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Repair Method for Cracks in Diesel Generator Cylinder Block and Cylinder Head

May 26, 2023 | Management News | 0 comments

Epoxy resin bonding

Epoxy resin adhesive is composed of epoxy resin, curing agent, plasticizer, accelerator, diluent, filler, coupling agent, flame retardant, stabilizer and so on. Among them, epoxy resin, curing agent and toughening agent are indispensable components.
He decides whether to add or not according to need. Epoxy resin bonding has the advantages of strong adhesive force, small shrinkage, and fatigue resistance. At the same time, the process is simple, the operation is convenient, and the cost is low. Its main disadvantage is that it is not resistant to high temperature, impact resistance, etc. When it is repaired once, it will fall off after being boiled and washed in hot alkaline water, and it needs to be bonded again. Therefore, except for the high-temperature areas such as the combustion chamber and the cylinder head, the rest of the cylinder block and cylinder head can be repaired by this method.
(1) Epoxy resin
Epoxy resin is a high molecular compound with two or more epoxy groups in its molecule and relatively low molecular weight. 1. Classification There are many varieties and grades of epoxy resin, but bisphenol A glycidyl ether epoxy resin is usually Bisphenol A epoxy resin is the most important class. It accounts for 90% of the total epoxy resin production. The molecular structure is very long and I won’t talk about it here! If you want to know it, you can click on the epoxy resin and there will be a detailed description! Bisphenol A epoxy resin is also known as general-purpose epoxy resin and standard epoxy resin. It is named E-type epoxy resin in China. It is composed of bisphenol (BPA or DPP) and epichlorohydrin (ECH) It is obtained by polycondensation under sodium hydroxide. root depending on the ratio of raw materials, reaction conditions and methods used, viscous liquids with low relative molecular weights and solids with high relative molecular weights and high softening points can be prepared with different degrees of polymerization. The average relative molecular mass is 300~7000. The appearance is almost colorless or light yellow transparent viscous liquid or flaky brittle solid. Epoxy resin itself is a thermoplastic linear polymer. When heated, the viscosity of the liquid resin becomes lower, and the solid resin softens or melts. Soluble in acetone, methyl ethyl ketone, cyclohexane ketone, ethyl acetate, benzene, toluene, xylene, absolute ethanol, ethylene glycol and other organic solvents.
(2) Hydrogenated bisphenol A epoxy resin
The chemical name of hydrogenated bisphenol A epoxy resin is hydrogenated bisphenol A diglycidyl ether, which is obtained by polycondensation of hexahydrobisphenol A obtained by hydrogenation of bisphenol A and epichlorohydrin under the catalysis of sodium hydroxide. is a very low viscosity, gel time long-lasting, fairly weather-resistant epoxy resin.
(3) Bisphenol F epoxy resin
The chemical name of bisphenol F type epoxy resin is bisphenol F diglycidyl ether, referred to as DGEBF or BPF. polycondensation reaction a colorless or light yellow transparent viscous liquid should be obtained.
(4) Bisphenol S type epoxy resin
The chemical name of bisphenol S type epoxy resin is bisphenol S diglycidyl ether, referred to as BPS or KGEBS, which is prepared from bisphenol S and epoxy propane under the catalysis of sodium hydroxide. Bisphenol S type epoxy Resin with high heat resistance, heat deflection temperature it is 60~700C higher than bisphenol A epoxy resin, and the cured product is stable and has good solvent resistance.
(6) Bisphenol P type epoxy resin
Bisphenol P type epoxy resin is obtained by synthesizing bisphenol P with 3-aminopropene and phenol as the main raw materials, and then polycondensing epichlorohydrin with sodium hydroxide under the catalysis. The epoxy value of bisphenol P type epoxy resin is 0.45eq/100g, and the organic chlorine content 1.38*10-3eq/100g, inorganic ammonia content 1.84*10-4eq/100g Bisphenol P type epoxy resin has large molecular chain flexibility, good fluidity at low temperature, lower viscosity than bisphenol A epoxy resin, compressive strength and impact Stronger than bisphenol A epoxy resin.
(7) Novolak epoxy resin
Novolac epoxy resins mainly include phenol novolac epoxy resin and o-cresol novolac epoxy resin, as well as resorcinol novolac epoxy resin. In addition, tetraphenol-based Z-alkane epoxy resins also belong to novolac epoxy resins.

Screw filling

This method is suitable for some plane parts with little stress, small strength requirements and short crack range (generally below 50mm). The repair quality is high, but it takes more time. The specific filling process is as follows:
(1) Drill a limiting hole at both ends of the crack to prevent the crack from continuing to extend.
(2) Drill holes 3, 4, and 5 along the crack, the diameter of the hole depends on the diameter of the thread, and ensure that the holes overlap by 1/3 of the hole diameter.
(3) tap the thread in the above-mentioned 1, 2. 3, 4, 5 holes.
(4) In the tapped thread, screw the pre-threaded copper rod (the part of the screw is painted with white paint), and cut off the copper rod after screwing, so that the cut part is 1.1.5mm higher than the crack surface.
(5) Holes 6, 7. 8. 9 have been drilled between the cut off screws, and tapped and screwed into the screws according to the above method to fill the cracks and form a screw chain.
(6) In order to make the filling tight, lightly tap between the cut off screws with a hand hammer, and finally smooth it with a file. If necessary, it can be soldered to prevent leakage.

Repair board sealing

On the part 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 plates to seal around the damaged part.
(1) Drill holes at the ends of each crack to limit its extension.
(2) Use 3, 5mm thick copper plate or 1.5, 2mm thick iron plate, cut into a patch similar to the outline of the breach, and the surrounding area is 154~20mm larger than the breach. If there is a convex part on the cracked surface, it is necessary to knock out the same convex shape on the repair board, so that the entire patch can be attached to the surface of the patch.
(4) Press the repair board on the break, use a stylus to make a drilling mark on the cylinder block from the repair board hole, remove the repair board, drill a hole with a depth of about 10mm at the mark, and tap out the required diameter thread.
(5) Fill the asbestos liner 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. Tighten the bolt further to increase its tightness.

Welding repair

Cracks in the cylinder block and cylinder head, if they occur in parts with high stress or high temperature, and parts that are not easy to operate by several methods, are mostly repaired by welding. The welding repair process is as follows.
(1) Drill a hole of 3~5mm at each end of the crack to prevent the extension of the crack.
(2) According to the specific situation, chisel the crack into a V-shaped groove of 60°~90°, and clean it up to reveal the luster.
(3) When electric welding is used, DC electric welding should be used; when acetylene welding is used, the cylinder body or cylinder head should be flattened, the welding area should be preheated slowly to about 500°C, and heated to 500~550°C after welding repair 1h, and then slow down in no less than 16h let cool to room temperature.

Plugging agent plugging

The plugging agent is usually a colloidal liquid composed of water glass, inorganic coagulant, organic flocculant, inorganic filler and adhesive. It is suitable for plugging defects such as small cracks and sand holes in cast iron or aluminum cylinders. When using plugging agent to repair cracks, the leaking part should be found first, and the length and width of the crack or the aperture of the trachoma should be determined. If the crack length exceeds 40~50mm, limit holes of 3~4m can be drilled at both ends of the crack, and screws can be screwed on by spot welding or tapping to prevent the extension of the crack. At the same time, drill holes (not drill through) every 30, spot weld or tap screws and screw on the screws to avoid crack expansion due to vibration during work. If the crack width and sand hole diameter exceed 0-3mm, it is best not to repair it with this method. The plugging agent is only suitable for small cracks or when there is a small amount of leakage.

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