Repair Methods for Diesel Generator Crankshaft Journal Wear

Diesel generator set crankshafts may experience accelerated and uneven journal wear due to improper use, poor lubrication, or excessive/insufficient bearing clearance. The primary manifestations of wear are journal out-of-roundness (ovality) and non-cylindricity (taper). How to repair such wear and correct deviations in roundness and cylindricity? Guangxi Dingbo Power Equipment Co., Ltd., a professional diesel generator manufacturer, provides a detailed explanation:

Causes of Journal Wear

After prolonged use, crankshafts undergo uneven wear due to periodic variations in the magnitude and direction of forces acting on connecting rod journals and main journals. Improper use, poor lubrication, or inappropriate bearing clearance accelerate wear and unevenness, resulting in out-of-roundness and taper.

Connecting rod journal taper wear is primarily caused by uneven accumulation of mechanical impurities in oil passages. Inclined oil passages leading to connecting rod journals cause lubricant-borne impurities to accumulate on one side of the journal under centrifugal force (as shown in the diagram), leading to localized wear. Additionally, asymmetrical connecting rod big ends (designed to shorten rod length in some engines) result in uneven load distribution along the journal axis, exacerbating wear irregularities.

Repair Procedures (Dingbo Power’s Recommendations):

1.Repairing Minor Journal Scratches

If journal roundness and cylindricity are within tolerance but minor scratches, grooves, roughness, or burn marks exist: Wrap the journal with fine sandpaper strips (matching journal width), secure with hemp rope or cloth strips, and pull the ends reciprocally to polish. Alternatively, use specialized grinding fixtures. After removing scratches, clean the journal and grinder, apply lubricating oil, and perform final polishing to reduce surface roughness.

2.Correcting Excessive Roundness/Cylindricity Deviations

When journal roundness or cylindricity exceeds 0.025 mm (main journals) or 0.04 mm (connecting rod journals), repair options include:

Grinding to the next standard repair size.

Vibration surfacing or chrome plating followed by grinding to specified dimensions.

Crankshaft grinding is typically performed on dedicated crankshaft grinders or modified lathes. In small repair shops, skilled fitters may manually file journals to roundness (with repeated inspection) and polish using rope or fixtures, though this requires proficient craftsmanship to ensure quality.

Guangxi Dingbo Power Equipment Manufacturing Co.,Ltd was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. The company has a registered capital of 218.88 million yuan. The company covers an area of 86,000 square meters and a building area of 55,000 square meters. There are more than 660 employees, including 456 professional technicians and 106 senior technicians. It has 46 sales and service outlets nationwide. The main products are diesel engines, generator sets, and diesel generators, providing users with a one-stop service of design, supply, debugging and maintenance at any time. Dingbo has always insisted on using first-class talents, building first-class enterprises, manufacturing first-class products, creating first-class services, and making every effort to build a first-class domestic enterprise. If any question please feel free to visit our website https://www.dieselgeneratortech.com/ or send email to [email protected].