Repair method of cracks in cylinder block and cylinder head of diesel generator set

The repair method of cracks in the cylinder block and cylinder head of a diesel generator set should be determined according to the degree of cracking, the location of damage, the repair conditions and the equipment condition. There are five commonly used repair methods:

1. Epoxy resin adhesive bonding
Epoxy resin adhesive bonding has the advantages of strong bonding, small shrinkage, fatigue resistance, etc., and the process is simple, easy to operate and low cost. The main disadvantage is that it is not resistant to high temperature and impact. During the next repair, it will fall off after being boiled and washed with hot alkaline water, and needs to be re-bonded. Therefore, except for high-temperature areas such as the combustion chamber and valve seat, the rest of the cylinder block and cylinder head can be repaired by this method.

2. Screw filling
This method is suitable for some flat parts with low stress, low strength requirements and short crack range (generally less than 50 mm). Its repair quality is high, but it is more time-consuming. The specific filling process is as follows:
1. Drill a hole at each end of the crack to prevent the crack from continuing to extend;
2. Drill holes along the crack and tap the thread. The diameter of the hole depends on the diameter of the thread. Ensure that the holes overlap by 1/3 of the hole diameter;
3. Screw in the pre-threaded copper rod in the tapped thread. After screwing, cut the copper rod so that the cut-off point is 1~1.5 mm higher than the crack surface;
4. In order to fill it tightly, use a hand hammer to gently tap between the cut screws, use a file to smooth it, and solder it if necessary to prevent leakage.

3. Filling with patching
In the parts of the cylinder block and cylinder head where the stress is not large, if the crack is long or there is a hole, use patching around the damaged part. The specific process is as follows:
1. Drill holes at the ends of each crack to limit its extension;
2. Use a 3~5 mm thick copper plate or a 1.5~2 mm thick iron plate to cut into a patch plate similar to the outline of the crack and 15~20 mm larger than the crack on all sides. If there is a convex part on the cracked surface, it is necessary to knock out the same convex shape on the patch plate so that the entire patch plate can fit the surface of the sealed part;
3. Drill holes with a diameter of 4~6 mm every 10~15 mm around the patch plate, about 10 mm away from the edge of the patch plate. Make drilling marks on the cylinder block according to the position of the patch plate drilling, then drill a hole with a depth of about 10 mm and tap out the thread;
4. Fill the asbestos gasket coated with white paint between the cylinder block and the patch plate, and then fasten the patch plate to the cylinder block with flat head bolts.

IV. Welding repair
Cracks in the cylinder block and cylinder head, such as those occurring in areas with greater stress or higher temperature, and areas that are difficult to operate with the above methods, are often repaired by welding repair. The specific process is as follows:
1. Drill a 3~5 mm hole at both ends of the crack;
2. Chisel the crack into a 60~90 degree V-shaped groove;
3. Use DC welding. When using acetylene welding, the cylinder block or cylinder head should be leveled, the welding area should be slowly preheated to about 500℃, and after welding, it should be heated to 500~550℃ for 1 hour, and then slowly cooled to room temperature within no less than 16 hours.

5. Leakage plugging with plugging agent
When using plugging agent to repair cracks, first find the leaking part and determine the length, width or sand hole diameter of the crack. If the crack width and sand hole diameter exceed 0.3 mm, it is best not to use this method.
If the crack is in a key position, such as the cylinder hole edge, the main bearing seat and other stress-bearing parts, the cylinder block or cylinder head should be replaced. All repaired cylinder blocks and cylinder heads should be subjected to water pressure tests to check for leakage.