In the industrial field, diesel generator sets are indispensable backup power equipment for many enterprises and facilities. However, many people may not know that when assembling a diesel generator set, the connection between the generator and the diesel engine is not simply a mechanical connection, but has strict technical requirements, among which the most critical is centerline alignment. If this step is not handled properly, it will trigger a series of serious problems, not only affecting the normal operation of the equipment but also potentially causing safety hazards. This article will deeply explore the importance of centerline alignment of diesel generator sets, common problems, cause analysis, and solutions, helping everyone better understand and master this key technical process.
During the operation of a diesel generator set, the crankshaft of the diesel engine and the generator shaft need to remain on the same centerline. This is the basis for ensuring smooth operation of the equipment. If the two shafts are not aligned, many problems will occur during operation.
First, the machine body may vibrate violently, which not only affects the operational stability of the equipment but may also cause damage to instruments, oil pipes, and water tanks due to vibration. Second, the rubber hinge will wear out quickly, shortening its service life. More seriously, the crankshaft bearings and generator bearings will experience uneven stress, accelerating wear or even leading to fracture, which will directly result in the equipment being unable to operate normally and may even trigger more serious safety incidents.
In addition, misalignment of the centerline will also reduce the operating efficiency of the equipment. Due to increased vibration, energy loss rises, and resonance may occur, reducing power generation efficiency. This not only increases operating costs but also affects the service life of the equipment. Therefore, after the diesel generator set is assembled, its centerline must be carefully checked and corrected to ensure it meets technical requirements.
Centerline misalignment of a diesel generator set mainly manifests as the rotor axis and stator axis not coinciding, showing a certain degree of eccentricity. Such misalignment usually causes unstable operation and increased vibration. Causes of generator misalignment may include faulty bearings, loose or deformed rotors, etc.
Centerline misalignment of diesel generator sets mainly shows in two forms: offset and angular misalignment.
Offset refers to the two axis centerlines being parallel but separated in the vertical or horizontal direction.
Angular misalignment refers to the two axis centerlines not being parallel, forming a certain angle.
The main reasons for diesel generator set centerline misalignment are as follows:
Base nuts not tightened: If the generator base nuts are not tightened, displacement may occur during operation, causing misalignment.
Failure to recalibrate after maintenance or part replacement: If the generator is disassembled for maintenance and not properly realigned, or if rubber hinges are replaced without carefully recalibrating the centerline, misalignment will occur.
Environmental factors: Improper humidity, temperature, and other environmental conditions may affect the centerline. For example, temperature changes can cause parts to expand or contract, changing the centerline position.
Equipment aging or wear: After long-term use, components may loosen or deform due to wear, affecting centerline alignment.
Centerline misalignment not only affects the operating efficiency of the diesel generator set but also brings a series of serious hazards. First, it causes excessive wear of rotors, bearings, and other components, leading to decreased performance and increased failure rates. Second, misalignment may cause severe vibration and equipment imbalance, eventually leading to forced shutdown, rotor detachment, or catastrophic accidents. These incidents can result in huge economic losses and may endanger personnel safety.
In addition, misalignment can affect the sealing of the equipment. If misalignment is severe, it may damage seals, allowing dust to enter the machine, harming internal components. Therefore, regular inspection of bearings, rotors, and other parts for wear and deviation is critical for ensuring normal operation and production safety.
To ensure normal operation of diesel generator sets, centerline must be regularly inspected and corrected. Common methods include:
Visual inspection: First, conduct a visual inspection to see if there are obvious loose, deformed, or damaged parts. Check if nuts are tightened and whether rubber hinges show signs of wear.
Vibration detection: Use vibration instruments to detect equipment vibration. If abnormal vibration is found, it may be caused by misalignment. Vibration detection can help quickly locate problems, but requires professional equipment and personnel.
Dial indicator measurement: A dial indicator is a high-precision measuring tool capable of detecting very small distance changes. When aligning shafts, it measures micro changes caused by offset. Install the dial indicator properly and measure every 90 degrees to ensure accuracy.
Offset correction: If an offset between the two shafts is found, adjust the thickness of the generator base shims. Loosen the four base bolts and appropriately adjust the shim thickness (increase or decrease by the offset amount). For example, if the generator is too high, reduce the thickness of all shims at the generator base by 0.15 mm to correct the offset.
Angular misalignment correction: Angular misalignment correction is more complex. First, loosen the four base bolts, slightly lift the generator base, appropriately reduce the shim thickness according to: adjusted thickness (mm) = distance between front and rear base (m) × angular misalignment (mm/m), then place the generator back flat (it may move slightly, ensure it returns to its original position), and tighten the four bolts. The basic rule for adjusting angular misalignment is: larger shim on top, smaller on bottom to add, smaller on top, larger on bottom to remove. That is, when measuring, if the distance from the top parallel bolt to the iron circle is greater than the bottom (then rotate the flywheel 180°) distance, add shims at the generator rear to adjust the angular misalignment; if the top distance is smaller than the bottom, remove shims at the generator rear to adjust the angular misalignment.
Horizontal and vertical correction: When correcting horizontally and vertically, thermal expansion and contraction must be considered. For example, for long-distance installations, the main generator input shaft is usually higher than the diesel engine crankshaft to compensate for vertical thermal expansion, flywheel sag, and crankshaft lift from main bearing oil film. During measurement, it is best to rotate both diesel engine and generator together to eliminate dial indicator errors caused by part roundness. Because elastic couplings cause incorrect readings, the main generator should be disconnected from the diesel engine during alignment.
To reduce misalignment and improve equipment stability and safety, the following preventive measures and maintenance recommendations are suggested:
Select high-quality components: When assembling diesel generator sets, choose high-quality seals, bearings, rubber hinges, and other components. High-quality components effectively reduce misalignment caused by component quality issues.
Install strictly according to technical requirements: During installation, operate strictly according to technical requirements. Ensure all nuts are tightened, and components are correctly installed. After replacing parts, recalibrate the centerline to meet technical requirements.
Consider environmental factors: Pay attention to environmental conditions, especially humidity and temperature. Apply necessary protection and maintenance to ensure normal service life and maximum efficiency. For example, protective covers can be installed around the equipment to prevent dust and moisture from entering.
Regular inspection and maintenance: Regularly check bearings, rotors, and other components for wear and deviation, and address issues promptly. A full inspection and maintenance every quarter is recommended to ensure normal operation.
Correct misalignment promptly: If misalignment is found, repair it immediately. For early-stage hub misalignment, align the hub; for overall misalignment, adjust and rebalance the generator set.
Record and analyze: During each inspection and maintenance, record the operating status and inspection results in detail. Analyzing these data helps better understand equipment conditions, detect potential problems in time, and take corresponding measures.
Centerline alignment of diesel generator sets is a key step to ensure stable operation. By understanding the importance, common problems, causes, and solutions of centerline alignment, operators can better master this technical point. In practice, installation and maintenance must strictly follow technical requirements, regularly inspect the operating condition of the equipment, and promptly detect and correct misalignment. Only in this way can diesel generator sets operate normally, improve efficiency, prolong service life, and ensure production safety.
In summary, centerline alignment of diesel generator sets is a complex but extremely important task. It is hoped that this article can help everyone better understand and master this technical point, providing strong support for stable operation of equipment.
