than 25% of the unit's rated power and 30%.
The unit runs at full load for a long time, which can not only improve its own performance, find out hidden safety hazards, but also avoid major communication accidents.

Third, the basis for the replacement of domestic diesel generators
Due to the tens of times of the AC load current, the capacity of the original unit in the equipment room cannot keep up with the requirements. In order to ensure safety and avoid safety accidents, the previous small-capacity units, diesel generators and belts that have been used for an excessive number of years should be replaced Diesel generator set with reduced load capacity.
Suggestions for replacing the unit:
1. Can not be considered solely from the service life of the unit;
2. Consider according to the load rate of the unit;
3.The over-age unit with a load rate exceeding 70% should be replaced