The diesel engine has a complex structure with many components, and requires high technical requirements for tight coordination. The correct and reasonable dismantling and inspection of diesel generators is one of the important links to ensure repair quality, shorten maintenance cycles, and improve economic benefits. If the dismantling work is not done in accordance with principles and technical processes, it will inevitably affect the quality of repairs and even create new hidden dangers. The general principle of disassembly based on work experience is to first drain all fuel, engine oil, and cooling water; Secondly, it is necessary to adhere to the steps of starting from the outside and then the inside, starting from the accessories and then the main body, starting from the connecting parts and then the parts, and starting from the assembly and then the assembly, assembly, and parts.
1、 Safety precautions
1. Before carrying out repairs, repair personnel should read all preventive and precautionary measures specified on the machine nameplate or diesel engine manual.
2. When carrying out any operation, personal protective equipment should be worn: safety shoes, safety helmets, work clothes<clothing should not be too loose or have red buttons falling off); When striking parts with a hammer or grinding them with a grinding wheel, it is necessary to wear protective goggles.
3. If welding repair is required, it must be carried out by trained and skilled welders. When welding, welding gloves, sunglasses, masks, work hats, and other suitable clothing should be worn. 4. When operated by two or more workers. Before starting any step, notify your partner.
5. Maintain all tools well and learn to use them correctly.
6. A suitable place for storing tools and dismantled parts should be designated in the repair workshop. Tools and parts must be placed in the correct place. To keep the workplace clean and ensure that there is no dust or oil on the ground, smoking can only be done in designated smoking areas. Smoking is strictly prohibited during work.
2、 Preparation work
1. Before disassembling the engine, it should be placed on a solid and level ground, and fixed with wedges to prevent the engine from moving.
2. Before starting work, the lifting tools should be prepared: one 2.5-ton forklift, one 12mm steel wire rope, and two 1-ton unloaders. In addition, it should be ensured that all control levers are locked and warning signs are hung on them.
3. Before starting the disassembly work, rinse the engine surface of oil stains, drain all engine oil inside, and clean the engine repair site.
4. Prepare a bucket for storing waste engine oil and an iron basin for storing spare parts.
5. Tool preparation before starting disassembly and assembly
(1) Wrench width<mm:
10. 12, 13, 14, 16, 17, 18, 19, 21, 22, 24
(2) Inner diameter of sleeve mouth<mm:
10. 12, 13, 14, 16, 17, 18, 19, 21, 22, 24
(3) Special sleeve for crankshaft nut:
Kilogram wrench, oil filter wrench, diesel filter wrench, feeler gauge, piston ring disassembly and assembly pliers, snap ring pliers, valve guide special disassembly and assembly tools, valve seat ring special disassembly and assembly tools, nylon rod, valve special disassembly and assembly tools, connecting rod bushing special disassembly and assembly tools, file, scraper, piston special installation tools, engine frame.
- Preparation for pressing work: cylinder sleeve pressing workbench, jack, and special tools for cylinder sleeve pressing.
- 3、 Precautions for disassembling diesel engines
- ① It must be carried out when the diesel generator is completely cooled. Otherwise, due to the influence of thermal stress, permanent deformation of components such as the cylinder block and cylinder head will occur, which will affect the various performance of the diesel engine.
- ② When disassembling components such as cylinder heads, connecting rod bearing caps, and main bearing caps, the loosening of their bolts or nuts must be symmetrically and evenly divided into 2-3 disassembly steps in a certain order. It is absolutely not allowed to loosen the nuts or bolts on one side before loosening the other, otherwise, due to uneven force on the parts, deformation may occur, and some may even cause cracks and damage.
- ③ Carefully carry out the verification and marking work. For parts such as timing gears, pistons, connecting rods, bearing shells, valves, and related adjusting gaskets, make a note of the marked ones, and make a mark of the unmarked ones. The marking should be placed on a non working surface that is easy to see, without damaging the assembly reference surface, in order to maintain the original assembly relationship of the diesel generator as much as possible. Some parts, such as the joints between the wires of the diesel engine and the generator, can be labeled using methods such as paint, scratches, and labeling.
- ④ When disassembling, do not forcefully tap or strike, and use various tools correctly, especially special tools. For example, when disassembling piston rings, piston ring loading and unloading pliers should be used as much as possible. Spark plug sleeves should be used when disassembling spark plugs, and the force should not be too strong. Otherwise, it is easy to injure one’s hands and damage the spark plug.
- When disassembling threaded connectors, it is necessary to use various wrenches and screw drivers correctly. Often, incorrect use of wrenches and screw drivers can damage nuts and bolts. For example, when the width of the wrench opening is larger than that of the nut, it is easy to make the edges and corners of the nut round; The thickness of the screw screwdriver head does not match the groove of the bolt head, which can easily damage the groove edge; When using a wrench and screw driver, starting to rotate without properly placing the tool in the nut or groove can also cause the above-mentioned problems. When the bolts rust or are tightened too tightly and difficult to disassemble, using an excessively long force rod can cause the bolts to break. Due to lack of understanding of the front and back fastening of the bolts or nuts or unfamiliarity with disassembly
- Turning it upside down can also cause the bolt or nut to break.
4、 Precautions for disassembling and assembling AC generators
Before disassembling a synchronous generator, a preliminary inspection and recording of the winding status, insulation resistance, bearing status, commutator and slip ring, brushes and brush holders, as well as the coordination between the rotor and stator, should be carried out to understand the original faults of the inspected motor, determine the maintenance plan and prepare materials, and ensure the normal progress of the maintenance work.
① When disassembling each connection joint, attention should be paid to the wire end labeling. If the labeling is lost or unclear, it should be re labeled.
When reassembling, reconnect in situ according to the circuit diagram and cannot be adjusted incorrectly.
② The removed components should be properly placed and not placed randomly to avoid loss. The components should be handled with care to avoid deformation or damage caused by impact.
③ When replacing rotating rectifier components, pay attention to the direction of conduction of the rectifier components being consistent with the direction of the original components. Using a multimeter to measure its forward and reverse resistance can determine whether the silicon rectifier component is damaged. The forward (conduction direction) resistance of the rectifier element should be very small, usually several thousand ohms, while the reverse resistance should be very large, generally greater than 10k0.
④ If replacing the excitation winding of the generator, attention should be paid to the polarity of the magnetic poles when making connections. The magnetic pole coils should be sequentially connected in series, one positive and one negative. The permanent magnet on the stator of the excitation machine has a polarity of N facing the rotor. The magnetic poles on both sides of the magnet are s. The end of the excitation winding of the main generator should still be wrapped with a steel wire clamp. The diameter and number of turns of the steel wire should be the same as before. After insulation treatment, the generator rotor should be positively balanced in the dynamic balancing machine. The method of correcting dynamic balance is to add weight to the fan of the generator and the balance ring at the non drag end.
⑤ When disassembling the bearing cover and bearings, be sure to cover the removed parts with clean paper properly to prevent dust from falling into them. If dust invades the bearing grease, all the bearing grease should be replaced.
⑥ When reassembling the end cover and bearing cover, in order to facilitate disassembly again, a little engine oil should be added to the end cover stop and the fastening bolts. The end caps or bearing bolts should be rotated one by one in a cross pattern, and one should not be tightened first before the others.
⑦ After the generator is assembled, slowly rotate the rotor by hand or other tools, and it should rotate flexibly without any friction or collision.
Post time: Mar-12-2024