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Basic Process of Overhaul for Diesel Power Generating Set

Aug. 21, 2020


As a generator set maintenance technician, it is necessary to know the basic process of overhaul for diesel power generating set. Today Starlight Power shares the overhaul methods for diesel engine and alternator of generator set.


1.Overhaul of diesel engine of generator set

The overhaul of diesel engine is a restorative repair. It is mainly to restore the dynamic performance, economic performance and fastening performance of diesel engine parts to ensure the good condition and long service life of diesel engine.

Basic comments of overhaul of diesel engine

A. Repair or replace crankshaft, connecting rod, cylinder liner, valve seat and valve guide;

B. Repair eccentric bearing;

C. Replace the plunger pair, oil delivery valve pair and needle valve pair;

D. Repair and welding of oil pipe and joint;

E. Repair and replace water pump and governor, and remove water jacket scale;

F. Check, repair and adjust the circuit, instrument, charging generator and starting motor in the power supply system;

G. Install, monitor, test, adjust each system and load test.

diesel engine


When overhaul diesel engine, generally according to specified working hours data and technical situation. Different overhaul working hours for different type of diesel engine. For example, due to improper use and maintenance or poor working conditions of diesel engine (dusty, often working under overload conditions, etc.), it may not be able to continue to use before the working hours are reached.

Therefore, in determining the overhaul of internal combustion engine, in addition to the working hours, it is also necessary to determine the following overhaul conditions.

A. The internal combustion engine can not work well (the speed drops greatly after loading, and the sound suddenly changes), and the exhaust emits black smoke.

B. It is difficult to start the internal combustion engine at normal temperature. After heating, the crankshaft bearing, connecting rod bearing and piston pin have knocking sound.

C. When the temperature is normal, the cylinder pressure can not reach 70% of the standard pressure.

D. Significant increase in fuel and oil consumption.

E. Loss of roundness of cylinders, shape, clearance between piston and cylinder, the roundness of the connecting rod journal exceeds the specified limit.


When overhauling diesel engine , we should repair main parts. The whole engine is divided into assembly and parts, and inspected and classified. In addition, it has more technical conditions for repair, so that it can be thoroughly inspected, repaired and assembled.


2.Overhaul process of alternator for generator set

The overhaul period of generator is generally 2-4 years. The main contents of the overhaul are as follows:

1)Disassemble the body and take out the rotor

A. Mark the screw, pin, gasket and cable head before disassembly. After the cable head is disassembled, it shall be wrapped with clean cloth, and the rotor ring shall be wrapped with neutral Vaseline soil and then wrapped with green shell paper;

B. After removing the end cover, carefully check the clearance between the rotor and stator, and measure the upper, lower, left and right clearances;

C. When taking out the rotor, it is not allowed to collide or rub with the stator. After taking out the rotor, it should be placed on a stable hardwood pad.

 diesel generator set

2)Repair stator.

A. Check the base and shell and clean them. The paint is required to be in good condition;

B. Check the stator core, winding and the inside of the frame, and clean the dust, oil dirt and sundries. The dirt on the winding can only be removed with a shovel made of wood or plastic, and wiped with a clean cloth. Pay attention not to damage the insulation;

C. Check whether the connection between the stator shell and the core is tight and whether there is crack at the welding part;

D. Check the integrity of stator and its parts, and complete the missing parts;

E. Use 1000-2500V megohmmeter to record the insulation resistance of two or three-phase winding. If the resistance value is unqualified, find out the reason and take corresponding treatment;

F. Check whether the stator slot is loose, broken and protruding, and check whether the winding bar in the ventilation ditch is bulging. If Qizi and insulating sleeve are blackened, it indicates overheating phenomenon. It is necessary to eliminate poor ventilation or reduce load operation. Check the end insulation for damage. When the insulation pad and the insulation clip have dry shrinkage, the pad can be added or replaced. If the end binding is loose, the long-term binding wire can be removed, and the new binding wire can be used to bind again;

G. Check whether the clamping screw of stator core is loose. If the insulation pad under the clamping nut is damaged, replace it. When measuring the insulation resistance of clamping screw with 500-1000v megger, it should be 10-20m Ω in general;

H. Check the fastening of the connection between the head and the cable caused by the generator;

I. Check whether the bearing splashes oil to the end of winding. If there is oil dirt on the end of winding, clean cloth can be dipped in gasoline or carbon dioxide to wipe. If the end insulation is seriously corroded by oil, a layer of oil resistant protective paint can be sprayed if necessary.;

J. Inspect and trim the end cover, sight glass, felt pads on the stator housing and other seams.

3)Inspect rotor

A. Use 500V megger to measure the insulation resistance of rotor winding, if the resistance value is unqualified. Find out the cause and deal with it;

B. Check the rotor surface for discoloration. If so, it indicates that there is local overheating on the iron core, retaining ring, and the causes shall be found out and handled. If it cannot be eliminated, the output power of generator shall be limited;

C. Check the balance block on the rotor, which should be fixed firmly without increasing or decreasing or changing position, and the balance screw should be locked firmly;

D. For the hidden pole rotor, check whether the groove is loose, broken and discolored, check whether the collar and the core ring have cracks, rust spots and discoloration, and check whether there are signs of looseness and displacement at the joint between the collar and the rotor;

F.For the rotor, check for rust. Whether the screw is tight, whether the magnetic pole winding is loose, and measure the insulation resistance of the winding, which should be qualified;

G. Check the fan to remove dust and grease. The fan blade shall be free from looseness and breakage, and the locking screw shall be tightened;

H. Check slide, brush and brush holder.


Starlight Power manufacturer also provides various brands diesel generator set, such as Cummins, Volvo, Perkins, Deutz, Doosan, Yuchai, Shangchai, Weichai, Wuxi and Ricardo. Welcome to contact us by email sales@dieselgeneratortech.com. 

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