Engine installation precautions

1. Why is it necessary to measure the original length of the connecting rod bolt when assembling a new one?

A: Since the connecting rod big end bolt is a critical component connecting the crankshaft, its breakage could lead to a serious accident. Therefore, when assembling a new connecting rod bolt, its original length should be measured and recorded for future reference. This is to prevent the connecting rod bolt from undergoing permanent deformation due to stress and elongation, which could cause a breakage accident. If the original length of the connecting rod bolt is known, measure its length again after a certain period of use. If the measured length exceeds the original length, it proves that the connecting rod bolt has undergone permanent deformation and should be replaced according to the requirements in the machine manual.

2. What should be paid attention to when installing connecting rod bearings?

A: When installing connecting rod bearings and bolts, clean and tidy the work area, prepare the tools and parts to be installed, and conduct a final inspection of the journal and bearing surface, cleaning them as well. Check the oil holes, rotate the crankshaft, add lubricating oil, and then install the bearing. At this point, check if the bearing markings are correct. Lower the connecting rod, and then install the lower half of the bearing. Clean, lubricate, and check the markings again. If shims are used, check that they are properly positioned. The side of the shim closest to the journal should be close to the journal, but not touching it. Then reinstall the bolts and nuts in their original positions. At this point, remember to check that the pins or notches on the bolt heads that prevent rotation are properly seated. Do not blindly tighten the bolts, as this may damage these mechanisms. When tightening the bolts, alternate between both sides, gradually increasing the force until the specified torque is reached.

3. What issues should be considered when installing the engine base?

A: The engine base is the foundation of the entire diesel engine, and its installation accuracy will affect the overall assembly quality; therefore, it should be given special attention. Before the engine base is hoisted onto the ship, the main bearings and crankshaft have already been fitted in the workshop. Generally, the engine base and crankshaft are hoisted onto the ship together and placed on the engine room base, supported by temporary adjustable bolts to adjust their position. The engine base position is initially determined according to the shaft centerline reference point.

The main technical requirements for engine base installation are:

1. The upper surface of the engine base should be flat.

2. The crankshaft's turning radius difference must not exceed the allowable range. 3. The shims provided between the engine base and the base should maintain good contact with the lower surface of the engine base and the supporting surface of the base.

After the engine base is installed, the frame, cylinder block, and guide plate can be assembled.

4. What issues should be considered when installing the frame, cylinder block, and guide plate?

A: The main issue in installing the frame, cylinder block, and guide plate is ensuring the accuracy of the relative position between the cylinder centerline, the crankshaft centerline, and the guide plate plane. The main technical requirements are:

1. The mating surfaces between components such as the engine base, frame, and cylinder block should fit tightly. Poor fit will not only cause oil and air leaks during operation but also easily lead to loosening of the mating surfaces, resulting in severe vibration during diesel engine operation that could cause the connecting bolts to break. Tightening the through bolts can deform the frame and also disrupt the perpendicularity of the cylinder centerline to the crankshaft centerline.

2. To prevent displacement of components such as the frame and cylinder block during engine operation, each connecting bolt should have at least four tight-fitting bolts or locating pins, evenly distributed.

3. The cylinder centerline should be perpendicular to and intersect the crankshaft centerline, with a perpendicularity not exceeding 0.15 mm per meter and an intersection not exceeding 1.0 mm.

4. The guide plate should fit tightly against the mounting surface. Each guide plate should have at least two evenly distributed tight-fitting bolts. After installation, the working surface of the guide plate should meet the following requirements:

1) Parallelism between the guide plate working surface and the crankshaft centerline should not exceed 0.10 mm per meter;

2) Parallelism between the guide plate working surface and the cylinder centerline should not exceed 0.10 mm per meter;

3) Within the same cylinder, the parallelism between the working surfaces of corresponding guide plates should not exceed 0.15 mm.

5. The parallelism between the working surface of the side guide plate and the cylinder centerline should not exceed 0.15 mm per meter. 

Only by meeting the above requirements can the normal operation of the diesel engine be guaranteed.