Diesel generator set parts repair technology machining (2)
The previous part has introduce the use of the partial replacement method, transposition method and inserting method in matching of diesel generator set parts repair technology. We will continue introducing more information about this method in this post. Please find more information about repairing techniques of metal buckles for diesel generator sets.
The metal buckle method is a process method that uses a special connecting member made of a high-strength alloy material to mechanically reconnect the damaged mechanical parts into one body to achieve the purpose of repair. It is mainly suitable for the repair of cracks or broken parts of large castings. According to the nature and characteristics of the fastening, it can be divided into four processes: strong fastening, strong fastening, superior fastening and thermal fastening.
I Strong Buckle Legal
This method is applicable to the repair of thin-walled parts with a general strength requirement of 8-40mm. The process to first process a wave groove having a certain shape and size in a direction perpendicular to the crack or the cross section of the machine member, and then inset a high-strength alloy wave key having a shape matching the shape groove into the groove. And riveting at normal temperature, the waveform key is plastically deformed to fill the cavity, so that the flange of the damaged two sides are firmly connected to each other.
When designing and manufacturing the waveform key, the flange diameter d, width b) and pitch 1 (wave groove pitch t) of the waveform key (Fig. 2-18) are usually specified as standard sized, according to the force of the machine and the wall thickness of the casting. Determine the number of flanges of the waveform key, the number of waveform keys installed in each broken part, and the pitch of the waveform groove. Generally, b is 3-6mm, other dimensions can be calculated according to the following empirical formula:
Usually, the number of flange of waveform key is 5, 7, 9. Usually, lCr18Ni9 or 1Cr18Ni9Ti austenitic nickel-chromium steel is often used in general waveform bond materials. The high nickel alloy steel such as NI36 or NI42, which has the same or similar thermal expansion coefficient as the component material, can be used for the waveform bond at high temperature.
II Strong Deduction
The application of the strong buckle law can guarantee a certain strength condition, and for the parts with sealing requirements, such as the cylinder with high pressure, the strong buckle law should be adopted, as shown in Figure 2-19. It is based on the strong buckle legal method, processing the stitching bolt hole between the two wave keys, the crack or the cross section of the cross section, and making the second plug form a sealed metal tie to prevent the fluid from leaking under pressure. The sewed plug can be made of soft material such as low carbon steel or pure copper with a diameter of 5-8mm, which is convenient for riveting. The connection between the sewed plug and the mechanism is the same as the waveform key.
III Super Deduction
It is mainly used to repair thick-walled parts that are required to withstand high loads during work. In order to distribute the load to more areas and away from cracks or breaks, steel brick reinforcements must be inlaid in the direction perpendicular to the cracks or fractures, connected by stitching bolts, and sometimes reinforced with wave keys. As shown in Figure 2-20. The reinforcing members can be designed into a cross shape, a wedge shape, a rectangular shape, an X shape, and the like as needed.
IV Hot Buckling Method
It uses a heated fastener to create a contraction during cooling to lock the cracked mechanism. This method is suitable for repairing cracks and fractures of large flywheels, gears and heavy equipment fuselage. As shown in Figure 2-21, the annular fastener is suitable for repairing the damage of the contour part. The I-shaped fastener is suitable for cracking or breaking of the wall of the machine.
The advantage of the metal buckle law is that the repaired machine has sufficient strength and good sealing performance; the required equipment and tools are simple and can be constructed on site; the mechanical parts do not generate thermal deformation and thermal stress during the repair process. The disadvantages are mainly that thin-walled castings (<8mm) are not suitable; the production of waveform keys and corrugated grooves is troublesome.
Repair size method and adjustment method in generator set repair technology.
I Repair size method
In the repair of defective parts of diesel generator sets, the repair method of the original design size and other technical requirements and standard sizes can be achieved after repair. The original design size is not considered in the repair, and the shape accuracy accuracy, surface roughness and other technical conditions are restored by cutting and other processing methods to obtain a new size, called repair size. The parts that match this are made into new parts or repairs according to the repair size. This method is called repairing the size method. Its essence is to solve the dimensional chain in the repair.
When determining the repair size, remove the thickness of the surface layer. First, consider the possibility of the structure of the part and the strength and rigidity of the parts after repair. For example, the reduction of the journal size generally does not exceed 10% of the original design size; the keyway on the shaft can be expanded by one stage; for the hardened journal, the hardness requirement should be considered after repair. In order to achieve limited interchangeability, it is sometimes possible to standardize the repair dimensions of diesel generator sets, such as the repair dimensions of cylinder liners for internal combustion engines, which are usually specified in several standard sizes to accommodate pistons of size classification. The size and grade of the standard size also depend on the amount of wear on the cylinder liner, the machining allowance, the safety factor and the geometry change after wear.
The repair size method is widely used in the maintenance of engineering machinery and other industries. This method is commonly used to repair many parts such as the crankshaft main journal of the diesel generator set, the connecting rod journal, the cylinder liner, the cylinder, and the piston. The repair size method is usually a maintenance method with a minimum repair workload. It is easy to work, simple in equipment, and economical. It can maintain the interchangeability of parts within a certain repair size range, and it is more meaningful for expensive and complicated parts. However, it weakens the strength and rigidity of the parts, and needs to replace or repair the parts and parts, complicating the interchangeability of the parts; the relevant departments need to expand the supply of spare parts, and the parts must be matched.
II Adjustment Method
Use the method of increasing or decreasing the gasket or adjusting the screw to make up for the increase of the matching clearance caused by the wear of the parts. This is the most common method used in maintenance. For example, the wear of the tapered roller bearing and various friction plates causes an increase in the play gap, and the normal condition can be restored by the adjustment method.