With the extension of operation time, the following five hazards will appear when the diesel generator set operates under small load

1. The piston cylinder liner seal is not good, the engine oil moves up, enters the combustion chamber for combustion, and the exhaust emits blue smoke;

2. For turbocharged diesel engine, the supercharging pressure is low due to low load and no-load. It is easy to cause the sealing effect of supercharger oil seal (non-contact type) to decline, and the oil enters into the supercharging chamber and enters the cylinder with the intake air;

3. A part of the oil that goes up to the cylinder participates in combustion. Some of the oil can't burn completely. Carbon deposits are formed at the valve, intake port, piston crown and piston ring, and some of them are discharged with exhaust. In this way, engine oil will gradually accumulate in the exhaust passage of cylinder liner, and carbon deposit will also be formed;

4. When the oil in the supercharger chamber accumulates to a certain extent, it will leak out from the joint surface of the supercharger;

5. Long term small load operation will lead to more serious wear of moving parts and deterioration of engine combustion environment, which will lead to earlier overhaul period. Therefore, foreign diesel engine manufacturers emphasize that low load / no-load operation time should be reduced as far as possible, and the minimum load should not be less than 25% - 30% of the rated power of the unit.

Long time full load operation of diesel generator can not only improve its performance, find out potential safety hazards, but also avoid major communication accidents.

1、 Preparation before start-up. Every time before starting the engine, it is necessary to check whether the cooling water or antifreeze in the water tank of the diesel engine meets the requirements. If it is insufficient, it should be filled up. Pull out the oil dipstick to check whether there is a lack of lubricating oil. If it is missing, it should be added to the specified "static full" scale, and then carefully check whether there is any hidden trouble in the relevant parts. If any fault is found, it should be removed in time before starting the machine.

2、 It is forbidden to start the diesel engine with load. Before starting the diesel engine, the output air switch of the generator must be in the off state. After the diesel engine of ordinary generator set is started, it will run at idle speed for 3-5 minutes (about 700 RPM). The temperature is low in winter, so the idle running time should be extended for several minutes. After the diesel engine is started, it is necessary to observe whether the oil pressure is normal and whether there is oil leakage, water leakage and other abnormal phenomena (under normal conditions, the oil pressure must be above 0.2MPa). In case of any abnormality, immediately stop the engine for maintenance. If there is no abnormal phenomenon, the diesel engine speed is increased to the rated speed of 1500 rpm, and the generator display frequency is 50 Hz and the voltage is 400 V, then the output air switch can be closed and put into use. The generator set is not allowed to run without load for a long time. (for a long time of no-load operation, the diesel oil ejected from the fuel injection nozzle of the diesel engine can not be completely burned, resulting in carbon deposition and air leakage of valves and piston rings. )If it is an automatic generator set, it does not need to run at idle speed, because the automatic unit is generally equipped with water heater to keep the diesel engine cylinder block at about 45co. After the diesel engine is started, it can send power normally within 8-15 seconds.

3、 Pay attention to observe the working state in operation. In the work of generator set, special person should be on duty to observe a series of possible faults, especially the changes of oil pressure, water temperature, oil temperature, voltage, frequency and other important factors. In addition, enough diesel oil should be prepared. In case of fuel interruption during operation, the load shutdown will be objectively caused, which may cause damage to the excitation control system and related components of the generator.

4、 It is forbidden to shut down with load. Before each shutdown, the load must be cut off step by step, and then the output air switch of the generator set shall be turned off. Finally, the diesel engine shall be slowed down to idle speed for about 3-5 minutes before shutdown.

The following are the safety operation procedures:

1、 The operation of the engine part of the generator powered by diesel engine shall be carried out according to the relevant provisions of the internal combustion engine.

2、 Before starting the generator, it is necessary to carefully check whether the wiring of each part is correct, whether the connecting parts are reliable, whether the brush is normal, whether the pressure meets the requirements, and whether the grounding wire is in good condition.

3、 Before starting, put the resistance value of excitation rheostat at the maximum position, disconnect the output switch, and the generator set with clutch shall release the clutch. First start the diesel engine with no load and start the generator after running smoothly.

4、 After the generator starts to run, pay attention to the mechanical noise and abnormal vibration at any time. After confirming that the condition is normal, adjust the generator to the rated speed, adjust the voltage to the rated value, and then close the output switch to supply power to the outside. The load should be gradually increased to achieve three-phase balance.

5、 The parallel operation of generators must meet the conditions of the same frequency, same voltage, the same phase and the same phase sequence.

6、 All generators ready for parallel operation must be in normal and stable operation.

7、 After receiving the signal of "ready for parallel connection", adjust the speed of the diesel engine according to the whole device, and switch on at the moment of synchronization.

8、 The load of generators in parallel operation should be adjusted reasonably and the active power and reactive power of each generator should be evenly distributed. The active power is regulated by the throttle of diesel engine, and the reactive power is regulated by excitation.

9、 The generator in operation should pay close attention to the sound of the engine and observe whether the indication of various instruments is within the normal range. Check whether the operation part is normal and whether the temperature rise of generator is too high. And make operation records.

10、 When stopping, reduce the load first, restore the excitation rheostat to reduce the voltage to the minimum value, then cut off the switch in sequence, and finally stop the diesel engine.

11、 If a diesel engine in parallel operation needs to be shut down due to load drop, the load of one generator that needs to be shut down shall be transferred to the generator that continues to operate, and then the single generator shall be shut down. If it is necessary to stop the whole generator, the load shall be cut off first, and then the single generator shall be shut down.

12、 Before using the mobile generator, the underframe must be placed on a stable foundation, and it is not allowed to move during operation.

13、 When the generator is running, even if it is not excited, it should be considered as having voltage. It is forbidden to work on the outgoing line of the rotating generator, touch the rotor by hand or clean it. The generator in operation shall not be covered with canvas.

14、 After the generator is overhauled, it is necessary to carefully check whether there are tools, materials and other sundries between the rotor and stator slots, so as to avoid damaging the generator during operation.

15、 All electrical equipment in the machine room must be reliably grounded.

16、 It is forbidden to stack sundries, inflammable and explosive articles in the machine room. Except for the personnel on duty, other personnel are forbidden to enter without permission.

17、 The room shall be equipped with necessary fire-fighting equipment. In case of fire accident, power transmission shall be stopped immediately, generator shall be shut down, and carbon dioxide or carbon tetrachloride fire extinguisher shall be used to put out the fire.