Analysis of several hidden safety hazards in diesel generator sets

Analysis of several hidden safety hazards in diesel generator sets

First of all, I think that diesel generators must first understand an industry, that is, the communication industry. Now, because the rear-end load of diesel generators used in the communication industry has not reached full load, or even most of them are below half load, it belongs to "Malaysia. "Pushing a trolley" phenomenon, so that it is not easy to find and deal with problems in a timely manner. In case of emergency, after the mains is stopped, the diesel generator set must provide power to the back-end load immediately. Although the communication equipment has backup power sources such as batteries and UPS, these are all short-term power supply equipment, so the diesel generator set becomes The last guarantee of the communication backup power supply, once the load capacity and various electrical characteristics of the diesel generator set do not meet the communication power requirements, the power supply will not be normal, and communication will be interrupted. Such accidents occur from time to time throughout the country Both have, we can analyze the cause of this accident in order to propose effective solutions.

According to our long-term investigation and research on backup power in the communications industry, the following points need to be paid special attention:

I. Acceptance after completion of 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; the environmental noise is reduced after the installation of noise reduction equipment in some unit rooms. 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 how much the unit's reasonable power loss is guaranteed.

 How to extend the service life of the generator and allow the generator to exert its maximum energy, the early installation of the diesel generator set is very important. The following are installation precautions:

     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 larger than the area of the water tank; the air inlet is not smooth or does not meet the requirements, and less air enters the cylinder. This 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, cause carbon deposits, and affect the load capacity of the diesel generator set.

    2. The surroundings of the installation site should be kept clean, and avoid placing nearby items that can produce corrosive gases such as acid and alkali, and steam. If possible, fire extinguishing equipment shall be provided.

    3. For indoor use, the smoke exhaust pipe must be led to the outdoor, the pipe diameter must be ≥ the diameter of the smoke pipe of the muffler, and the elbow of the connected pipe should not exceed 3, to ensure the smooth exhaust of the smoke, and the pipe should be Tilt down 5-10 degrees to avoid rainwater injection; if the exhaust pipe is installed vertically upwards, a rain cover must be installed. In order to increase the output power of diesel generator sets, given the capacity and number of cylinders, only by forcing more air into the cylinders to fully burn the fuel in the cylinders can the average effective pressure of the units be increased. At present, diesel generator sets use turbine boosters. Compressor, which has stricter exhaust requirements for diesel generators. Once the exhaust is not smooth or the exhaust gas speed cannot meet the requirements, the air entering the cylinder will be 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 to fix the unit on a level foundation. There should be special anti-vibration pads or foot bolts between the unit and the foundation.

    5. The unit casing must have reliable protective grounding. For generators that need to have a neutral point directly grounded, a professional must perform neutral grounding and be equipped with lightning protection devices. It is strictly prohibited to use the mains grounding device for the neutral point. Connect directly to ground.

    6. The two-way switch between generator and city power must 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 must be firm. In summary, after the installation of the diesel generator set is completed, it must be checked and accepted, mainly the load capacity test and electrical characteristic test. Whether it can reach the power level required by the original bidding or whether it meets the capacity requirements of the original design. There are several to avoid the occurrence of security accidents.

Limitations in daily maintenance of diesel generators

At present, the implementation of maintenance work plans for diesel generator sets is limited to the following maintenance methods:

   1. Check 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 supply 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 power equipment;

   2. Test the electrical characteristics of diesel generators under full load and full load for a specified time

   3. A large amount of carbon deposits from no-load test machine and low-power load.

Note: The diesel generator set will have different degrees of power reduction according to the environment of the machine room, the service life, inadequate daily maintenance, and replacement of equipment and components. This has important safety hazards, and the diesel generator set has no load for a long time or Idle operation will cause carbon deposits, which will reduce the engine output power, affect the 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 set cannot operate normally.

Formation of carbon deposits:

Because the temperature of the combustion chamber is too low, it is impossible to completely burn the fuel, which will cause carbon deposits, which will block the nozzle holes and piston rings of the injectors, and there will be "black oil" overflow from the exhaust pipe, and the valve may be 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 diesel generator set runs under a small load. As the running time continues, the following faults will occur:

   1. The piston-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 decrease, 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 degree, 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 the overhaul period.

Therefore, regardless of the use of naturally aspirated or supercharged models, foreign diesel engine manufacturers emphasize that the low-load / no-load running time should be minimized, and the minimum load must not be lower than 25% -30% of the rated power of the unit. The diesel generator set runs at full load for a long time, which can not only improve its own performance, find hidden safety hazards, but also avoid major communication accidents.

Third, the basis for the replacement of diesel generators

  After nearly two decades of rapid development in the communications industry, equipment in the equipment room has been increasing, causing AC load currents to increase tens of times. This has caused the capacity of the original diesel generator set in the equipment room to keep up with the requirements. In the event of an accident, the previous small-capacity diesel generator set, the diesel generator set that has been used for an excessive number of years, and the diesel generator set with a reduced load capacity must be replaced.

 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. It is necessary to replace the over-age unit with a load rate exceeding 70%.